SPA Comet News, January 2005

We now have a bright comet gracing the evening sky, however it isn’t that spectacular and appears much as a large globular cluster. Discovered by American amateur astronomer Don Machholz on August 27 with a 0.15m f8 reflector x30, it has the designation 2004 Q2, signifying that it was the second comet discovered in the second half of August. The first was also an amateur discovery, but this time by CCD observer Roy Tucker, and this has remained much fainter. Don spent nearly 1500 hours searching for his latest find, which is his tenth.

2004 Q2 reaches its closest point to the Sun outside the orbit of the Earth, but it conveniently does this when it is nearly at opposition, so we get a good view. Comets that remain more distant from the Sun than we do rarely have significant tails, and this one is no exception. Under dark skies you can see a thin gas tail, with the dust tail at quite an angle to it. For the next week it remains close to the Pleiades and about magnitude 3.5, providing an excellent opportunity for photographs or CCD images. It is still moving northward and becomes circumpolar by the end of the month. It should remain a naked eye object well into February, at least from dark sky sites, so there is plenty of time to observe it. You should be able to observe it with binoculars into May, and this provides an excellent opportunity to practice making magnitude estimates.

Because of its brightness and favourable observing circumstances I expect comet Machholz to go zooming up the list of best observed comets, which is currently headed by Hale-Bopp, Ikeya-Zhang and Hyakutake. Comet 2001 Q4 (NEAT), which put on a good show last May is currently 6^th, but I expect it to climb further as there are still many more observations come in. Quite a few observers are following comet Machholz, and I’ve already had reports from Mark Allison, John Coates, Mike Feist, David Frydman, Cliff Meredith and Ken Whayman. I suspect these will be the first of a deluge! Do send in your reports, but understand if a reply is not immediately forthcoming as I may have drowned in the flood! Ken set me an interesting poser as he observed a faint point of light moving across the comet’s coma. Investigation suggests that this was a satellite in equatorial orbit some 40,000 km from the Earth.

Comet 2003 K4 (LINEAR), mentioned in my last report, had something of an unusual light curve and peaked in brightness some three weeks before perihelion. It was visible as it passed through the LASCO fields, with an unexpected addition in the shape of comet 2004 R2 (ASAS). This second comet was a rather small object and didn’t survive perihelion. Comet LINEAR will probably start fading rapidly this month, so we won’t get a chance to observe it again. Comet 2004 H6 (SWAN), also mentioned last time, faded very rapidly and few observers followed it after July. Another SWAN comet appeared in the SOHO coronagraph fields in November and a few observers in more equatorial locations have seen it. The professional search programmes are finding more and more “odd” asteroids and a recent one is 2002 RN₁₀₉, which has perihelion at 2.7 AU and a period of 36,000 years.

Comet 2003 T4 (LINEAR) is brightening fairly slowly and at the moment doesn’t look like becoming a naked eye object. It is currently about 10^th magnitude and could brighten by another three magnitudes. It is best observed in the early morning, but can also be glimpsed in the early evening. Not many people are following it, perhaps because of its location low in the north west. We can follow it in the evening sky for another week or two, with Vega making a convenient beacon to begin star hopping from. In the morning sky it remains visible until mid March, by which time it should be around 7^th magnitude.

I’ll be describing all the exciting objects that have been visible during 2004, which has been a record year for naked eye comets, at the January meeting and will give an update on the prospects for 2003 T4. I’ll also give a demonstration on how to make magnitude estimates, which are perhaps the most difficult aspect of cometary observation. I hope to see many of you at the meeting.

Jonathan Shanklin