Ordinary meeting, 2008 January 30 held at the Royal Astronomical Society Lecture Theatre, Burlington House, Piccadilly, London WI.Roger Pickard, President Ron Johnson, Nick James and Hazel Collett, Secretaries
The President opened the third meeting of the 118th session and welcomed members to the newly refurbished RAS lecture theatre, which would be our regular London meeting venue from now on. He invited Mrs Collett to read the minutes of the previous meeting and these were duly approved.
Mr Pickard said there were 18 candidates for membership proposed this month and 20 candidates proposed for election last time had been approved by Council during the meeting earlier in the day; the audience formally confirmed their election. Nick James then advised that Council had approved two papers for publication in the Journal:
'Miyamori's Valley, in myth and reality' by Nigel Longshaw; 'The orbital period of the eclipsing dwarf nova CG Draconis' by Jeremy Shears et al.
Mr Pickard reminded the audience that there were a number of meetings in February and March including the Observers' Workshop on February 23 in Milton Keynes, and the Deep Sky Section meeting on March 1 in Cheltenham. The next Ordinary Meeting would be on Wednesday 2008 March 26 at Burlington House.
The President then explained that the two guest speakers arranged for today had unfortunately had to cancel, and instead we would have a number of shorter presentations from Section Directors and others who had kindly stepped in at the last moment. The first of these was Mrs Valerie White.
The Otford solar system scale model
Mrs White recounted a visit to the scale model of the solar system in Otford, Kent. The story began when she and her husband, Andrew, visited the Griffith Observatory in Los Angeles, in 2007 August, for a solar eclipse conference. The Observatory had just re-opened after a multi-million dollar refurbishment, and by the door of the gift shop they saw a model of Proxima Centauri, the nearest star to the Sun, with an information plaque indicating that this was one component of a huge scale model of the solar system. The last line of the inscription read 'To see the rest of this large solar system scale model, please visit Otford, England'. So, they decided to do just that!
The opportunity arose in 2007 December, following a short holiday flying from Gatwick, so they made their way back home to Warrington via Otford. (Apart from the solar system model, Otford's main claim to fame is that the duck pond, which serves as a roundabout in the centre of the village, is a listed building.) The Sun and planets as far as Jupiter are located on the playing field opposite the Heritage Centre. The Sun, Mercury, Venus and Earth were easy to find. The Sun is represented by a 12 inch (303mm) diameter metal dome on top of a concrete pillar, almost a metre high. The location of each planet is given by another pillar, on top of which is a metal plate of the same diameter as the model of the Sun, with a drawing of the planet, to the same scale as the Sun model, etched in the centre of the plate. The speaker explained that the model was not a linear one, as in some other solar system scale models at e.g. Jodrell Bank, but the positions of the pillars reflected the positions of the planets at midnight on 2000 January 1. (The model was constructed as part of the Millennium celebrations). Gordon Taylor, Director of the BAA Computing Section, assisted in providing information for the calculation of the positions and orbits of the planets.
On the photo showing the pillars for the Sun, Mercury, Venus and Earth, the speaker pointed out that the orbits were also mown into the grass of the playing field. The next planet to find was Mars, but the pillar for that could not be seen. However, by following the orbit for Mars mown into the grass, it soon became clear that there wasn't a pillar for Mars, only a plaque level with the ground--since the location was between two football pitches, it had been considered dangerous to erect a concrete pillar there.
Jupiter's pillar was located by the hedge further down the playing field. A short walk round to the doctor's surgery was required to find the model of Saturn. Uranus was found near a bus stop after a 15 minute walk down the High Street and, after a further 10 minute walk, Neptune was found in front of someone's garden wall. The walk to Pluto took about 30 minutes along public footpaths across farmers' fields. Returning to the Sun took about 40 minutes.
An information leaflet, picked up in the Heritage Centre, explained the reasoning behind the size of the model--it had to be big enough for the engraving of the smallest planet, Pluto, to be seen by the naked eye and small enough for the distances between the planets to fit into the parish boundaries. This meant that Pluto had to be at least 0.5mm across, which is close to the limit of normal sight. Since Pluto is about five billion kilometres from the Sun, the scale for the model had to be about one to five billion to allow it to fit within the 1km radius parish boundaries. The pillars for the planets had to be positioned so they could be visited by the public at any time. This means that the position for Pluto is just slightly displaced from where it ought to be, so it could be located by a public footpath.
