Anne’s Picture of the Day: Interacting Galaxies VV 340

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

January 5, 2012

VV 340, a pair of interacting galaxies in Boötes

Image Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

VV 340 (also known as UGC 9618 or Arp 302) is a pair of interacting spiral galaxies located about 450 million light-years away in the constellation of Boötes, while speeding away from us at 10,166 kilometers per second. VV 340A (or MCG+4-35-19) is seen edge-on to the left, and VV 340B (or MCG+4-35-18) face-on to the right.

This galaxy pair is the 302nd galaxy in Arp’s Atlas of Peculiar Galaxies, a catalog of 338 peculiar galaxies produced by Halton Arp in 1966.

The two very gas-rich galaxies are in the early stage of an interaction that will eventually lead to them merging in millions of years, much like the Milky Way and the Andromeda galaxy will likely do in approximately 4 billion years from now. The two interacting galaxies are evolving at different rates.

At a very high rate, similar to the most vigorous giant star-forming regions in our own Milky Way, massive stars are being formed within the galaxies. Violent star formation is always considered a sign of a collision or at least a close encounter of two galaxies, because such an encounter disturbs and compresses the gas in the galaxies, what stimulates new star formation. Other signs of a collision or close encounter are the tidal star clouds, especially around the edge-on galaxy.

The blue face-on galaxy is showing lots of star-forming regions but isn’t considered a starburst galaxy, while the red edge-on galaxy, however, is classified as a starburst galaxy that is showing active star formation and a very active core with a rapidly growing supermassive black hole.

Normally red spirals are considered dead spirals. Ones in which star formation has ceased and all the young blue stars are long burned out, leaving only yellow and red stars, giving it a reddish hue. But strangely enough massive stars are being formed in VV 340A, though this is hidden to us by warm dust that appears red. But you might notice that the very ends of its arms are blue.

This image of VV 340 and an abundance of background galaxies was taken by the Hubble Space Telescope on January 6, 2002.

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