Hubble Spots a Jet
In a dress rehearsal for the rendezvous between NASA's Deep Impact spacecraft
and comet 9P/Tempel 1, the Hubble Space Telescope captured dramatic images of
a new jet of dust streaming from the icy comet.
The images are a reminder that Tempel 1's icy nucleus, roughly half the size
of Manhattan, is dynamic and volatile. Astronomers hope the eruption of dust
seen in these observations is a preview of the fireworks that may come July 4,
when a probe from the Deep Impact spacecraft will slam into the comet, possibly
blasting off material and giving rise to a similar dust plume.
The two images, taken seven hours apart on June 14, show Tempel 1 and its new
jet. The image at left, taken at 2:17 a.m. (EDT), is a view of the comet before
the outburst. The bright dot is light reflecting from the comet’s nucleus, which
appears star-like in these images because it is too small even for Hubble to
resolve. The nucleus, a potato-shaped object, is 8.7 miles (14 kilometers) wide
and 2.5 miles (4 kilometers) long. Hubble's viewing the nucleus is as difficult
as someone trying to spot a potato in Salt Lake City from New York City.
The photo at right, snapped at 9:15 a.m. (EDT), reveals the jet [the bright
fan-shaped area]. The jet extends about 1,400 miles (2,200 kilometers), which
is roughly half the distance across the U.S. It is pointing in the direction of
Image credit: NASA, ESA, P. Feldman (Johns Hopkins University), and H. Weaver
(Johns Hopkins University/Applied Physics Lab)
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