Orwell Astronomical Society (Ipswich)
Archived Astronomy News 1972-97
This page contains archived astronomy news articles by members of OASI, taken from OASI Newsletters 1972-97.
An international team of astronomers has suggested that nearly every galaxy may harbour a supermassive black hole which once powered a quasar (an extremely luminous galactic nuclei) but is now quiescent. This conclusion is based on a census of 27 nearby galaxies carried out by NASA's Hubble Space Telescope (HST) and ground-based telescopes in Hawaii. As part of the census, the telescopes are conducting a spectroscopic and photometric survey of galaxies to find black holes which have consumed the mass of millions of Sun-like stars; the team has already announced the discovery of black holes in three "ordinary" galaxies.
The findings, presented at the 189th Meeting of the American Astronomical Society in Toronto, Canada, should provide insights into the origin and evolution of galaxies, as well as clarify the role of quasars in galaxy evolution. The key results are as follows:
We believe we are looking at "fossil quasars" and that nearly every galaxy at one time burned brightly as a quasar, said team leader Doug Richstone of the University of Michigan, Ann Arbor, Michigan. These conclusions are consistent with previous HST observations showing quasars dwelling in a variety of galaxies, from isolated "ordinary-looking" galaxies to colliding pairs.
Three of the black holes studied have masses and are located as follows:
Critical ground-based observations to identify the three objects were made by John Kormendy with the Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii. Hubble's high resolution then allowed the team to peer deep into the cores of the galaxies with extraordinary resolution unavailable from ground-based telescopes, and measure velocities of stars orbiting the black hole. A sharp rise in velocity means that a great deal of matter is locked away in the galaxy's core, indicating a very massive black hole with a powerful gravitational field that accelerates nearby stars. The team is confident that its statistical search technique has allowed it to pinpoint all the black holes they expect to see above a certain mass limit. However, our result is complicated by the fact that the observational data for the galaxies are not of equal quality, and that the galaxies are at different distances, said Richstone.
Though several groups have previously found massive black holes dwelling in galaxies the size of our Milky Way or larger, the new results suggest smaller galaxies have lower-mass black holes, below the detection limit of the HST. Challenges remain to explain why black holes are so abundant and why their masses should be proportional to that of the host galaxy. One idea, supported by previous HST observations, is that galaxies form out of smaller protogalaxies consisting of star clusters. A massive "seed" black hole may be present in each protogalaxy. The larger number of protogalaxies needed to merge to form a large, luminous galaxy would naturally provide more seed black holes to coalesce into a single, massive object residing in the nucleus of the galaxy eventually formed.
An alternative model is that galaxies start at some early epoch with a modest black hole (not necessarily approaching the large masses discussed above). The black hole consumes some fixed fraction of the total gas shed by the stars in the galaxy during the normal process of their evolution. If the fraction is around a modest one percent, the black holes could easily grow to the masses discussed above, and would naturally track the luminosity of the galaxy.
One of the features of the February 1997 servicing mission to the HST will be the installation of the Space Telescope Imaging Spectrograph (STIS). The instrument will greatly increase the efficiency of projects, such as the black hole census, that require spectra of several nearby objects. The work will continue with the refurbished telescope.
In the letters pages of New Scientist magazine, A Orr, responding to an article by Moshe Elitzur in Scientific America, February 1995, has proposed sending several radio telescope dishes into space to points in the Earth's orbit around the Sun. He claims that the technology to co-ordinate the dishes exists and would be cost-competitive and that such an array of dishes would offer far better resolving power even than the ten radio telescopes in the US Very Long Baseline Array stretching from Hawaii to the Virgin Islands.
Source: New Scientist, letters, 29 April 1995.
After four years of delays, NASA has successfully launched the Hubble Space Telescope (HST). One of the largest payloads ever carried by the space shuttle, the HST weighed in at 11 tonnes and measured over 13 m long by 4.25 m in diameter. The mirror is 2.4 m in diameter and has been figured to higher tolerances than any telescope on Earth. The optics should give the HST a resolving power of 0.1 arcseconds or better, an improvement by an order of magnitude over Earth-bound instruments which are limited by atmospheric turbulence to approximately one arcsecond.
The lack of atmosphere and the quality of optics will give the HST a sensitivity four magnitudes superior to that of the Mount Palomar five metre telescope. In addition, the HST benefits from special optical coatings that allow observations in the entire ultra-violet, visible and infrared portion of the spectrum. HST carries five main observing instruments:
During the next six months or so the HST will undergo rigorous testing of all its systems before being handed over to the astronomical community for what is hoped to be a ground-breaking observational programme. In the short term, there will be limited capture of spectacular pictures, but it is hoped that some test images of Jupiter and Saturn will be taken during the next few weeks.
The increased capabilities of HST over Earth-bound instruments, both in terms of resolution and light grasp, will be similar to the gain that Galileo's small telescope provided over the naked eye almost 400 years ago. It is to be expected that the discoveries which follow will be on the same scale!
The Search for Extra-Terrestrial Intelligence (SETI) is the endeavour to listen through the radio spectrum for signs of intelligent life in the universe.
Project META has been instituted in the USA to search the sky for transmissions from an alien civilisation. It presupposes that a civilisation would set up a giant radio beacon away from the rotating surface of the planet concerned. If this were not so, the signal would be difficult to direct to a specific target, could only be heard intermittently due to rotation of the planet and would suffer from Doppler shift and vary in pitch as the planet orbited its parent star.
Project META has already completed a search of the sky at 1420 MHz where background noise levels are very low. Scientists are now combing the sky for emissions at 2840 MHz which is another frequency "window" that an intelligent civilisation could use to advertise its presence to others. However because of financial restraints this search will not begin in earnest until 1992 and will not complete before the turn of the century. Project META will search the 1000 nearest stars at 1-10 GHz and the entire sky at 1-3 GHz.
All the processes exhibited by comets, from formation of comas and tails to fragmentation of the nucleus, suggest a progressive loss of material. This means that comets age and have limited lifetimes. To find out more about the histories of comets, we need to know how long individual specimens survive in different orbits. As cometary orbits typically have periods of several millions of years, we do not usually get opportunities to check aging over multiple revolutions of the Sun.
Lubor Kresak of the Astronomical Institute of the Slovak Academy of Sciences, Czechoslovakia, has attempted to estimate comet lifetimes by analysing data from single apparitions. He used observing records of all 400 long-period comets discovered since 1840, paying attention to the circumstances of their last sightings. In 80% of cases, a comet disappeared when it became too faint for observation. In another 18%, observations were terminated when the comet passed behind the Sun and returned to the night sky too faint to be detected. In eight cases (2%) there was apparent extinction, and observers reported that the untimely fading of these comets was preceded by the disappearance of the central condensation in the coma and by a rapid dimming.
Kresak says his results agree well with the idea that a comet's effective aging is determined by the cumulative amount of solar radiation to which it has been exposed. He derives a mean lifetime of 20 revolutions for long period comets that penetrate the inner-Solar System as far as the Earth's orbit. The life expectancy increases approximately as the square root of the perihelion distance. In general, the orbits of returning comets tend to become smaller with time, due to perturbations by objects in the Solar System. Short period comets have a mean lifetime of about 300 revolutions if they come within one astronomical unit of the Sun.
Kresak believes that only objects of unusual tenacity are able to survive long enough to undergo stepwise decelerations by the planets and evolve into short-period comets. It is precisely those objects that are most likely to leave behind extinct, asteroid-like remnants.
A telephone information service on Halley's Comet will be available on 01 790 3400, 24 hours a day for the next 17 months. It will be updated weekly.
Europe's first all-electronic planetarium opens this month in The Hague, Holland. There are only two others operating in the world, both in the US. The computer in the planetarium at The Hague contains information on 6700 stars in a sphere centred on the Earth with a radius of 650 light years. These are the stars visible from the Earth at the limit of naked eye visibility under ideal conditions. This information is fed to a graphics processor which transforms the data into images on a cathode ray tube, and these images are projected on to the planetarium dome by a wide-angle lens. The illusion of motion is created by projecting images 25 times a second.
A special programme will be put together at the planetarium next year when the Giotto mission to Halley's Comet is complete. The European Space Agency, which is coordinating the mission, will send the first Giotto pictures to the planetarium probably the day after they are received. Then, in a programme lasting 7.5 minutes, the computer will project the stars that Halley's Comet passes through on its journey past the Sun.
A young astronomer from the University of Texas at Austin claims to have become the first person to observe an eclipse of the planet Pluto by its moon, Charon. The observation was made shortly after 2.00am on Sunday 17 February 1985. The eclipse lasted 2.5 hours.
The eclipse is one of the first in a series lasting five years. The astronomers expect to make accurate measurements of the size of both Pluto and Charon as the configuration of the eclipses changes over the next three to five years. At the moment the eclipses are shallow, with Charon barely skimming the edge of the planet, but eventually Charon will move centrally across Pluto. Observations will also help astronomers to learn more about Pluto's surface and eventually to produce a map of the planet.
Neptune almost certainly has a narrow, incomplete ring around it, according to Bill Hubbard of the University of Arizona. This ring is in fact responsible for previous observations that suggested the existence of a small third moon.
Astronomers know of the rings around Saturn and Uranus. The rings around the latter were discovered in 1977 when the planet occulted the star SAO 158687 and the rings obscured the star before and after the planet.
Hubbard has now analysed observations made when Neptune passed near a star in July 1984. Two observatories in Chile both recorded a dip in the star's light, to about two-thirds of its original intensity, at about the same time. The length of the obscuration indicates that the object hiding the star is only a few tens of kilometres wide. But to be seen at both observatories it must have been more than a hundred kilometres long. The shape and partial transparency of the object mean it is almost certainly a ring segment, rather than a satellite.
Astronomers at the University of Arizona claim to have detected the first planet in orbit around another star; but the object may instead be intermediate between a star and a planet. The astronomers investigated the infrared emission from a very dim star, called VB8, and found that it is accompanied by another object that emits infrared frequencies.
VB8 is one of the intrinsically dimmest and coolest stars known, emitting only one hundred thousandth as much light as the Sun. Although it is only 21 light years distant, it is not visible to the naked eye, emitting only 0.01% of the light that would be necessary for this. It is part of a star trio, orbiting another pair of stars that are each a thousand times brighter. VB8 is red dwarf star with a surface temperature of only 2400 K.
It is estimated that the newly discovered infrared companion of VB8 has a mass so low that cannot sustain nuclear reactions to make it shine as a star. Its infrared emissions come from heat generated as it shrinks. The object has been called a planet 30-80 times heavier than Jupiter. Such a high mass means that it is different from planets in our Solar System. Astronomers have searched for other isolated infrared "stars" with very low mass and have found an object called LHS2924 which may be only as massive as 50 Jupiters; they have dubbed it a brown dwarf.
Astronomers working in Chile claim to have seen flashes of light from a mysterious source previously known to emit bursts of gamma radiation. The source lies in the remains of an exploded star in the nearest galaxy to the Milky Way, the Large Magellanic Cloud. Equipment in spacecraft has detected 16 bursts of gamma rays from the object which, theory tells us, is almost certainly a neutron star. Now a team of 13 European astronomers has used an optical telescope in Chile to monitor the gamma ray source for a total of 910 hours. They have recorded three flashes of light, the longest only 0.4 seconds in duration. The team is confident that it eliminated other potential explanations for the flashes. If the object is indeed brighter at optical wavelengths than in gamma radiation, simple ground-based studies may crack the mystery of gamma ray bursters.
In early 1984, La Palma in the Canary Islands became the home of Britain's newest Earth-based optical telescope. The site was first tested 10 years previously using smaller instruments and, from May 1984, the 2.5 m Isaac Newton Telescope (INT) has been producing results. Staff at the Royal Greenwich Observatory were most impressed with initial results (mainly spectra of stars, galaxies and quasars). It is hoped that the INT will bridge the gap between ground-based telescopes and the Space Telescope due for launch in 1986.
The quality of results from the INT is due in part to advances in the technology of spectrographs but most credit goes to the excellent atmospheric conditions of La Palma. Initial site tests omitted the darkness of the sky and its potential for infrared astronomy. The site however turns out to be among the best in the world in regard of both aspects.
Both artificial and natural airglow are at a minimum on the island. There is little in the way of artificial illumination and associated skyglow. Natural airglow caused by atoms in the upper atmosphere is only 30% as bright as some Australian observing sites. The lack of natural airglow is due to the position of the site in relation to the Earth's magnetic field. The field, when it dips into the upper atmosphere, brings down charged particles from space which increases the airglow. Many observatories are relatively close to the magnetic poles (in North America, Australia or South America) and therefore subject to airglow by this mechanism. La Palma is located close to the equator and therefore does not suffer from the focussing effect of the magnetic field on charged particles.
Viewing conditions are excellent due to the very dry air above La Palma. Spectroscopic equipment using infrared wavelengths is prone to loss of sensitivity through absorption of light by water vapour in the atmosphere. The atmosphere above La Palma (at an altitude of 2400 m) is similar to that above Mauna Kea on Hawaii (at 4200 m), which is exceptional in this respect.
Another important feature of the seeing on La Palma is the lack of air turbulence. Most observatories suffer image blurring due to turbulence which limits resolution to 1.0-2.0 arcsec. However, on La Palma the overall average resolution is 0.8 arcsec and the worst night of initial use maintained a resolution of 1.1 arcsec.
The superb seeing on La Palma and the comparative cheapness of Earth-based telescopes must surely mean that there is still a place for them in modern astronomy!
A photograph of a flattened disc of material surrounding a star 50 light years distant is being regarded as the most concrete evidence yet that planets exist outside our Solar System. The way in which this disc was discovered suggests that planetary systems could be commonplace. The disc was seen around the star β Pictoris by Richard Terrile of Pasadena. It was photographed from the University of Arizona. The disc may be material left over after planets were formed. Terrile says he has not seen any planets directly.
Until last year, the best evidence for planetary bodies outside the Solar System was was small wobbles in the proper motions of some nearby stars, which could be due to gravitational forces from orbiting planets. Last year IRAS (the Infra-Red Astronomical Satellite, launched January 1983) returned data showing that four stars, among them β Pictoris, had gas clouds around them. This indicated a possibility that planets were being formed.
β Pictoris was observed through the 2.5 m telescope at the Las Campinas Observatory in Chile. A disc was spotted, a shape which should be produced during planetary formation. The composition of the disc is not yet clear but Terrile believes it may be similar to that of the planets in our Solar System. The disc is roughly 10 times bigger than our Solar System. Even at 50 light years distant, such a disc is large enough to see with a telescope; it subtends an angle of 50 arcseconds, larger than the diameter of Jupiter as seen from the Earth. But the disc is so faint that it is overwhelmed by light from the central star. To make the disc visible, Terrile used a mask to block out the light from the central star, and then processed the data through a computer to remove the effects of scattering of light by the atmosphere. The density of the disc seems to increase nearer the star, but Terrile thinks the disc may be hollow, because the interior material has already formed planets.
Eventually, Terrille says, the motion of the large planets in the system will disperse the debris that makes up the disc. The five billion years since the formation of our Solar System have been enough for such debris to be removed from the region of the Sun.
When IRAS, the Infra-Red Astronomical Satellite (launched in January 1983) discovered several point sources of infrared radiation, it was not known whether they were objects in our own galaxy or very distant extragalactic objects. Now, it can be revealed that some sources have been identified with distant galaxies, by virtue of which they are intrinsically very bright.
The University of Arizona and the Dominion Astrophysical Observatory in British Columbia made the identifications. They used a charge-coupled device (CCD) capable of detecting very faint light, to find the optical counterparts of IRAS sources. They concluded that most of the IRAS sources at high latitudes (i.e., out of the plane of the Milky Way) have an extragalactic origin.
Obviously extragalactic sources visible from the Earth are intrinsically very bright. But how bright? This question can only be answered by estimating the distance to the source. This has already been done for one galaxy, whose redshift has been measured. The galaxy, labelled 0422+009, is shining 35 times more brightly in the infrared than the well-known active galaxy M82. The prodigious energy involved cannot be explained by active star formation. One possible source of power could be an active central region to the galaxy, an energetic nucleus that is similar to those found in active galaxies such as the Seyferts, or, on a much larger scale, in quasars.
A Soviet astrophysicist claims that a peculiar supernova explosion, observed in 1961 in galaxy NGC 1058 in Perseus, must have resulted from the disruption of a supermassive star, possibly 2000 times heavier than the Sun. Astronomers realised that the supernova was unique because of its very long outburst: it took a year to reach maximum brightness instead of a few days as normal, then declined very slowly and erratically.
The observed light curve of the supernova matches that expected for the explosion of a star of 2000 solar masses and a diameter of 100 times that of our Sun. Just before it exploded, the star had a core of silicon, surrounded by oxygen and carbon, with outer layers containing about 95% helium and 5% hydrogen. The energy of the explosion was at least 10 times that of any "normal" supernova.
The world's largest telescope, valued at $100m and financed in part by a grant, is to be built on Mauna Kea, a 4250 m high mountain peak on the island of Hawaii.
