It was good wasn’t it? The weather was kind and lots of amateur astronomers and traders came along to make it a day to remember. The speakers were as usual all leading authorities in their fields and all spoke with great authority and enthusiasm about their particular topic.
First a report from Aylesbury AS
The Federation of Astronomical Societies’ convention took place at the Cavendish Laboratories, Cambridge on Saturday 5th October. Once again we were treated to some excellent talks by the professionals as well as having plenty of time to visit the trade stands and collect books, information on astronomical products or just chat to members of other societies.
The first talk was light-hearted but with a serious point by Dr Francisco Diego of U.C.L. about the links between amateur and professional astronomy. He pointed out the most important link; that the interest which drives both comes from a thirst for knowledge for it’s own sake. The long term benefits of astronomy cannot be calculated or used to determine whether it is worth doing. We must all stimulate interest by the public so that it continues to attract funding and interest.
Dr. Gerry Gilmore of the UK H.S.T. Facility Cambridge showed some fascinating results, some only hours old, from the ISO mission to map the inner regions of our own Milky Way at infra-red wavelengths. The resolution of the images was unprecedented and each one contained new discoveries. One such discovery is that close to the galactic centre where the stellar radiation levels are very high, there are still many dark clouds of material which have not formed stars and there are many star-forming regions, even larger than the Orion complex.
Dr. Allan Chapman told the tale of the discovery of Neptune which members will recall he gave to the Society in July, though he included additional details this time.
Dr. Bob Thomson of the University of Hertfordshire talked about when galaxies collide; the dynamics of the collisions and the behaviour of the patterns of stars within them. Galaxies which collide produce almost no collisions of stars because of the relatively wide spacing of the stars. Recent research also indicates that the spiral form of many galaxies is caused by the close approach or collision of another galaxy, and he gave the Whirlpool Galaxy M51 as an example. It’s famous satellite galaxy is moving so fast that it will not remain close for long. Computer simulations indicate that the spiral arms are caused by the gravitational disturbance of the main galaxy by the intruder.
Finally, Sir Martin Rees of Cambridge University spoke about the famous Dark Matter and what it could or could not be. Studies of the way in which galaxies move and rotate indicate that the visible matter represents only 1 % of the mass required to explain the behaviour. Large numbers of hitherto undetected objects in the galaxies like faint stars, or strange atomic particles may be the cause. Some recent observations of gravity microlensing (light from far objects being bent by the gravity of a nearer object and the far object’s intensity varies with time in a unique way) mean that many things in the Universe just have not been observed yet. Look forward to the AGM and Convention next April.
Next a report from Jerry Workman.
This is one of the highlights of the “ASTRONOMICAL YEAR” for many people including myself. The Cavendish laboratory just outside the centre of Cambridge, was the venue for an excellent range of speakers. Dr. Gerry Gilmour gave a brilliantly & light-hearted presentation on “ISO Images of the Inner Milky Way’.
The Infra-Red Space Observatory I.S.O was launched recently. Its intention was to supersede I.R.A.S or the Infra-Red Astronomical Satellite, the only other true infra-red orbiting satellite, which was in operation in the 1980’s. This mission was chiefly looking for “heat-sources”. Many of the H.S.T images gave pointers to the I.S.O scientists about where they should look for such sources. An infra-red picture gives completely different information to the usual visible image, which we are accustomed to. Looking at such images of stars about to explode, we see huge quantities of carbon in the form of soot, Carbon monoxide, Carbon dioxide & water. This proves it is just as polluted in outer space, as it is on the Earth. Previous so called bland areas, under the intimate eyes of I.S.O displayed much stellar activity. The spiral arms are just as active as the galactic nucleus. Stars are so densely populated that they appear to be colliding & ripping each other apart. I.S.O was not allowed to look at bright areas, because this light would simply ruin the delicate instruments on board the spacecraft.
Dr. Allan Chapman gave one of the best lectures that I have ever heard, when he spoke about “The Discovery of Neptune” This is a story which has been told incorrectly many times.
Newton’s law of gravity had already been known over 150 years, hut could this law be applied to undiscovered bodies. As it turned out it could. After the discovery of Uranus in 1781, it became apparent that this body did not stick to its predicted orbit. Some unknown body then was pulling Uranus out of position, also this body had to be more remote. John Couch Adams a brilliant young Cambridge mathematician was the first to under take this task theoretically, soon he was to produce some results. Adams showed them to James Challis, who recommended that he should show them to George Biddel Airy, the of the time. Adams arrived unannounced at Airy’s house, it was believed to be early afternoon. Airy could not see Adams at that particular time, so eventually Adams left some calculations with the butler. At this particular time Adams was not very well known & being of a rather retiring nature did not put himself forward. It is also possible that Adams was somewhat disorganised & could have made an official appointment with Airy. Despite this however, Airy did write to Adams asking him to confirm his mathematics, rather foolishly Adams did not reply to this letter. These events took place in the Autumn of 1845.
In France Urbain J. J. Le Verrier, another brilliant mathematician became interested in this problem. Le Verrier was quite well known & had a much more forthright personality, this was an opportunity not to be missed. Le Verrier started on this project in the early summer of 1846, more than 6 months after Adams had tackled the same problem. The predicted position of the planet was very similar for both men. Le Verrier was quick to communicate his work to the various prominent observatories of the times.
George Challis actually saw Neptune on several occasions, using Le Verrier’s calculations, but failed to notice it for what it was. Finally Johann Galle & Heinrich D’arrest located the planet on the night of 23/9/1846, at the Berlin Observatory. The discovery was no surprise & was expected anytime, it helped that Galle & D’arrest were using a new star-chart.
Professor Sir Martin Rees gave an account about “Dark Matter”. It is obvious that this stuff exists. Astronomers have not decided exactly how much “Dark Matter” is present in the Universe, but for the “BIG CRUNCH” to occur it is estimated that there should be ~Ox as much “Dark Matter” to ordinary matter. Precisely what this stuff is also remains a mystery, suggestions have been:- Brown Dwarfs, That Neutrinos have a slight mass, Dark Dusty Material, material which is “Non-Baryonic” so could be quite different to “ordinary” matter.
This article first appeared in FAS Newsletter Issue 47, Winter 1996.