Ancient star receding from galaxy found in rare discovery

Astronomers looking for something completely different spotted a lightning-fast star that is one of the oldest in the galaxy.

Scientists noticed that the fast-moving star is traveling at 1.3 million miles per hour, nearly three times the speed of our own sun, which orbits our Milky Way galaxy at about half a million miles per hour.

This fast star, which has been named CWISE J124909+362116.0 (“J1249+36”), is moving fast enough to potentially escape the galaxy’s gravity entirely. That’s according to new research reported at the 244th meeting of the American Astronomical Society in Wisconsin and soon to be published in The Astrophysical Journal Letters.

The discovery happened by chance when astronomers spotted a star hurtling through space while combing through data looking for evidence of a “Planet 9” in our solar system. It was part of a citizen science project called Backyard Worlds: Planet 9, which involved 80,000 volunteers poring over data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission over the past 14 years in hopes of discovering a secret hidden planet on outskirts. our solar system. Instead, J1249+36 was observed hurtling through the galaxy at 372 miles per second.

This star’s impressive speed makes it a potential “hypervelocity” star, an extremely rare star moving fast enough to eventually leave the galaxy entirely.

“Its speed and trajectory indicated that it was moving fast enough to escape the Milky Way,” researcher Adam Burgasser, a professor of astronomy and astrophysics at the University of California, San Diego, said in a statement.

According to the scientists’ models, the star was discovered as an L subdwarf, a rare type of low-mass, low-temperature star known to be among the oldest in the Milky Way.

“It was exciting to see that our models were able to accurately match the observed spectrum,” UC San Diego researcher Efrain Alvarado III said in a statement.

Exactly how this star began to travel so quickly remains unclear, although astronomers have proposed a number of theories. One posits that J1249+36 may have been in a binary star system with a white dwarf—the remnant of the core of a star that has exhausted its nuclear fuel and shed its outer layers—that has accumulated enough mass from its companion to explode in a huge explosion. called a nova.

“In this kind of supernova, the white dwarf is completely destroyed, so its companion is ejected and flies away at the orbital speed it was originally traveling at, plus a little kick from the supernova explosion,” Burgasser said. “Our calculations show that this scenario works. However, the white dwarf is no longer there, and the remains of the explosion, which probably occurred several million years ago, have already dissipated, so we have no definitive proof that this is its origin.” .”

Alternatively, they suggest that J1249+36 came from a narrow group of stars known as a globular cluster that contained a black hole, and that black hole eventually catapulted the star outward at tremendous speed.

“When a star meets a black hole binary, the complex dynamics of this three-body interaction can eject that star right out of the globular cluster,” Kyle Kremer, an assistant professor at UC San Diego, said in a statement. “It demonstrates a proof of concept, but we don’t really know what globular cluster this star is from.”

Scientists hope to study the star further and look for evidence of one of these scenarios, such as white dwarf nova trails or globular clusters in its wake.

“Essentially, we’re looking for a chemical fingerprint that would pinpoint exactly what system this star came from,” UC graduate student Roman Gerasimov, a University of Notre Dame researcher, said in a statement.

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