Source: Sunday Express
When IRAS (the Infra-Red Astronomical Satellite) discovered a warm dust cloud around Vega (see report for September 1983, above), scientists suggested that the material could represent the beginnings of planetary accretion. Situated some 13 billion kilometers (about twice the radius of Pluto's orbit) from the bright young star (spectrum AO) the dust grains are at least a millimetre across and may be much larger. Anything smaller, the scientists reason, would soon be either swept into Vega or flung deep into space - depending on how the material absorbed and interacted with the star's intense radiation.
One possibility overlooked by the IRAS team is that Vega may be surrounded by comets. Paul Weissman of the NASA Jet Propulsion Laboratory explains that at the distance of the dust from Vega, the most common molecules to condense as the primordial star formed would have been ices - especially water ice - and lesser amounts of carbon and silicate dust. Sublimation of the ice (and collisions?) would create a swarm of particles on a continuing basis. He notes that our own Solar System is also surrounded by billions of comets (the Oort cloud) far beyond the orbit of Pluto.
An astronomy hotline has been opened on 01 246 8055. The service plays a recorded message listing current astronomical news and events and providing information on current space missions. There is also a "night sky" section giving data on meteor showers, comets, etc.
The two X-ray satellites currently in orbit are the Japanese Tenma and the European Exosat. Recently, Japanese and European astronomers have been using the satellites to investigate the characteristics of fluctuating X-ray sources.
In 1973, a Vela satellite launched to monitor X-rays from terrestrial nuclear tests observed an outburst of X-rays from an object catalogued as V0332+53. Detectors on Exosat have subsequently shown that the X-ray flux from V0332+53 is irregular and flickers on time scales as short as 0.03 seconds. Exosat has also observed rapid irregular variations in the most promising candidate as a black hole, Cygnus X-1.
On 15 November 1983, the Japanese were using Tenma when they discovered an unexpected source of X-rays. After checking that the source was indeed real, Exosat was focussed on it and found that it was flickering rapidly. The signals have now virtually disappeared. The source is therefore in the class of X-ray transients. The source is thought to be a double star system comprising one "normal" star and one compact object, either a neutron star or a black hole, in an eccentric orbit. When the two objects are close together, the intense gravity of the compact body pulls gas from its companion. The gas heats up as it falls towards the compact body and emits X-rays. At first the compact body was thought to be a black hole. However, recent analysis of the observations has shown that the intensity of X-rays peaks every two seconds. Such regular fluctuations indicate that it cannot be a black hole and instead is a condensed object having periodic influence on in-falling gas, most likely a rapidly spinning neutron star. However, astronomers remain to find a convincing explanation for the flickering of the X-rays and why a mix of regular variation and rapid flickering together has been observed only for this particular source.
Optical observatories have found a star at the exact position of the source. This is presumably the companion of the compact star. It is a supergiant, some 20 times the size of the Sun. Astronomers have been observing it with the UK infrared telescope in Hawaii.
1983TB, the asteroid that gives rise to the annual Geminid meteor shower seen every December, can come extremely close to the Earth. Apparently the close encounters will be ever closer until 2115 when it will pass closer than the Moon. There is a small chance that the kilometre-sized body could hit the Earth or the Moon!
IRAS, the hugely successful infrared satellite, is dead! Its supply of liquid helium is exhausted. The helium kept the telescope and its infrared detectors cold so that heat from them would not interfere with signals from space. The helium was expected to run out in summer 1983 but it lasted longer than expected. Towards the end of 1983 it was hoped that the helium would last until the end of December but it suddenly ran out at the end of November.
However, IRAS is not totally deceased; it is still in very good condition and will probably he revived in a few years time by refilling the tanks with liquid helium. This will likely be performed by an unmanned servicing mission, carried out by a "space tug" launched from a space shuttle in low Earth orbit.
Yet again, IRAS makes new discoveries, four reported in recent months!
Research reported at the Natural Satellites Conference at Cornell University in New York State indicates that Neptune's moon Triton has an atmosphere. Triton is roughly the same size as our Moon, about 3350 km in diameter. Its orbit around Neptune is unstable and this has a considerable effect upon its atmosphere. The plane of its orbit undergoes rapid precession about Neptune leading to a large variation in both the amount and direction of sunlight reaching different parts of the surface: this creates extreme variations of temperature on the cold world. As a result, the volume of the atmosphere can vary one thousand-fold. All the volatile substances are at the poles and it is the temperature there that governs the properties of the atmosphere (like the solid carbon dioxide polar caps of Mars).
Underneath the atmosphere of Triton lies a liquid nitrogen ocean, according to scientists using NASA's 3 m infrared telescope on Hawaii. Triton's surface temperature is -218°C which would allow solid methane "icebergs" to float in the ocean. Triton is now the second moon in the solar system on which nitrogen has been detected - the other being Saturn's satellite Titan.
Source: New Scientist vol 100, no. 1380, p.177.
IRAS (the Infra-Red Astronomical Satellite, launched January 1983) makes the headlines again! It has already discovered four comets, a star being formed and perhaps a planetary system. Most recently it discovered a cometary tail where none had been suspected. So all comets could have tails, even where these are not visible optically.
The comet in question is a regular visitor to the Solar System, Comet Tempel 2. It is extremely faint, and has a period of 5.28 years. IRAS was engaged in hunting asteroids crossing the Earth's orbit. It detected a swarm of objects moving through space in formation. Astronomers suspected that the swarm was in fact a cometary tail, and this was confirmed when IRAS detected radiation from the head of the comet itself. The tail is over 30 million km long, but only 300,000 km wide. Although IRAS has tracked several comets it hasn't previously detected a tail on any. Tempel 2 was close to the plane of the Earth's orbit, virtually edge-on in fact, so IRAS was observing the greatest density through the dust tail when the discovery was made. When the comet is observed again in December 1983, the tail will be out of plane, and likely therefore invisible. Unfortunately Tempel 2 at maximum brightness will only reach magnitude 16.9, too faint for most amateur telescopes!
Source: New Scientist vol. 22, no. 1374, p.685.
According to observations by the orbiting Infra-Red Astronomical Satellite (IRAS), the star Vega could have a planetary system. The discovery, if confirmed, is the first direct detection of planets around another star.
IRAS was systematically checking bright stars at infrared (IR) wavelengths. (Normally IRAS only observes cool stars; Vega is a hot, bluish-white star.) The observations cannot be readily carried out from the ground because of absorption of IR by the atmosphere. IRAS detected IR radiation from Vega, which was totally unexpected. The observations were checked and it became certain that the radiation was coming from around Vega and not from a source in front of or behind the star. The discovery was made in mid-July 1983 but was kept secret until a month later.
If there are planets around Vega they will be relatively young with much dust present, so it is very doubtful that life has evolved. IRAS is now going to observe the IR emissions from the 40 nearest stars before its mission ends in four months time when its supply of cooling gas runs out.
Source: New Scientist vol. 99, pp.455-6.
A supernova has been discovered in the galaxy NGC 4258 by its radio emission. This is the first time that a supernova has been discovered in wavelengths other than light, suggesting that many others may have been missed. There could be repercussion for many branches of astrophysics: for example, shocks from exploding stars can trigger stellar formation and accelerate cosmic ray particles to produce radio emissions from spiral galaxies.
Pulsars are the collapsed cores of Type II supernovae. Counts of the number of pulsars in our galaxy indicates that one is formed every 10 years on average. However, the rate at which supernova explode in spiral galaxies similar to ours is approximately one every 50 years, based on observations in visible light. Detection by radio emission is expected to raise the estimated rate of supernovae occurrence, helping to reconcile the two figures.
Source: New Scientist 1983, vol. 98, no. 1362, p.778.
The IUE (International Ultraviolet Explorer) satellite is currently observing a bright type l supernova. Type 1 supernovae are the brightest and most mysterious of supernovae because they show no trace of the commonest element, Hydrogen. The latest supernova is in M83 and some early spectra were obtained about two weeks before maximum brightness. During the last week in July the Infra-Red Astronomical Satellite (IRAS) will observe the object and so too will radio observatories (although so far no type 1 supernovae have been detected at radio wavelengths).
The IUE's observations revealed that the pattern of UV emission from the supernova changed in a few hours, indicating rapidly moving gas clouds. The actual elements which cause the UV lines are a mystery at present. Some astronomers have suggested that these stars are exploding white dwarfs whose carbon and oxygen content reacts in a thermonuclear explosion to produce radio active cobalt and nickel. The decay of these nuclei to iron produces the light of the supernovae. This theory can be examined now that spectra are available covering UV through visible light taken before, during and after maximum brightness.
Source: New Scientist 21 July 1993, vol. 99, p.190.
Kiyomi Okazaki and Robert Evans independently discovered a supernova in the galaxy NGC 3044 in Virgo, at co-ordinates RA 21h 49.8m, dec -0° 55' (1950). The magnitude of the galaxy is 10.0, and the estimated magnitude of the supernova in early April 1983 was 13.0.
A team of astronomers at Palomar has confirmed that redshift measurements of quasars do relate to their velocity of recession and distance. Using a new spectrographic system, they measured the spectrum of nebulosity surrounding the quasar 3C48 and found the nebulosity to comprise clusters of hot young stars, similar to those in the arms of a spiral galaxy. The redshifts of the clusters are identical to that of the quasar.
This discovery means in turn that British and Australian astronomers have discovered the most remote known object in the universe - a quasar called PKS 2000-330, which, with a redshift of 3.78, breaks the ten-year-old record of 3.53 held by quasar OQ172. PKS 2000-330 also becomes the most luminous known object, equivalent to 10,000 times the luminosity of the Milky Way, but packed into a region only a few light years across. It is receding from us at over 90% of the speed of light, and lies at a distance of 13,000 million light years. The light that we receive from the object was emitted when the universe was only one tenth of its present age.
Both the Russian probes Venera 13 and Venera 14 have successfully landed descent modules on the surface of Venus and returned colour pictures and chemical analyses of rocks to Earth. Though the probes landed within 1000 km of one another, they arrived in very different geological regions; this is known from information provided by the American Pioneer Venus Orbiter which mapped the planet's surface by radar.
As the Russian probes descended through the atmosphere, taking an hour to do so, they measured atmospheric composition, the intensity of lightening strokes and the brightness of diffused sunlight. After touchdown, the probes were intended to relay images and analyses of rocks for 30 minutes before succumbing to the intense heat and pressure (approximately 750 K and 90 atmospheres respectively), but in fact Venera 13 survived for over two hours. The pictures returned by the probes revealed that the surface of Venus is brownish in colour, with large flat areas of bedrock, littered with smaller jagged rocks in the vicinity of Venera 13 and covered with light, brown sandstone in the vicinity of Venera 14. The latter probe registered the colour of the sky as bright orange. Both probes tested the electrical conductivity and physical-mechanical properties of the ground and deployed seismometers.
The analysis of data from the probes will take some weeks, but initial results have shown that surface rocks are predominately high alkaline potassium basalts, which also occur on the surface of the Moon, and on the Earth only in deep oceanic trenches.
Source: New Scientist, 11 March 1982
The Soviet Union has launched two new spacecraft towards Venus: Venera 13 on 30 October and Venera 14 on 04 November 1981. They are due to reach the planet in March 1982. The missions appear to be similar to those of Veneras 11 and 12 in 1978. Veneras 13 and 14 will launch landing capsules onto the surface of Venus; the landing craft will analyse soil samples, photograph the surface and take various measurements. It is thought that the mother craft will move off into deep space after orbiting the planet. The latest report from the flight control centre for Veneras 11 and 12 on 25 March 1980 stated that Venera 12 is being used to study Comet Bradfield.
Source: New Scientist
A team of astronomers from Birmingham University observing from Tenerife has announced that the Sun's core is rotating every three days, much more rapidly than the surface which takes some 25 days. The team reached this conclusion by analysis of the effect of rotation on the vibration of a spinning body. The results agree with current theories that the Sun rotated much faster in its early days, then lost momentum due to the outflow of particles of the solar wind. Such mass loss would have slowed the rotation of the outer layers while leaving the fluid core rotating at its original rate.
American astronomers using the Kitt Peak National Observatory have announced the discovery of the biggest empty space in the observable universe. They discovered a giant void behind the constellation Boötes during a deep survey of galaxy red shifts. In three separate areas of sky separated from each other by 35°, they found galaxies clumped together at distances of 300 million and 600 million light years with few at intermediate distances. The void has a diameter of 300 million light years and a volume of 3*1025 cubic light years, a few percent of the volume of the observable universe. The void has a mass density of approximately one tenth the rest of the universe. It may have been created during the Big Bang: large empty voids and clumps of galaxies are almost certainly the frozen remnants of hot bubbles and blobs in the newly-born universe.
Source: New Scientist, 05 October 1981
Astronomers at the University of Wisconsin have discovered, from analysis of observations by the International Ultraviolet Explorer satellite, what they believe to be a supermassive star. The object, known as R136a, lies at the centre of the Tarantula Nebula, a bright cloud of ionised hydrogen in the Large Magellanic Cloud. Optical observations show that the star is 200-1000 times heavier than the Sun, but ultraviolet observations put the figure at 2500 times heavier - 20 times more than the next most massive star known.
Like the Orion Nebula, the Tarantula Nebula is illuminated by the light of exceptionally bright young stars embedded within it. Spectral observations of the heart of the nebula show that most of the ionising radiation originates in a compact region 0.3 light years in diameter, and that this region also suffers a rapid loss of mass in the form of stellar wind. No previous observations of single stellar objects can account for such phenomena, and the cause is unlikely to be a cluster of supergiant stars because of the small volume of the region and its highly detailed spectrum (a cluster would produce some blurring of the spectrum).
Some theorists have suggested that supermassive stars existed in the early years of the universe, and generated the microwave background radiation. Others think that they are the centres of active galactic nuclei. Still others believe that supermassive stars do not live long enough to be observed. Take your pick!
Source: New Scientist, 30 July 1981
Voyager 2, now on its way to Saturn, has discovered that Jupiter has an enormously elongated magnetic field stretching over 480 million km from the planet. The spacecraft originally left Jupiter's magnetosphere in August 1979 and entered interplanetary space, where the solar wind streams through on its way out of the solar system. Theory predicted that Jupiter should have a magnetosphere in the shape of a tear-drop, elongated by the solar wind, but scientists were surprised when Voyager 2 re-entered the planet's magnetic influence for a few days in February 1981. It is now believed that Jupiter's magnetic tail reaches out to the orbit of Saturn and that Voyager 2 may be able to study the region where it merges with interplanetary space. Alternatively, Jupiter's magnetic tail may be long enough and wide enough to encompass Saturn and its magnetosphere, in which case Voyager 2 will have an unique opportunity to study the interaction of the magnetic fields of two planets.
Source: New Scientist
NASA's scientists have completed their preliminary analysis of observations by Voyager 1 of Saturn and its moons. However, some of the puzzles raised during the flyby remain unanswered.
It is now known that the "braiding" in the F ring extends well beyond the region originally photographed, with two of the ringlets twisting around each other at least eight times. One theory is that one of the ringlets is electrically charged and is affected by Saturn's magnetic field. Alternatively, the twisting may be caused by the eccentric orbits of the two small moons whose gravity affects the particles of the ring.
The total number of ringlets in the whole system is over 1000, and the average size of the icy rocks in the rings ranges from 2 m in the dark inner C ring to 8 m in the Cassini division ringlets, and 10 m in the bright A ring. The "spokes" are made up of much smaller particles possibly lifted out of the plane of the rings by Saturn's magnetic field.
Saturn's moons have densities similar to that of ice - Tethys is pure ice and Dione is 60% ice, 40% rock. Titan is a 50/50 mix of ice and rock, as is Jupiter's largest moon, Ganymede.
In fact, the NASA team was surprised to find that Titan is only 5140 km in diameter, smaller than Jupiter's moon Ganymede (the largest moon in the Solar System). Titan's nitrogen atmosphere has a pressure of 1.6 bar at the surface and a temperature of -180° C, and the nitrogen should not be liquid at the moon's surface as previously thought. Methane, though, will be close to its triple point condition (where solid, liquid and vapour can co-exist), so there could be methane rain, rivers and glaciers on the surface. Other trace elements in Titan's atmosphere include ethane, acetylene, ethylene and hydrogen cyanide, and the orange clouds which envelope the moon probably consist of organic polymers of these chemicals.
Voyager 1 has confirmed the explanation for Saturn radiating more energy than it receives from the Sun: this is due to hydrogen and helium separating out within the planet, meaning that helium should be depleted in the atmosphere. Voyager 1 observed helium depletion.
Voyager 1 measured Saturn's rotational period as 10 hours, 39 minutes and 26 seconds while the equatorial clouds rotate in 10 hours and 14 minutes implying wind speeds of 1100 km/hr.
Another puzzle which remains unanswered is the existence of high altitude hazes on Saturn, 150 km above the normal haze layer. An inexplicable amount of heat is required to support dust and aerosols at this height, and the haze structure indicates that this heat does not come from within Saturn.
