Williams College Continues Its Studies of Pluto with NASA Grant
WILLIAMSTOWN - Williams College has received a grant from NASA's Planetary Sciences Division to continue its studies of Pluto and objects beyond it in the outer solar system.
The grant will support the work of Williams faculty Jay Pasachoff, Bryce Babcock, and Steven Souza and extend their use of stellar occultations, occasions when one astronomical object goes in front of a distant star. By studying the changes in the starlight over a crucial few minutes, the size and the structure of the atmosphere of Pluto or of other occulting objects can be studied.
The NASA grant, for a three-year total of $196,500, continues and extends a previous three-year grant under which the three Williams faculty members and their students made several observations of Pluto and of its largest moon, Charon. Their work has been in close collaboration with an MIT team headed by Professor James Elliot and also including Amanda Gulbis and Michael Person. Elliot had pioneered the use of stellar occultations, marked by a major success in 1977 in his discovery of rings around the planet Uranus.
The grant covers summer stipends that include student participation, travel to expedition sites and to relevant meetings, shipping of equipment, and some computer expenses.
The Williams-MIT team had also received a joint grant from NASA for the purchase of special electronic cameras suitable for their occultation studies. Three of the cameras are at Williams and three are at MIT. They are called POETS, for Portable Occultation, Eclipse, and Transit System. Pasachoff, Babcock, and Souza have also used them to observe the 2006 total solar eclipse and the 2006 transit of Mercury.
Previously, their 2002 observations from Hawaii of an occultation of a distant star by Pluto had led to the discovery of, as they termed it in an article in the journal Nature, "Global Warming on Pluto." The trend was based on the lone previous Pluto occultation that had been observed in 1988. In 2006, from Australia, and in 2007, from Arizona and New Mexico, they had found little further change in Pluto's atmosphere. In 2005, from Chile, the Williams-MIT team placed severe limits on how much atmosphere Charon could have and measured Charon's size sufficiently accurately to comment on its shape, density, and its rock-ice fraction.
The 2008 observations included observations extended over time to see if there are rings or other debris in the Pluto system, some of special interest since the Hubble Space Telescope discovered two small additional moons around Pluto. Williams College senior Adam McKay '08 of North Adams studied occultation data last summer from the 2006 event; they comprise a major part of his senior thesis. He had helped take some of the data for the 2007 event, on site in New Mexico.
A further Pluto occultation, of a star that is particularly bright by the standards of their previous observations, is scheduled for June 22, to be observed from Australia.
Pasachoff, Babcock, and Souza and their MIT colleagues hope, during the period of the new grant, to be able to extend the technique to study other dwarf planets and further objects beyond Neptune, known as Kuiper-belt objects.
The discovery by Michael Brown of Caltech and his colleagues of an object beyond Pluto yet slightly larger made it untenable to retain Pluto as a major planet without prospectively adding dozens of other planets. As a result, Pluto was reclassified as a "dwarf planet" by the International Astronomical Union in 2006, a decision that remains controversial and that will be discussed again in a NASA-sponsored meeting in Maryland this summer and an International Astronomical Union meeting in Rio de Janeiro in 2009. The object that caused the trouble has also been classified as a dwarf planet and has been named Eris, after the Greek goddess of discord (perhaps referring to the discord in classifying it), and its moon has been named Dysnomia, after the goddess of lawlessness. Brown has a half dozen Kuiper-belt objects being followed that are of potential interest for further occultation research. Pasachoff will spend a 2008-09 sabbatical leave at Caltech's Division of Geophysics and Planetary Sciences, sponsored by Brown.
The previous NASA grant for Pluto occultation research had, as an Education and Public Outreach Supplement, three years of Teachers Workshops based at Williams College's Milham Planetarium, along with sponsored visits from Berkshire County schools. The NASA program under which it was funded has now ended.
