Violent Merger

• ‹ Previous program
• 67 of 1972
• Next program ›

For the most part, the galaxy known as M85 is pretty ordinary. It's about the same size as our own galaxy, the Milky Way, but it consists mostly of old, small stars.

A couple of years ago, though, M85 put on a bit of a show. Astronomers detected an explosion inside the galaxy -- perhaps the result of a merger between two of its stars.

At its brightest, the explosion produced several million times more energy than the Sun does. It slowly faded away, but it retained an "afterglow" in the infrared -- a form of energy that's produced by relatively cool objects.

The astronomers who discovered the star classified it as a Luminous Red Nova. They suggested that it formed when two fairly old, fairly small stars merged to form a single star. The merger triggered the explosion, blasting a cloud of debris into space. Over time, the expanding cloud of debris cooled and its atoms joined together to form tiny grains of dust. These grains produced the infrared afterglow.

The star seems to resemble several other explosions detected in recent years, so Luminous Red Novae could form a separate class of exploding stars. But many astronomers want to wait and see a few more of them before they open up a new category.

M85 is a member of the Virgo Cluster of galaxies. The cluster is low in the east on March evenings, above and to the left of the bright star Spica, and climbs high across the sky later on. A small telescope reveals many of its galaxies.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.