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A star's rosette-shaped path around a black hole confirms Einstein's theory of gravity. Rather than tracing out a single ellipse (red), its orbit rotates over time (blue, rotation exaggerated in this illustration for emphasis). L. CALÇADA/ESO

Decades of observations revealed the rotation of the star’s elliptical orbit

Emily Conover - ScienceNews

The first sign that Albert Einstein’s theory of gravity was correct has made a repeat appearance, this time near a supermassive black hole.

In 1915, Einstein realized that his newly formulated general theory of relativity explained a weird quirk in the orbit of Mercury. Now, that same effect has been found in a star’s orbit of the enormous black hole at the heart of the Milky Way, researchers with the GRAVITY collaboration report April 16 in Astronomy & Astrophysics.

The star, called S2, is part of a stellar entourage that surrounds the Milky Way’s central black hole. For decades, researchers have tracked S2’s elliptical motion around the black hole. The researchers previously had used observations of S2 to identify a different effect of general relativity, the reddening of the star’s light due to what’s called gravitational redshift (SN: 7/26/18).

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