Astronomers have detected the fastest known star in the Milky Way, hurtling around the supermassive black hole at the galaxy’s centre at speeds reaching 25,000 kilometers per second, around 8.5% of the speed of light.
The star, named S301, orbits Sagittarius A* on an incredibly tight 8.7-year journey, approaching the black hole at a distance of just 136 Schwarzschild radii, about 10 times closer than the previous record holder, the well-studied star S2.
The European Southern Observatory’s Very Large Telescope Interferometer in Chile’s Atacama Desert, which combines light from four 8-meter telescopes to achieve unprecedented resolution. S310’s extreme proximity to the black holes makes it uniquely sensitive to the predicted effects of black hole drags spacetime along with it, wrapping the orbits of surrounding stars, a phenomenon known as Lense-Thirring precession.
S301 is believed to have been created somewhere else and dragged into the black hole through the “Hills mechanism” that involves the breaking apart of a binary star system by gravitational forces from the black hole. The very high eccentricity of the orbit, 0.98, favors this theory.
If scientists are able to determine the spin of Sagittarius A* through the S301 orbit, then this will be the first such determination for a quiescent galaxy.
