Wednesday, January 03, 2007

The Dark Side revealed!

What you see above is an image, made by Chandra, of two colliding clusters of galaxies. The red areas at the center of the image are normal interstellar gas heated by the collision. The outer blue areas are the first visual evidence of the "dark matter" that theorists have posited as making up most of the mass of the universe. The dark matter is not heated because units of such matter do not interact with each other or with normal matter in ways that generate heat. The dark matter is detected by gravitational lensing; that is, by the distortion of the light from more distant objects behind it.

I found this image, as in my earlier "Galactic Greetings" post, through a link in Cosmic Log. This link took me to a post of the "Top Ten Astronomy Images of 2006" in a superb blog called Bad Astronomy. The other images are well worth perusing.