Astronomers have discovered the closest, fastest star ever seen orbiting Sagittarius A* (Sgr A*), the 4.3 million-solar-mass black hole at the heart of our galaxy. The faint star, named S301, completes a lap every 8.7 years and skims past the black hole at roughly 55 million mph (90 million km/h) — about 8% the speed of light. Its orbit is so tight that, within about a decade, researchers should be able to measure its spin rate. The discovery was reported Aug. 19 in the journal Nature.
Stars as lanterns in warped space
The center of the Milky Way, some 27,000 light-years away, is one of the best natural laboratories physicists have. A few dozen stars swarm the galaxy's central black hole on tight orbits, and because gravity there is far stronger than anywhere else we can watch closely, those stars behave in ways Isaac Newton never anticipated.
"Stars orbiting Sgr A* are very interesting objects, as they serve as luminous probes of the curved spacetime around the black hole," study co-author
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