S62 (star)

S62 is a star in the cluster surrounding Sagittarius A* (Sgr A*), the supermassive black hole in the center of the Milky Way. S62 orbits Sgr A* in 9.9 years, the shortest known (as of August 2019) orbital period of any star around Sgr A*. The previous record holder, S55 has a 12.8-year period.

In addition, S62 has a highly eccentric orbit which makes it pass very close to Sgr A*, only 16 AU, less than the distance between Uranus and the Sun. The star therefore passes only about 215 times the Schwarzschild radius of Sgr A* (the Schwarzschild radius of Sgr A* is approximately 0.082 AU, or 12 million km). It is closer to Sgr A* than the previous record, around 45 AU (6.7 billion km, 550 Schwarzschild radii) held by the star S175, and much closer than the better-studied S2 (118 AU, 18 billion km, 1,440 Schwarzschild radii).

S62 passes so close to Sgr A* that its orbit has a very large precession: its orbit shifts by about 10° with each revolution. At closest approach, its velocity is about 0.10c (10% of the speed of light) relative to Sgr A*. S62's most recent approach to Sgr A* was towards the end of 2022.

The discovery of S62 improved the bounds on the mass distribution in the center of the Galactic Center, showing that $4.15$ are concentrated within 16 AU of the center, fully consistent with Sgr A* being a supermassive black hole.