Source: New Scientist
A team of American astronomers from the University of California has made the first discovery of a cluster of quasars, which up till now have been found singly in the sky (apart from gravitationally split images and neighbouring quasars with differing red-shifts).
The team developed a combination of a diffraction grating and a prism (termed a grism) which when placed in front of a telescope causes each image to become a miniature spectrum. When the team photographed galaxy M82 in this way, they found the spectra of three quasars lying in a nearby group, within 1.8 arcmin of each other. A detailed investigation by the Lick Observatory revealed the red-shifts to be 2.048, 2.054 and 2.040 - close enough for the quasars to be at the same distance, but different enough not to be a multiple image of the same quasar. The cluster is 9 million light years in diameter, similar in size to a galaxy cluster, and the red-shifts indicate velocities of recession of a few hundred km/sec, again typical of a galaxy cluster. From these arguments, the team has concluded that the quasars are probably the active nuclei of three galaxies in a cluster so distant that the neighbouring galaxies are invisible.
Source: New Scientist
Christmas night 1980 provided an unusual feast of activity with no less than three fireballs (one of them man-made) and the discovery of a new comet by Roy Panther of Northampton.
The first of the natural fireballs became visible over south-east England at 19:20 on Christmas Day at magnitude -4, and the second at 02:45 on Boxing Day morning at about magnitude -6.5. The most spectacular display was provided by the re-entry of the Russian rocket which launched the satellite Cosmos 749 in 1975. Burn-up during re-entry became visible at 21:08 over the English Channel at magnitude -9, in the form of six white fragments travelling in line towards the coast at Newhaven; the fragments disintegrated into 20 smaller pieces, fading away over Sussex. Any surviving pieces would have landed in the Medway or Thames estuaries. The BAA received 250 fireball reports, almost all from non-astronomer members of the public (which says little for the dedication of astronomers when confronted with more earthly liquid temptations!)
However, one man well rewarded for Yuletide abstinence was Mr Panther, whose 33 years of patient skywatching finally brought him fame in the form of Comet Panther, the first comet to be discovered by a British amateur in 15 years. It can be seen in Lyra at magnitude 10, and will gradually fade over the next few weeks.
Source: New Scientist
The US Air Force is to build a world-wide network of space observatories to monitor the skies for unusual events. A prototype observatory has been built in Newbury Park, near New York. Five more sites are proposed, in New Mexico, Hawaii, Korea, Spain and an island in the Indian Ocean.
Each observatory will consist of one 0.6 m and two 1.0 m telescopes mounted to enable rapid scanning of the sky. The primary objective of the network is to watch for satellites orbiting the Earth above an altitude of 5000 km where radar monitoring is unreliable, and in particular at 36,000 km where spy satellites can lurk in geostationary orbit, hoping to remain inconspicuous. The network will also provide astronomers with a tool to rapidly observe unpredictable events such as novae, supernovae, variable stars and quasars which can change suddenly in brightness. These changes often pass unnoticed simply because astronomers cannot observe many different areas of the sky simultaneously, which is exactly what the new network is designed to do. This all depends, of course, on the premise that results from the new network will be declassified!
Source: New Scientist, 04 December 1980
Photographic images taken by Voyager 1 during its flyby of Saturn revealed curious "spokes" in the planet's rings. Images taken while still 52 million km distant showed a distinct spoke in Saturn's "B" ring. In subsequent images, other such items were visible, some lasting for comparatively short times and others for much longer periods. Scientists do not have an explanation for this phenomenon because the outer and inner parts of the ring rotate at vastly different rates.
On 28 October 1980, Paul Wild of the University of Berne discovered a supernova in the spiral galaxy NGC 6946. After confirming its existence the following night, he alerted the International Astronomical Union (IAU) which in turn distributed the news to astronomers throughout the world. The International Ultraviolet Explorer (IUE) satellite was the first to obtain a spectrum, three hours after the IAU alert. The spectrum revealed the supernova to be near maximum brightness and at a temperature of 20,000° C. Subsequent observations by astronomers at the RGO in Herstmonceux, Sussex revealed its maximum magnitude to be 11.5, which subsequently reduced by 30% by 04 November. The position of the supernova in a spiral arm of NGC 6946 indicates that it is a Type II supernova involving a heavy star of about 10 solar masses.
NGC 6946 is a prolific source of supernovae, producing five in the last 63 years. Supernovae as bright as the current discovery are very rare, occurring on average twice per decade.
Source: New Scientist, 13 November 1980
Dr Stephen Synnott of the Jet Propulsion Laboratories, after discovering the 15th moon of Jupiter a few months ago, has done it again and discovered a 16th, tentatively named 1979 J3. Dr Synnott made the discovery by examining images from the NASA probes Voyagers 1 and 2. The new moon has an orbital period of 7 hours, 4 minutes and 30 seconds and has a diameter of about 40 km. For a while, Synnott thought that the satellite was J14 but, following extensive calculations concerning the orbits of J14 and the new body, they were found to be different.
The two Voyagers are now headed for Saturn. Voyager 1 will encounter the ringed planet in mid-November 1980.
Astronomers at Mount Wilson Observatory have discovered that the gas making up the outer layers of the Sun moves in belts parallel to the equator of the body, and that these belts appear to control the solar sunspot cycle.
In 1966, the Mount Wilson team began observing the velocities of 24,000 points on the Sun's surface. In 1979, when they analysed their data, they discovered a totally unexpected pattern of velocities. It has long been known that the poles of the Sun take eight days longer to make a revolution than the equator (which takes 25 days) and, in the 1950s, it was proposed that this differential rotation "winds up" the Sun's magnetic field, causing the 11 year sunspot cycle. (The cycle actually lasts 22 years, accounting for magnetic polarity reversal.) The Mount Wilson team discovered that there are also streaming motions within the Sun's outer layers: at any time there are two fast currents and two slow currents in each hemisphere, which vary from normal rotation velocity by approximately 5 km/s. These currents move from the poles to the equator over a period of 22 years and the regions of greatest sunspot activity occur precisely on the boundary between fast and slow currents.
The team can already identify adjacent fast and slow currents near the poles which will produce the next sunspot maximum even though the first spots will not appear for another three years.
Source: New Scientist
The Pioneer spacecraft now in orbit around Venus has been mapping the surface of the planet by radar, enabling NASA to produce pictures of topographic features. The main features to emerge are three continental masses, surrounded by smooth plains which are cut by great rift valleys. This is similar to how the Earth would look if it were devoid of water (except that Earth has seven continents, of course). The radar pictures strongly suggest that not only is Venus a rocky, Earth-like planet, but also that the tectonic processes of floor spreading and continental drift associated with the rift systems have occurred on Venus as on Earth. The discovery of these features also rules out the contoversial theory, propounded by Immanuel Velikovsky in 1950, that Venus was formed as a brilliant comet ejected by Jupiter circa 1600 BC.
Source: New Scientist
Yes, at last, we will have a way of talking about locations on Venus without using expressions like a little left of centre, just above that greyish mark. Using data from the radar mapper aboard the Pioneer-Venus orbiter, a working group has come up with names for newly identified features on the surface of the masked planet. Pioneer-Venus has mapped 83% of the surface from 75° N to 63° S latitude. The data has revealed deep rift valleys, rolling plains, high plateaus and mountains. On the basis that topographical features should be named after mythological women from various cultures we will now start to see names such as Ishtar Terra and Aphrodite Terra in textbooks. MIT and the US Geological Survey are collaborating to produce a detailed relief map of the planet that has been hidden for so long by clouds. Although completion of the map will take some time, it will be fascinating to see at last what the surface of Venus looks like.
Ten hours and 39.9 minutes on Saturn, according to scientists using data from the two Voyager interplanetary probes. The measurements were based on radio noise from Saturn, and will now supersede the Earth based estimate of 10 hours and 15 minutes.
Investigators have given accounts of the main discoveries made during the last two years by IUO (International Ultraviolet Observer), operated by the Goddard Space Flight Centre. Investigations have included the use of IUO to learn more about the "halo" which surrounds our galaxy, estimating it to have a temperature of about 100,000 K and be composed of oxygen, sulphur, iron, silicon and carbon. Scientists have also studied binary stars where X-rays are emitted by material spiralling (under the influence of gravity) into one of the stars. Investigators also found that quasars lying close to each other in the sky were in fact the same object.
Observations of 17 Sun-like stars by Myron Smith of the University of Texas have shown that all except one rotate faster than the Sun. It has long been known that stars much heavier than the Sun spin more quickly, but it is difficult to measure the rotation of slowly turning stars. Smith used a technique based on measuring the width of narrow spectral lines, applying this technique with a high-sensitivity detector on the 2.7 m telescope at the university's McDonald Observatory. He found that the average rotation time for a spectral class G star (like the Sun) is 10 days as opposed to 25 days for the Sun.
In the Solar System, most of the angular momentum is carried by the planets rather than by the Sun itself. Some astronomers believe that the planets have acquired angular momentum lost by the Sun in the early days of the Solar System. If this is the case, Smith's result indicates that other Sun-like stars may not have planets, or at least not Jovian-type planets, depressing news for extra-terrestrialists who believe that life on planets orbiting Sun-like stars should be common in the universe!
Source: New Scientist
Radio astronomers at Mullard Radio Astronomy Observatory (MRAO), Cambridge have recently produced maps of radio sources showing greater detail than ever before attained. Using their 5 km radio telescope, consisting of eight dishes spread along an east-west line, they have obtained a resolution of 0.32 arcsec at a wavelength of 1 cm (compared to a resolution of 1 arcsec with the best optical telescopes). Usual radio observation wavelengths are 6 and 11 cm but the Mullard astronomers opted for the l cm wavelength to achieve the greater resolution, although this creates the problem of interference by water vapour in the atmosphere. The best conditions for the Mullard team's observations are cold, still winter nights so they did not welcome the recent mild weather, although they still managed to attain their remarkable success.
The best maps shows a region called W3(OH) where new stars are forming. For the first time a hole can be seen in the hydrogen cloud, where the gas has been blown aside by the intense radiation from a young star. This achievement is equivalent to seeing the hole in a Polo Mint sweet from 3 km!
Source: New Scientist
A team from the Rand Corporation of Santa Monica has used many of the 33,000 Voyager pictures to map and chart the major Jovian satellites. They have devised a system to compute
the geographic co-ordinates of any feature at any time. In addition, the researchers have produced new estimates of radii for Io, Europa, Ganymede and Callisto:
Following the Jupiter encounter, Voyager 2 is due to arrive at Saturn in November 1980 and Voyager 1 in August 1981.
Two astronomers from Cornell University's Laboratory for Planetary Studies, P Thomas and J Veverka, have predicted that up to a quarter of all asteroids smaller than 100 km in diameter will be found to have surfaces covered with long trough-like grooves. Their prediction is the result of analysis of the grooves found on Phobos by Viking Orbiter I (see article July 1978 above). These grooves, 150 m wide and 15 m deep, were initially thought to be caused by tidal stresses pulling Phobos apart or associated with its capture by Mars. Later investigations showed that they are associated with the formation of Stickney, the largest impact crater on Phobos.
Astronomers have studied the effects that impacts of various magnitudes would have on asteroids: below a certain level of impact, a simple crater is formed and, above it, grooves are formed together with the crater. The actual appearance of the grooves depends on the thickness of the asteroids' regolith (the loose material between the surface and the bedrock). Thomas and Veverka believe that metallic M-type asteroids, thought to have very little regolith, will exhibit sharp fractures, while stony S-type asteroids, with deep regolith, will have rounded fractures, caused by material of the regolith draining into them.
Source: New Scientist
Two American astrophysicists, Webster Cash and Philip Charles, have discovered from X-ray images obtained by the HEAO-1 satellite, the presence of a giant gas cloud in the Milky Way. It lies about 6000 light years distant, in a spiral arm of the galaxy next to the arm that contains our Solar System.
Measurements of the gas cloud (dubbed a superbubble by the US press) indicate that it has a diameter of 1200 light years and an amazingly high temperature of two million K. According to Cash, there is no known phenomenon in the galaxy that produces sufficient energy to maintain the cloud at such a high temperature.
Small pieces of the bubble had been spotted previously, but they had not been thought linked together. Even the HEAO-1 images did not reveal the whole cloud, as much of it is obscured behind the Great Cygnus Rift, a dense cloud of gas and dust. The presence of the Rift has given an idea to Cash and Charles as to how the bubble might have formed. Their explanation begins with a single supernova which exploded behind the Rift, compressing the gas and dust in the Rift so greatly that perhaps a thousand new stars condensed there, some ten or so of which themselves became supernovae a million years later, thereby creating yet more new stars. The resulting chain reaction produced a huge expanding cloud of gas that is continuously spreading outwards as an ever-growing bubble. Cash and Charles now plan to search for more gas bubbles, which they believe are scattered throughout the galaxy.
Source: New Scientist
A team from the University of California has proposed the hypothesis that the extinction of 75% of all terrestrial life 65 million years ago was caused by a wayward Apollo-type asteroid some 7-10 km in diameter which collided with the Earth. Their theory is based on the existence of a one centimetre thick layer of iridium-rich clay which covers the Earth's surface at the level coinciding with the extinction period. (Iridium is comparitively rare on Earth compared to its abundance in space, and is thus a good indicator of an influx of extra-terrestrial material.) The theory says that the asteroid impact caused a 100 million megaton explosion, creating a 175 km diameter crater and throwing material amounting to 100 times the mass of the object into the Earth's atmosphere. The resultant dust layer remained in the stratosphere for three to five years, creating global darkness before settling on the surface to form the layer of clay.
The period of darkness suppressed photosynthesis, giving rise to the pattern of extinctions observed in fossil records. The team further suggests that statistically the Earth is hit by such an asteroid every 100 million years, a figure which roughly matches the interval between major extinctions.
Chinese workers have identified a similar clay layer at the Permian/Triassic transition level, a period of mass extinction of even greater proportions.
Source: New Scientist
Using a converted U-2 spy plane, a NASA/University of California at Berkeley team may have discovered the largest galaxy group to date. Measurements taken during 1978 of the microwave background radiation indicate that our galaxy is hurtling toward the constellation of Virgo, but at a speed greater than expected. Astronomers believe the supercluster in that region of space to have 30% to 40% more matter than normally found in a similar galaxy conglomeration. One of the researchers, Dr Smoot, has indicated that insufficient time has elapsed since the beginning of the universe for such a supercluster to form by gravitational forces. Therefore the only credible explanation is that the supercluster was part of a lumpy "primordial atom" at the time of the Big Bang.
Source: NASA press release
Following the threat to radio astronomy from the proposed solar power satellite project (see entry for January 1979 above), British radio astronomers have identified a further threat associated with radiation produced by microwave ovens. Tests were carried out on various ovens, all of which "leaked" radiation over the range 1-6 GHz, covering four of the most important frequency bands used by radio astronomers.
A team at Jodrell Bank calculated from the results of the tests that at a distance of 1 km, a microwave oven will typically raise by a factor of 12 the background noise experienced by a radio telescope operating at 1.4 GHz, and a telescope tracking an object in space will typically be affected by any microwave oven within a 25 km radius. The team further estimated that some 10% of all radio astronomical measurements are affected by radiation from microwave ovens.
Source: New Scientist and Nature
A Canadian astronomer, Dr Harvey Richardson, has proposed constructing future space telescopes out of plastic bubbles, enabling far larger mirrors than could possibly be fabricated on Earth. The three basic components - a gas cylinder, a container of liquid plastic, and a metal ring to form the outer rim of the mirror, would be carried into orbit by the Space Shuttle. The liquid plastic would be blown into a bubble by gas from the cylinder until it formed a spheroid, the diameter being governed by the metal rim. The pressure would then be reduced slightly, forming a perfect paraboloid. The plastic would then solidify, either by chemical hardening or naturally due to the low temperature of a near-Earth orbit. Unwanted material would be cut away, leaving the framework of a mirror. With space acting as a vacuum chamber, aluminium could be evaporated onto the surface to form a reflective coating. Dr Richardson sees the prototype as a modest 1.5 m diameter, but envisages eventually increasing the size to 125 m diameter, this size representing the amount of material that could be carried into orbit on one Shuttle flight.
Source: New Scientist
On 10 October 1979, the United Kingdom Infrared Telescope (UKIRT) was inaugurated on the summit of Mauna Kea in Hawaii, 4200 m above sea-level. It is the world's largest infrared telescope, with an aperture of 3.8 m. It will be working alongside two other telescopes on the mountain and, although it is the largest, it has the smallest support structure and was the cheapest to build. This is due to a bold break from traditional mirror design. The primary mirror of a large telescope normally has a diameter to thickness ratio of 6:1; however the mirror of UKIRT has a ratio of 16:1 and, instead of being constructed from glass, it is made of a low-expansion ceramic called Cer-Vit. It weighs six tonnes as opposed to the 15 tonnes that a traditionally-designed mirror would weigh: hence the lightweight support structure.
