Yay Dark Matter!

This was in the Washington Post this morning and, being an astronomy dork, I found it fascinating:

Ring of Dark Matter Found Around a Galaxy



Scientists believe they have found a ring of mysterious dark matter surrounding a distant galaxy -- a potential breakthrough in identifying the most widely distributed but least understood particles in the universe.

Using the Hubble Space Telescope, astronomers identified the ghostly ring that they said was created by the long-ago collision of two galaxy clusters. The dark matter itself was not visible -- it does not shine or reflect light -- but it left a distinct "footprint" in the shapes of background galaxies. Although the presence of dark matter has been detected before, it has always been far more interspersed among the hot gases and galaxies that make up galaxy clusters.

"This is the strongest evidence so far for the existence of dark matter," said astronomer M. James Jee of Johns Hopkins University. He likened dark matter to the wind -- which we cannot see except through its effects on other objects.

Astronomers have long theorized the existence of the invisible substance because without its mass, galaxy clusters would not have sufficient gravity to keep from flying apart.

The ring is huge, measuring 2.6 million light-years across. It was found in a galaxy cluster 5 billion light-years from Earth. Jee said he was first annoyed when he saw the ring because he assumed it was a distortion or artifact. It took months of checking and rechecking before his team became convinced that the ring was actually a manifestation of dark matter.