Anne’s Image of the Day: Starburst Galaxy NGC 3310

read more at Anne’s Astronomy News http://annesastronomynews.com/

July 21, 2013

NGC 3310, a starburst galaxy in Ursa Major

Image Credit & Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona
(http://skycenter.arizona.edu/gallery/Galaxies/NGC3310)

NGC 3310 (also known as Arp 217) is a spiral galaxy of some 22 thousand light-years across, located about 46 million light-years away from the Earth in the northern constellation of Ursa Major (the Great Bear). It is receding from us at approximately 993 kilometers per second.

This galaxy is a so-called “starburst” galaxy. Most galaxies form new stars at a fairly slow rate, but members of the rare class starburst galaxies blaze with extremely active star formation. Measuring the clusters’ colors yields information about stellar temperatures. Since young stars are blue, and older stars redder, the colors can be related to the ages.

NGC 3310 is forming clusters of new stars at a prodigious rate. There are several hundred star clusters in NGC 3310, visible in the image as the bright blue diffuse objects that trace the galaxy’s spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young, luminous stars can be seen throughout the galaxy.

Once formed, the star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements of the wide range of cluster colors show that they have ages ranging from about one million up to more than one hundred million years. This suggests that the starburst “turned on” over 100 million years ago. It has likely been triggered when one of its satellite galaxies collided and merged with NGC 3310.

Starbursts were once thought to be brief episodes, resulting from catastrophic events like a galactic collision. However, the wide range of cluster ages in NGC 3310 suggests that the starbursting can continue for an extended interval, once triggered.

More evidence of a merger with a companion galaxy are several tidal features surrounding the main disk, as well as two large hydrogen tails extending to the north and south. There is also a closed loop consisting of stars emerging from the eastern side of the disk and rejoining in the north. This faint structure appears to consist of tidal debris from the companion galaxy and is distinct from the rest of the shells surrounding NGC 3310. It is the first of its kind to be detected in a starburst galaxy.

This image was taken on March 3rd and 4th, 2011 with a SBIG STX16803 CCD Camera on the 32-inch Schulman Telescope (RCOS) at the Mount Lemmon SkyCenter.

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