Another feature of UKIRT is the earthquake protection mechanism, necessary because of the close proximity of active volcanoes. The system comprises a series of brass pins in the underfloor assembly, serving as mechanical "fuses" which shear under strong horizontal forces. The telescope has already suffered two earthquakes this year, which bodily moved it 4 mm. The shear pins worked perfectly and the structure was jacked back to its original position within the hour on both occasions.
UKIRT is managed from the Royal Observatory, Edinburgh, and is open to any British astronomer who can satisfy a panel of experts as to the importance of his/her observing proposals. A team from London is flying to Mauna Kea in November to install a receiver to enable the telescope to study microwave radiation in addition to infrared, enabling it to contribute to research into gas clouds from which stars are formed. According to the team, UKIRT will without doubt be the best telescope in the world to undertake such observations.
Source: New Scientist
According to Dr Minas Kafatos of George Mason University, large black holes could be responsible for the large output of energy from active galaxies and quasars. The mass of a back hole is typically estimated at between a million and a billion times that of the Sun (2*1030 kg). Dr Kafatos says that it is theoretically possible to extract energy from the region surrounding a black hole, a region called the ergosphere, by processes known in the Theory of Relativity as Penrose Processes. An object could approach a black hole and split into two. One half would approach the black hole at half the speed of light while the other would fly outwards with more energy than it had before the split, the extra energy coming from the rotational energy of the black hole. Dr Kafatos put forward his theory on the basis of observations of Cygnus A, a radio galaxy which is thought to be a quasar.
The discovery of two "puddles" of water on Mars has demonstrated that the planet is not entirely the arid desert that it has lately been thought. The two areas were first noted by Robert Huguenin of the University of Massachusetts in 1973, when they brightened as Mars made its closest approach to the Sun. The areas, called Lacus and Noachis Hellespontus, are just south of the Martian equator, in the warmest region on Mars. The discovery has been confirmed by the Viking Orbiter which recorded 10-15 times more water vapour over the two sites than over any other place on Mars. Assuming that the areas are associated with water which is liquid during the day and frozen at night, the topsoil would contain 5% water by weight. If the water is present in pure form, it would be liquid only for a few hours each day during the warmest half of the Martian year. However, if it is present as brine, it could remain liquid during the day all year round. Huguenin says that in the latter state, the water could support many terrestrial organisms, and the two "puddles" might be places where life on Mars might linger from earlier times when water was more abundant.
Source: New Scientist, 23 August 1979
On 29 July 1979, minor planet 704 Interamnia occults the 9th magnitude star SAO 144829. The path of the occultation is predicted to be approximately 300 km wide and, although it does not pass close to the UK, observers there are asked to monitor the brightness of the star to provide a control measurement. A possible dip in brightness of the star off the predicted path may indicate the presence of a satellite of Interamnia; although the chances of such a companion body are small, scientists entertain the possibility as the sphere of gravitational influence of a body within the inner solar system is approximately 100 times its diameter.
Jack Eddy, of the Smithsonian Observatory in Massachusetts, recently reported that the Sun is decreasing in size at the rate of 10 km per year. His announcement was greeted with disbelief by many astronomers who think that it challenges one of the foundation stones of astrophysics, the belief that the Sun is a steady, unvarying star.
This is the latest announcement from Eddy, who has already published a wealth of evidence gleaned from historical records that the Sun varies on a timescale of centuries. His discoveries have implications for two current topics of research. The first is added weight to the argument relating the little ice age of the 17th century to changing solar activity. (Of course, any improved understanding of solar activity can help to predict climate changes over tens and hundreds of years.) Secondly, since the ten-year search for solar neutrinos that should be produced by nuclear fusion reactions in the Sun's core has proved fruitless, some astrophysicists have argued that the Sun may have temporarily become less active and shut down some nuclear reactions. A shrinking of the outer layers as the heat flow from the interior is reduced is exactly what theory predicts in this case, so presents problems for the proponents of the steady state Sun, who could well have to do some re-thinking of solar basics.
Source: New Scientist
Radio astronomers at the Hale Observatories think that they may have picked up bursts of radio waves less than a thousandth of a second long from M87, the largest galaxy in the Virgo Cluster, 60 million light-years distant. If confirmed, it supports the long-held assumption that the energy of radio galaxies (such as M87) and quasars comes from gas spiralling into massive black holes.
Optical astronomers at Hale had previously found indirect evidence for a massive black hole in M87, and astronomers at Jodrell Bank are now using the 76-metre Mark 1A radio dish to try to confirm the existence of the radio pulses. If they do so, they will at last have seen right into the heart of an active galaxy!
Source: New Scientist
If you are able to, have a look for the nova-like object in Vulpecula. Up to approximately a year ago, the object was usually of magnitude 16.0-16.5, with occasional increases in brightness to magnitude 15.0 (for example in 1926 and 1955).
Harvard College's Damon Patrol (please note, not Demon Patrol!) has established from photographic plates taken at Harvard Observatory that the magnitude of the object has significantly increased during the past 18 months or so:
|02 Nov 1977||12.5|
|01 Jul 1978||10.9|
|26 Nov 1978||9.5|
G M Hurst of The Astronomer journal suggests that the brightness of the object is still increasing but that insufficiently many observations are being made. Observers should concentrate on the object, which may be an "extra-slow" nova. It should be within the light grasp of moderately-sized amateur instruments. The object is at the following position (B1950.0, as notified in BAA circular 594): RA 20h 19m 01.08s, dec +21° 24' 43.1".
Source: The Astronomer
The Pioneer Orbiter spacecraft currently orbiting Venus has detected by radar a mountain taller than Everest and a plateau larger than the Tibetan plateau. The plateau measures 3000 by 1600 km, and lies in the planet's northern hemisphere at an altitude 5 km higher than the land to the south of it. It is bordered by three mountain groups, on its western, northern and eastern edges. The most spectacular is that to the east, which boasts a mammoth peak, unofficially named Maxwell, that rises over l2,000 m above mean ground level. Scientists on the project were reportedly "astounded" by the steep contours around the peak, which had previously shown up only as a bright spot in Earth-based radar images. Two other spectacular mountain ranges have been found also in the northern hemisphere, rising up to 6000 m and together being part of a chain 1000 km long.
Another discovery, this time in the Venusian atmosphere, is that of a 650 kph wind in the middle cloud layer, where most of the sunlight and infrared radiation reflected back from the planet's surface is absorbed. This link between the strongest winds and strongest heating effects merely highlights the simplicity of the virtually waterless Venusian atmosphere.
Source: New Scientist
According to Russian scientists Yuri Polkanov and Eduard Vitrichenko, the Earth benefits from an annual income of approximately 10 kg of diamonds, delivered in the form of meteorites! While the bulk of the meteorite is destroyed in the passage through the Earth's atmosphere, any diamonds inside are tough enough to survive and arrive intact on the Earth's surface.
Source: Weekend, 11-17 April 1979
Mounting evidence now links quasars, originally thought to lie at vast distances from the Earth, with galaxies situated much nearer. Astronomers at Hale Observatory, California have carried out studies of two separate galaxy systems which point to this conclusion. The first study found a group of eight quasars in the vicinity of the triple galaxy system NGC 3379/3384/3389. Six of the objects have similar redshifts and all eight are aligned approximately along the rotational axle of the elliptical galaxy NGC 3384. The two closest are aligned exactly through the galactic nucleus and have identical red shifts, while the next pair out are similarly positioned, again with identical red shifts, slightly higher than those of the first pair. One explanation for this arrangement is that quasars are formed in violent events in the nuclei of galaxies, and are ejected in pairs in opposite directions.
In the second study, three quasars appear to be embedded in the arms of the barred spiral galaxy NGC 1073. The Hale astronomers believe the quasars to be clearly associated with the galaxy since each of two spiral arms which appear to contain quasars splits shortly before encountering the quasar and continues past weakly on either side. In addition, each quasar has ultra-violet objects at points diametrically opposite across the galactic nucleus. In previous galaxy-quasar associations, the quasars have generally been located some distance away from the central galaxy, but the NGC 1073 study suggests that quasars formed in the nucleus of a spiral galaxy are gently carried out by materials forming in the arms, rather than violently ejected as in the case of elliptical galaxies. If this is correct, then similar quasars should be associated with other barred spirals, such as the Milky Way. Initial checks on some galaxies have already revealed positive results.
The two studies demonstrate that high red shift quasar/low red shift galaxy associations can no longer be dismissed as coincidences. The vital question now in whether all quasars can be linked with galaxies in this way: if so this would rule out the possibility that they are distant cosmological objects.
Source: Astrophysical Journal, New Scientist
The minor planet found in 1977 by Charles Kowal, orbiting between Saturn and Uranus, originally called Object Kowal-Meech-Belton and now known as Chiron, has been found by scientists at the University of Denver to have a chaotic orbit. They say that within a few million years, the 160 km lump of rock will encounter either Saturn or Jupiter and will be pulled into a hyperbolic orbit and ejected from the Solar System. This raises a mystery as to its origin, because if it can spend only a few million years more in the Solar System, it cannot possibly have been around at the formation of the latter. It either came from outside as a short-period comet, or formed within the Solar System like an asteroid. (There is evidence that asteroids can be temporary objects.) Since we don't know how either of these classes of body are formed, Chiron's origin is unknown.
Source: New Scientist
New measurements by the High-Energy Astronomical Observatory-2 satellite (HEAO-2), otherwise known as the Einstein satellite, launched in November 1978 and equipped with an X-ray telescope, have given more weight to the ever-expanding universe theory, in opposition to the expansion-contraction theory. The satellite has found unexpectedly intense X-ray emission from quasars more than 10,000 million light-years distant. It is thought that the X-radiation may account for a significant proportion of the low-level background of X-rays in the heavens, which had formerly been attributed to hot interstellar gas. If it existed, such gas would provide the missing mass required to cause the universe to be gravitationally closed. But identifying the cause of the intense X-radiation as distant quasars suggests that there isn't enough hidden mass in the form of this gas to prevent the Universe from expanding eternally.
Source: New Scientist
Just before it flew past Jupiter, Voyager 1 "accidentally" discovered a sparse ring around the planet. The ring, estimated to be 8000 km wide and 30 km thick, circling some 55,000 km above Jupiter's cloud-tops, appeared edge-on in an 11 minute exposure image that Voyager's narrow-angle camera took of the Praesepe star cluster. The ring was visible only because of the spacecraft's oscillation which blurred the ring's edges and produced kinks in the images of background stars. At magnitude 22, against the glare from Jupiter itself, the ring is not visible from Earth.
Source: JPL, New Scientist
On 26 February 1979, a total solar eclipse occurred over North America. The path of totality extended from Manitoba in the east, through Washington State in the west of the continent. Totality lasted between 2 minutes 5 seconds and 2 minutes 43 seconds depending on location. Unfortunately, the eclipse, not to be repeated for Americans for 38 years, was largely obscured by cloud. However, several universities and institutes, together with the Wallops Flight Canter and several satellites, ensured that some eclipse science was undertaken. Sounding rockets took photographs and returned information about effects on the Earth's atmosphere. Analysis of the data is being co-ordinated by four bodies based in Canada.
Source: NASA, Daily Telegraph
Recent study has found the largest object yet discovered in the universe. It to a galaxy containing about two trillion stars and measuring over 600,000 light-years in diameter, ten time as massive an our own Milky Way galaxy. It is 250 million 1ight-years distant.
Astronomers at the Anglo-Australian Observatory at Siding Springs have found what could be a giant black hole, 100 million times larger than the Sun. One of the team of investigators, Dr Alan Wright, has said that it is possibly one of the most energetic objects over discovered. It lies 10,000 million light-years distant and is 100 million miles in diameter. It appears so brilliant because it is swallowing stars at an estimated rate of one per week.
Source: Daily Telegraph
On 07 March 1979, NASA announced plans to explore Jupiter's moons with an oven more advanced spacecraft than Voyager. The new spacecraft, named Galileo after the Italian astronomer Galileo Galilei (1564-1642), will visit 11 of the 13 Jovian moons by using the gravitational pull of each to speed it to the next. The main mission objective will be to map the satellites' surfaces and their magnetic fields. Galileo will also send a spaceprobe into Jupiter's atmosphere to radio back measurements and analysis of its chemical composition; eventually, the immense pressure of Jupiter's atmosphere will crush the probe. Galileo is due to launch in 1982.
Source: New Scientist, Daily Telegraph
Photographs sent back from Voyager on 07 March 1979 have revealed a large volcano on Io, the innermost Galilean moon of Jupiter. The slopes of the volcano are lacking in meteorite craters, indicating that it is very young. This means that the rocky surface of Io probably contains an active molten interior similar to that of the Earth. NASA scientists have suggested that dissipation of energy from the tides induced in Io by Jupiter may produce a runaway melting process resulting in the molten interior. The volcanic nature of Io also provides an explanation for its surprisingly smooth surface, which scientists had previously assumed would be heavily cratered like that of our own Moon. Instead, Io is probably continually recycling its interior onto the surface, which is therefore covered with a smooth layer of volcanic salts, giving it a dark red and yellow appearance.
Source: New Scientist
Comet West, the brilliant comet of 1976, was racked by five violent events as it passed within 30 million km of the Sun. New methods of analysing the movements of the debris produced by the events show that a series of brief but massive outbursts of gas and dust accompanied the break-up of the large, icy nucleus into at least four fragments. Only two other comets have ever split into as many pieces, and only four in the past 120 years have shown such clearly defined dust bands in their tails. Computer enhancement of yellow-light photographs of the comet's tail shows five prominent, narrow bands. Scientists at the Harvard-Smithsonian Center for Astrophysics and the Los Alamos Scientific Laboratory were able to trace the motion of the dust particles, and concluded that each band originated in a single outburst lasting at most an hour.
A further study followed the motions of the separating fragments of the comet's nucleus, and found that some of the splitting events not only occurred at the time of the dust bursts, but were accompanied by sudden flares in the comet's overall brightness caused by gas bursts. For example, the initial splitting of the nucleus into two on 19 February 1976 produced a huge cloud of dust which formed the brightest dust band. The comet became brighter within hours as gas also poured off.
More subdued break-up of the nucleus and dust and gas flares have been observed in many comets, but events as violent as those affecting Comet West have never been recorded in such detail. The disruptions probably occur when a compacted dust-rich surface bakes hard and traps more volatile materials below. Pressure builds up within the comet's head and the surface eventually ruptures in spectacular fashion. Comet West was a classic example of a fragile new comet rich in volatile materials making its first close approach to the Sun. The four fragments now receding into deep space will each return in about a million years' time at intervals of a few centuries. But when they do return they will be pale shadows of their parent body after their rough handling by the Sun in 1976.
Source: New Scientist
Two astronomers from the Lunar and Planetary Laboratory, Arizona, have concluded from an examination of photographic plates that there may be a new satellite close to the outermost of Saturn's rings, ring A. Also, two astrophysicists of the Harvard-Smithsonian Center have said that the region between Mimas (the second closest satellite to the planet) and ring A could contain two or more satellites. 1979-80 will be an ideal time to search for the two new possible moons, as the Earth will be passing through the plane of Saturn's rings, and their glare is thus much reduced. The last crossing of the ring plane was in 1966, when Janus, the tenth and innermost moon of Saturn, was discovered.
It is common knowledge amongst astronomers that Pluto's highly eccentric orbital path brings it inside Neptune's orbit for part of its 248-year path around the Sun. "Crossover" occurred on 23 January 1979, when the two planets were equidistant from the Sun at 30.3 AU. For the next twenty years, Pluto will be closer to the Sun than Neptune (but still at a very dim magnitude 14). There is no chance of the planets ever colliding at the time of crossover, as they are locked in an orbital resonance, Pluto completing exactly two revolutions for every three of Neptune. In fact, the closest the planets come to each other is 18 AU, when Pluto is at aphelion.
Source: New Scientist
The Crab Nebula (M1) may be the product of a second supernova explosion in a binary system that had already undergone one such upheaval, according to Dr R K Kochhar of Gottingen University. The acceleration of the filaments in the nebula and the abundance of helium within them suggests an explosion of a helium-rich star of three solar masses. Such a star can be produced by mass transfer in a binary system, after which its partner star explodes, stripping off the outer layers of what remains as the helium star, and leaving a neutron star pulsar in orbit around it. If the separation between the two stars after the explosion is small enough, the neutron star would be slowed by the outer layers of the helium star's atmosphere, eventually spiralling in to trigger a second explosion. This in turn could "spin up" the neutron star, disguising a relatively old pulsar as a new one.
Dr Kochhar suggests that the site of the original Crab explosion was in the star group Iota Geminorum, and that the explosion gave the pair a velocity of 125 km/s, so that it took 3 million years to travel the 380 parsecs to the site of the 1054 AD explosion in Taurus, where the pulsar PSR 0532 was produced in its modern form.
