This Is Racing Through Our Galaxy at Top Speed

J1249+36 is flying 1,500 times faster than sound
By Neal Colgrass,  Newser Staff
Posted Jun 19, 2024 7:30 PM CDT
Updated Jun 23, 2024 7:20 AM CDT

When you fly by at a million miles an hour, it can turn some heads—which is just what happened with this runaway star. Snappily named J1249+36, it's going fast enough to break free of our galaxy's gravitational pull and launch into intergalactic space, Newsweek reports. The question is what kicked J1249+36 so hard that it's flying three times faster than the sun and 1,500 times faster than sound. mulls one theory, that J1249+36 once played binary companion to a "dead" white dwarf—a former sun-like star that exhausted its hydrogen supply but, in this case, fed off its mate and sucked up mass until it exploded (see video).

"In this kind of supernova, the white dwarf is completely destroyed, so its companion is released and flies off at whatever orbital speed it was originally moving, plus a little bit of a kick from the supernova explosion as well," says lead researcher Adam Burgasser of UC San Diego in a statement. In another theory, two black holes formed a binary in a globular cluster and gave J1249+36 the boot: "When a star encounters a black hole binary, the complex dynamics of this three-body interaction can toss that star right out of the globular cluster," says an assistant professor at UC San Diego.

The hope now is to unpack the star's elemental composition and see if it was "polluted" by a white dwarf explosion, or originated in a globular cluster likely to host black holes. Such "hypervelocity" stars aren't that rare—an old Smithsonian article estimates roughly 1,000 are zooming around our galaxy—but this story contains two other nice tidbits: J1249+36 belongs to a class of the galaxy's most ancient stars called subdwarfs, per Science Daily, and volunteer scientists who stumbled on it were combing through data for evidence of the mysterious "Planet 9." (Planet 9 might not be a planet.)

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