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1996-01-12
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CONTACT: Ray Villard, STScI FOR RELEASE: November 8, 1993
(410) 338-4514
PRESS RELEASE NO.: STScI-PR93-23
Dr. Richard Griffiths
(410) 516-4194
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.
********
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).