Source: Nature, New Scientist
The Solar Power Satellite (SPS) project, if implemented, could wipe radio astronomy off the face of the Earth, said Sir Bernard Lovell of Jodrell Bank at the January 1979 Royal Society meeting on solar energy. The project entails putting solar cells into geostationary orbit to convert sunlight into microwave radiation, which would be beamed down to Earth. The beam of radiation would be considerably more intense than that which radio telescopes are designed to process, and an SPS could create stray radiation which could concentrate at the focus of a radio telescope resulting in its destruction. Sir Bernard said that if SPS technology became prevalent, radio astronomy could become a dead science by the turn of the century. He admitted that the problem could be overcome by building radio telescopes in space, but large investments in radio astronomy are now under consideration, and money spent on these would he wasted if SPS goes ahead.
Source: New Scientist
Astrometry, the precise measurement of stellar positions, proper motions and distances, is at present a such neglected branch of astronomy. However, ESA's plans to launch an astrometric satellite, named Hipparcos, in the early 1980's, may rejuvenate astrometry and improve our knowledge of the stellar distance scale. Astronomers all over Europe are supporting the project. Hipparcos would fly for two-and-a-half years in a geosynchronous orbit, measuring the absolute positions and tracing the motions of 100,000 of the brighter stars. It would also determine stellar parallaxes, by the familiar method of triangulation, using the diameter of the Earth's orbit as a baseline for angular displacement. The results would improve on ground-based parallax measurements in two ways:
Source: New Scientist
NASA scientists at the Johnson Space Center have estimated that due to the steady increase in satellite launchings, a belt of debris will encircle the Earth within 50 years, formed by collisions between satellites, and then between subsequent fragments, in much the same way as the asteroid belt is believed to have formed. The debris could quickly become so dense that new orbiting vehicles with a long life expectancy would have to avoid the 500-1200 km altitude range.
It seems that little can be done to halt the process. Scientists predict that the first major collision will occur in the next 10 to 20 years. Measures such as reducing the number of launches, re-entering and burning up spent vehicles, and design improvements to reduce the number of accidental break-ups (already 30 satellites have exploded or disintegrated) would merely slow down the inevitable formation of the debris belt.
Source: New Scientist
Using a space-borne telescope such as the 2.4 metre instrument proposed by NASA for launch in the early 1980s, it may be possible to search for planets in star systems up to 10 parsecs away by using the lunar limb as an occulting edge. The spacecraft's Earth orbit could be matched with that of the Moon, allowing the dark lunar limb to be aligned precisely to cover the star under investigation, leaving planets visible a fraction of a second of arc to one side of the limb. It would be possible to maintain the lunar limb stationary in the field of view of the telescope for two hours. Only 20 minutes of observation would be required to detect a Jupiter-sized planet, even though it would shine with a luminosity only 3*10-8 times that of its parent star. Repeated viewing of prospective stars over a number of years would cover all likely orbits of giant planets.
The telescope would also be able to record slow lunar occultations of virtually any object, with resolution of at least as good as 0.001 arc-second, which would provide accurate structural details of stellar disks, binary systems, pulsars and quasars. Some scientists believe that such a telescope would be one of the most productive and valuable scientific satellites ever placed into orbit.
Source: New Scientist
Dr H J Klein of JPL's Planetary Atmosphere Research Section and Dr Turegano, a visiting research associate from the University of Zarogosa, Spain, have found that radio emissions from Uranus' atmosphere have become 30% stronger in 10 years. Observations were made with the 64 metre antenna at Goldstone, California. The researchers say that radio emissions from the surface of Uranus can only be explained by changes in the radio opacity of the atmosphere. They argue that due to the unusual inclination of the planet, the temperature in the atmosphere could become 30% warmer in 10 years.
L Kresak, writing in the Bulletin of the Astronomical Institutes of Czechoslovakia, proposes, from re-evaluated data inferred from eyewitness accounts, that the Tanguska catastrophe in 1908 was caused by a fragment of Comet Encke. The co-ordinates of the Tanguska object appear to align with those of a hypothetical impacting meteorite from the Beta-Taurid meteor shower, which was at its peak on the very day of the catastrophe. The Beta-Taurids are associated with Comet Encke in that they represent the debris strewn in the wake of the comet as it crosses the Earth's orbit. Comet Encke is, in fact, a prolific producer of interplanetary debris, and may well have produced several cometary fragments. Kresak favours an extinct remnant as the culprit rather than an active cometary nucleus, in view of the absence of sightings prior to impact, and the 100-metre estimated size of the Tunguska object: it is thought that a small comet would have been visible for perhaps an hour in the dawn sky before impact.
Source: New Scientist
Recent photographs of Pluto have shown a marked elongation of the planet. Analysis points to the probable existence of a moon orbiting at a centre-to-centre distance of 17,000 km, with a diameter of as much as 40% that of Pluto and an orbital period of 6.4 days, the same as Pluto's rotation. Various calculations and a new theory of Pluto's formation have been derived from these observations.
Pluto's mass turns out to be one-fortieth that previously accepted. This fact, combined with a diameter of 3000 km (estimated from infrared observations made in 1977), means that the planet has a density lower than that of water, and is nothing more than a snowball of frozen gases.
According to a new theory of Pluto's genesis, the planet was once a satellite of Neptune orbiting every 6.4 days (with captured, synchronous rotation) which was ejected into its own solar orbit by the infamous "tenth planet" which passed through Neptune's system, violently disrupting it. Tidal forces ripped a chunk off Pluto, producing a moon with an orbital period of 6.4 days. The intruding planet was thrown out into an orbit 50 to 100 astronomical units from the Sun, and is still there waiting to be found.
Source: New Scientist, 27 July 1978
Gamma rays are highly penetrating, very short wavelength radiation lying beyond ultra violet and X-radiation in the electromagnetic spectrum. They have been studied since 1958 and, since then, only about a million have been detected. It's estimated that gamma ray photons hit the Earth's atmosphere at the rate of one every ten days per square metre. (Compare this with photons of light from a first magnitude star reaching Earth at the rate of a million per second.)
Scientists use balloons at an altitude of 40 km to study gamma rays. Each balloon carries a gamma ray telescope, essentially a spark chamber consisting of a series of metal plates which transform a photon of gamma radiation into an electron and positron. A detected gamma ray photon has to be distinguished from the background incidence of cosmic rays.
Various powerful gamma ray sources detected so far include the Milky Way (the radiation possibly originating from neutron stars); the Vela pulsar, which is the faintest optical pulsar, but the strongest gamma ray pulsar; and the Crab Nebula (M1), which emits radiation over the whole electromagnetic spectrum. Satellites monitoring the Earth's atmosphere have detected approximately 40 gamma ray bursts, but the origin of these is at present unclear; possible explanations include comets hitting neutron stars, emission from supernovae, and giant flares on distant stars (not the Sun).
Gamma ray astronomy will explore several avenues in the future. The Milky Way emission requires much investigation, and gamma rays will help to determine the composition of dust in nebulae. Another phenomenon to be studied is the evaporation of black holes due to gamma ray emission.
Source: BBC Sky At Night programme
It has long been speculated - in fact for almost as long as black holes have been known - that there is a link between black holes and quasars. Black holes, of course, are objects so massive that light cannot escape them. They can only be detected by radiation emitted by matter spiralling inwards at high speed. Quasars have been an enigma since their discovery in 1963; they are thought to be very distant objects, and some are now known with redshifts as great as z=3.53.
Recently, two pieces of evidence have come to light supporting the hypothesis of a link between black holes and quasars. The first came from observations of an extremely small jet emanating from the nucleus of galaxy NGC 6251, providing support to the hypothesis that surface effects associated with black holes are responsible for the prodigious energy output of quasars and some radio-galaxies.
But the most exciting recent development in the theory of quasars comes from a new observational technique pioneered by a British astronomer at the Institute of Astronomy in Cambridge.
In 1928, Edwin Hubble at Mount Wilson discovered a relationship known as Hubble's Law, which states that all distant objects in the universe are receding from one another and that the velocity of recession, v, of two objects is proportional to the distance between the objects, D. That is v = HD where H is a constant known as Hubble's constant. Hubble's Law does not apply to the local group of galaxies, members of which share a common velocity and do not recede from one another. It is not known whether Hubble's Law applies for very large distances. As the graph below shows, there are three possible behaviours at large distances.
q=1: Hubble's Law holds at great distances and the velocity of recession is always directly proportional to distance.
q>1: More distant objects recede more rapidly than Hubble's law indicates, implying that the rate of expansion of the universe was greater in the past than it is at present (since we see the most distant objects as they were millions of years ago).
q<1: The rate of expansion of the universe speeds up as time goes by.
Until now, the measurement of D has not been accurate enough for astronomers to decide which case holds good. However, this was changed recently when Professor J A Baldwin, together with three American astronomers, made observations of the Carbon III line in the spectra of quasars. Knowing that the intensity of this particular spectral line depends in a known way upon the absolute luminosity of a quasar, Baldwin has calculated the absolute magnitudes of 31 quasars. Comparison of these values with the apparent magnitudes gives an accurate estimate of the distance of the objects.
A plot of v against D for the 31 quasars shows that the case q>1 holds, meaning that the expansion of the universe is slowing and will eventually stop, to be replaced with a contraction. Although Baldwin's conclusion remains to be confirmed by further observations, it seems that his results have provided deep insight into the structure of the universe.
In 1977, photographs taken by the Viking Orbiter showed that the surface of Mars' larger satellite, Phobos, is deformed by grooves running across most of the surface. Now two American researchers have come up with two new convincing pieces of evidence that the grooves were formed by the same catastrophic event, occurring approximately 1000 million years ago, when a huge meteorite collided with the moon to create the crater Stickney.
Firstly, more recent Viking photographs reveal that the grooves radiate from Stickney and run completely around Phobos before fading out at the opposite side to it.
Secondly, a comparison of the density of craters found in the grooves with that outside shows that the grooves are approximately 1,000 million years old, about the same age as Stickney. The other main theory of the formation of the grooves - that they were formed by gravitational tidal stresses - demands that they be much more recent.
Source: Nature, Times News Service
The magnitude of the comet increases from 9.0 to 8.5 during the month. This is not as bright as originally predicted!
It appears likely that there are six rings around Uranus, the divisions being caused by the interacting gravitational pulls of Uranus' satellites in the same way that Saturn's moons maintain the Cassini and Encke divisions in its ring system. The evidence comes from observation of the variations in light intensity during the occultation by Uranus of the star SAO158687 on 10 March 1977. However, W H Ip, of the University of California, suggests that the exact position of divisions in the rings could be explained only by the presence of a sixth, inner satellite. The moon would have a mass similar to that of Miranda and periapsis (closest approach to Uranus) of 103,000 km.
Source: New Scientist
R Meier of Ottawa discovered the comet that bears his name in the early hours of 27 April at coordinates RA 07h18.7m, dec +53°47' in the constellation Lynx. At discovery, the comet was described as a diffuse object of magnitude 10 with central condensation, moving towards the Sun and becoming brighter. The object is currently visible for most of the night, moving southwards at approximately 24 arcsec daily, and should achieve magnitde 8.7 by mid-May and 8.3 by the end of the month. By the beginning of June, it should be at magnitude 7.9;
Astronomers at the California Institute of Technology and Kitt Peak National Observatory in Arizona have observed a dark, circular patch, believed to be a black hole of 5000 million solar masses, in the centre of the giant galaxy M87 in Virgo, at a distance of some 50 million light years.
Source: The Guardian
Astronomers at the Kitt Peak National Observatory in Arizona have discovered evidence to support the theory that vagaries of the solar atmosphere affect the climate on Earth. Observations made since 1975 show that in the second half of 1977 the temperature of the Sun's visible surface (photosphere) fell by 6°C whereas in previous years the temperature remained constant to within 2°C. This change in characteristics coincides with the beginning of a new sunspot cycle.
The evidence comes from spectroscopic observations and depends on the fact that the light-absorbing capacity of atoms in the photosphere depends on the temperature.
Source: Nature-Times News Service
Two astronomers at a French observatory have shown that American measurements of the Moon reveal an oscillation of approximately 20 m amplitude with a period of three years. The astronomers believe that the oscillation was caused by a meteor impact on the Moon 800 years ago which was observed by the monk Gervase of Canterbury in June 1178. The crater which the impact created, named Giordano Bruno, is 20 km in diameter and was discovered by satellite observations.
Source: The Sunday Times
There is now some evidence that speculation of a link between black holes, radio galaxies and quasars is essentially correct. The evidence comes from observations by radio-astronomers at the California Institute of Technology of a small, narrow jet, less than 10 light years (ly) long, within the nucleus of the giant galaxy NGC 6251. A larger jet some 720,000 ly long is already known, and the newly-discovered jet is aligned along the same axis. Flow in the jet appears to be supersonic, indicating that the jet emanates from near to a black hole with a mass of 100 million Suns. The theory used to interpret these observations can also explain the output of quasars, and it appears likely that quasars and other radio galaxies in most cases share the same sources of energy.
The International Ultraviolet Explorer satellite (IUE), a project jointly funded by the Science Research Council, NASA and the European Space Agency, is already bearing fruit. NASA launched IUE on 26 January 1978 and since then has used the craft's 45 cm Cassegrain reflector to make the following observations:
Source: New Scientist
The long-beloved concept of science fiction writers, that of a space-bridge connecting our universe with others, will have to be abandoned. This is the conclusion of theoretical work by Birrell and Davies of King's College, London.
Source: Nature-Times News Service
Molecules of cyano-octatetrayne, HC9N, have been discovered in gas clouds in Taurus. With a molecular weight of 123, this is the largest molecule yet detected in space.
Source: New Scientist
W A Bradfield of Adelaide discovered Comet Bradfield 1978c on 04 February 1978. The comet achieved a maximum brightness of magnitude 3.9 on 13 March. Although the comet is now fading rapidly, it is moving northwards so is becoming better placed for observation from Orwell Park.
On Thursday 09 November 1977, Professor C Kowal discovered a new asteroid-like object (see the entry above for December 1977). The object has been designated a minor planet, named Chiron, and our current knowledge of it is as follows:
|Perihelion distance||8.5 AU (just inside the orbit of Saturn)|
|Aphelion distance||18.9 AU (just inside the orbit of Uranus)|
|Inclination to ecliptic||7°|
|Orbital period||50.7 years|
|Diameter||circa 100 km|
Further information on Chiron's diameter and albedo should become available in the 1990s when the object, presently at magnitude 18, will brighten to magnitude circa 14.5.
The American Astronomical Society, whose first woman president is Dr Margaret Burbidge, has announced that it will hold no more meetings in states which have not ratified the Equal Rights Amendment to the US Constitution. This follows reports of severe discrimination against women in astronomy, such as being denied telescope time at observatories because they are women.
Astronomers on board the Apollo-Soyuz spacecraft have used a specialised telescope to detect ultraviolet (UV) radiation from stars. It was previously thought that the amount of interstellar gas in the region of the Sun was too great to allow UV radiation from other stars to reach the Earth, but this is clearly incorrect. UV observations can provide much information about the relationship between surface temperature and total energy output of stars, information that is important to understanding stellar evolution.
Source: Nature-Times News Service
Uhuru, the X-ray satellite, has completed its fourth sky survey, and a new catalogue, containing 339 X-ray sources, has just been released. Many of the sources have been optically identified, including the following:
Source: New Scientist
Astronomers working at the Kitt Peak National Observatory, Arizona, have discovered a star formed possibly less than 100 years before the birth of Christ. The star, which lies in Orion, is 50,000 years younger than the previously known youngest star.
Source: Sunday Times
Astronomers are in a state of high excitement because they have found an infant star which is about 3500 years old. The star will become visible to the naked eye in about 20,000 years' time.
Source: Daily Mail, 10 January 1978
Observers should keep an eye open during February for Comet Schwassmann-Wachmann. The comet has been known to suddenly increase in brightness by more than 1600 times. It is usually an object of magnitude 18, but can become as bright as magnitude 10 or even brighter. At its brightest, it would be visible with the Orwell Park Refractor.
It is possible that the Sun has a companion star at a distance of approximately 1000 AU, i.e. 25 times the distance of Pluto. The companion star would have to be very faint to have escaped observation to date but such stars are common, and it is not impossible that the companion is a black hole.
Speculation about a possible companion star of the Sun originates with anomalous observations of pulsars, which can be explained by assuming that the Sun is accelerating towards the pulsars in question. This in turn provides some circumstantial evidence that the Sun may be in orbit around a companion star.
Source: Nature-Times News Service
During January, Comet Kohler will fade from magnitude 9 to magnitude 10.
On Thursday 09 November 1977, Professor C Kowal discovered a new asteroid-like object on photographic plates taken with the 1.2 m Schmidt telescope at the Hale Observatory on Mount Palomar. (Kowal is a prolific observer and has discovered several extra-galactic supernovae and several comets, and recovered several other comets.) Subsequently, Tom Garrelis found the object on pre-discovery plates.
Object Kowal (as this mini-planet is currently known) is in a near-circular object around the Sun, slightly inside the orbit of Uranus, with a period estimated at between 66 and 70 years. Its orbit is inclined at 3° to the ecliptic. The object shines dimly at magnitude 19. Kowal believes that the object is an asteroid, as a comet would appear more fuzzy and dimmer.
