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94_52a.txt
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1994-12-13
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PHOTO RELEASE NO.: STScI-PR94-52A
EMBARGOED UNTIL: 1:00PM (EST) DECEMBER 6, 1994
DISTANT CLUSTER OF GALAXIES
[left]
One of the deepest images to date of the universe, taken with NASA's
Hubble Space Telescope (HST), reveals thousands of faint galaxies at
the detection limit of present day telescopes. Peering across a large
volume of the observable cosmos, Hubble resolves thousands of
galaxies from five to twelve billion light-years away. The light from
these remote objects has taken billions of years to cross the
expanding universe, making these distant galaxies fossil evidence"
of events that happened when the universe was one-third its
present age.
A fraction of the galaxies in this image belong to a cluster located
nine billion light-years away. Though the field of view (at the
cluster's distance) is only two million light-years across, it contains
a multitude of fragmentary objects. (By comparison, the two million
light-years between our Milky Way galaxy and its nearest large
companion galaxy, in the constellation Andromeda, is essentially
empty space!)
Very few of the cluster's members are recognizable as normal
spiral galaxies (like our Milky Way), although some elongated
members might be edge-on disks. Among this zoo of odd
galaxies are ``tadpole-like'' objects, disturbed and apparently merging
systems dubbed "train-wrecks," and a multitude of faint, tiny shards
and fragments, dwarf galaxies or possibly an unknown population
of objects. However, the cluster also contains red galaxies that
resemble mature examples of today's elliptical galaxies. Their red
color comes from older stars that must have formed shortly after
the Big Bang.
The image is the full field view of the Wide Field and Planetary
Camera-2. The picture was taken in intervals between May 11
and June 15, 1994 and required an 18-hour long exposure, over 32
orbits of HST, to reveal objects down to 29th magnitude.
[bottom right]
A close up view of the peculiar radio galaxy 3C324 used to locate the
cluster. The galaxy is nine billion light-years away as measured by
its spectral redshift (z=1.2), and located in the constellation Serpens.
Based on the colors and the statistical distribution of the galaxies in
3C 324's vicinity, astronomers conclude a remote cluster is at the same
distance as a radio galaxy.
[center right]
This pair of elliptical galaxies, seen together with a few fainter
companions, is remarkably similar in shape, light distribution, and
color to their present day descendants. This Hubble image provides
evidence that ellipticals formed remarkably early in the universe.
[top right]
Some of the objects in this compact tangled group resemble today's
spiral galaxies. However, they have irregular shapes and appear
disrupted and asymmetric. This might be due to a high frequency
of galaxy collisions and close encounters in the early universe.
Credit: Mark Dickinson (STScI) and NASA