In addition to Proxima Centauri, three other star models, to the same size and distance scale, have been placed around the world: Barnard's Star, in Stanley Museum, Falkland Islands; Sirius, in Sydney Observatory, Australia; and Ross 154, in Christchurch Museum, New Zealand. The speaker said she had been to these other locations, but unfortunately before these star models were put there--so it would be a good excuse to travel to these places again, in order to complete the tour of the scale model!
Further information can be obtained from the website www.otford.org/solarsystem or from the Heritage Centre in Otford. There is also an article about the construction of the model and the official opening ceremony in the 2003 October Journal of the BAA.
Before she closed, the speaker showed a photo of the Lovell Telescope--made out of straw! An almost life size 'straw sculpture' was built at Snugburys Ice Cream dairy near Nantwich last summer, to celebrate fifty years of the dawn of the space age and the construction of the Lovell telescope at Jodrell Bank. In addition Jodrell held a 'sound and light' show, projecting images of the space age, the construction of the radio telescope and Hubble photos onto the dish of the Lovell telescope. The most enduring image of the show was a photo of the dish of the telescope projected onto the actual dish.
Following a couple of questions, the President recalled that he, together with Gordon Taylor, had attended the official opening of the model at Otford, carried out by Commander Henry Hatfield in 2001 July. Just near the end of the opening speech, the heavens opened and it poured with rain, so attendees without umbrellas had to run for shelter! The President thanked Mrs White for her delightful talk and introduced the Director of the Mercury and Venus Section, Dr Richard McKim.
Images of Mercury from the Messenger spacecraft
Dr McKim spoke about the results of the recent Messenger flyby of Mercury. First of all he expressed his pleasure that BAA meetings were once again being held in Burlington House. He reviewed the past work of the Mercury and Venus Section, and showed that the albedo details captured by the spacecraft, in particular the Caloris basin, agreed well with drawings and images by Section members and by Schiaparelli and Antoniadi. Caloris was a rather young impact basin, and one of the largest known features.
The rougher terrain at the south pole led this part of the planet to appear darker than the north when viewed telescopically. Many new geological faults had been discovered, confirming that the crust had shrunk in the past. Messenger would return in October. So far only part of the previously unmapped hemisphere of the planet had been revealed, but soon we would see the rest. More details can be found in the Section notes in the Journal for 2008 February and April.
Sky notes for February and March
The President then gave the Sky Notes for 2008 February and March. He began by showing details of the first sunspots from the new solar cycle as observed by Peter Meadows on January 5, following observations by SOHO at 06:24 UT the previous day. These were seen at a latitude of 28[degrees], too high to be members of the old cycle.
Of the planets, Mars was fading from mag--1.5 on Jan 1 to 0.2 by Feb 28, and being in Taurus was still well placed although rapidly growing smaller. Saturn was at opposition on February 24 and well placed in Leo. The ring tilt was now about 7[degrees] with the south face of the rings towards us. The inclination of Saturn now allows satellites from Dione inwards to show transits and occultations.
Next, the President showed some lightcurves by Jeremy Shears; one of the dwarf nova HT Cas in outburst showing deep eclipses, and the other of the newly discovered dwarf nova in Canis Minoris which displayed superhumps with a period of 0.0572d. Finally the President showed an image of the long period variable star omicron Ceti at maximum taken by Maurice Gavin and an outstanding image of the Horsehead Nebula by Gordon Rogers.
After concluding his Sky Notes, Mr Pickard handed over to Sheridan Williams to talk about February's two eclipses. Sheridan detailed the location and circumstances of Antarctica's annular solar eclipse on February 7, followed by a more detailed description of the February 21 total lunar eclipse which would be visible in its entirety from the UK.
Mr Pickard then introduced the Director of the Jupiter Section, Dr John Rogers.
