Friday, February 09, 2007

Mapping the earliest quasars

This is my fifth post for the weeklong orgy of science blogging, Just Science. There hasn't been much astronomy, so here goes with a discovery from the early universe.

The Sloan Digital Sky Survey has been taking pictures of nearly the entire sky, mapping the universe bit by bit. the project is in its second phase.

Astronomers have been mining this for data. A group reports on new findings concerning the clustering of quasars in the universe's first billion years. Quasars are the superbright cores of active galaxies and are probably powered by black holes at the galaxy's nucleus. We only see them at far distances, which implies we are seeing them in their youth.

A map of 4000 quasars shows they are much more tightly clustered than expected. "Previous maps showed that more nearby quasars cluster like 'normal'galaxies," explained Princeton University graduate student Yue Shen, wholed the study. "But the clustering in our map is ten times stronger, the difference between a high contrast photograph and a washed out xerox."

Quasars and their galaxies cluster together, bringing together normal and dark matter. Dark matter is thought to far outweight the amount of normal matter in the universe. (See here for interesting simulations showing the distribution of the two types of matter.)

The strong clumping of the quasars suggests dark matter is also especially thick in these clumps. These kind of calculations help astronomers, astrophysicists and cosmologists figure out why our universe is the way it is now.