Tasmania briefly ‘Centre’ of the Universe
By SHEVILL MATHERS | Stargazers with large telescopes and attached suitable cameras will be able to make useful contributions to science when they attempt to capture one of astronomy’s rare events – an ‘occultation’ of a star by a planet. This rare event will occur on 13 June 2006. So, what’s an occultation? Well, it has nothing to do with mysticism or astrology but everything to do with astronomy.
An occultation is an astronomical event that occurs when one celestial object is hidden by another celestial object that passes between it and the observer. Compared to astronomical transits and eclipses, an occultation is said to occur when the nearer object appears larger and completely hides the more distant object.
Stars can be occulted by planets. In 1959, Venus occulted Regulates. Uranus’ rings were first discovered when that planet occulted a star in 1977. On the evening of 2-3 July 1989, Saturn passed in front of the 5th magnitude star 28 Sagittarius. It is also possible for one planet to occult another planet.
The planet Pluto will occult the star astronomers have catalogued ‘UCAC 2603 9859’ at the early hour of 2.25am on June 13. The main visibility areas of the occultation by Pluto itself will be New Zealand, Tasmania, and southern Australia. Amateurs from various mainland locations will take part and make significant contributions to the project, given clear skies.
Mt Canopus sets the pace
The prime location however will be Mt Canopus, on the outskirts of Hobart. Our local amateur astronomers are heavily involved including Associate Editor of the ‘New’ Sky & Space Magazine, Shevill Mathers, who has been invited to use his own local observatory facilities near Mt Canopus, to record the event with his 12’’ telescope and camera/timing equipment, as part of the German team. Observations will be made some hours prior to the actual occultation to gather baseline data.
Astronomers from America, France and Germany have arrived in Hobart to set up their special occultation cameras on various telescopes to record this event. The American team will use a 1-metre telescope and the French and German team will use a 16” model. Also, a French team member — together with another astronomer – will head up to Campbell Town, an hour and half north of Hobart.
A ‘Pluto’ workshop at the University Physics Department enabled all participants to meet and discuss their equipment and techniques, with the usual friendly rivalry.
For many weeks leading up to this rare event, astronomers from the University of Tasmania and two members from the Astronomical Society of Tasmania (AST), Shevill Mathers (Southern Cross Observatory) and Laurie Priest have been preparing the equipment.
Much work had to be done on the old 16” telescope to bring it up to modern-day requirements for serious astronomy. Likewise, a 20-year old Celestron C14 telescope has been equipped with the latest digital setting circles and a computer
Shevill has been very busy in his workshop manufacturing focusers and re-coating mirrors as well as working on the observatory dome. A bit of swapping around and loaning of equipment to the visitors is all part of the deal. Shevill is loaning them all sorts of equipment including some to an overseas group to save them lugging heaps of heavy gear from Germany.
Shevill will be recording the event using a very sensitive camera and a specially made German GPS timing device supplied by German team member, Wolfgang Beiker. A full Moon a few degrees away from Pluto, plus the very cold nights with high humidity could make the task very tricky. With unseasonably high humidity and plummeting temperatures, outdoor telescopes could be dripping wet with condensation in minutes.
The scientific goals of an observation of this important occultation are to determine the development of Pluto’s atmosphere and the loss of energy due to its increasing distance from the sun and to determine details of winds in Pluto’s atmosphere by a possible measurement of a central flash from Tasmania or New Zealand.
Other goals are to determine the diameter and the mean density of P1 and P2, two newly discovered moons of Pluto which all appear to rotate counter-clockwise around the planet.
The results are of special interest to NASA’s ‘New Horizons’ mission which has just been launched to Pluto, because possible smaller bodies and/or a ring system around Pluto may have a significant impact on the mission.
UPDATE: The Pluto occultation was successfully recorded by local and visiting overseas atronomers who made a special journey from the northern hemisphere.
Data was obtained by the American team using the Mt Canopus 1-metre telescope, courtesy the University of Tasmania. Dr Wolfgang Beisker and local amateur astronomer, Shevill Mathers, obtained image data using the 40cm telescope in a smaller dome, and Dr Stefan Dieters with visiting French astronomer, Alain, used a C14 telescope. Both telescopes were fitted with cameras specially developed for the occultation. Images of the occultation were sent directly to each computer.
The evening was esentially cloud free for much of the time, however, as is usual during such important events, fast moving cloud from the south west kept obscurring the vital area of sky that all three telescopes were pointed at.
The event was sucessfully recorded by all three teams on Mt Canopus and the data obtained will provide much vital information. The USA team in NZ were without power due to the intense snowstorms, so were unable to record the occultation, which must have been a great disappointment for them.
Melbourne astronomers were also clouded out. Being in the right place at the right time does play a big part in being able to observe/record such important events.
Tasmania is in a prime position to observe Pluto occultations because the distant 9th planet is now high up in the southern Milky Way, which means that it is very close to the horizon in the northern hemisphere. Shevill, with email assistance fro Wolfgang, may well be able to record the next Pluto occultation with his nearly completed 16” reflector telescope. Expert astronomers are working on Pluto’s orbit to see where and when the next occultaion will be.
There were smiles all round at the success of the Pluto project. This data will be sent to the team at NASA for their New Horizons apace mission to Pluto.
Over the coming weeks, the data will be analysed and eventually published in the leading science magazines. Shevill Mathers