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Optical
image of the Whirlpool Galaxy - another spiral galaxy like the
Milky Way. The individual reddish clumps Scattered throughout
the galaxy's spiral armes are huge nurseries of stellar newborns.
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The
first clumps of matter to form in the universe began to pull themselves
together within a few hundredmillion
years after the Big Bang. Each of these giant clouds of gas and
dust included an enormous amount of material, aggregating perhaps
a trillion times the mass of our Sun. Within the first billion years
or so after their formation, these newly formed galaxies had given
birth to their first generation of stars. But even these youngest
galaxies
are sites of star death as well as star birth. Within a few million
years after the first galaxies had formed, the most massive of the
galaxies' earliest generation of stars had already burnt themselves
out. These stars exploded as supernovas to seed their galaxies with
the heavy elements synthesized within their nuclear-fusing cores.
To
observe galaxies as they form and during their earliest youth requires
infrared-detecting telescopes. Except for the most distant ones,
young galaxies reveal themselves in the light from their newly formed
blue stars. The expansion of the universe shifts all the light from
young galaxies toward the red end of the spectrum, so that today
we observe as red the light that their stars emitted as blue billions
of years ago. These young galaxies, so distant that their light
must travel billions of light-years to reach us, can be observed
with a new generation of advanced telescopes on the ground and in
space. Ground-based telescopes can observe the portions of the infrared
domain closest to visible light, making highly detailed spectroscopic
measurements using complex instruments too large and heavy to launch
into orbit.

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