Credit: NASA, ESA, and H. Weaver (The Johns Hopkins University/Applied Physics Lab)
Hubble Probes Comet 103P/Hartley 2 in Preparation for DIXI/EPOXI Flyby
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Hubble Space Telescope observations of comet 103P/Hartley 2, taken on September 25, are helping in the planning for a November 4 flyby of the comet by NASA's Deep Impact eXtended Investigation (DIXI) on NASA's Deep Impact Spacecraft performing the EPOXI mission."
Analysis of the new Hubble data shows that the nucleus has a diameter of
approximately 0.93 miles (1.5 km), which is consistent with previous estimates.
The comet is in a highly active state, as it approaches the Sun. The Hubble data
show that the coma is remarkably uniform, with no evidence for the types of
outgassing jets seen from most "Jupiter Family" comets, of which Hartley 2 is a
Jets can be produced when the dust emanates from a few specific icy regions,
while most of the surface is covered with relatively inert, meteoritic-like
material. In stark contrast, the activity from Hartley 2's nucleus appears to be
more uniformly distributed over its entire surface, perhaps indicating a
relatively "young" surface that hasn't yet been crusted over.
Hubble's spectrographs - the Cosmic Origins Spectrograph (COS) and the Space
Telescope Imaging Spectrograph (STIS) -- are expected to provide unique
information about the comet's chemical composition that might not be obtainable
any other way, including measurements by DIXI. The Hubble team is specifically
searching for emissions from carbon monoxide (CO) and diatomic sulfur (S2).
These molecules have been seen in other comets but have not yet been detected in
103P/Hartley has an orbital period of 6.46 years. It was discovered by Malcolm
Hartley in 1986 at the Schmidt Telescope Unit in Siding Spring, Australia. The
comet will pass within 11 million miles of Earth (about 45 times the distance to
the Moon) on October 20. During that time the comet may be visible to the naked
eye as a 5th magnitude "fuzzy star" in the constellation Auriga.
› More images of Hartley 2
› NASA's Hubble web site
The Hubble Space Telescope is a project of international cooperation between
NASA and the European Space Agency. NASA's Goddard Space Flight Center manages
the telescope. The Space Telescope Science Institute (STScI) conducts Hubble
science operations. STScI is operated for NASA by the Association of
Universities for Research in Astronomy, Inc., in Washington, D.C.