Little else is known about Object Kowal! If it is an asteroid, its magnitude suggests a diameter of 200-400 km. However, diameter estimates for such small, dim bodies are notoriously unreliable - for example, current measurements indicate that the diameter of Pluto is anomalous. Speckle interferometry (the technique used recently to show the surface of Betelguese as a disc with visible detail) is difficult to perform on such dim objects: astronomers may need to wait for the space telescope before they can measure Object Kowal accurately.
Astronomers hope that Object Kowal is just one of a whole belt of asteroids lying between Saturn and Uranus. The only known asteroid belt in the Solar System lies between the orbits of Mars and Jupiter. There can be no asteroid belt between the giant planets Jupiter and Saturn, because the planets are massive enough to perturb severely any orbits lying between them. A second asteroid belt would be welcomed by theoreticians of the Solar System, since the formation of the Solar System should have created more residual debris than astronomers can currently identify.
Small objects at the distance from the Sun of Saturn or Uranus could easily have been unnoticed until now. The albedo of asteroids is typically only 2-3%, so such objects in the outer Solar System appear very dim indeed.
On 23 December 1977, the planet Uranus occults the magnitude 10 star BD -15° 3969. It is possible that the planet's rings, discovered on 10 March 1977 when Uranus occulted the star SAO 158687, may cause a number of disappearances and reappearances of the star. Predicted times of occultation by the outer, epsilon, ring are: D: 06:55 UT, R: 07:46 UT. Orwell Park Observatory will be open for observation of the event.
Studies by scientists at NASA's Jet Propulsion Laboratories (JPL) of grooves on the surface of Mars' larger moon, Phobos, have revealed that it may soon (on astronomical timescales) be broken apart by tidal stresses to produce a ring system similar to those of Saturn and Uranus. Tidal stresses are caused by the gravitational pull of Mars having different strength at different distances from the centre of the planet. The presence of the grooves, or cracks, could also be explained by the impact of a large meteorite (there is a very large crater on Phobos); however, calculations by the JPL scientists show that the tidal stresses explanation is more likely.
Source: Nature-Times News Service
Observations of Her X-1 by the British satellite Ariel 5 support the theory that bursts of X-rays from certain binaries are caused by cyclotron emission (i.e. the emission of radiation by charged particles accelerated in a magnetic field). A team of astronomers from Imperial College, London has observed a strong emission line in the X-ray spectrum of Her X-1 and calculated the size of its magnetic field (assuming that the radiation is due to cyclotron emission). The result agrees with the value calculated by other means, and the results are supported by observations by a satellite of the Max Planck Institute in Munich.
Source: Nature-Times News Service
A giant meteorite split into two pieces before it hit Madagascar in August 1977. One of the fragments created a crater 200 m in diameter.
Source: Sunday Times
Nigerian geologist Muo Chuku-Ike, now in the final stages of study for his PhD at Imperial College, London, has produced remarkable findings indicating that the bulge of North-West Africa, from Algeria through to Morocco and down to Nigeria, was caused when the Earth was young by an impact from a gigantic meteorite.
The event may have occurred well over 1000 million years ago when America and Africa were still joined together as a huge land mass. It has long puzzled geologists why the continents split apart as they did and why the North-West Africa coastline bulges in a huge semi-circle into the Atlantic, rather than separating from America along a linked series of straight fault-lines. Mr Chuku-Ike and his co-workers believe that the cause was a meteorite over 150 km across which hit the Earth with such force that the planet was lucky to survive intact.
Ultraviolet observations of quasars from a rocket suggest that the Universe is indeed going to stop expanding at some time in the future and will then begin to contract. This supports the so-called oscillating Universe theory of cosmology. At the end of 1977, an Explorer satellite will carry into orbit an ultra-violet telescope which should provide more information.
Source: The Times
Astronomers have discovered that 61 Cygni, the first star to have its distance measured (Bessel, 1938), has three giant planets in orbit around it. The planets were revealed by the same method that Peter van de Kamp used in 1966 to show that Barnard's Star has two gas giants in its system. Deutsch and Orlova of Pulkova University studied 1400 photographic plates showing the motion of 61 Cygni over the past century. Their analysis of perturbations of the motion of the star showed that it is a binary and there are three other perturbing bodies in the system.
The planets have orbital periods of six, seven and twelve years and masses of seven, six and eleven times that of Jupiter respectively. It is possible that the middle planet orbits one component of the star while the other two planets orbit the other component.
Source: New Scientist
Russia has just brought into operation a new radio telescope with a collecting area of 100 m2 and a resolving power of 12 arcsec. The telescope has made observations of "radio granules", knots of radio emission about 7500 km across, in the Sun's chromosphere. Scientists hope that in the future, similar techniques may be used to predict sunspot eruptions.
Source: New Scientist
Studies of the 1966 observations of Saturn which resulted in the discovery of the tenth satellite, Janus, have revealed the possible existence of another satellite. The eleventh satellite, if it exists, is thought to orbit the planet every 16.5 hours at a distance of 150,000 km.
Source: New Scientist
Astronomers now believe that Jupiter's innermost Galilean satellite, Io, may have a surface composed largely of salt. infrared observations support this conclusion. If true, the conclusion would explain how Io affects Jupiter's radio emission.
Source: Nature-Times News Service
Comet Kohler will be visible in evenings throughout the month. Binoculars or a small telescope will be necessary.
Absorption lines in the spectra of interstellar gas clouds can be explained as due to the presence of cellulose. This suggestion comes from Sir Fred Hoyle (controversial as ever!) and Professor N C Wickramasinghe of the University of Cardiff. Cellulose is a complex substance, chemically very similar to starch, which forms the main constituent of cell walls. Sir Fred and his team compared the properties of the clouds to those of known cellulose-like materials, and found close agreement. A mixture of water-ice and magnesium silicate could also explain the majority of the abosrption lines, but not all of them. If cellulose is present in interstellar space it could provide strong evidence for the extra-terrestrial origin of life.
After some 4000 years, the ancient British observatory (of slightly uncertain function!) at Stonehenge is due to close to the public! Today, Stonehenge is one of Britain's leading tourist attractions and there can be few people in the civilised world who have not heard of it. Over 700,000 people a year visit the site, and the traffic of 1.4 million feet is wearing away the ground and the monument itself, especially its ancient banks and ditches.
The Department of the Environment (DoE)scheduled the closure of the monument for early 1977, but because of local pressure the date has been rescheduled and the DoE is considering instead roping off only the central 30 m of the monument, enabling the public to see the central area at reasonably close quarters and walk over the surrounding banks and ditches.
Source: JAS Hermes
Comet Kohler was discovered on 04 September 1977, and is now visible through the Orwell Park refracting telescope.
According to Dr B A Smith of Arizona University, the rings of Uranus are dissimilar to those of Saturn. The main difference is that the particles forming the rings of Uranus consist of dull, meteorite-like material, while those forming the rings of Saturn are small and coated in ice (responsible for their great brilliancy). This comparison is based on the fact that the rings of Uranus are invisible even when the glare of the planet is reduced by observing in the infrared (Uranus emits hardly any infrared radiation). If the rings were coated with ice, they would be visible in this way.
Source: Nature-Times News Service
Scientists in Russia claimed recently that Jupiter is in fact a small star with a core temperature of 300,000 K (cf the temperature of 14,000,000 K at the core of the Sun). They believe that Jupiter will accrete inter-planetary matter which will increase its mass and eventually, in three billion years time, will glow as brightly as the Sun. However, Western scientists generally regard these claims as unlikely: they argue that Jupiter is too light (one thousandth the mass of the Sun) for it to use deuterium (heavy hydrogen) as nuclear fuel, and that the planet's rate of mass accretion is much too low for its mass to grow significantly, even over a period of billions of years.
Source: New Scientist
Researchers at the University of Arizona and NASA have discovered a solar system in the making. Observations with spectroscopes and infrared telescopes have revealed a flat, disc-shaped, highly luminous object in Cygnus which is thought to be only 1000 years old. The researchers believe that the object is a young star in the process of forming, with a planetary system in which planets may already have partially formed. The star is about 30 times as heavy as the Sun, and hence when it eventually "lights up" and nuclear fusion begins, it will shine very, very brightly, lasting for only about 100 million years.
Source: New Scientist
Astronomers at Kitt Peak National Observatory, Arizona, have developed a new technique for estimating the size of a star based on measuring its scintillation. (Recall that, to the naked eye, planets do not twinkle whereas stars do, because the former have appreciable angular diameters whereas the latter do not.) So far, the astronomers have measured stars with angular diameters from 0.018-0.054 arcsec, as well as a compact object inside the quasar 3C273 and the gas shell emitted by Nova Cygnii 1975.
Source: New Scientist
The gamma-ray satellite COS B, operated by the European Space Agency, has identified 13 point sources of radiation in the galactic plane. Two of the sources have been identified with the Crab and Vela pulsars.
Source: New Scientist
Observers should keep an eye open during August for Comet Schwassmann-Wachmann. The comet has been known to suddenly increase in brightness by more than 1600 times. It is usually an object of magnitude 18, but can become as bright as magnitude 10 or even brighter. At its brightest, it would be visible with the Orwell Park Refractor.
Certain gas clouds in our galaxy emit very narrow emission lines attributed to molecules of water vapour. These lines are polarised and vary moderately in strength over a period of a few months. The great nebula known as W3 (a giant gas cloud, within the galaxy, where stars are being formed) contains several radio hot-spots, many of them no larger than our Solar System. The emission lines from these comparatively small regions of space are millions of times stronger than can be achieved by thermal mechanisms; they are therefore termed celestial masers (microwave amplification by stimulated emission of radiation), and scientists consider that there is a strong connection between the masers and sites of star birth.
The Haystack Observatory, MA, USA, has detected the activation of a maser in the nebula W3. Another maser in the same nebula increased in intensity by 10% per day during the period 08-17 May 1977.
Source: New Scientist
X-ray bursters are a class of recently-discovered objects that are thought to originate in connection with mass-transfer in close binary stars. Astronomers now believe that X-ray bursters cluster towards the centre of the galaxy rather than being evenly spaced around the galactic equator, as indicated by previous surveys.
Source: New Scientist
According to astronomers at Kitt Peak National Observatory, Arizona, Neptune is surrounded by changing clouds of methane and argon. Spectroscopic observations have indicated changes in infrared radiation from Neptune due to condensation of these atmospheric gases, showing that the planet is not completely inert, as thought previously.
Source: Nature-Times News Service
Two scientists at the University of Virginia have proposed a theory of the formation of black holes inside neutron stars. One claims that if a black hole is capable of devouring the entire remainder of a neutron star in a few milliseconds it could create a release of energy of 1048 J which would appear to observers like a supernova outburst. It is possible that such events could be responsible for the flux of high-energy cosmic rays.
Chinese astronomers were among those observing the occultation of the star SAO158687 by Uranus on 10 March 1977. Secondary dips in the magnitude of the star when it was well clear of the planet revealed the existence of a ring around Uranus.
Observations of Jupiter by Earth-based observatories and by the Pioneer spacecraft indicate that the Great Red Spot is indeed a cloud formation floating some 2-5 km above the neighbouring cloud tops, formed by a deep region of convection, similar to the light zones. A similar model can be used to explain the smaller oval spots often seen on the planet.
Source: BAA Journal
A gamma-ray telescope has discovered a new emission line in the spectrum of the Crab Pulsar. The line is due to annihilation of positrons and electrons at an energy of 511 keV, but it appears at a red-shifted energy of 400 keV. As the magnitude of the red-shift depends on the strength of the gravitational field, it is possible to deduce the mass of the pulsar, which turns out to be approximately 1.4 solar masses.
Source: New Scientist
A new method for estimating the age of the Universe has arrived at a figure of 10-15 billion years. The method is based on observations of the relative abundance of isotopes of the element rhenium: rhenium-185 and rhenium-187. The new method is analogous to the well-known process of carbon dating, however, whereas carbon dating relies on estimating the relative abundance of carbon-14 with a half-life of 5000 years, rhenium dating relies on estimating the abundance of rhenium-185 with a half-life of 40 billion years.
Early supernovae formed the stable isotope rhenium-185 some 10-100 million years after the Big Bang. At present, the relative abundance of rhenium-185 cannot be estimated with accuracy and the new method therefore does not add significantly to the precision with which the age of the Universe is known. However, the new method may produce more accurate results once mankind gains a better understanding of the nuclear processes involved in supernovae.
Orbital analysis of observations by Kitt Peak National Observatory indicate that the X-ray star Cygnus X-1 has an invisible companion of mass 8.5 solar masses. There may also be a third component, a neutron star, of mass 1.5 solar masses. The Cygnus X-1 system is the top candidate within our galaxy for being a black hole.
Quasars may be energised by giant rotating magnets. Two Russian physicists point out that certain quasars exhibit a cyclic phenomenon that would be explained by rotating magnetic nuclei. They also claim that the galaxy 3C371 has a period of 163 days and an amplitude of over one magnitude, and that the Seyfert Galaxy NGC 4151 fluctuates over a timescale of 130 days.
Two physicists from Texas think that quark stars may exist and that quarks can provide enough pressure to slow the collapse of a dying star. Advances in particle physics and general relativity now make it possible to predict how matter composed entirely of its basic ingredients, called quarks, will behave. Models of such matter indicate that at very great densities, quarks can exert a degeneracy pressure, rather like a gas of electrons or neutrons. However, the physicists believe that quark stars are unstable, and that any radial disturbance could send the star crashing into into its own gravitational well to form a black hole.
Herschel may have seen rings around Uranus long before their modern discovery on 10 March 1977 - but more likely he suffered from faulty optics! He thought that Uranus was not round, and he postulated a sort of double ring. He rotated the mirror of his telescope by 90° and still saw the ring; again he rotated the mirror and still saw the ring. But in his log book on 04 February 1787 he wrote: no appearance of any ring. Then he had a new mirror constructed for his telescope, and with it he did not see the ring. He observed Uranus again in 1794 and 1795 looking for the ring but to no avail.
See also the article Ring Discovered Around Uranus, May 1977 (above).
Old stars near the centre of our galaxy are thought to be arranged in a short bar, meaning that our galaxy is in fact a barred spiral. The bar sweeps dust and gas from the area between the galactic centre and the surrounding spiral arms. As the bar rotates, shock waves at its leading edge force interstellar material towards the core of the galaxy. Shock waves at the trailing edge of the bar force other gas and material to spiral slowly outwards.
Kitt Peak National Observatory is planning to build an optical telescope five times larger than any existing today. It will be a composite instrument, operating on a principle similar to that employed by arrays of radio telescopes.
Source: New York Times
NASA is unofficially planning a Mars roving lander mission in 1984. It will be capable of covering 100-1000 km and will carry "penetrators" which will burrow several metres deep and record seismic activity and perform chemical analysis of the soil. NASA scientists at the recent Viking symposium in Paris emphasised that their planetary exploration programmes are open to international collaboration.
Astronomers using the 3.9 m Anglo-Australian Telescope at Siding Springs have identified a pulsar in Vela with a magnitude 26 star. The Vela pulsar is the third fastest known, with a period of 90 ms.
Source: The Guardian
Professor Martin Rees of Cambridge University has suggested that exploding black holes may be detected by the bursts of radiation which would be generated when relativistic particles from the explosion interact with neighbouring magnetic fields. His suggestion may provide the easiest method of detecting black holes, which at present are only theoretical postulates.
Source: Nature, Times News Service
Uranus, the seventh planet from the Sun, has a ring like Saturn. On 10 March 1977 Uranus occulted the star SAO158687. Professional astronomers use occultations to investigate planetary atmospheres, and several observatories monitored the occultation of the star. Astronomers unexpectedly observed a sequence of secondary occultations when the star was well clear of the planet.
Recent calculations have shown that the ring forms a circular belt in the equatorial plane of the planet (the latter is inclined at 98° to the plane of the Solar System). The belt lies between 44,000 and 51,000 km from the centre of the planet, which puts it 20,000 km above the cloud tops. One disappearance of the star lasted for nine seconds, which suggests that the ring particles are large, up to 100 km in diameter. Uranus' ring is probably the remains of a satellite that was torn apart by gravitational forces.
Note: Herschel, who discovered Uranus, thought that he saw a ring around the planet. However, the newly-discovered ring is of magnitude +19 lying only some 3-4 arcsec from the planet so cannot be seen directly from Earth, and in particular could not have been observed by Herschel.
Source: New Scientist
During late August - early September 1977 NASA will launch two spacecraft named Project Voyager on long flights through the Solar System. The trajectories of the spacecraft will take them to Jupiter and Saturn, and enable them to study some of the moons of both planets. If all goes well, one of the craft will be sent on to Uranus and Neptune, arriving when the planets are respectively 2700 million km and 4300 million km from the Earth. The first Voyager will reach Jupiter in March 1979, Saturn in November 1980 and Uranus in January 1986.
