Stellar Occultations by Pluto and Hydra Observable from Bosscha Observatory June 27, 2011
PHOT team Leader : Dr. Leslie A. Young1,
Scientists visiting Bosscha Observatory, Indonesia : Dr. M. Bullock1, Dr. J. Stansberry2
Host scientists at Bosscha Observatory, Indonesia : Dr. Hakim L. Malasan, M.Irfan, M.Sc.3
1 Southwest Research Institute, Colorado, USA
2 Steward Observatory, Arizona, USA
3 Bosscha Observatory, FMIPA, ITB, West Java, Indonesia
Official website :
Supporters: NASA Planetary Astronomy; The New Horizons mission to Pluto, National Geographic; and Southwest Research Institute.
Pluto, like Earth, has a nitrogen atmosphere, but Pluto is so cold that the nitrogen exists both as frozen ice on the surface and as a gas. As Pluto's nitrogen ice warms up or cools down, the atmosphere will expand or freeze out onto the surface. We have already seen Pluto's atmosphere double since 1988. As it moves away from the sun, it should eventually decease again. When will it start to collapse? The answers will tell us about how the interactions of surfaces and atmospheres of Pluto and other nitrogen-covered worlds at at the edge of our solar system.
The only way to measure Pluto's changing pressure is by *stellar occulation*, when a body passes between an observer and a distant star.
We plan to observe stellar occultation by Pluto and two of its moons from 15 locations across the width of the Pacific in June, 2011. An occultation is similar to a solar eclipse in that there are only certain places we can observe from. Previous occultations have taken us to Chile, USA, Mexico, Australia, New Zealand, Namibia, South Africa, Reunion Island, and Europe. We use portables that we ship to the location, large, modern telescopes, telescopes at astro-tourism
sites, and historic telescopes built in the early 1900s.
On June 23 and 27, 2011, Pluto and two of its moons will occult bright stars as seen from various sites in the Pacific. Pluto's atmosphere defocuses the starlight gradually, at a rate that depends on the atmospheric pressure and temperature, which will let us track how Pluto's atmosphere changes as it moves away from the sun. Charon and Hydra will block the starlight abruptly, which will tell us their sizes and orbits.
At Bosscha observatory, we will be observing the Pluto occultation on June 27. Bosscha observatory has a large telescope, which will help understand weather and climate on Pluto.