Chandra Release - December 6, 2012

Visual Description: NGC 922

 In this composite image, a ring galaxy named NGC 922 is beautifully displayed with a tight framing in swaths of red, pink, cream, blue and purple. The galaxy has a semi-circular shape, almost like a sea shell, and is scattered with bright stars, dust and other structures in the dark sky. The central region of the galaxy is visible, appearing as a small, bright spot near the center of the image. This composite image contains X-rays from NASA's Chandra X-ray Observatory (colored in red and showcasing a number of bright red spots) and optical data from the Hubble Space Telescope (appearing as pink, cream and blue). NGC 922 was formed by the collision between two galaxies - one seen in this image and another located outside the field of view. This collision triggered the formation of new stars in the shape of a ring. Some of these were massive stars that evolved and collapsed to form black holes.  Most of the bright X-ray sources in Chandra's image of NGC 922 are black holes pulling material in from the winds of massive companion stars. Seven of these are what astronomers classify as "ultraluminous X-ray sources" (ULXs). These are thought to contain stellar-mass black holes that are at least ten times more massive than the sun, which places them in the upper range for this class of black hole.