Hubble discovers 6 massive, dead galaxies from early universe

Hubble discovers 6 massive, dead galaxies from early universe

The reason why these galaxies died during the universe's most prolific period of star birth is still a mystery.

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Scientists studying early galaxies were stunned earlier this year when they discovered six massive galaxies that seem to have died during the universe's most active period of star birth. NASA's Hubble Space Telescope spied the six galaxies, which appeared to have run out of the cold hydrogen gas needed to make stars while most other galaxies were producing new stars at a rapid pace.

"At this point in our universe, all galaxies should be forming lots of stars. It's the peak epoch of star formation," Kate Whitaker, a University of Massachusetts, Amherst assistant professor of astronomy and lead author of a recent study on the six galaxies, said in a press release. "So what happened to all the cold gas in these galaxies so early on?"

Without the cold hydrogen gas necessary to fuel stars and birth new ones, the galaxies are essentially dead. They're also unable to rejuvenate, even if they have absorbed nearby smaller galaxies and gas clouds. Whitaker said that the act of absorbing just "puffs up" the dead galaxies.

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But the reason why they died in the first place is still a mystery.

"Did a supermassive black hole in the galaxy's center turn on and heat up all the gas?" Whitaker posited. "If so, the gas could still be there, but now it's hot. Or it could have been expelled and now it's being prevented from accreting back onto the galaxy. Or did the galaxy just use it all up, and the supply is cut off?"