Dark matter galaxy discovered

February 23, 2005 Astronomers claim they have discovered the first galaxy made entirely of dark matter.

The galaxy was found 50 million light years away using the University of Manchester's Lovell Telescope in Cheshire and confirmed with the Arecibo telescope in Puerto Rico.

While it contains mass that rotates like a normal galaxy, it contains no stars. Rather, it appears to entirely comprise dark matter, mysterious matter that differs greatly from the normal (baryonic) matter with which we're familiar.

The discovery came from a five-year project to study the distribution of hydrogen atoms throughout the Universe. Hydrogen gas releases radiation that can be detected by radio telescopes.

In the cluster of galaxies known as Virgo, an international team from the UK, France, Italy and Australia led by researchers at Cardiff University found hydrogen atoms amounting to 100 million times the mass of the Sun.

They have named the find VIRGOHI21.

The find is considered incredibly important because cosmological models suggest that dark matter is five times more abundant than baryonic matter in the Universe yet is difficult to study from Earth because of the planet's proximity to the Sun.

"The Universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way," says Jon Davies of Cardiff. "It's a really exciting discovery."