Scientists have identified the fastest-known star S301 near the Milky Way’s centre, moving at over 8% of the speed of light while orbiting the supermassive black hole Sagittarius A*.
The study, published in Nature, says S301 reaches roughly 25,000 kilometres per second and completes an eccentric orbit in about 8.7 years.
At its closest approach, the star comes within about 12 to 24 astronomical units of Sagittarius A*, according to the supplied study summary.
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Astrophysicist Stefan Gillessen said the star’s orbit should remain stable and is not expected to decay soon. Instead, Sagittarius A* pushes S301 onto a slightly different orbit during each close passage, Gillessen said.
Tracking that gradual orbital shift for another decade could allow researchers to directly calculate the black hole’s spin. S301 is estimated to be about 50% more massive than the Sun.
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Sagittarius A* contains roughly four million solar masses and lies about 26,000 light-years from Earth at the centre of the Milky Way.
Because black holes emit no light, their rotation is difficult to measure directly. S301’s changing orbit could provide an indirect method.