Eighty percent of respondents to a questionnaire sent to members of the AAS (American Astronomical Society) say that UFOs "possibly" or "certainly" deserve scientific investigation. Of the 2611 members of the AAS, 1351 replied, and of the replies only 20% thought study of UFOs unnecessary. Thirteen members of the AAS had strong objections, both to the questionnaire and to reports of UFO sightings. I object to being quizzed about this nonsense, said one.
On the evening of 05 January 1977, the Canadian Fireball Photography Network recorded a fireball of duration five seconds which dropped a meteorite, of magnitude -10, over SE Alberta. After computing the point of impact, field searches led to the recovery of the fallen object, only the third ever to be linked to its fireball. Teams recovered 2.1 kg of meteorite material, and searches are continuing for more. The recovered material is being examined in laboratories. The meteorite was discovered only 12 days after its fall, and its early recovery will enable the study of short-lived radioactivity associated with it. The meteorite is a chondritic stone type.
The three photographed meteorite falls as of mid-1977 are:
|Pribram, Czechoslovakia||07 April 1959||-19||5.8 kg|
|Lost City, USA||04 January 1970||-11.6||17.3 kg|
|Innisfree, Canada||05 January 1977||-10.5||2.1 kg (to date)|
Boron has at last been identified in the Solar System. Scientists have previously looked for its characteristic atomic lines without success. Analysis by two Harvard astronomers of data from a rocket mission revealed an encouraging hint of boron and further analysis has now confirmed its presence. Boron exists in the Earth's crust and also in carbonaceous chondrite meteorites. Analysis of the chondrites implies a boron abundance of approximately 0.035% that of silicon. Boron has been detected in the stars Kappa Cancri and Alpha Lyrae, though at much lower abundance.
It was suggested at a recent British Interplanetary Society conference on interstellar travel that fusion engineers and spacecraft engineers should join forces to help each other's work. Advances in fusion technology now offer the prospect of propelling a spacecraft to the stars.
An 11-man team, headed by former Rolls Royce rocket engineer Alan Bond, outlined at the conference the results of a four year design study of a robot probe to reach Barnard's Star, the second closest star to the Sun, some six light years distant. The robot probe, named Daedelus, would build up a top speed of 12% of the velocity of light using electron beams to ignite hydrogen "bombs" at the rate of 250 per second. After fifty years, it would reach Barnard's Star and transmit to Earth images of the star and any planets orbiting it.
The plan foresees titanium and aluminium for the structure of the probe being mined from the Moon, with Helium-3 for the "bombs" being sifted from Jupiter's atmosphere. The team claim that the technology would be feasible next century at an estimated cost of $100 billion (equivalent to one year's defence spending by the US).
But if interstellar travel is so easy, why has the galaxy not already been overrun by millions of other civilisations which came into existence? One view advanced very strongly at the conference was that Mankind may be the only technologically advanced form of life in the galaxy.
The Tanguska Event, a mysterious occurrence in 1908 when some kind of object from space crashed into a remote part of Siberia, causing devastation over a radius of 50 km but leaving no crater.
Now, a calculation by Professor Ari Ben-Menahem at the Weizmann Institute of Science, Israel suggests that the event involved a release of energy equivalent to 12.5 megatons of TNT at a height of 8.5 km. The estimate is based on a computer study of seismic and acoustic data recorded at the time of the event.
Comet Grigg-Skjellerup is now visible in the morning sky. It is faint, The Astronomer putting it at magnitude 10 and the BAA Handbook at 13, so a large telescope will be needed to observe it properly. Opportunity to observe the comet during the month will be limited: full moon is on 05 May and moonlight will wash out the skies for a few days either side of that date. By mid-May the comet will likely be too dim for amateur observations.
Comet Schwassmann-Wachmann has undergone several episodes of sudden brightening during the winter. It is currently in conjunction with the Sun but will emerge from the solar glare as a norning object in August.
Comet Encke is currently invisible. It will become an evening object in September-October 1977.
On 07 May 1977, the Moon will occult the star cluster M25 in Sagittarius. M25 is a loose open cluster approximately half a degree in diameter, situated in the Milky Way. It has an integrated magnitude of 6.5. There will be many occultations of individual stars between 03:35 UT and 05:00 UT.
Exobiologist Carl Sagan has written a paper with astrophycisist E E Saltpeter postulating the existence of large floating creatures in the primitive Jovian atmosphere. They envision three different types of gas-bag-like organisms labelled sinkers, floaters and hunters, which could move by expelling helium gas. Jupiter is the target of fly-by mmissions Mariners 11 and 12 which are to be launched in Autumn 1977, and an entry mission has been mooted for 1982.
Source: New Scientist
Astronomers at the Kitt Peak National Observatory, Arizona, have made spectroscopic observations of the limbs of Uranus. By measuring the spectral shift (Doppler shift) of the approaching and receding limbs, they have estimated the rotation period of the planet as approximately 23 hours, as opposed to the 10.8 hours previously accepted. Using the same technique, they have revised the estimate of the length of the day on Neptune from 15.8 hours to 22 hours. Thus it appears that Uranus and Neptune have days which are closer in length to those of the terrestrial planets than to those of the gas giants Jupiter and Saturn.
Source: Nature-Times News Service
On 23 April 1977, the Earth will pass 0.0123 AU from the ascending node of comet 26P/Grigg-Skjellerup, 12 days after the comet itself. There is therefore the possibility of a meteor shower associated with debris travelling in the wake of the comet. If a shower occurs, it will likely centre on a radiant at RA 07h18m, dec -44°.
Source: The Astronomer
As Mars went into conjunction with the Sun on 25 November 1976, NASA transmitted signals to the Viking landers on the planet's surface from Goldstone, California and Canberra, Australia. They measured the round-trip times of the signals to an accuracy of 1 in 2x1012 and found evidence in support of Einstein's General Theory of Relativity, which predicts that the signals will be bent slightly by the Sun and hence slightly retarded. This experiment is analogous to that conducted at the total solar eclipse of 29 May 1919.
Source: The Times
For the first time, scientists have detected gamma-ray emission from atomic nuclei outside the galaxy. Centaurus A, the nearest radio galaxy, is the source of the radiation. A gamma-ray detector at Rice University, Houston, Texas, detected the radiation. Gamma-rays are high-energy photons which have a much higher frequency than visible light and are even more powerful than X-rays.
Source: New Scientist
Three astronomers of the University of Hawaii, at Kitt Peak National Observatory, have made spectroscopic observations of Pluto which appear to show that the planet's surface is wholly or partly covered with frozen methane. This means that the albedo of Pluto is higher than previously thought; calculations based on the new figure and the planet's observed magnitude of 13.7 give an estimate of its diameter of 3000 km. Thus Pluto is smaller than the Moon, and, unless improbably dense, not massive enough to cause the supposed perturbations of Uranus and Neptune which led to its discovery in 1930.
Source: Science, vol. 194, p. 835.
Comet West reached perihelion on 24 February. All predictions now indicate that it could become very favourable for observation, even visible in daylight with limited optical aid. It should become visible to the naked eye in early March, and might be brighter than Jupiter
A JAS report in late 1975 indicates that dramatic changes have taken place in the South Equatorial Belt (SEB) of Jupiter. The Great Red Spot (GRS), the most prominent feature in the SEB, has been moving at an unprecedented rate in longitude of up to 8° per month and, at the end of November 1975, was at longitude 50° System II. An eruption has occurred and the GRS has spewed out dark material which has spread along the previously invisible part of the SEB.
In addition, observations from New Mexico indicate two bright spots along the south edge of the North Temperate Belt (NTB) at longitude 234°, moving very rapidly in longitude.
Comet Bradfield was discovered in Adelaide on 11 November 1975 as a diffuse, magnitude 10 object in Antlia. It is now in Serpens at magnitude 4, slowly drawing away from the Sun, and should shortly become visible to the naked eye low in the SW soon after sunset. Perihelion distance is predicted as 2.2 AU.
Comet West was discovered on 10 August 1975 in photographic plates captured with the 1 m Schmidt camera at La Silla. Perihelion will occur on 24 February 1976 at a distance of 0.2 AU from the Sun.
The comet will be conveniently placed for northern-hemisphere observers in mid-March 1976, when it could attain magnitude 5. It is currently at magnitude 11.
Discovered by Honda on 29 August 1975, Nova Cygni is the brightest nova in the northern hemisphere since Nova Puppis in 1942. Its coordinates are RA 21h 10m, dec +47° 50' (B 1950)and its magnitude at the time of disovery was +3. The RGO at Herstmonceux captured a spectrum on the night of its discovery, but details have not, as yet, been revealed. Observers generally agree that the colour of the object 29-31 August was yellowish: this is as expected, as the colour of a nova at maximum generally resembles that of a type F, G or K giant star.
On the morning of 05 October 1975, Mori, Sato and Fujikawa independently discovered a magnitude 11 comet moving SSE in the constellation Hydra. All three observers described the comet as diffuse without condensation or tail. It will probably brighten over the coming days.
Also discovered on the morning of 05 October 1975, and again by three independent observers, Comet Suzuki-Saigusa-Mori was found in Ursa Major, moving SE. It was described as diffuse without condensation or tail, magnitude 9.
Charles Kowal may have discovered the fourteenth satellite of Jupiter at the beginning of October 1975. The object in question is 21st magnitude and orbits very close to Jupiter. It is not clear at present whether it orbits pro-grade or retro-grade.
News has recently arrived of a new comet, currently magnitude 5 and brightening, in the constellation Ursa Major, moving towards Leo Minor. The object was discovered independently by Toru Kobayashi from near Fukui, Japan on 02 July 1975 July, by Douglas Berger, Union City, California on 05 July and by Denis Milon, Mount Washburn, Wyoming on 07 July 7. Milon reported the new comet as magnitude 7.5, diffuse with condensation.
Yes, Dr Luboš Kohoutek does it again! On 09 February 1975 he discovered another comet, a diffuse magnitude 9 object in Taurus. It has now faded to magnitude 16.
The Reverend Leo Boethin, observing in the Philippines, discovered a magnitude 11 comet on 04 January 1975. The discovery was confirmed on 01 February and precise positions were obtained on 05 February. The object is described as very diffuse with slight condensation.
Dr K Osaina, Director of Tokyo Astronomical Observatory, reports a recent outburst of GK Persei. Variable star observers are urged to monitor the object.
Jupiter will pass within 16 arcsec of the star SAO 146789 at 21:48 UT on 14 February 1975. The star has a visual magnitude of 7.5. Jupiter will be moving at 12 arsec per hour. A small telescope will be adequate to observe the event. Unfortunately, from the UK, the planet sets approximately two hours before closest approach.
Charles Kowal discovered a new satellite of Jupiter on photographic plates taken at the beginning of September 1974 with the 1.2 metre Schmidt telescope at Mount Palomar. His discovery brings the total number of satellites of Jupiter to thirteen. Preliminary data for the new moon, Jupiter XIII, is as follows: orbital period 282 days; distance from planet 0.08 AU; magnitude 20. Patrick Moore is of the opinion that Jupiter XIII is a captured asteroid.
At 04:42 UT on 11 January 1975 there will be an appulse of Saturn with the magnitude 9 star SAO 79057. Saturn at mean opposition has an outer ring diameter of 43.96 arcsec; the planet will come within 2.1 arcsec of the star (i.e. a small fraction of the size of the ring system), moving at a speed of 5 arcsec per hour.
Orwell Park Observatory will be opened from midnight on Friday 10 January to observe the event.
Eros is currently moving due south in Lynx at a rate of approximately 3 arcmin per hour. It is currently at magnitude 8.6, brightening to 7.8 at opposition on 23 January. Eros moves into Gemini on 15 January; passes 45 arcmin east of Pi Geminorum (magnitude 5.1) at 16:00 UT on 16 January and 22 arcmin east of Pollux (magnitude 1.1) at 04:00 UT on 21 January. The most spectacular event will be at 00:30 UT on the 24th of the month when Eros will appear very close to the star Kappa Geminorum, magnitude 3.6. The apparent approach is so close that, from some locations on the Earth, an occultation may be seen, with the magnitude of the combined object fading briefly to magnitude 8 then the star appearing to recover its customary magnitude.
On 12 January, Earth will pas through the plane of Eros' equator and, since the asteroid is "banana-shaped", observers will be able to see a variation of approximately 1½ magnitudes in its brightness, the period between successive maxima being five hours and 16 minutes.
Comet Bennett 1974h was discovered on 12 November 1974 by J C Bennett, observing from Pretoria. On discovery, in the constellation Hydra, the object was diffuse and at magnitude 9. The comet became visible to observers in the northern hemmisphere from mid-December. It reached perihelion on 01 December 1974, and has now become large and diffuse with the central condensation being less prominent.
In January 1975 there will be an appulse of Saturn with the magnitude 9 star SAO 79057. The event will be visible as an occultation from California and Hawaii, and from the UK will be seen as an approach of the planet to the star at a minimum apparent distance of 2.1 arcsec. Although Saturn takes 29½ years to complete an orbit of the Sun, and its mean daily motion is therefore only 0.033°, this equates to 5 arcsec per hour against the background stars, so the movement of the planet relative to SAO 79057 should be spectacular to see.
Closest apparent approach is at 04:42 UT on 11 January 1975. Orwell Park Observatory will be open for the event.
Asteroid (433) Eros is currently moving south in the constellation Lynx at a rate of approximately 1° per day. It is currently at magnitude 10.1, brightening to 8.7 by the beginning of January 1975. On Christmas Day at 10:00 UT it will pass 7' W of the magnitude 4.8 star 27 Lyncis.
In January 1975, Eros reaches opposition and later in the month may occult the magnitude 3.6 star Kappa Geminorum. (If an occultation does not take place, a very close appulse will ensue.)
Io exhibits sporadic anomalous behaviour. For example, occasionally it will appear brighter than anticipated after emerging from eclipse by Jupiter. Synoptic observations will be made on an international scale during "Io Week", 06-16 November 1974 to develop a broader understanding of the mechanisms involved.
The extent to which observers with optical telescopes can participate is limited. Magnitude estimates could be made using a step tablet to monitor the magnitude of Io throughout its orbit. Some reports indicate that the Galilean satellites show distinct characteristics during transits of the planet, Europa being light coloured, Callisto particularly dark, and this too could be investigated optically.
Asteroid (433) Eros will pass from Auriga to Lynx on 04 November 1974, at magnitude 11. It will pass 1°07' N of the magnitude 5.6 star 19 Lyncis on 23 November and, on 29 November, will attain maximum northern declination of 56°39' N, making it circumpolar as seen from Orwell Park Observatory. Eros will reach magnitude 8 in January 1975, which will place it within the range of moderate telescopes. Opposition occurs on 23 January 1975.
A nova was discovered in Sagitarius on 06 October 1974. On discovery, it was at magnitude 9, but is now fading. Coordinates are: RA 17h45.7m, dec 18°44'.
Astronomers have set aside 06-16 November 1974 for international study of Io, the innermost Galilean satellite of Jupiter. Io has revealed some sporadic, enigmatic features to observers using radio, infrared and optical instruments. For example, occasionally it appears brighter than expected after emerging from eclipse by Jupiter. The Centre For Earth And Planetary Physics at Harvard University is holding a workshop in February 1975 to correlate observations of Io.
Three minor planets are visible in the constellation of Aquarius during October 1974, all at approximately magnitude 9. Juno passes close by 57 and 58 Aqr during 12-20 October; Ceres passes close to the magnitude 5 star at RA 22h33m, dec -24° during 18-20 October; and Flora will be moving between 35 and 41 Aqr during most of the month.
Those interested in celestial photography may wish to take photographs over several days to show the movement of the objects against the background stars. Excellent results can be obtained by manually guiding a telescope with a camera mounted on it.
Comet Lovas 1974c was discovered on 21 March 1974. When discovered, the comet was at magnitude 14, described as diffuse, with condensation but without tail. It will reach perihelion in August 1975 at a distance of 3.0 AU. When near opposition in 1975, the comet could reach magnitude 9.
Supernova SN 1974G was discovered in Coma Berenices on 20 April 1974. It is currently at magnitude 13 and should be visible in the Orwell Park refractor. It is located 27" east and 56" south of the galacy NGC 4414. Members of OASI are encouraged to use the refractor to compare the brightness of the object with that of stars in the vicinity.
Comet Bradfield starts the month in Taurus and moves into Cetus on 15 May. It is fading and was not well seen by members of OASI due to bad weather during the last three weeks of April, the best time for observing it. Full Moon is on 06 May 1974 and moonlight will hamper searches for the comet around this date, after which it will likely be too faint to be found in amateur instruments.
Comet Encke will attain maximum brightness of magnitude 4.1 on 03 May. Unfortunately, at this time it is too close to the Sun to be observed. It will subsequently fade to magnitude 13.5 on 22 July.
Comet Bradfield has already orbited through perihelion and passed its peak brightness and is growing dimmer, predicted magnitude 6.1 at the start of April, falling to magnitude 9 at the end. Approximate coordinates on 02 April 1974 are RA 02h21m, dec +32°. The path of the comet takes it far out of the ecliptic: it enters the Milky Way on 06 April, lies only a few degrees from the Double Cluster on 13-14 April and is 1°E of Iota Cassiopeia on 20-21 April. It is likely to become lost to all but large telescopes in late April.
