Ancient Galaxy 'Bursting' with Stars

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Most of the early galaxies that astronomers have been able to observe are small with a low-to-moderate amount of star production. But now the Herschel Space Observatory has found a massive dust-filled galaxy churning out stars at an incredible rate, with all of this taking place back when the cosmos was a just 880 million years old. The galaxy is about as massive as our Milky Way, but produces stars at a rate 2,000 times greater, prompting the researchers to call it a "maximum-starburst" galaxy.

The astronomers involved in its discovery say its mere existence challenges our theories of galaxy evolution.

"Massive, intense starburst galaxies are expected to only appear at later cosmic times," says Dominik Riechers, currently an assistant professor at Cornell.

"Yet, we have discovered this colossal starburst just 880 million years after the Big Bang, when the universe was at little more than 6 percent of its current age. Riechers is the first author of the paper describing the findings in the April 18 issue of the journal Nature.

The prevailing thought on early galaxy and star formation has been that the first galaxies to form were relatively small and lightweight, containing only a few billion times the mass of our Sun. They form their first stars at rates of a few times that experienced by the Milky Way today, and the galaxies would grow by merging with other small galaxies. In theory, galaxies as massive as the newly found galaxy – named HFLS3 -- should not be present so soon after the Big Bang.

HFLS3 appears as little more than a faint, red smudge in images from the Herschel Multi-tiered Extragalactic Survey (HerMES). The extreme distance to HFLS3 means that its light has travelled for almost 13 billion years across space before reaching us. We therefore see it as it existed in the infant Universe, just 880 million years after the Big Bang or at 6.5% of the Universe's current age.

[caption id="attachment_101535" align="aligncenter" width="580"]

This artist's impression shows the "starburst" galaxy HFLS3. The galaxy appears as little more than a faint, red smudge in images from the Herschel space observatory. Image credit: ESA-C. Carreau.[/caption]

Even at that young age, HFLS3 was already close to the mass of the Milky Way, with roughly 140 billion times the mass of the Sun in the form of stars and star-forming material. After another 13 billion years, it should have grown to be as big as the most massive galaxies known in the local Universe.

"Looking for the first examples of these massive star factories is like searching for a needle in a haystack; the Herschel dataset is extremely rich," said Riechers.

Tens of thousands of massive, star-forming galaxies have been detected by Herschel as part of HerMES and sifting through them to find the most interesting ones is a challenge.

"This particular galaxy got our attention because it was bright, and yet very red compared to others like it," said co-investigator Dave Clements of Imperial College London.

While the discovery of this single galaxy isn't enough to overturn current theories of galaxy formation, finding more galaxies like this one could challenge those theories, the astronomers say. At the very least, theories will have to be modified to explain how this galaxy formed, Riechers says.

"This galaxy is just one spectacular example, but it's telling us that extremely vigorous star formation was possible early in the universe," says Jamie Bock, professor of physics at Caltech and a coauthor of the paper.

Read the team's paper:

A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34

Sources:

ESA

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JPL

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Caltech

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com