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fbgalax.txt
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1996-01-12
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PHOTO CAPTION NO.: STScI-PRC95-08B
FOR RELEASE: JULY 24, 1995
HUBBLE'S "DEEP" VIEW OF EARLY UNIVERSE
HELPS SOLVE THE FAINT BLUE GALAXY MYSTERY
One of the deepest images of the sky taken to date with NASA's Hubble
Space Telescope reveals a population of faint blue galaxies which turn
out to be the most common class of objects in the universe. Their
distances are estimated to range from three to eight billion
light-years, meaning that they were abundant when the universe was a
fraction of its present age, but are rare or harder to find today
because they have faded or self-destructed.
This picture, in combination with a series of images from the Hubble
Space Telescope Medium Deep Survey that covers a larger area of sky, is
allowing astronomers to solve the longstanding "faint blue galaxy
mystery" by showing the true nature of these dim and remote objects.
Deciphering the formation and evolution of these blue dwarf galaxies
may provide new clues to understanding the process of galaxy evolution,
including the formation of our Milky Way Galaxy.
Hubble's high resolution shows that most of these faint galaxies do not
resemble elliptical and well-defined spiral galaxies that are common in
the present universe. Instead, they have a wide variety of shapes
suggesting that galaxy collisions and other interactions were more
common in the past. The galaxies are blue because they are undergoing
episodes of intense star-formation which produce a lot of young, hot,
and blue stars.
This picture is a true-color image made from separate exposures taken
in blue, green, and far-red light with the Wide Field and Planetary
Camera 2. It required a total of 48 orbits around the Earth (amounting
to roughly one day of exposure time) to make the observation and detect
objects about four billion times fainter than the unaided eye can see
(30th magnitude). The image resolution is about 0.06 arc seconds. The
image covers a relatively small area of sky -- only one tenth the
diameter of the full moon -- in the constellation Hercules.
Credit: Rogier Windhorst and Simon Driver (Arizona State University),
Bill Keel (University of Alabama), and NASA