Unusual Feeding Habits

There's a fascinating sight just about 10 billion light years away from Earth, and an international team of astronomers have their eyes set on it. Because of its distance, what astronomers see is a cluster of still-forming protogalaxies as they were when the universe was just 3 billion years old — called the Spiderweb Galaxy. The surprising thing about it is that it's not growing how other galaxy clusters have.

"This is different from what we see in the nearby Universe, where galaxies in clusters grow by cannibalizing other galaxies," explained lead researcher Bjorn Emonts from Spain's Center for Astrobiology, "In this cluster, a giant galaxy is growing by feeding on the soup of cold gas in which it is submerged."

The team of astronomers detected the carbon monoxide (CO) gas pool surrounding Spiderweb using the Australia Telescope Compact Array (ATCA) and the National Science Foundation's Karl G. Jansky Very Large Array (VLA). They published their research in the December 2 issue of the journal Science.

Refining Our Understanding

Galaxies are not all cannibals, it would seem. The Spiderweb Galaxy's relatively refined "eating habits" are giving us a new perspective into the early billion years of the universe. Spiderweb is a massive galaxy cluster which wasn't formed by clashing with other galaxies, as what usually occurs.

“Spiderweb is an astonishing laboratory, which lets us witness the birth of supergalaxies in the interiors of clusters, which are the 'cosmic cities' of the Universe," said co-author George Miley of the University of Leiden in the Netherlands. "We are beginning to understand how these giant objects formed from the ocean of gas which surrounds them.”

Instead, it feeds off from the dense, cold molecular gas surrounding it. The carbon and oxygen probably came from supernova explosions of older stars, and is indicative of large quantities of molecular hydrogen.

This molecular gas, the astronomers estimate, is more than 100 billion times more massive than the sun and has temperatures of about minus-200 degrees C (-328 F) — it's surprisingly huge and cold. It's the perfect raw material for the formation of stars.

As NRAO's Chris Carilli commented, "These observations give us a fascinating look at what we believe is an early stage in the growth of massive galaxies in clusters, a stage far different from galaxy growth in the current Universe."

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