Jupiter's global upheaval in 2007
Most of the major belts and zones on Jupiter presented a fairly constant appearance from 1996 to 2006. Sometimes the planet shows a very different aspect, particularly during a 'global upheaval' (e.g. 1990), which involves planet-wide changes including colouration of the Equatorial Zone (EZ), fading and vigorous revival of the South Equatorial Belt (SEB), and a super-fast outbreak on the North Temperate Belt (NTB). At the start of 2007, changes suggested a global upheaval was starting: exceptional darkening of the EZ, and quiescence of the SEB which, as predicted, soon led to fading. Then in March, a super-fast NTB outbreak began. Detailed amateur coverage of this event has been reported not only in our bulletins and the Journal throughout the year, but also in Nature (2008 January 24), in an article which praised the quality and value of modern amateur imaging. Synthesis of amateur and professional imaging and modelling implies that the super-bright, super-fast plumes had billowed up from a sub-surface layer of water clouds where the winds were even stronger than at the surface.
Meanwhile the SEB began to fade as we predicted, leading to a violent outbreak initiating an SEB Revival. This started surprisingly early, on 2007 May 17. It generated dark spots in a rapid westward jet-stream, heading for a newly formed 'disturbance', and as predicted these spots performed a U-turn there, one after the other, in a spectacular and well-documented display of the 'Circulating Current' that had not been fully seen since the BAA Jupiter Section first described it in the 1920s and 1930s. Both European and Japanese observers compiled animated strip-maps showing this remarkable circulation.
In 2007 Sept., as the apparition drew to an end, the global upheaval was approaching completion. The SEB had revived at all longitudes (though it was still double), the EZ was becoming lighter again, and the revived NTB had become vividly orange. While most latitudes were reverting to a more normal appearance, it remained to be seen whether they would again remain that way for many years, or would re-enter another cycle of fading and outbursts.
Following the applause for Dr Rogers' presentation, Mr Pickard introduced Bob Marriott, Curator of Instruments.
Opening of the Wrottesley Observatory
On 2007 October 19 Mr Marriott attended the opening of this new observatory at the Black Country Museum, Dudley. This is an open-air museum dedicated to the Victorian era, which incorporates, among many features, a small town, a tramway, a Newcomen beam engine and a coal mine. The observatory is the latest of several established by the Pendrell Hall Observatories project, Staffordshire, led by BAA member John Armitage.
After introductory speeches by Ian Walden (Director of the Museum), Mr Armitage, Roger Pickard (then the Association's President Elect) and Bob Marriott, the observatory was officially opened by Professor John Dowell, FRS. The building is a classic Romsey observatory, designed by the Rev E. L. Berthon in the early 1870s, with a telescope room housing a 7-inch f/11 reflector by George Calver (BAA instrument no.150), and a side room housing a transit instrument. The telescopes at Pendrell Hall include a 12 1/4-inch Calver reflector (see R. A. Marriott, 'BAA instrument no.93', Journal, 116(2006), 299; and J. Armitage, 'Astronomical weddings for astronomers', Journal, 118(2008), 230). Several additional instruments--including other BAA instruments--are designated for various Pendrell Hall sites in the West Midlands, and all are intended for both public and private use.
Finally Mr Pickard asked Nick James to speak about some recent Near Earth Objects.
Mr James noted that a number of NEOs had been in the news recently. Information about these objects was frequently misreported in the media since a good panic was always worth more than simple scientific facts. This applied even if the target was not the Earth and, in late 2007 December, one media outlet reported 'Mars asteroid 2007 WD5 will blow up planet'. In fact 2007 WD5 missed Mars by a large margin and, even if it had hit it would have done little damage.
The next object, 2007 TU24, was more interesting. This large object had made a close pass of the Earth last night (2008 January 29/30) at a distance of around 538,000km. Richard Miles of the ARPS issued a BAA e-bulletin to alert observers on January 23 and radar data from Goldstone obtained on the same date indicated that the asteroid was asymmetrical with a diameter of roughly 250m. The NEO reached a maximum magnitude of 10.3 at its closest and so was well within the range of amateur telescopes although it was now fading rapidly. Analysis of the many amateur observations of this object was continuing.
Following the applause for Mr James' contribution, Mr Pickard thanked all the speakers for stepping in at the last moment and rescuing what had turned out to be a very interesting evening. He then adjourned the meeting until Wednesday March 26 at the same venue.
Hazel McGee (prepared from notes of their talks by the speakers themselves).