A Record-Breaking Star
In a groundbreaking discovery, astronomers have located the Milky Way's speediest star, S301, which whizzes around the supermassive black hole Sagittarius A* at the galaxy's core. This star's velocity is an astonishing 25,000 kilometers per second, or 8% of light speed, making it 100,000 times quicker than a commercial jet. S301 completes an orbit in just 8.7 years, reaching as near as 11.5 astronomical units to the black hole, a distance slightly farther than Saturn's from the Sun.[S1][S2][S3]
S301's orbit is uniquely close and elliptical, bringing it nearer to the black hole than any other star. This closeness causes the star to experience the black hole's rotation, a phenomenon predicted by Einstein's theory of general relativity. The theory explains that a rotating black hole pulls spacetime with it, distorting the paths of nearby stars.[S1][S2]
A Window into Black Hole Spin
Scientists have long faced the challenge of directly measuring the spin of Sagittarius A*, a supermassive black hole. The recent discovery of S301, the fastest star in the Milky Way, presents a groundbreaking opportunity. Stefan Gillessen, a senior scientist at the Max Planck Institute for Extraterrestrial Physics (MPE) and co-author of the study in Nature, explains, "This is a significant breakthrough as it allows us to directly measure the spin of a massive black hole, providing a crucial test for Einstein's theory." The star's proximity to Sagittarius A* enables an unprecedented exploration of the black hole's properties and its extreme environment.[S1][S2]
Scientists have calculated S301's path since 2017 and aim to collect sufficient data during its 2031 close approach to determine the black hole's spin within 10 years. They utilized the Very Large Telescope Interferometer of the European Southern Observatory in Chile, merging light from four telescopes to form a high-resolution virtual telescope.[S1][S2][S3]
Origin and Future Observations
S301's peculiar path through space is likely the aftermath of a powerful gravitational event. Astronomer Gillessen theorizes that this star was once part of a binary system that ventured perilously close to the black hole. In a dramatic three-body interaction, the gravitational forces ripped the pair apart, ejecting one star from the galaxy and trapping S301 in a tight orbit around the black hole.[S2][S3]
S301's orbit is secure, despite its close approach to the black hole. It won't cross the event horizon, as its orbit is stable and not decaying, according to Gillessen. The star was discovered in 2023, and ongoing research aims to uncover more details with the aid of future telescopes.[S2][S3]
