September 3, 2009

Study Finds Cannibalistic Neighboring Galaxy

Astronomers have reported that the neighboring Andromeda Galaxy appears to have cannibalistic tendencies as it has expanded by "digesting" stars from other nearby galaxies.

Writing in the journal Nature, an international team of astronomers made the discovery using the Canada-France-Hawaii Telescope and its MegaCam/MegaPrime digital camera to conduct an ongoing survey.

Experts have previously considered the concept of a cannibalistic galaxy, but the new study is the first to bring detailed images of the process.

"What we're seeing right now are the signs of cannibalism," said study lead author Alan McConnachie of the Herzberg Institute of Astrophysics in Victoria, British Columbia.

"We're finding things that have been destroyed ... partly digested remains."

The study took in an area with a diameter equivalent to one million light years, which allowed for the development of the deepest panoramic image of a galaxy every made.

"Ironically, galaxy formation and galaxy destruction seem to go hand in hand," Dr Scott Chapman, reader in astrophysics at the Institute of Astronomy, University of Cambridge, told BBC News.

In order to test the cannibalistic theory of galaxies, astronomers have used a method that involves searching for the planetary remains of the absorption process.

The new study used a method to discover streams and structures on the fringes of Andromeda which appear to be the leftovers from exactly this sort of process.

"This is a startling visual demonstration of the truly vast scale of galaxies," said Dr Mike Irwin, from the University of Cambridge's Institute of Astronomy and one of the report's lead authors.

"The survey has produced an unrivalled panorama of galaxy structure which reveals that galaxies are the result of an ongoing process of accretion and interaction with their neighbors."

At about 2.5 million light years away Andromeda is the closest neighboring galaxy to the Milky Way.

"Andromeda is so close that we can map out all the stars," Pauline Barmby, an astronomer from the University of Western Ontario, Canada, who was involved in the study, told BBC News.

"And when you see a sort of lump of stars that far out, and with the same orbit, you know they can't have been there forever."


Image Caption: A stroboscopic projection of a high resolution numerical simulation of a possible orbit of the Triangulum galaxy around Andromeda, that reproduces much of the observed details of these galaxies. These simulations suggest that Triangulum will eventually be devoured by its massive neighbour, contributing to the ongoing formation of the Andromeda Galaxy. Illustration by John Dubinski and Larry Widrow


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