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| “This artist’s concept illustrates a hypothetical white dwarf (left) that has exploded as a supernova, ejecting the object CWISE J1249 (right), a star or brown dwarf, from the system. This scenario is one possible explanation for the origin of CWISE J1249. |
In a groundbreaking discovery, citizen scientists have identified a rare hypervelocity object zooming out of the Milky Way, using data from NASA’s WISE telescope, which later became the NEOWISE mission. Unlike most stars that orbit the center of the Milky Way, this object is moving so fast that it will eventually escape the galaxy’s gravity and shoot into intergalactic space.
The discovery was made by participants in NASA’s Backyard Worlds: Planet 9 project, a program that uses images from the WISE mission. Originally active from 2009 to 2011 and later reactivated as NEOWISE in 2013, the mission mapped the sky in infrared light and was retired on August 8, 2024.
The object, dubbed CWISE J124909.08+362116.0 (CWISE J1249 for short), was first spotted by citizen scientists Martin Kabatnik, Thomas P. Bickle, and Dan Caselden. They noticed its faint, fast-moving trajectory in the WISE images. The object is traveling at approximately 1 million miles per hour and has a low mass, making it difficult to classify definitively. It could either be a low-mass star or a brown dwarf, a type of object that sits between a gas giant planet and a star.
Ordinary brown dwarfs are not uncommon—Backyard Worlds volunteers have discovered over 4,000 of them. However, none of those are known to be on a path out of the galaxy.
Adding to its uniqueness, data from the W. M. Keck Observatory in Hawaii revealed that CWISE J1249 contains much less iron and other metals than typical stars and brown dwarfs, suggesting it is quite old, possibly originating from one of the first generations of stars in the Milky Way.
The high speed of CWISE J1249 raises intriguing questions. One theory suggests that it may have originated in a binary system with a white dwarf, which could have exploded as a supernova, propelling CWISE J1249 into space. Another possibility is that it was ejected from a globular cluster—a tightly bound group of stars—after a close encounter with a pair of black holes.
This discovery highlights the power of collaborative efforts between volunteers, professionals, and students. The study, led by Adam Burgasser of the University of California, San Diego, includes contributions from citizen scientists who played a crucial role in the search. Kabatnik, for instance, credits fellow citizen scientists Melina Thévenot and Frank Kiwy for their invaluable assistance and tools, which were instrumental in the discovery.
The team will continue to study CWISE J1249’s composition to better understand its origins and the forces that propelled it on its journey out of the Milky Way. The findings have been published in the Astrophysical Journal Letters, marking a significant achievement for the Backyard Worlds: Planet 9 project and its dedicated participants.
