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.

Source

Credit: Florian Peißker

The distance of SgrA* stars at closest approach.

Our galaxy's supermassive black hole is known as Sagittarius A* (SgrA*). It is a mass of about 4 million suns, and we know this because of the stars that orbit it. For decades, astronomers have tracked the motion of these stars.

By calculating their orbits, we can determine the mass of SgrA*. In recent years, our observations have become so precise that we can measure more than the black hole's mass. We can test whether our understanding of black holes is accurate.

Source / Image Courtesy

Credit: ESO/M. Kornmesser

A simulation of how S2 moves so fast that it’s redshifted.

Source / Image Courtesy

Credit: Luís Calçada/ESO

Orbital precession of a star near a supermassive black hole.

Source / Image Courtesy

Tour of Sgr A*

At the heart of the Milky Way galaxy, there is a supermassive black hole that has the mass equivalent of some four million Suns.