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1994-01-23
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HUBBLE SPACE TELESCOPE DEEP-SKY SURVEY FINDS
INTERACTING GALAXIES IN A CLUSTER
In one of the deepest celestial surveys yet made by NASA's Hubble Space
Telescope, astronomers have discovered a small group of previously
unknown,interacting galaxies estimated to be three billion light-years
away*.
Hubble caught the galaxies in an early stage of evolution, and so they
offer new clues to developing a much clearer understanding of how
galaxies have changed over time.
Nearly half the galaxies appear to be merging with one another in the
Hubble image. This suggests a very rapid evolution of galaxies and
clusters of galaxies over very short time spans, according to
astronomers. These results might help improve theories which predict
that galaxies evolved faster than earlier thought, perhaps due to the
influence of dark matter -- invisible or undetected mass pervading the
universe.
A galaxy is a city of stars that are held together by their mutual
gravitation. Galaxies are considered the basic building blocks of the
universe and HST's high resolution image reveals that many early
galaxies "building blocks" are in pairs. "In many of the pairs, at
least one galaxy is blue, which indicates that star formation is under
way at a high rate, possibly triggered by interaction with the neighbor
galaxy," says Dr. Richard Griffiths of The Johns Hopkins University,
Baltimore. "Such mergers and interactions may be the rule within
galaxy clusters rather than the exception."
"Though the largest galaxy in the image is about the size of our own
Milky Way galaxy, most of the galaxies detected are much smaller than
our own. They might eventually merge to form the many large galaxies
that we see in the universe at the present day," he says.
Over the past two years, Griffiths and colleagues at Johns Hopkins
University, with a team of astronomers in the U.S. and Britain, have
used the Hubble Space Telescope to carry out a serendipitous survey of
small areas of sky. This is done with the Wide Field Camera, which is
used to take a picture of a piece of sky close to a main target such as
a quasar or galaxy that is being observed by a different Hubble
instrument.
The survey is one of several Key Projects using Hubble. In previous
images the deep survey has uncovered remote and unusual galaxies never
before resolved by an optical telescope. HST's new level of detail
reveals a bizarre variety of shape and structure in these distant
galaxies, which only previously appeared as fuzzy blobs from ground
based telescopes.
*The distance to the largest galaxy in the image has been measured by
Prof. Rogier Windhorst and his group at Arizona State University, using
the Multi-Mirror Telescope in Arizona, operated by the University of
Arizona and the Smithsonian Institution.
CONTACT: Ray Villard, STScI
(410) 338-4514
Dr. Richard Griffiths
(410) 516-4194
PRESS RELEASE NO.: STScI-PR93-23
********
The Space Telescope Science Institute is operated by the Association of
Universities for Research in Astronomy, Inc. (AURA) for NASA, under
contract with the Goddard Space Flight Center, Greenbelt, MD. The
Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency (ESA).