A star spinning at 15,000 miles per second tests Einstein theory of relativity
Popular Science...
The Milky Way galaxy is anchored by a supermassive black hole named Sagittarius A*, that has a mass over four million times greater than the sun. While Sagittarius A* exerts an influence on everything inside its cosmic neighborhood, astronomers have detected one particular cosmic thrall that may offer a glimpse into some of the universe’s most profound and puzzling concepts. As researchers detail in a study published today in the journal Nature, a star dubbed S301 exists so close to Sagittarius A*, that it races around the black hole at over 15,500 miles per second. S301’s circumstances are so unique that astrophysicists described the stellar object as “unprecedented.”
“What is special about this star is that it’s orbiting Sagittarius A* on a very tight orbit, taking just 8.7 years to complete it, and is approaching the black hole at a mere 12 times the distance of Earth to the sun,” Felix Mang, a study co-author and astrophysicist at the Max Planck Institute for Extraterrestrial Physics (MPE) in Germany explained in a statement.
S301’s closest passes by the supermassive black hole are roughly the distance between Earth and Saturn. Not only does this make it the nearest star to Sagittarius A* ever observed, but also the fastest. During its orbit, S301 attains speeds more than 100,000 times faster than a commercial airliner—over eight percent the speed of light.
“Because it orbits so close to Sagittarius A*, S301 opens a new window to the fundamental properties of spacetime in this extreme black-hole environment,” explained Reinhard Genzel, a study co-author and recipient of the 2020 Nobel Prize in Physics.
Two billion times fainter than Betelgeuse, S301 is only detectable thanks to the European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI) in Chile. To study it, astronomers utilized the ESO’s GRAVITY+ instrument alongside the VLTI, which combines light from a quartet of 26-foot-wide telescopes to create a virtual composite with 15 times the spatial resolution as a single telescope.
The team first spotted the new star in 2023, and have been tracking it ever since in order to narrow down its orbit. Their data also helped them retroactively fill in S301’s orbital history back to 2017, showing that its previous closest pass by Sagittarius A* occurred only a few months before its discovery. S301 may have begun its stellar life as part of a binary pair ripped by the supermassive black hole’s tidal forces. Although this confined S301 to its current orbit, the companion star was likely ejected with such high velocity that it actually left the Milky Way galaxy entirely.
A better understanding of S301 itself could lead to additional breakthroughs, particularly when it comes to Sagittarius A*. Researchers have long theorized the black hole spins just like most other objects in the universe. Einstein’s general theory of relativity dictates that a twirling black hole would bring spacetime along for the ride, warping it in a process known as the Lense-Thirring effect. Hypothetically, this would influence particularly close stars like S301. Prior to the star’s discovery, astronomers estimated that it would take decades of examining multiple other stars to finally measure a black hole’s spin. S301 could shorten that window down to a single decade.
“For the first time, we would actually be able to measure very directly the spin of a massive black hole, which would be a key test of Einstein’s theory,” said MPE astronomer and study co-author Stefan Gillessen.
“That would be a dream come true,” added Mang.
The post A star spinning at 15,000 miles per second tests Einstein theory of relativity appeared first on Popular Science.