Citizen scientists collaborating with citizen scientists working on NASA’s Backyard Worlds: Planet 9 project have helped discover an object moving so fast that it will escape the Milky Way’s gravity and shoot into intergalactic space. This hypervelocity object is the first such object found with the mass similar to or less than that of a small star.
Backyard Worlds uses images from NASA’s WISE, or Wide-field Infrared Explorer, mission, which mapped the sky in infrared light from 2009 to 2011. It was re-activated as NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer) in 2013 and retired on August 8, 2024.
A Stellar Breakthrough by Citizen Scientists
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 here).
“I can’t describe the level of excitement,” said Kabatnik, a citizen scientist from Nuremberg, Germany. “When I first saw how fast it was moving, I was convinced it must have been reported already.”
Unraveling the Mystery of CWISE J1249
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.
Theories Behind the High-Speed Escape
Why does this object move at such high speed? One hypothesis is that CWISE J1249 originally came from a binary system with a Backyard Worlds: Planet 9 now — participation is open to anyone in any country worldwide.
Reference: “Discovery of a Hypervelocity L Subdwarf at the Star/Brown Dwarf Mass Limit” by Adam J. Burgasser, Roman Gerasimov, Kyle Kremer, Hunter Brooks, Efrain Alvarado, Adam C. Schneider, Aaron M. Meisner, Christopher A. Theissen, Emma Softich, Preethi Karpoor, Thomas P. Bickle, Martin Kabatnik, Austin Rothermich, Dan Caselden, J. Davy Kirkpatrick, Jacqueline K. Faherty, Sarah L. Casewell and Marc J. Kuchner, 8 August 2024, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ad6607
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