Newfound gas cloud may be graveyard of first stars

Scarcity of heavy elements points to universe’s earliest stellar inhabitants

star explosion simulation

ELEMENTAL DIVERSITY  Explosions of first-generation stars (one simulated here) produced elements heavier than helium and spread them throughout the cosmos. A newly discovered gas cloud may hold the signature of these ancient explosions. The densest gas in this explosion is shown in red.

B. Smith et al/ 2015

KISSIMMEE, Fla. — A newly discovered gas cloud contains hydrogen and helium but virtually nothing else. The scarcity of heavier elements suggests that the cloud houses the remains of the universe’s first stars, John O’Meara reported January 8 at a meeting of the American Astronomical Society. Scientists want to learn more about these ancient stars, which have never been observed directly, because they injected the first doses of carbon, oxygen and other crucial elements into the cosmos.

First-generation stars, forged from pristine hydrogen and helium gas produced just minutes after the Big Bang, burst onto the scene about 13.4 billion years ago. Astronomers don’t yet have the ability to see objects from that long ago.

O’Meara, an astronomer at Saint Michael’s College in Colchester, Vt., and colleagues looked at the next best thing by probing a roughly 12-billion-year-old gas cloud. Analysis of the gas’s absorption of light from a distant galaxy revealed that the cloud contains about 0.04 percent the concentration of heavy elements as that in the sun. The mix of ingredients matches the expected yield from explosions of the universe’s earliest stars, O’Meara reported.

O’Meara says he expects astronomers to find other objects that are similarly scarce in heavy elements, especially once NASA’s James Webb Space Telescope launches in 2018. “This cloud is not a cosmic unicorn,” he says. 

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