Ancient star found while zooming out on a rare discovery

A stunningly fast star that is one of the oldest in the Milky Way has been spotted crossing our Milky Way by astronomers looking for something completely different.

The scientists noticed that the fast star was moving at a speed of 2.1 million kilometers per hour, almost three times the speed of our own Sun, which orbits our Milky Way Galaxy at about half a million kilometers per hour.

Named CWISE J124909+362116.0 (“J1249+36”), this fast star is moving fast enough to potentially escape the galaxy’s gravity entirely. This is evident from the new research, which was announced at the 244th meeting of the American Astronomical Society in Wisconsin and will soon be published in The astrophysical diary letters.

This discovery was made by accident, with the astronomers spotting the star racing through the cosmos as they were sifting through data looking for evidence of “Planet 9” in our solar system. This was part of a citizen science project called Backyard Worlds: Planet 9, which involved 80,000 volunteers sifting through NASA’s Wide-field Infrared Survey Explorer (WISE) mission data from the past 14 years in hopes of finding a secret hidden planet in the suburbs to discover. of our solar system. Instead, J1249+36 was spied as it raced through the Milky Way at 600 kilometers per second.

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

“Its speed and trajectory showed it was moving fast enough to possibly 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 researchers’ models, the star was discovered to be an L subdwarf, a rare type of star with low mass and low temperature, 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,” researcher Efrain Alvarado III of the University of California San Diego said in the statement.

Exactly how this star started traveling so fast remains unclear, although astronomers have put forward a number of theories. It is suggested that J1249+36 could have been in a binary star system with a white dwarf – the leftover core of a star that has exhausted its nuclear fuel and shed its outer layers – that has gathered enough mass from its companion to form a huge explosion to explode. called a nova.

“In this type of supernova, the white dwarf is completely destroyed, so its companion is released and flies off at the orbital speed it was originally moving at, plus a bit of a kick from the supernova explosion,” Burgasser said. “Our calculations show that this scenario works. However, the white dwarf is no longer there and the remnants of the explosion, which probably took place several million years ago, have already disappeared, so we have no definitive proof that this is its origin.” .”

Alternatively, they suggest that J1249+36 originated in a close-knit group of stars known as a globular cluster, which contained a black hole, and that this black hole had eventually catapulted the star outward at enormous speeds.

“When a star encounters a binary star with a black hole, the complex dynamics of this three-body interaction can throw that star straight out of the globular cluster,” Kyle Kremer, an assistant professor at UC San Diego, said in the statement. “It shows a proof of concept, but we don’t actually know which globular cluster this star comes from.”

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

“We are essentially looking for a chemical fingerprint that could identify which system this star comes from,” UC alumnus Roman Gerasimov, a researcher at the University of Notre Dame, said in the statement.

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