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Posted by BeauHD from the hide-and-seek dept.
Citizen scientists from NASA’s Backyard Worlds: Planet 9 project discovered a hypervelocity object, CWISE J1249, moving fast enough to escape the Milky Way. “This hypervelocity object is the first such object found with the mass similar to or less than that of a small star,” reports NASA’s Science Editorial Team, suggesting the object may have originated from a binary star system or a globular cluster. From the report: A few years ago, longtime Backyard Worlds citizen scientists Martin Kabatnik, Thomas P. Bickle, and Dan Caselden spotted a faint, fast-moving object called CWISE J124909.08+362116.0, marching across their screens in the WISE images. Follow-up observations with several ground-based telescopes helped scientists confirm the discovery and characterize the object. These citizen scientists are now co-authors on the team’s study about this discovery published in the Astrophysical Journal Letters (a pre-print version is available here). CWISE J1249 is zooming out of the Milky Way at about 1 million miles per hour. But it also stands out for its low mass, which makes it difficult to classify as a celestial object. It could be a low-mass star, or if it doesn’t steadily fuse hydrogen in its core, it would be considered a brown dwarf, putting it somewhere between a gas giant planet and a star.
Ordinary brown dwarfs are not that rare. Backyard Worlds: Planet 9 volunteers have discovered more than 4,000 of them! But none of the others are known to be on their way out of the galaxy. This new object has yet another unique property. Data obtained with the W. M. Keck Observatory in Maunakea, Hawaii, show that it has much less iron and other metals than other stars and brown dwarfs. This unusual composition suggests that CWISE J1249 is quite old, likely from one of the first generations of stars in our galaxy. Why does this object move at such high speed? One hypothesis is that CWISE J1249 originally came from a binary system with a white dwarf, which exploded as a supernova when it pulled off too much material from its companion. Another possibility is that it came from a tightly bound cluster of stars called a globular cluster, and a chance meeting with a pair of black holes sent it soaring away.
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