S301 star discovery could reveal Sagittarius A* black hole spin

Astronomers have discovered S301, the fastest star in the Milky Way galaxy. The star orbits the central supermassive black hole, Sagittarius A*, reaching speeds of more than 8% the speed of light, or approximately 56 million miles per hour (25,000 km/s), at its closest approach.

S301 is the closest star to Sagittarius A* discovered to date, lying just 12 astronomical units (AU) from the black hole. Because of its proximity and extreme speed, researchers believe the star can be used to study the influence of warped spacetime in extreme environments. Specifically, astronomers hope the star’s elliptical orbit will reveal the spin of the central black hole for the first time.

The findings were published in the journal Nature on August 19, 2026, following decades of tracking stars orbiting the galactic center.