A Star Is Speeding Through the Milky Way at Nearly Two Million Miles an Hour

The star, which is officially called LP 40-365, is a piece of shrapnel from a cosmic explosion.

Scientists are the first to know about rare sightings out in the galaxy, and most recently, they discovered one extraordinary find: a star moving at lighting speed in the Milky Way. According to new research published in The Astrophysical Journal Letters, this star is a piece of shrapnel from a supernova (a cosmic explosion that happens when a white dwarf star gets too big to support itself and releases a massive amount of energy) that is still speeding its way through space. "This star is moving so fast that it's almost certainly leaving the galaxy…[it's] moving almost two million miles an hour," JJ Hermes, the assistant professor of astronomy at Boston University College of Arts and Sciences, said. "To have gone through partial detonation and still survive is very cool and unique, and it's only in the last few years that we've started to think this kind of star could exist," added Odelia Putterman, a former Boston University student and lab scientist.

With the use of data from NASA's Hubble Space Telescope and Transiting Exoplanet Survey Satellite (TESS), Putterman and Hermes were able to study the light information from the stars. Their findings? The researchers noted that the star, formally called LP 40-365, is rotating and slinging its way out of the Milky Way based on its brightness patterns. "We dug a little deeper to figure out why that star [was repeatedly] getting brighter and fainter, and the simplest explanation is that we're seeing something at [its] surface rotate in and out of view every nine hours," suggesting its rotation rate, Hermes said. While its commonplace for stars to rotate, its unusual to see a star fragment from a supernova to rotate slowly at a nine-hour pace.

full view of milky way galaxy from NASA's Spitzer Space Telescope
Courtesy of NASA/JPL-Caltech

The scientists' research can now help decode what happens after an explosion and more. "This [paper] adds one more layer of knowledge into what role these stars played when the supernova occurred," Putterman said. "By understanding what's happening with this particular star, we can start to understand what's happening with many other similar stars that came from a similar situation."

Since LP 40-365 had such a slow rotation rate, Hermes and Putterman think that it is shrapnel from a star that exploded when it had too much mass from its partner when orbiting around each other at a fast pace. As a result, both of the stars likely exploded and we now see LP 40-365 traveling through space. "These are very weird stars," Hermes said, as LP 40-365-like stars move fast and are high in metal contents, unlike the sun, which is filled with helium and hydrogen. The stars "we're seeing are the by-products of violent nuclear reactions that happen when a star blows itself up," Hermes said.

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