Ordinary Meeting, 2007 January 31

 

The January Sky

Mr Johnstone opened with an overview of the events of the past couple of months, though he noted that the weather had been poor throughout. On December 17, Tom Boles had added one further supernova discovery to his tally, 2006ss in NGC 5579 – his 105th discovery. The speaker had enquired after Damian Peach's planetary imaging work, but the weather had been so bad of late that he had not attempted any imaging since November 4.

In December, Asteroid 2006 XD2 – measuring around 150×350 m – had passed by the Earth, making closest approach at 0.026 AU on December 24. Several members had caught glimpses of it through breaks in the cloud around December 17-20, when it had been 0.04–0.06 AU distant. By combining their photometry to construct a light-curve, it had been possible to estimate its rotation period; the speaker warmly congratulated all involved.

Without doubt the most notable event of recent weeks had been the apparition of Comet 2006 P1 (McNaught). This had reached many newspapers, where it had been hailed as the greatest comet since Hale-Bopp (1997). Such attention was perhaps surprising, given that the apparition had been visible from the UK for only one week, around January 7–14, and only then in evening twilight, for a few minutes each day. Furthermore, the apparition had been announced at rather short notice because it had come as a surprise: it had out-performed even the most optimistic forecasts. Two days after Comet McNaught had reached perihelion on January 12, it had peaked at mag –5.5, placing it as the brightest comet since 1965 S1 (Ikeya-Seki). Many members had captured stunning images, though the greatest sights had been seen only in the southern hemisphere, after its disappearance from the UK sky; around January 23, its naked-eye tail had been reported to reach 35° in length.

Mr Johnstone then turned to outline the prospects for the next two months. Venus was already a glorious and conspicuous sight in the evening sky, and would continue to improve until reaching maximum solar elongation (SE) on June 9. Close by, Mercury's evening apparition would reach a rather miserly maximum SE of 18.2° on February 7. Its next morning apparition would reach a more favourable maximum SE of 27.7° on March 22. Mars had passed solar conjunction on 2006 October 23, but still did not rise until 06:45 UT; it would not be readily observable until the autumn. Jupiter also was a late riser: it presently rose at 04:30 UT, and even in April, it would not rise until shortly before midnight UT. Saturn, however, was well placed, and would reach opposition on February 10; for the next two months, it would be visible all night.

The speaker then gave brief mention to prototypical variable star Mira in Cetus, whose light-curve followed a regular cycle, brightening from mag 8.5–10 to mag 2–5 over a period of around 100 days, then fading back over a period of around 200 days. Its next maximum would be in mid-March.

There would be a lack of good comets in the UK sky in coming months: the best prospect was Comet 2P/Encke, which might be a binocular object in late March and early April, though it would be low in evening twilight in Pisces/Aries. It would then be lost to the southern hemisphere, reaching perihelion on April 19 at around mag 3.

The speaker selected three lunar occultations for mention: those of Uranus on February 8, the Pleiades on February 23, and Saturn on March 2. To close, he reminded members of the forthcoming lunar eclipse on March 3, which would be taking place at a very convenient hour: greatest eclipse would be at 23:20 UT.

Following the applause for Mr Johnstone's talk, the President invited Mr Bob Marriott, Curator of Instruments, to make a brief announcement. Mr Marriott reported that a 12.25-inch reflector from the Association's instrument collection had recently moved to a new home in the grounds of Pendrell Hall in Staffordshire, where it would be used by an adult education centre. Further details could be found in the 2006 December issue of the Journal.1

The President then introduced the evening's final speaker, Dr Peter Wheatley, associate professor at the University of Warwick. Dr Wheatley would be speaking about a project of which he was a founder member: the Wide-Angle Search for Planets (WASP).

Ashburn

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