Study: Old galaxies surprisingly energetic

Aug. 25, 2010 at 9:01 PM
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LOS ANGELES, Aug. 25 (UPI) -- Giant halos of ultraviolet light around ancient galaxies have some U.S. scientists re-thinking the evolution of galaxies in the universe, they say.

The odd ultraviolet formations were spotted around several aged galaxies that astronomers had presumed to be astronomically inactive, reported Wednesday.

"We haven't seen anything quite like these rings before," researcher Michael Rich at the University of California, Los Angeles, said. "These beautiful and very unusual objects might be telling us something very important about the evolution of galaxies."

Astronomers looked at 30 "early" galaxies to try to find out why, though ancient and exhibiting now visible evidence of star formation, were emitting such energetic light.

While young and lively galaxies have bluish hues from their active stars, older galaxies emit reddish collective starlight, researchers say. The reddish trait in ancient galaxies allowed scientists to peg the ages of most of their stars at around 10 billion years old.

Researchers have yet to explain how some of these galaxies received the infusion of fresh, cold gas that would produce the ultraviolet light halos.

The observation proves the cycle of galaxy birth and death could be more complex than previously thought, researchers say.

"In a galaxy's lifetime, it must make the transition from an active, star-forming galaxy to a quiescent galaxy that does not form stars," Samir Salim, an astronomer at Indiana University in Bloomington said. "But it is possible this process goes the other way, too, and that old galaxies can be rejuvenated."

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