A stellar stream is a rare linear pattern—rather than a cluster—of stars. After combining multiple datasets captured by the Gaia space telescope, a team of astrophysicists found 8,292 stellar streams—all named Theia. All of Theia 456’s 468 stars were born simultaneously and traveled in the same direction across the sky.
Jeff Andrews, a Northwestern University astrophysicist, said, “Most stellar clusters are formed together. What’s exciting about Theia 456 is that it’s not a small clump of stars together. It’s long and stretched out. There are relatively few streams that are nearby, young, and so widely dispersed.”
The stars that form in clusters are usually spherical. Only recently have astrophysicists started to find new patterns in the sky. They believe long strings of stars were once tight clusters, gradually ripped apart and stretched by tidal forces.
Andrews said, “As we’ve started to become more advanced in our instrumentation, our technology, and our ability to mine data, we’ve found that stars exist in more structures than clumps. They often form these streams across the sky. Although we’ve known about these for decades, we’re starting to find hidden ones.”
Theia 456 dwells within the Milky Way‘s galactic plane; hence it’s easily lost within the galaxy’s backdrop of 400 billion stars.
Andrews said, “We tend to focus our telescopes in other directions because it’s easier to find things. Now we’re starting to find these streams in the galaxy itself. It’s like finding a needle in a haystack. Or, in this case, finding a ripple in an ocean.”
Astronomers used Artificial intelligence algorithms to comb through huge datasets to find these structures. Then by cross-referencing those data with pre-existing catalogs of documented stars’ iron abundances.
They discovered that the 468 stars within Theia 456 had similar iron abundances, which means that—100 million years ago—the stars likely formed together. Adding further evidence to this finding, scientists examined the light curves dataset, capturing how stars’ brightness changes over time.
Astrophysicist Marcel Agüeros from Columbia University said, “This can be used to measure how fast the stars are spinning. Stars with the same age should show a distinct pattern in their spin rates.”
Using data from NASA’s Transiting Exoplanet Survey Satellite and the Zwicky Transient Facility, astronomers could determine that the stream’s stars share a typical age.
The team also found that the stars are moving together in the same direction.
Andrews said, “If you know how the stars are moving, then you can backtrack to find where the stars came from. As we rolled the clock backward, the stars became closer and closer together. So, we think all these stars were born together and have a common origin.”
“Combining datasets and data mining is essential to understanding the universe around us.”
“You can only get so far with one dataset. When you combine datasets, you get a much richer sense of what’s out there in the sky.”
Andrews presented this research during a virtual press briefing at the 237th meeting of the American Astronomical Society. “Theia 456: A New Stellar Association in the Galactic Disk” took place today (Jan. 15) as a part of a session on “The Modern Milky Way.”