March 10, 2009--The Medusa galaxy is seen in a composite of x-ray data from the Chandra X-ray Observatory and visible light captured by the Hubble Space Telescope in this image released March 10.

The x-ray data, rendered in blue, also shows a black hole on the left-hand side of the image.

Since x-rays can be sensed long after the stars that created them expire, x-rays can be used as "fossils" to study the history of a galaxy's star formation.

Astronomers also believe that stars that produce greater quantities of x-rays form more quickly.

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