Artist’s impression of the active galactic nucleus shows the supermassive black hole at the center of the accretion disk sending a narrow high-energy jet of matter into space, perpendicular to the disc in this image by Science Communication Lab in Kiel Germany, released on July 12, 2018. Courtesy DESY, Science Communication Lab

Albert Einstein’s theory of general relativity has passed another test. The result was reported today in the journal Astronomy & Astrophysics.


Researchers have watched a star race past the supermassive black hole at the heart of the Milky Way, verifying that its motion showed the effects of general relativity, as predicted by Albert Einstein.

Einstein’s 100-year-old general theory of relativity predicted that light from stars would be stretched to longer wavelengths by the extreme gravitational field of a black hole, and the star would appear redder, an effect known as gravitational redshift.

Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in the Atacama Desert, Chile, researchers demonstrated that the theory accurately predicted the motion of a star passing through the extreme gravitational field surrounding Sagittarius A*—the supermassive (4 million times that of the Sun) black hole that is thought to reside 26,000 light-years from Earth at the center of the Milky Way.

“The galactic center was our laboratory to test gravity,”

– Odele Straub, an astrophysicist at the Paris Observatory and co-author of the new study, said at an ESO news conference July 26.

The star’s wavelength stretched as it sought to escape the gravitational pull of the supermassive black hole, shifting its appearance from blue to red, according to Odele Straub from the Paris Observatory.

Credit: ESO/L. Calçada/
A simulation showing the orbits of stars extremely close to the supermassive black hole at the Milky Way’s core. The star S2, which orbits every 16 years, passed very close to the black hole in May 2018, letting astronomers examine the extreme effects of relativity.

This is the first time such a deviation from the Newtonian theory of gravity has been observed in a star around a supermassive black hole, the researchers said in the statement.

S2 is one of the stars near the center of the image. Credit: ESO/MPE

Astronomers will continue to observe and study S2 and hope to soon show general relativity’s effect on a small rotation of the star’s orbit as it travels away from the supermassive black hole, the researchers said.

The results of the new research were published online in the journal Astronomy & Astrophysics.