The Cannibalistic "Frankenstein Galaxy" Is Younger on the Inside Than the Outside

Monday, 11 July 2016 - 3:04PM
Space
Monday, 11 July 2016 - 3:04PM
The Cannibalistic "Frankenstein Galaxy" Is Younger on the Inside Than the Outside
Scientists have just discovered an idiosyncratic galaxy that is younger on the inside than on the outside. Researchers believe that the galaxy was essentially cobbled from parts of different galaxies after a rare type of merger, which consists of one galaxy "eating" another.

The galaxy, UGC 1382, which is 250 million light years from Earth, lies in a part of the galaxy that appears quiet and uneventful to astronomers. The galaxy appears completely normal under optical light, but when astronomers studied it under ultraviolet light, they found that it is much larger--and weirder--than they ever imagined. It's more than seven times wider than the Milky Way, and has spiral arms extending out of the galaxy, which ordinary elliptical galaxies wouldn't have.

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"This rare, 'Frankenstein' galaxy formed and is able to survive because it lies in a quiet little suburban neighborhood of the universe, where none of the hubbub of the more crowded parts can bother it," said study co-author Mark Seibert of the Observatories of the Carnegie Institution for Science in a NASA statement. "It is so delicate that a slight nudge from a neighbor would cause it to disintegrate."
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But the strangest quality of UGC 1382 is that it seems to have aged backwards; generally, galaxies are oldest in the middle and youngest on the outside, since the innermost portion forms the oldest stars and then accretes newer stars over time. But this galaxy had the opposite pattern, in which the center was the youngest part of the galaxy.

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"The center of UGC 1382 is actually younger than the spiral disk surrounding it," Seibert said. "It's old on the outside and young on the inside. This is like finding a tree whose inner growth rings are younger than the outer rings."
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The researchers believe that the strange galaxy formed when two or more galaxies came together after evolving independently from each other. Usually, this would cause a catastrophic event, but under exactly the right circumstances, it leads to a "Frankenstein" that has been stitched together from multiple galaxies.

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"We call it the Frankenstein galaxy because it formed out of a couple different galaxies," Lea Hagen, a graduate student at Pennsylvania State University who led the study, told Gizmodo. "The idea of galactic cannibalism, of galaxies eating their friends, is well-established. We think what happened is you had some tiny dwarf galaxies and then a few billion years later another galaxy formed nearby. At some point, those all came together."
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