天文学家发现了银河系中速度最快的恒星S301，其最高速度达每秒25,000公里，约为光速的8%。这颗恒星绕银河系中心的超大质量黑洞人马座A*运行，轨道周期为8.7年。人马座A*的质量相当于四百万个太阳，其巨大的引力将S301加速到如此惊人的速度。

S301沿著一条极度拉长的椭圆轨道运行，最近点与黑洞的距离大约相当于土星到太阳的距离。科学家认为S301原本属于一个双星系统，后被人马座A*的潮汐力撕裂，S301被黑洞引力捕获，而其伴星则被高速抛射，很可能已经离开了银河系。

天文学家期望在未来十年内，透过追踪S301轨道的微小偏差来测量人马座A*的自转。根据广义相对论，旋转的黑洞会拖曳周围的时空，这种效应会轻微改变S301的轨道。S301最早于2023年被欧洲南方天文台的GRAVITY仪器探测到，预计将于2031年再次接近黑洞。

Astronomers have identified S301 as the fastest known star in the Milky Way, reaching a peak speed of 25,000 km/s—about 8 percent of the speed of light. It orbits Sagittarius A*, the supermassive black hole at the galactic center with a mass four million times that of the sun, completing one orbit every 8.7 years.

S301 follows a highly elongated orbit, passing as close to the black hole as Saturn is to the sun. Scientists believe it was once part of a binary star system that was torn apart by Sagittarius A*'s tidal forces; S301 was captured by the black hole's gravity while its companion was ejected at high velocity, likely escaping the galaxy entirely.

Over the next decade, astronomers hope to measure the spin of Sagittarius A* by tracking subtle deviations in S301's orbit caused by the frame-dragging effect predicted by general relativity. First detected in 2023 using ESO's GRAVITY instrument, S301 will make its next close approach to the black hole in 2031, offering a unique opportunity to probe spacetime around a supermassive black hole.