The three stars that make up Orion’s belt, above, are in the center of a vast star-forming region that, using the European Space Agency’s new Gaia space telescope, helps inform scientists about the evolution of the galaxy and the ages and behaviors of its newest stars.

Once stars are born, where do they go, and why?

by John Thompson

Research utilizing data from the European Space Agency’s Gaia space telescope has shed new light on an old question: When families of stars are born in huge clouds of gases hundreds of light years in size, what happens next? Where do the new stars go, and why?

A new paper co-authored by Western Washington University Physics and Astronomy Postdoctoral Researcher Marina Kounkel and Associate Professor of Physics and Astronomy Kevin Covey shows that not only do stellar families — group of stars formed at about the same time in the same star-forming region — not split up and go their separate ways, they tend to stick together and move along the same path, called “co-moving,” in a galactic structure known as a string.

“We can systematically look at how stars move across the sky in ways we never could before.”

“We generally thought young stars would leave their birth sites just a few million years after they form, completely losing ties with their original family,” said Kounkel. “But it seems that stars can stay close to their siblings in these strings for as long as a few billion years.”

Understanding how and why these stars move together allows researchers to better use the data from Gaia to put dates on the approximate birth times of thousands of stars in the Milky Way, a hugely important set of facts for researchers like Kounkel.

“Putting all this together allows us to see into young star-forming regions and understand what will happen to the stellar families inside them as they grow up,” she said. “It’s a snapshot into the evolution of the galaxy that tells us so much that we didn’t know.”

Kounkel has been able to mine the open-source data released by the ESA from Gaia, which gathers data on tiny, incremental movements of stars up to 3,000 light-years away — about 10 times as far as researchers could see before Gaia.

“We can systematically look at how stars move across the sky in ways we never could before,” she said.

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