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upstart writes in with an IRC submission:

Fastest star ever seen is moving at 8% the speed of light:

In the center of our galaxy, hundreds of stars closely orbit a supermassive black hole. Most of these stars have large enough orbits that their motion is described by Newtonian gravity and Kepler's laws of motion. But a few orbit so closely that their orbits can only be accurately described by Einstein's theory of general relativity. The star with the smallest orbit is known as S62. Its closest approach to the black hole has it moving more than 8% of light speed.

[...] For years, S2 was thought to be the closest star to SgrA*, but then S62 was discovered. As a team recently discovered, it's a star about twice as massive as the sun that orbits the black hole every 10 years. By their calculations, at the closest approach, its speed approaches 8% of the speed of light. That's so fast that time dilation comes into play. An hour at S62 would last about 100 Earth minutes.

Because of its proximity to SgrA*, S62 doesn't follow a Keplerian orbit. Rather than being a simple ellipse, it follows a spirograph motion by which its orbit precesses about 10 degrees with each cycle. This kind of relativistic precession was first observed with the orbit of Mercury, but only as a small effect.

Journal Reference:
Florian Peißker, Andreas Eckart, and Marzieh Parsa. S62 on a 9.9 yr Orbit around SgrA* - IOPscience, The Astrophysical Journal (2020) (DOI: 10.3847/1538-4357/ab5afd)

Original Submission