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New research published this week reveals a “river of stars” that fill the sky in the southern hemisphere passing a little more than 300 light-years away from Earth.
The River of Stars
Researchers at the University of Vienna, Stafan Meingast, João Alves, and Verena Fürnkranz, have identified a “river of stars” in our stellar neighborhood that can help scientists identify essential information about our galaxy.
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The stars, part of what’s known as a stellar stream, are part of a star cluster that is slowly being stretched out into a stream swirling around the galactic center. The Milky Way is a collection of billions of stars, most of which are part of—or were once part of—clusters of stars containing anywhere from a few hundred to thousands of stars that share a common origin and are gravitationally bound together—at least for a time.
“Most star clusters in the Galactic disk disperse rapidly after their birth as they do not contain enough stars to create a deep gravitational potential well, or in other words, they do not have enough glue to keep them together,” said Meingast, lead author of the paper published in the journal Astronomy & Astrophysics.
“Even in the immediate solar neighborhood, there are, however, a few clusters with sufficient stellar mass to remain bound for several hundred million years. So, in principle, similar, large, stream-like remnants of clusters or associations should also be part of the Milky Way disk.”
Seeing the River Just Outside Our Interstellar Window
The stellar stream covers much of the southern sky, hiding in plain sight.
“Identifying nearby disk streams is like looking for the proverbial needle in a haystack. Astronomers have been looking at, and through, this new stream for a long time, as it covers most of the night sky, but only now realize it is there, and it is huge, and shockingly close to the Sun” said Alves.
“Finding things close to home is very useful, it means they are not too faint nor too blurred for further detailed exploration, as astronomers dream.”
The researchers utilized data from the European Space Agency’s Gaia spacecraft to create a 3D model of the movement of stars in the Milky Way.
Examining stars moving together in the vicinity of our Sun, the researchers were able to identify 200 stars that fit the pattern of a star cluster being pulled apart by the gravitational force of the galaxy.
They were able to extrapolate that the stream should have 4,000 stars at least, making it more massive than many other star clusters discovered up until now.
The researchers were also able to determine the age of the cluster to be around 1 billion years old, which indicates that the cluster has made about 4 revolutions around the galactic center, which is enough time to pull the cluster into its current stream structure.
“As soon as we investigated this particular group of stars in more detail, we knew that we had found what we were looking for: A coeval, stream-like structure, stretching for hundreds of parsecs across a third of the entire sky,” said Fürnkranz. "It was so thrilling to be part of a new discovery."
The discovery gives scientist an important new tool to help measure the total mass of the Milky Way and provides a host of new candidate stars to hunt for exoplanets.