Astronomers Spot Fastest Star Ever Seen Orbiting Milky Way's Black Hole

The star, designated S301, completes an orbit every 8.7 years, following a highly elongated elliptical path. At its closest approach, it reaches speeds exceeding 15,000 miles per second, nearly 8% of the speed of light, according to the researchers. This makes it the fastest star ever recorded in the galaxy.

The team used the Very Large Telescope in Chile, operated by the European Southern Observatory, to observe the star in infrared light, which can penetrate the dense cosmic dust and gas obscuring the galactic center. Felix Mang, a doctoral student at the Max Planck Institute, first noticed the faint, fast-moving object in the data a few years ago.

Gillessen said the star's speed is less important than its proximity to the black hole. "Thereby we can use the star as a probe to visualize how gravity is acting on space and time," he said. The discovery confirms aspects of Einstein's theory of general relativity, as the star's orbit was calculated using Newton's law with a small relativistic correction.

Erin Kara, an astrophysicist at MIT who was not involved in the study, called the result exciting. She said it could lead to measurements of the black hole's spin in the coming decade, which would be the first such measurement for a quiescent galaxy. This could help explain how the black hole formed and how it influenced the galaxy's evolution.

The black hole at the center of the Milky Way has a mass about four million times that of the Sun. Gillessen said it is "the best laboratory we have" for studying black holes because it is relatively close to Earth. The star's orbit reveals how the black hole warps space and time around it.