Comet Encke will be dimmer and nearer to the Sun than Comet Bradfield. On 13 April, Encke will be at magnitude 8.0 and should be visible in the Tomline Refractor, shortly after sunset. It will then brighten, attaining perihelion on 28 April at coordinates RA 03h36.87m, dec +19°27', on the boundary of Aries and Taurus. It will continue towards maximum brightness, magnitude 4.1, on 03 May before fading rapidly to magnitude 13.5 on 22 July.
Encke's comet, the second brightest periodic comet after Halley's, makes an appearance in 1974. At present it is at magnitude 15 in the morning twilight; in April it passes behind the Sun and, in April-May, may be visible with binoculars in the evening twilight. The comet is at maximum elongation of 15° at the end of April, on the border of Aries and Taurus. It will appear close to Mercury at this time; the planet will be at magnitude -1.4 and could be used as a guide to locate the comet. The latter achieves maximum brightness of 4.1 on 03 May.
To the best knowledge of members of OASI, only three people in Ipswich saw Comet Kohoutek during its recent apparition. One was Roy Cheesman (OASI Chairman). The most detailed reports of the comet came from Mr Barbrook (not a member of OASI) who photographed the comet with his 150 mm reflector using 1200 ASA film. The pictures confirmed the existence of the comet, but did not provide any detail. Mr Barbrook tracked the comet in January from Capricornus to Andromeda/Pegasus. During this period, the comet was a magnitude 6 object not visible to the naked eye from Ipswich.
It seems that bad weather contributed to the feeble display of Comet Kohoutek in skies over Europe. In the New Mexico desert, observers were able to see the comet well and to photograph it. To the naked eye, the comet presented a 17° tail and remained visible until 20 January 1974. Scientists have gathered a great deal of information about the comet.
Astronomers used the 70 m Goldstone radio dish to bounce radar waves off Mercury and map areas of its surface. They took soundings of 14 areas on the planet between latitude 12° N and 4° S. The results enabled astronomers to identify surface relief features with a resolution of 1 km. The hills on Mercury appear to be gently undulating. Signals from several areas indicated craters 50 km in diameter and 700 m deep. There was some evidence for craters up to 500 km in diameter. One feature, described as a "promontory", rises 1300 m from a base 120 km wide.
Radar and infrared observations of Saturn's rings performed in 1973, when the rings were wide open, have yielded some interesting results. Observers on Earth can see stars shining through the rings, yet radar reflections from the rings are very strong. This suggests that the rings must be composed of widely-spaced, large boulders (1 m-1 km in size). Radio observations suggest an average diameter of 2 cm, and infrared observations give an average diameter of 50-250 microns. The latter result is probably due to ice and silicates in the surface microstructure of the large boulders, so the radio estimate is probably more accurate. In order to reconcile all the above estimates, there must be a large amount of very fine dust and microscopic particles also in the rings.
One theory of formation of the rings is that they were formed by a moon of Saturn being torn into large chunks of rock by tidal forces. Subsequent meteor bombardments broke the chunks into smaller rocks, and as material in the rings underwent continuous collisions, it was gradually ground and pulverised into ever finer dust. The fine dust of the rings spirals in towards Saturn under the gravitational attraction of the planet while the larger rocks and particles remain in orbit. According to this theory, the rings will gradually, over a long period of time, eventually fade into obscurity as the material in them grinds to dust and spirals into the planet.
Now is the time to look for Comet Kohoutek! Throughout January 1974 it should be visible, but it is unlikely to live up to previous optimistic predictions. From 03 January onwards, search for the comet in the south-west sky after sunset, when the sky starts to darken. Binoculars are likely to give the best overall view. If observing the comet with the Orwell Park Refractor, make efforts to observe the coma and look for detail of the nucleus. The tail could become very extended during January.
To photograph the comet, use a 35 mm camera with fast film e.g. Ilford HP4 (B&W), Kodak Tri-X (B&W) or Agfa Isochrome (colour). Point the camera at the comet and make several exposures from 15 seconds to two minutes. Exposures of around 30 seconds are likely to give best results; longer exposures with an unguided camera will result in a blurred image.
Around 08-09 January, the comet will appear close to Jupiter and Venus. From 13 January until the end of the month, it will lie in Capricornus. It will appear close to the Moon on 26 January.
The IAU has nominated the following dates to observe the comet: 01, 04, 10, 15 and 22 January.
OASI is holding a Kohoutek Week in mid-January 1974 to enable the public to observe the comet from Orwell Park Observatory. We are also organising an exhibition on astronomy and Comet Kohoutek at the Ipswich Museum, Geology Section.
Comet Kohoutek will be at conjunction and perihelion on 28-29 December 1973. Before conjunction, the comet will be south of the ecliptic and after conjunction, north. The comet's tail will appear longer and brighter after conjunction. The comet will be best seen in January 1973, becoming most prominent around the 15th of the month.
Keep a sharp look out for Comet Kohoutek! It will reach greatest elongation west on about 13 November 1973, when it will be in Corvus, a few degrees north of the magnitude 2.5 star γ Corvi. On 18-19 November, it will be 1-2 degrees north of the magnitude 3.5 star δ Corvi, on the morning of 24 November, it will be within a few degrees of the Moon and on 28 November it will lie approximately 8° due south of Spica (α Virginis), rising at about 04:00 UT, followed by the Sun three-and-a-half hours later. As the date advances, the comet will grow brighter but its time of rising approach closer to sunrise. By mid-November it may be visible in binoculars and by the end of the month it should be visible to the naked eye. It will be best placed for naked eye observation in early January 1974.
Tsutomu Seki, a famous Japanese comet observer, recovered Comet Kohoutek on 23 September 1973. When he recovered the comet, it appeared at magnitude 11; this suggests a maximum brilliancy of magnitude -4.3. However, if it behaves like Comet Arend-Roland of 1957, it will achieve peak magnitude -2 and develop a tail of extent 21°.
The Cambridge Institute of Astronomy (IoA) recovered Comet Kohoutek on 01 October 1973. It was close to its predicted position and was about magnitude 9, slightly brighter than predicted, promising a spectacular display during winter 1973-74.
In early October 1973, the predicted magnitude of Comet Kohoutek is between 11.0 and 9.0 and it may be possible to recover the object with the Orwell Park Refractor. The comet starts October in Sextans, on 12 October it crosses into Leo, on 26 October into Crater, on 09 November it touches Virgo and on 10 November it crosses into Corvus. It will be visible in the morning sky before dawn, greatest elongation west being on approximately 15 November, after which it will move towards the Sun again and be lost in solar glare around 28 December. The comet will reappear in early January in the evening sky immediately after sunset.
The current season of mutual phenomena of Jupiter's Galilean satellites has already revealed new data about them. Dr Millis of Lowell Observatory, Flagstaff, Arizona, in a letter to Nature magazine, explained that during observation of an eclipse by Io (Jupiter I) of Europa (Jupiter II), the decrease in Europa's brightness was much greater than predicted, yet the predicted time of the eclipse was correct so the discrepancy cannot be explained by an error in calculating the orbits of the satellites. Millis concluded that Europa has a polar cap on its north pole, like the Earth and Mars, extending to a latitude of approximately 30° North. Europa's north polar cap is brighter than the rest of the satellite, explaining the large drop in brightness when it is eclipsed. This hypothesis also explains why Europa has an albedo greater than the other three Galilean satellites: Europa's true surface has approximately the same albedo as the material of the other Galilean satellites, but its extensive polar cap makes the moon appear brighter.
Millis urgently requests more observations of mutual eclipses of Europa, with estimates of the magnitude of Europa at maximum eclipse. Eclipses of Europa are predicted for 01, 15 and 22 October 1973.
Comet 41P/Tuttle-Giacobini-Kresák is a periodic comet with a period of 5.5 years. Astronomers recovered it on 08 January 1973, when it was shining at magnitude 21, very dim, and much dimmer than its predicted magnitude 17.5. However, subsequently, something very interesting happened: the comet was approaching the Sun when it underwent a sudden outburst on 27 May, reaching magnitude 4 (easily visible to the naked eye). The comet increased in brightness by circa 1000 times, a phenomenon never before witnessed. A further outburst occurred between 06 and 08 July. The likely explanation for such outbursts is the explosion of pockets of gas as the comet approaches the Sun. The comet is now moving away from the Sun and is therefore unlikely to suffer another such outburst. Its return in 1978/79 will be eagerly awaited.
Astronomers tracked Comet Kohoutek after its discovery until it moved into twilight in May 1973 and disappeared in the glare of the Sun, then moved behind the Sun. It is scheduled to reappear in September, and will hopefully make a spectacular apparition. Unfortunately, estimates of the magnitude of the comet are still little more than guesses; the most pessimistic is magnitude +1, the most optimistic is magnitude -10. (It is notoriously difficult to predict the magnitude of a comet. This is due largely to the uncertain expansion and fluorescence of the gas in a comet as it approaches the Sun and heats up.)
It should be possible to find Comet Kohoutek with the Orwell Park Refractor in October, in early mornings before sunrise. The comet will attain maximum elongation from the Sun of approximately 45° west on 16-17 November, when it will rise some three hours before the Sun. Predictions show the comet becoming visible to the naked eye around the same date. The best dates/times for observing the comet are pre-dawn 01-07 December 1973 or after sunset 07-14 January 1974.
After greatest elongation, the comet will start to move towards the Sun again and increase in brightness. It will reach conjunction at about the same date as perihelion, on 28-29 December. The comet will appear very close to the Moon on Christmas Eve and very close to Mercury on Christmas Eve and Christmas Day. On 08 January 1974, it will appear close to Venus and Jupiter.
Note also that Mr M J Hendrie of Colchester, an expert on comets, will be giving a lecture to OASI on 02 November on Comet Kohoutek.
We hope for a good apparition!
Astronomers have suspected for some time that the X-ray star Cygnus X-1 is a "collapsar" or black hole. An X-ray telescope aboard the satellite Copernicus (Orbiting Astronomical Observatory-3) has recently confirmed the suspicions. University College London built and operated the X-ray telescope.
On 07 March 1973, Dr Luboš Kohoutek, of Hamburg Bergedorf Observatory, discovered a dim, diffuse object, magnitude 16, with a central condensation but no tail. On 30 March and 02 April, Dr L Waterfield, D Griffiths and G H Rutter showed the object as a comet with a strongly condensed coma some 20 arcsec in diameter, slightly elongated. They estimated the object's magnitude as 15.8, still very faint.
It is too early for detailed predictions to be made of the comet. However, Dr B G Marsden has calculated an initial ephemeris, indicating that the comet will lie between Leo and Virgo in early November with an estimated magnitude 9, bright enough to be viewed with the Orwell Park Refractor. During November, the comet will move through Virgo, then during December through Libra into Scorpius, Ophiuchus and into Sagittarius. During January 1974, it will pass through Capricornus, Aquarius and Pisces, after which it will fade into obscurity. The comet will appear to traverse the entire sky from one horizon to the other in just four months. It should be visible to the naked eye during December and January and will be brightest on about 29 December, when it may be as bright as magnitude -2.5.
Unfortunately, the comet will have a southerly declination for much of its apparition and therefore will not be best placed for observation from Britain. In addition, for much of its apparition, it will be best seen in the very early-morning. However, we hope that it will be the brightest comet since Comet Bennet in 1970, and may be the brightest object in the sky apart from the Sun, Moon and Venus.
Robert Murphy, working at the Mauna Kea Observatory on Hawaii, measured the 20 micrometre infrared emission from Saturn's rings in August 1972. He estimated the temperature of the rings to be as follows:
These temperatures are consistent with the rings being composed of boulders about one kilometre in diameter. Note that this estimate is not consistent with the estimate of one metre boulders quoted above (March 1973). Comparison with previous results shows that the temperature of the rings depends on the angle of illumination by the Sun. When the Sun fully illuminates the ring system, shadows are short and the temperature rises. However, there is a puzzle: Saturn casts a shadow on the rings which means that the innermost ring should be a little colder than the others. The fact that it is not has led to speculation that it may be heated by interaction with particles in Saturn's van Allen zones, or that the outer rings may be formed of smaller, finer particles than the inner ring.
The atmosphere of Venus appears to "breathe"! Throughout the apparition of Venus in autumn 1972, investigators obtained nightly spectra which revealed a definite oscillation of four day's duration in the strength of the carbon dioxide line. The oscillation is not quite periodic, and its amplitude undergoes cyclic variation. A possible explanation would be the altitude of Venus' cloud deck changing by one kilometre over the entire surface of the planet; however at present the phenomenon is not fully explained.
During 1973, several very interesting phenomena occur of Jupiter's Galilean satellites. As well as the usual passes of the satellites in front of the planet, and occultations of the satellites by the planet, there are several mutual satellite phenomena, ocurring between 06 June and 30 October. A telescope of aperture 150 mm or above will be required to show the mutual phenomena.
Recently the first radar beam was bounced off Saturn's rings. It revealed that they are formed of many boulders circa one metre across. The boulders are closely packed and would be hazardous to any spacecraft venturing nearby. The rings are only about one kilometre thick, but measure 272,300 km from outer edge to outer edge. A Pioneer spaceprobe to be launched in 1977 will pass Jupiter and reach Saturn in 1981, passing at a safe distance of 270,000 km. The spaceprobe is the replacement for the proposed Grand Tour mission to explore the outer Solar System.
On 18 October 1972, Professor Sir Alan Hodgkin, President of the Royal Society, officially opened a radio telescope at Lords Bridge (some five kilometres from Cambridge). The new telescope is the most powerful instrument of its kind in the world and provides resolution equivalent to a single dish five kilometres in diameter. It cost £2.1m, and was funded by the Science Research Council. It consists of eight parabolic dish antennae, each 12.5 m in diameter, spaced at equal intervals along a five kilometre, absolutely straight railway track. (The track was originally part of the Cambridge to Bedford branch railway line.) Four of the dishes are fixed while the other four can be moved along the track. The Mullard Radio Astronomy Observatory, under the Astronomer Royal, Sir Martin Ryle, will operate the telescope.
Ideally, the radio astronomer needs a giant receiving dish with an aperture many times the wavelength of the radio waves being studied. Radio waves are typically up to several metres wavelength, so the dish ideally has a diameter of a few kilometres or more! Current technology does not permit giant dishes to be built to the requisite accuracy of a few millimetres, and even it if did, the cost would likely be prohibitive! Instead, by accurately placing a few relatively small antennae and appropriately combining the signals from them, a technique known as aperture synthesis, it is possible to obtain the same resolution as that provided by much larger aperture. The technique was pioneered at Cambridge.
The dishes of an aperture synthesis instrument need to be positioned very accurately (it is necessary to take the curvature of the Earth into account when positioning them). The new instrument at Lords Bridge required a site perfectly flat for at least five kilometres in extent. Scientists surveyed some 7500 km2 in East Anglia and found only two suitable sites: one in the Brecklands, the other at Lords Bridge. A one kilometre synthetic aperture telescope had previously been constructed at Lords Bridge. The Breckland site was ringed by USAF bases considered likely to generate considerable radio interference. Lords Bridge was therefore chosen for the new telescope; the site there is 80 ha in extent, level to within three metres and has a stable topsoil. It is free from man-made interference, especially radio transmitters, and is relatively close to Cambridge University.
However, at present the £4m worth of radio telescopes at Lords Bridge is under threat from interference generated by the engines of cars travelling along a planned motorway nearby. Astronomers are making attempts to persuade the Department of the Environment to re-route the motorway away from the Lords bridge site.
C T Kowal, of the California Institute of Technology, has reported discovery of a supernova on 13 May 1972. The object is of magnitude 8.5, in the irregular galaxy NGC 5253 (RA 13h 37.1m, dec -31° 24', B1950 co-ordinates). The supernova, confirmed on 15 May, is located 56 arcsec W and 85 arcsec S of the nucleus of the galaxy. NGC 5253 was also the location of a supernova in 1895, SN 1895B, Z Centauri.
The low declination of the object makes it almost impossible to observe from the UK and, in any case, by now it has probably faded. The extraordinary brilliance of this supernova is accounted for by the fact that NGC 5253 is is only a few million light years distant. Being of magnitude 8.5 (outshining its parent object!) the supernova is visible in binoculars or a small telescope from southerly latitudes. The object was blue when discovered, suggesting that it was shortly after maximum brilliance. Two satellites are searching for radiation from the supernova: the UHURU satellite is searching for X-rays and NASA's Orbiting Astronomical Observatory-2 is searching for ultra-violet.
Source: New Scientist, 01 June 1972, vol. 54, no. 798, page 478 and BAA circular no 542, 25 May 1972.
Charles Radley, John Deans, S Harvey, Wayne Brieske, Mark Howe, Paul Burt, David Barnard, Pete Richards, Trevor Williams, Steve Wenham, R Spooner, Peter Standridge, David Payne, Roy Adams, Michael Haxell