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Galactic Baby Factories Snapped

21 December 2004 (All day)
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New generation. As this artists' conception shows, young galaxies (right) are glaringly bright compared to older ones (left) in ultraviolet wavelengths.

A small satellite has glimpsed one of the biggest cradles in the modern universe. The Galaxy Evolution Explorer (GALEX) has returned snapshots of several dozen newborn galaxies, massive swirling regions of forming stars. Remarkably, these objects are nearby, not many billions of light-years away as all other known baby galaxies are. This closeness will give scientists a brand new way to study how galaxies formed.

Astronomers have long known that most galaxies coalesced when the universe was young; their birthrate peaked about five billion to ten billion years ago and has been declining ever since. As a result, astronomers who wish to scrutinize newly formed galaxies for clues about what forces give them shape must look at faint images billions and billions of light-years away to get a hazy glimpse of the past--at least until now.

The GALEX satellite, launched in April 2003, has an ultraviolet camera designed to spot the energetic light of young stars. When the GALEX researchers trained the satellite's eye on the heavens, they spotted several dozen small, bright galaxies being born nearby--within a few billion light-years of the Milky Way. "It's like looking out a window and seeing a dinosaur walking by," says Tim Heckman, an astrophysicist at Johns Hopkins University and member of the GALEX team. Heckman says the observations show that "galaxy birth is still happening today, though at a much reduced rate compared to when the universe was young." Indeed, says Caltech astronomer and GALEX team member Chris Martin, "the newborn galaxies are near us, but they are very rare."

The very distance and faintness of newborn galaxies studied in the past make it hard to get detailed information about their structure, says astronomer Alice Shapley of the University of California, Berkeley. "The nearby newborn galaxies, in every way that we can tell … [are] the same kind of object" as the distant newborn galaxies, she adds. If they are, then scientists could use the Hubble Space Telescope and other instruments to make detailed observations of nearby newborns and use those observations to figure out what's going on in the distant ones. Astronomers would truly be able to rock the galactic cradle.

Related sites
GALEX
Jet Propulsion Laboratory's GALEX page

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