Scientists prove Einstein was right, 105 years after his theory
A star orbiting a supermassive black hole at the heart of the Milky Way has proven Albert Einstein’s general theory of relativity to be right, astronomers have found.
Einstein’s theory, published in 1915, explains gravity as a consequence of the curvature of space-time created by the presence of mass and energy. It has never before been proven in the existence of a star orbiting a supermassive black hole.
But scientists can now confirm that the orbit of the star, called S2, is shaped like a rosette, which is supported by the theory. The star orbits once every 16 years around the supermassive black hole named Sagittarius A* (pronounced A-star), 26,000 light years from the sun.
Einstein’s theory was first evidenced in Earth’s orbit around the sun during an eclipse in 1919 and can also explain the orbit of Mercury, said astronomer Guy Perrin, one of the French lead scientists on the project.
But it has taken more than a century to confirm it in a star orbiting a supermassive black hole.
The findings, published in the journal Astronomy and Astrophysics, are a result of 27 years of observations of the star, including with the European Space Observatory’s Very Large Telescope, located in the
Atacama Desert in Chile.
Perrin said: “It’s hard to test this theory because you have to reproduce the same kind of experiment in the case of supermassive black holes, which are quite distant from us and they’re very tiny. So you need a huge experiment, large telescopes and access to infrared light. Another thing missing 100 years ago was the ability to combine these large telescopes into an interferometer with precision and accuracy. The measurements we made are like being able to see pennies on the moon.”
Supermassive black holes like Sagittarius A* are the largest type of black hole. At its closest, S2 is less than 13 billion miles away from Sagittarius A*, about 120 times the distance between Earth and the sun.
This makes S2 one of the closest stars found in orbit around the supermassive black hole.
As it orbits Sagittarius A* the star follows an ellipse, but as it moves around the supermassive object it creates the shape of a rosette — a Schwarzschild precession.
General relativity provides a precise prediction of how much this orbit changes and, according to the scientists, the measurements from their current research match exactly Einstein’s theory.
Perrin said the study had tried to address two questions: confirmation of his theory and the existence of supermassive black holes, which he said scientists are “quite close” to achieving.
Reinhard Genzel, a director at the Max Planck Institute for Extraterrestrial Physics in Germany and architect of the programme, said: “This observational breakthrough strengthens the evidence that Sagittarius A* must be a supermassive black hole four million times the mass of the sun.”