No Stars Shine in This Dark Galaxy

"An international team of astronomers have conclusive new evidence
that a recently discovered "dark galaxy" is, in fact, an object the
size of a galaxy, made entirely of dark matter. Although the object,
named VIRGOHI21, has been observed since 2000, astronomers have been
slowly ruling out every alternative explanation."

"Astronomers first suspected there was an invisible galaxy out there
when they spied galaxy NGC 4254. This unusual-looking galaxy appears
to be one partner in a cosmic collision. All the normal evidence is
the gas is being siphoned away into a tenuous stream, and one of
its spiral arms is being stretched out.

But the other partner in this collision is nowhere to be seen.

The researchers' calculated that an object with 100 billion solar
masses must have careened past NGC 4254 within the last 100 million
years, creating the gas stream, and tearing at one of its arms. This
was the clue that an invisible dark matter galaxy might be lurking
nearby."

"It could be that there are many of these dark galaxies out there. A
new sky survey, carried out with the 305-metre (1000-foot) Aricebo
radio telescope in Puerto Rico should tease out more of these objects
in the future. The survey is called the Arecibo Galaxy Environment
Survey (AGES)."

http://www.universetoday.com/2007/06...s-dark-galaxy/

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