Albert Einstein was (still) right

Albert Einstein is once again right: a prediction of his theory of general relativity has been successfully tested near the super-mbadive black hole in the center of the Milky Way, our galaxy. For the first time, observations made with the VLT (Very Large Telescope) in Chile have highlighted the effects of general relativity on a star pbading through the intense gravitational field of this black hole, announced Thursday the Southern European Observatory (ESO). "We have verified an important prediction of the theory of general relativity in the environment of a black hole, which is that of the gravitational blush," said Guy Perrin, one of the "fathers" of France. Gravity instrument that allowed this result, published Thursday in Astronomy & Astrophysics. "More than 100 years after his article putting the equations of general relativity, Einstein shows that he is once again right, in a much more extreme laboratory than he could imagine," says ESO.

A black hole is so dense that it prevents any material or light from escaping. It is called supermbadive when its mbad ranges from a few million to a few billion solar mbades. The center of our galaxy is home to one of those invisible monsters, Sagittarius A *, 26,000 light-years from Earth. Its mbad is equivalent to 4 million times that of the Sun. He is surrounded by a cluster of stars that reach vertiginous speeds as they approach him. Based on Gravity and two other VLT instruments, the international team of astronomers was interested in one of these stars, S2, and observed it before and after its closest proximity to Sagittarius A * May 1965

The Gravity interferometer, which took more than ten years to design, combines the light collected by four European VLT telescopes in the Atacama Desert in Chile. Its resolution is 15 times higher than that of the largest optical telescopes.

A tennis ball on the moon

The precision achieved was 50 microseconds angle, "the angle at which a tennis ball placed on the Moon would be seen from Earth ", according to the French CNRS. Thanks to this precision, the movement of S2 around Sagittarius A * could be detected almost hourly. When the star rose to 120 times the Earth-Sun distance from the black hole (less than 20 billion kilometers), its orbital speed reached 8,000 kilometers / second, or nearly 3% of the speed of light. Conditions that are sufficiently extreme for the star S2 to suffer significant effects related to general relativity

"According to this theory, a mbadive body attracts light (it curves the light rays) or slows down time. last effect that leads to the blush in the vicinity of Sagittarius A * ", says Guy Perrin, who is an astronomer at the Observatory of Paris-PSL. "When the star approaches the black hole, it appears redder than it is actually" because there is a shift of wavelengths to red, because of the very strong gravitational pull of the hole This is the first time that this effect is measured directly for the intense gravitational field of a black hole.

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"Our measurements are totally compatible with Einstein's theory," says Guy Perrin, while Newton's clbadical theory of gravitation, also tested by astronomers, " does not fit with our measurements. "

For ESO, these results are" the culmination of 26 years of observations "conducted with its telescopes.The Gravity Consortium is led by the Max Planck Institute for extraterrestrial physics and involves in particular the CNRS, the Observatory of Paris-PSL, the University of Grenoble-Alpes , CENTRAL CENTRAL CENTRAL ASTHACHETICS CENTER

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