Ordinary Meeting, 2003 November 29
The November Sky
The speaker took the opportunity to congratulate the President upon the discovery of his 58th supernova, only hours before the meeting, and the audience greeted this news with enthusiastic applause. Closer to home, the Sun had caught the attention of many observers of late, its surface intensely active at the present time. As well as flares, which the speaker illustrated with a number of Hα images, the activity had also resulted in enhanced auroral activity. Around the time of the October meeting, the Earth had been buffeted by an exceptional flare, and the speaker had seen clear images of the northern lights taken as far south as John Rogers' observatory in Cambridge on October 29.
A week later, November 8/9, a total lunar eclipse had been visible across the UK, although only the midlands had a window in the cloud at the appropriate time. This had been accompanied by a total solar eclipse at the following New Moon on November 23, though visible only across Antarctica. Whilst, perhaps unsurprisingly, few BAA members seemed to have made the trip, Michael Maunder had braved the elements, extending the length of totality by viewing from an aircraft window. The best still photographs of which Mr Mobberley was aware had been taken from the window of an Airbus A340 by William Whiddon and Dennis DiCicco using a Nikon digital SLR camera with 200mm lens. Another observing party, organised by Astronomical Tours, watched from the ground after chartering an Airbus A400 to fly from Cape Town to Novolazarevskaya Base, with tickets priced just over $13,000.
The speaker proceeded to tell the curious tale of asteroid Hermes, discovered in 1937, but soon lost and not recovered until Brian Skiff stumbled upon it on 2003 October 15. Whilst the 1937 approach had been to within 460 thousand miles, the present flyby was at a distant 4 million miles. In the meantime, it had followed a chaotic orbit with perihelion between the Earth and Venus, and of the intervening 31 orbits, four had come within 6 million miles, in 1942, 1954, 1974 and 1986. The 1942 approach came within 400 thousand miles, but was evidently missed. The 1986 approach should have been easily detectable by the Shoemakers, but the 18" Palomar Schmidt was temporarily down for maintenance at the time. It seemed that this remarkable object was not a single asteroid, but two disconnected rocks in a close orbit about one another.
The UK's supernova hunters had been hard at work, with a total of 22 discoveries between July 1 and November 28. Among the professional discoveries in the same period, SN2003iq in NGC772, discovered on October 26, was notable in that an earlier event, SN2003hl, had already been detected in the same host galaxy. This was only the tenth instance of multiple observed extragalactic supernova explosions within a single host galaxy to date.
Moving onto comets, the speaker displayed images of comet Encke, now fading after closest approach on November 17 at around mag 7, and heading towards perihelion on December 29. Encke's tail was an exceptionally diffuse and fan-shaped green smudge, and as a result it appeared as if it were several magnitudes brighter when viewed with a small aperture telescope of limited resolving power. Jonathan Shanklin had published a variety of magnitude estimates from various instruments. However, with Encke sinking fast through Ophiuchus into dusk, and moonlight becoming an increasing problem, Mr Mobberley thought the prospects for further observations were minimal.
Comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) remained exciting prospects for spring 2004, both expected to peak around mag 1 in mid-May in the northern and southern hemispheres respectively. The latter would be lost to northern observers around mid-February, by which time it would be around mag 6, and passing close by the south-eastern corner of the Square of Pegasus. More challenging targets would be 43P Wolf-Harrington and C/2001 HT50 (LINEAR-NEAT), which the speaker illustrated passing within ~5° of one another on January 17, whilst travelling in opposite east-west directions, about 3° south of the Square of Pegasus.
Mr Mobberley extended his congratulations to Vello Tabur, an Australian amateur comet hunter who had discovered C/2003 T3 near Telescopium on October 14 using a 140mm f/2.8 camera with CCD. The total magnitude was 11.7, and the coma 30" across. This added to his previous discoveries of two comets, a nova, and over 200 variable stars. Also notable was Juel's recovery of 157P/Tritton on October 6 using 0.12m f/5 refractor with CCD. Previously, this comet had been discovered and tracked for a month in 1978 before being lost. For asteroid-hunters, 4205 DavidHughes remained a realistic target at mag 15.4, presently around a degree from 51 Andromedae.
For planet watchers, Mars, whilst receding fast and appearing ever-smaller, was moving north to more favourable declinations. At the time of the meeting, it was crossing the Prime Meridian at 7pm, and had angular size 11"4, reducing to 8" by New Year. The speaker displayed an image taken semi-live by Damian Peach beside the Isaac Newton Telescope on La Palma during the filming of the BBC's All Night Star Party. In his previous Sky Notes, Mr Mobberley had challenged members to image the Martian moons, and he displayed one successful response by Maurice Gavin.
Jupiter and Saturn would both be visible in the UK skies in the New Year, transiting the Prime Meridian at 6.45am and 2.30am respectively at the time of the meeting. Though Jupiter was exclusively an early-morning sight at present, it would soon be visible earlier in the night. Among the most notable Saturn images of the past month, the speaker identified those by Jim Phillips (S. Carolina) of the occultation of a mag 8.9 star on November 15. As the background star passed behind the rings, it could clearly be discerned reappearing through the Cassini divide. Venus was shortly to become an evening planet, emerging over the south-western horizon into the evening twilight during December.
Finally, the speaker recommended two imminent meteor showers: the Geminids, December 7-16, and the Quadrantids, having a narrow peak on January 4. On both occasions, the lunar cycle was sub-optimal: the Geminids would share the sky with a waning Moon reaching its last quarter on December 16, and the Quadrantids a near-full Moon setting shortly before dawn, allowing perhaps a half-hour window of darkness. However, of all events in December, the speaker recommended watching the developments of the British-led Beagle 2 probe, due to touch down on Mars on Christmas morning, after separating from host Mars Express on December 19. To close, the speaker showed Michael Maunder's excellent video footage of the November 23 Antarctic solar eclipse.
After the applause for Mr Mobberley's lively summary, the President called upon the afternoon's final speaker, Mr Geoffrey Johnstone.