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Rodney Austin's comet-hunting career
Rodney Austin
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I have been involved in a formal sense in astronomy since I was 11 years old.My mother was interested from a young age, and encouraged my interest as a means of focussing my life. Comet-hunting came almost as an accident, when I 'discovered' Comet Honda 1968c about two months late while observing from Ohakea AirBase.
After leaving the RNZAF in the beginning of 1971, I joined the staff of the Mt John University Observatory as an Observer/Technician observing Eclipsing Binary stars for researchers from the University of Florida, and the University of Canterbury. Over the next eight years I filled in my 'spare' time with my own observations of minor planets and comets, and occasionally hunted for new comets. On leaving Mt John in late 1979, I returned to New Plymouth where I still reside. Over the next 11 years I spent my time after my night job at the Daily News, comet-hunting. My working hours of 6pm -2am, fitted in well with my hobby.
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Comet-hunting can be considered the 'sport' of astronomy. By international convention any new comet bears the name of its discoverer, or discoverers up to a total of three names. Some comet names can be real jaw-breakers. The name also includes an international designation with the year of discovery and a letter denoting the fortnight of the year with a number giving the order of discovery in that fortnight. When I first started hunting there were generally 12 to 15 new comets found every year. These days with huge automatic search programmes with large telescopes, the numbers have soared to nearly 100 new comets each year.
In the main time of my active role as a comet-hunter, I have been fortunate to discover three new comets. Also I was the sole discoverer in each case. The three comets are now known as 1982 M1(Austin), discovered 18 June 1982; 1984 N1 (Austin), discovered 8 July 1984; and 1989 X1 (Austin), discovered 7 December 1989.
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My first comet- 1982 M1, taken at Mt John by Alan Gilmore on 26 June 1982. The tail is not visible, or barely so as it is a telescopic shot.
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My second comet - 1984 N1, is probably one of the best taken of it, by Alan Gilmore at Mt John Observatory on 26 July 1984. The comet itself probably would not have been discovered if it had not passed so close to the Earth. This comet developed what is known as an 'Anti-tail' where the orientation of the Earth and comet give rise to scattering along the more massive dust particles which then appear as a tail pointing towards the sun, instead of away from it. In this comet the anti-tail was at times stronger than the main tail. |
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The third one - 1989 X1, is much better. It was taken in the USA by Dr Tim Hunter at the Grasslands Observatory Arizona, when I was actually present on 28 April 1990. |
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The techniques for comet-hunting are really very simple. One carefully sweeps the sky in overlapping strips using binoculars or a telescope, carefully noting any fuzzy object and carefully checking the identification against a high quality star chart. Herein lie several problems. A very dark clean sky is essential, and consequently most comet-hunters seek out the dark lonely places in the country far from any source of light pollution. Then there are literally millions of objects that look just like comets - galaxies, patches of nebulosity, faint star clusters etc. Most of these appear just like comets. There are also all the other comets around some of which may be bright enough to be visible in the telescope, so accurate information regarding their positions in the sky at the time of observation is essential. These days with the Internet, such information is readily available. Not so when I started out.
The main distinguishing feature of a comet, is its motion against the
background stars. Comet lookalikes such as galaxies stay in the same relative
position to the stars, but due to the relative orbital motions of the Earth and comets,
they move slowly through a field of stars. The motion can be quite rapid if the comet
is close to the Earth or very slow indeed. My second discovery was made with the
comet being at its closest to Earth, and it was moving at about half a degree an hour
(about the angular diameter of the moon). This is extremely fast and through the
telescope the motion could be seen in just a minute or so. Also it was just visible to
the naked eye, in an area of the sky where there are no bright fuzzy objects.
Discovery was instant! However, my third comet was so faint, just barely visible in
the telescope, and so far away, that it took deep sky photographs from the Perth
Observatory in Western Australia to detect its motion over several hours.
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So how did I know I had a comet at all? I have a photographic atlas of the
southern sky called the Canterbury Sky Atlas, which was produced at Mt John in the
1960s and 70s. They are very deep photographs and show everything too much
fainter than my telescope is capable of showing. There was nothing at the position,
so it had to be a comet.
Reporting a comet discovery has a convention of its own. Normally one
reports the object to a professional observatory, giving as accurate position as
possible from a star chart, with other important information such as the magnitude,
and appearance (diameter of the coma, any tail etc), also if known, the direction of
motion, so cameras can be set on the area and the new object identified. In the case
of a fast moving object, this is very important, as the comet may have moved several
degrees across the sky before anyone can confirm the comet. This was definitely the
case with my second discovery.
Follow-up observations are also important. It can happen that no one
else has clear weather, so continue observing the comet over the next few nights and
report the positions as well. Once the comet is confirmed, the pressure is off the
discoverer, and the professionals continue to follow new comet and determine its
orbit and possible future behaviour.
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