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Observing Pluto's Atmosphere
Jay M. Pasachoff | | June 22, 2006 |
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| For the last few years, we have been using fast CCD cameras not only to observe eclipses but also to observe the atmosphere of Pluto. If Pluto had no atmosphere, when it went in front of a star, the starlight would wink out instantly (or almost). But the atmosphere bends and scatters the starlight, so Pluto dims gradually, and then at the end, a couple of minutes later brightens gradually.We successfully observed a Pluto occultation in 2002 from Mauna Kea, and we found that Pluto's atmosphere had expanded a bit and warmed since the previous occultation was observed, in 1988. Now we had another chance on June 12, when Pluto was to go in front of a 16th magnitude star. Working with my colleagues at Williams College and MIT, we arranged four telescopes in Australia and one in New Zealand. Making the prediction is very difficult and the MIT group does a great job with it, but there is still a last minute uncertainty of hundreds of kilometers. |
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| colleagues David Ramm (U Canterbury) and Bryce Babcock (Williams College) |
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Anyway, I went to Mt. John, New Zealand, with my Williams College colleague Bryce Babcock to use their 1-m telescope for the occultation. We got there a few days in advance, and got our NASA- supplied camera onto the telescope and tested. But the night before the event, a storm came through.It was the worst storm they have had in 50 years, which brought two feet of snow to the mountain and which shut off power for 100 miles around. So instead of observing--and the next night was sometimes very clear, though clouds sometimes came--we were huddled in all our clothes under covers, with no electricity and therefore no opportunity of opening the dome or of operating our equipment. We were trapped on the mountain top. |
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| Jay Pasachoff |
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Eventually, the Observatory Manager got a neighbor farmer's tractor to plow the quantity of snow and, with sunlight on the road and lots of shoveling, we were just able the next afternoon to get down the steep Observatory road and to the town of Tekapo, where we stayed the night. They had electricity restored but the phones were still out; interestingly, broadband Internet was working. The road to Christchurch, about 3 hours away if the road was clear, was still cut through the high pass, but managed to get through a day later (though there was still a detour and the drive took 5 hours).As we left the mountaintop, we heard on the radio that "14 astronomers are stranded on Mt. John." I had heard Pam Kilmartin, the wife of the Observatory Manager, give similar information to a reporter yesterday; the two of them are coauthors on the 1988 Pluto occultation paper. I had amused because of the old- fashioned nature of it to see her 1988 plots of that previous occultation, in pencil on graph paper from their data logger. Coincidentally, she and her husband, Alan Gilmore, were coauthors of that original 1988 paper. |
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| colleagues Bryce and Phyllis Babcock (Williams College) |
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If anybody had asked me in advance if 80% success would be satisfactory, I would surely have said "yes," and that is what we got. Our four Australia stations got excellent data: the 2.3 m at Siding Spring, a 2.0 m at Mt. Stromlo, a 1 m at Hobart (operated by my colleague Steve Souza and student Anne Jaskot, both from Williams College), and a 0.75 m Newtonian of amateur astronomer Ian Bedford, run together with Lynton Hemer and Fraser Farrell helping our people Joe Gangestad of Williams and Mike Person of MIT. We're working on data reduction now and we hope to submit scientific papers soon. We hope we will soon know more about Pluto's atmosphere and whether it will still be there when NASA's Deep Impact mission arrives in 2015. |
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| The dome of the 1-m telescope of the Mt. John University Observatory, New Zealand |
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| The dome of the 1-m telescope and the dorm building, Mt. John University Observatory |
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| Classifications: Beginning Observing, Advance Observing, General| 0/0/0 - 0/0/0 |
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