Comet Section - Annual Report
The directorship of the section changed hands during the year, though the handover of section records is not yet complete. Thanks go to Graham Keitch, the retiring Director, for all his work over the past two years. A disappointingly small number of observations have been received considering the recent spate of moderately bright comets. Observers are encouraged to send their observations to the Director.
A record number of comets (34) were discovered or recovered during 1989, and during the first half of 1990 a further 8 comets have been given letter designations. Seven comets became bright enough to be visible in small telescopes during the session. Several of these were observed and photographed by BAA members and a number of photographs have appeared in the pages of the Journal.
Comet P/Brorsen-Metcalf 1989 o was eventually recovered in July, by Elenor Helin, some 13° from its predicted position. It brightened to 6m at perihelion in September and showed interesting features in its plasma tail. Comet Okazaki-Levy-Rudenko 1989 r discovered in August, put on a repeat performance, reaching perihelion in November. The third of the trio of bright comets visible in the last half of 1989, and the brightest of the year, reaching 3m, was Aarseth-Brewington 1989 a1. This reached perihelion in late December, though by then was only visible from the Southern Hemisphere.
Comet Austin 1989 c1, discovered by Rodney Austin in December (his third), promised to be another bright comet, and initial magnitude estimates lead several pundits to predict a spectacular display in April. This might have been the case had it come as close as New Scientist suggested (37 km!), but alas once it had passed 1.5 AU on its way into perihelion it brightened less rapidly (as many comets do) and only reached 5m in a bright twilight sky. After perihelion it faded even more rapidly, suggesting that perhaps it had used up its supply of volatiles. Comet Levy 1990 c (David Levy's 6th) promises to do better, but at the time of writing it is still just a promise.
Other notable comets include P/Schwassmann-Wachmann (1) which had outbursts in July, September/October and December. It is worth photographing the comet regularly as the outbursts seem to be quite frequent. The Solar Maximum Mission satellite discovered a further two sungrazing comets (1989 q and 1989 x) bringing its haul up to ten before it burnt up in the Earth's atmosphere in early December.
The section's astrometric observers continue their excellent work in providing precise positions to the Smithsonian Centre. Although not glamorous work, the positions are often vital in helping to determine comet orbits, and the observers deserve every encouragement.