Star’s Strange Orbit Around Black Hole Proves Einstein Right—Again




Albert Einstein’s general theory of relativity has passed another test. Researchers have detected a subtle shift in the orbit of the closest known star to the supermassive black hole at the center of the Milky Way after nearly three decades of monitoring—and the movement precisely matches Einstein’s theory.

The star, known as S2, has a 16-year elliptical orbit. Last year, it came very close to our black hole, Sagittarius A*, passing within 20 billion kilometers of it. If Isaac Newton’s classic description of gravity is correct, S2 should then continue on its previous orbit’s path through space. But it didn’t.




It instead took a slightly diverging path, with the axis of its ellipse shifting slightly, according to research published in Astronomy & Astrophysics by a team using the European Southern Observatory’s Very Large Telescope. As predicted by general relativity, the phenomenon known as Schwarzschild precession would eventually cause S2 to trace out a spirographlike flower pattern in space (as shown in the video above).

The researchers believe that their detailed tracking of S2 will allow them to study how much invisible material, including dark matter and smaller black holes, exists around Sagittarius A*, in addition to another stringent test of relativity. This could help them in understanding how such behemoths grow and evolve.