The Fastest Star in the Milky Way Will Test Relativity

Astronomers discovered a new star, S301, in the Milky Way's center that is the fastest S-star ever detected. It orbits the supermassive black hole, Sagittarius A*, at a speed of 25,000 kilometers per second and takes 8.7 years to complete its orbit. The star is so close to the black hole that its motion is influenced by its spin, making it an opportunity to test Einstein's General Relativity. The star is also the closest S-star to the SMBH and is positioned at a distance of 12 astronomical units from it. The discovery was made using the GRAVITY instrument on the Very Large Telescope Interferometer and involves a multi-year campaign to track the star's motion. The star's orbit is determined with 19 astrometric positions, outlining an ellipse on the sky. The star's proximity to the SMBH allows researchers to measure the black hole's spin directly, which would be a key test of relativity. The study's lead author is K. Abd El Dayem from the Paris Observatory. The star's formation likely involved a binary system that was disrupted by a Hills instability, leading to its current orbit. The discovery is published in *Nature* and is expected to provide new insights into the behavior of spacetime near a supermassive black hole.

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