A newly detected star named S301 is hurtling through the center of the Milky Way at an astounding 25,000 kilometers per second—about 8% of the speed of light—making it the fastest star ever recorded in our galaxy.
Located deep within the galactic center, S301 orbits Sagittarius A*, the supermassive black hole at the heart of the Milky Way. The star completes a full orbit in just 8.7 years along a highly eccentric, lopsided path. At its closest approach, S301 comes within a distance equivalent to just 12 times the gap between the Earth and the Sun, roughly matching the distance from the Sun to Saturn.
This extreme proximity offers astrophysicists an unprecedented opportunity to test Albert Einstein’s general theory of relativity. Einstein predicted that a rotating black hole drags the surrounding framework of spacetime along with it, distorting the trajectories of nearby objects. Because S301 passes so exceptionally close to Sagittarius A*, scientists believe tracking its trajectory will allow them to directly measure the black hole’s spin for the first time—a milestone previously thought to require decades of observations across multiple stars.
Researchers at the Max Planck Institute for Extraterrestrial Physics in Germany tracked S301 using the European Southern Observatory’s Very Large Telescope Interferometer in Chile. By combining data traced back to 2017 with upcoming observations during the star's next close approach in 2031, astronomers hope to determine the black hole's spin within the decade.
Despite its harrowing trajectory, scientists emphasize that S301 will not be swallowed by the black hole. Its orbit remains stable outside the event horizon, offering a front-row seat to the extreme gravitational forces governing the heart of our galaxy.