Astronomers in search for 'dark' galaxies

Oct. 30, 2012 at 7:59 PM

OXNARD, Calif., Oct. 30 (UPI) -- Astronomers say they've detected a predicted type of "dark" galaxy devoid of stars and made predominately of dense gas, a U.S. science foundation reports.

The California-based Kavli Foundation says the discovery of dark galaxies, which would normally be unseen against the black backdrop of the universe, sheds light on their role in the evolution of our universe.

"Dark galaxies are composed of dark matter and gas, but for some reason they have not been able to form stars," Martin Haehnelt, of the Kavli Institute for Cosmology at the University of Cambridge, said.

"Some theoretical models have predicted that dark galaxies were common in the early universe when galaxies had more difficulty forming stars -- partly because their density of gas was not sufficient to form stars -- and only later did galaxies begin to ignite stars, becoming like the [normal] galaxies we see today."

The team of international astronomers said they detected several dark galaxies by observing the fluorescent glow of their hydrogen gas, illuminated by the ultraviolet light of a nearby quasar.

Some astronomers say they believe dark galaxies are the building blocks of modern galaxies.

"In our current theory of galaxy formation, we believe that big galaxies form from the merger of smaller galaxies," team member Sebastiano Cantalupo of the University of California, Santa Cruz, said.

"Dark galaxies bring to big galaxies a lot of gas, which then accelerates star formation in the bigger galaxies."

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