Ordinary Meeting, 2003 January 4
The January Sky
Mr Mobberley opened with a summary of the events of the past year: there had been 38 comet discoveries, and over 300 supernovae, including 5 galactic events. Of the comet discoveries, LINEAR had taken a firm hold with 20 discoveries, compared to 8 by NEAT. Five comets had been found by amateurs. The speaker commented on the contrast with 2001, when LINEAR and NEAT had been neck-and-neck with numbers of comet discoveries. The greatest of the supernovae was undoubtedly 2002ap, discovered by Hirose on January 29, which had been classed as hypernova. BAA members Tom Boles and Mark Armstrong had made 11 and 6 discoveries respectively.
The speaker gave some background to the observations in his report with a slideshow of the observatories of the members whose observations he would be showing. These included Ed Grafton, who the speaker believed to be the world's greatest planetary imager. Damian Peach had recently moved from northern Tenerife to a new observing site to the south of the island. This was perched on a balcony above a nightclub! Mr Peach's images of Saturn continued to show a small SPC, with greenish tint around it. There was also a steel grey tint to the A Ring. Both Peach and Grafton had resolved 3-4 pale spots on the surface of Saturn in the past month, each one persisting for a few days. These were around half a second of arc in diameter and hence it would not have been possible to resolve such objects prior to the CCD era. Images by the HST were of one of the same spots that Grafton had noted, and confirmed his observations.
Moving onto Jupiter, ovals A2 and A3 in the South South Temperate Belt (SSTB) had been of recent interest. It appeared that they were moving closer together, squashing the material between them, which included a cyclonic white oval. There was interest as to whether they might eventually merge. Looking back to data from earlier in the year, it was unclear as to whether the white oval currently labelled A2 was the same oval that featured in the earlier observations, or whether that oval had been subsumed into A3 and a new oval formed in its place.
The North Temperate Belt (NTB) was not clearly visible in the wake of the Great Red Spot (GRS). This fading had been anticipated as it follows a ten-year cycle, although on this occasion had not recurred for over 12 years. A comparison of images from October 22 and December 7 showed a marked contrast in the NTB colour. The GRS itself had acquired a dirty appearance, with a dark rim. On December 21, Peach had imaged a dark spot close to the rim, and this appeared in Grafton's December 22 images as a doughnut shape. Damian Peach had continued his search for the Ashen Lights of Venus, but despite very sophisticated image processing his latest images remained negative.
On the comet front, Comet 2002X5 (Kudo-Fujikawa) presented exciting prospects in the early evening sky until mid-January. Discovered on December 14, it was anticipated to reach perihelion on January 27 at around mag 0. It would not be observable after January 19, however, when it would be mag 3. It would reappear in March at mag 8 as a binocular object. 2002Y1 (Juels-Holvorcem) would brighten from mag 15 to mag 13 whilst passing through Bootes in the latter half of January. 2002RX14 was presently around mag 11, but was showing a spectacular tail even at 2 a.u. On December 14, this comet had provided a good photo opportunity as it had passed close by NGC3726. 2002V1 was currently passing through Pegasus, and would reach mag 10 by February. Estimates for its magnitude at perihelion on February 18 ranged from 2 to –15, making it a comet worth watching. 154P/Brewington would brighten to mag 12 by Januiary 21 and mag 11 by February 10. It was currently in Aquila.
Recent supernova discoveries included Ron Arbour's seventh, 2002jy, on December 17 in NGC477; and Tom Boles' 30th, 2002jn, on December 9 in UGC11523. The total solar eclipse of December 4 had been clouded out for African observers, but many BAA members had enjoyed good weather during the 26 seconds of totality in Australia.
The occultation of a mag 7.73 star (TYC 0231-00063-1) by minor planet 441 Bathilde would be visible across southern England on January 11, and would be scientifically interesting. When 345 Tercidini had recently occulted a mag 5.5 star on September 17, a tremendous number of observers had submitted timings, which allowed 55 chords to be placed across the minor object. This gave superb measurement of the shape of the object. On January 8, YY Piscium (mag 4.4) would graze the darkened part of the six-day old moon. In Exeter, a graze would be observed, while in London a near miss was anticipated.
The speaker commented that some spectacular events were anticipated involving the moons of Jupiter. These events would be enhanced as a result of the ability of the moons to totally eclipse one another. On January 10, Europa and Io would simultaneously cast shadows onto the Jovian surface. At 21:10UT, the shadow of Io would overtake that of Europa, with an annular eclipse of Io to a maximum of 74% for 254 seconds. The whole eclipse would last from 20:54UT to 21:23UT.
This could be seen as a warm up for an even more spectacular event on January 17/18. On this occasion, Europa would first eclipse Io from 19:25UT until 20:16UT (low in the eastern sky). At this time, Callisto would also be casting a shadow onto the Jovian surface, with the shadow leaving the surface at 21:52UT. Io's shadow would pass onto the surface at 22:31UT, with Callisto still in transit. Io itself would enter transit at 22:54UT. This would be closely followed by the shadow of Europa, appearing on the face of Jupiter at 23:05UT. Finally, Europa itself would enter transit at 23:52UT, while simultaneously Io's shadow would pass under Callisto. At this time, there would be five objects on the surface of Jupiter – surely a once in a lifetime occurrence. Additionally, a mag 9.2 star (GSC 14011341) would pass behind Jupiter for 2.5 hours, also at 23:52UT. Io's shadow would leave the surface at 00:48UT. Then, from 00:51UT until 01:05UT, Io would pass under Callisto and be occulted by it. Away from the Jovian surface, Europa would later pass under Callisto from 04:50UT until 05:12UT.
To close, the speaker recommended observation of a close pass of 4 Vesta (mag 7.1) within 20 arc-seconds to the south of δ-Vir (mag 3.4). Following the applause for Mr Mobberley's lively and informative report, the President welcomed the afternoon's final speaker, Mr Peter Hingley, librarian of the Royal Astronomical Society.