used NASA's Hubble Space Telescope to look out into the universe
over distances exceeding 12 billion light-years. These "deepest"
views of the heavens, made with Hubble's visible and infrared
cameras, are collectively called the Hubble Deep Field.
the starlight harvested from remote objects began its journey
toward Earth billions of years ago, Hubble, as well as all
large telescopes, look farther back into time the farther
they look into space. Hubble has seen back to a time when
the universe was only about five percent of its present age.
These "long exposures" of the universe have revealed galaxies
that existed when the universe was less than one billion years
old. Some of the objects viewed were so dim that seeing them
would be as difficult as discerning a flashlight on the Moon
as seen from Earth.
Deep Field uncovered more than 1,000 galaxies in a patch of
sky no larger than a grain of sand held at arm's length. Extrapolated
across the entire sky, this means the universe contains at
least 120 billion galaxies. These thousands of galaxies are
at various stages of evolution and are strung along a corridor
of billions of light-years.
high resolution enables astronomers to actually see the shapes
of galaxies in the distant past and study how they have evolved
over time. They found that galaxies looked more fragmentary
in the distant past and took time to evolve to the majestic
spirals and giant elliptical galaxies of today. They also
found that the universe formed most of its stars when it was
less than half its present age. Astronomers will spend years
sorting the myriad shapes of the galaxies in this image to
understand how they formed and how have evolved since the
variety of other telescopes, with sensitivities ranging from
X-rays to radio waves, have also been aimed at the Deep Field
to see if astronomers can match various astronomical phenomena
to the visible-light galaxies.
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