Super-Bright Galaxy CR7 Reveals Signs of First Stars in the Universe

by Sarah Lewin, /  / Updated  / Source:

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Astronomers have found what looks like some of the very first stars ever formed in the universe, forged from hydrogen created in the Big Bang.

Such stars, while long theorized, have never been observed before now, according to scientists with the European Southern Observatory who announced the discovery on Wednesday. The stars act as a bridge from the universe's early, hydrogen-filled existence to the many heavy elements surrounding us today. ESO officials created a video animation of the bright galaxy, called CR7, to illustrate their find.

The newly discovered pocket of stars perches in an extremely bright, old galaxy called CR7. Researchers identified the galaxy while using the European Southern Observatory's Very Large Telescope to peer back to a time about 800 million years after the Big Bang, when the first stars and galaxies were forming from residual hydrogen. The universe is about 13.7 billion years old. [From the Big Bang to Now in 10 Easy Steps]

"The discovery challenged our expectations from the start, as we didn't expect to find such a bright galaxy," David Sobral, lead author on the new paper, said in a statement.

Sobral and his colleagues were searching for distant galaxies, but found that one in particular was an anomaly. The group soon realized that not only was the galaxy incredibly bright — the most luminous distant galaxy ever found, he said in the statement — but it had the hallmarks of the universe's earliest stars.

Earth's sun shows its age by the elements it contains: mostly hydrogen and helium, but also a multitude of metals that formed in earlier stars. The first stars to condense after the Big Bang, called Population III stars, would have been up to a 1,000 times larger than the sun and at first would have contained only hydrogen, helium and lithium.

These Population III stars would have been short-lived, exploding as supernovas after just 2 million years of blazing life, releasing the elements they created. Later stars formed from those remnants and forged even heavier elements.

The researchers found that CR7 had areas that didn't emit signals for any elements heavier than helium — suggesting that they were probably clusters of Population III stars.

The research was detailed in a paper accepted for publication June 4 in The Astrophysical Journal.

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