It was the first time that the displacement of one of the stars orbiting the supermassive black hole in the center of the Milky Way was observed, in a phenomenon that confirms the one defended by Albert Einstein in his Theory of General Relativity. According to ESO's Very Large Telescope (VLT), the orbit of the star has the shape of a rosette and not the shape of an ellipse as predicted in Newton's Theory of Gravitation.
Einstein's General Relativity predicts that the linked orbits of one object around another are not closed, as described in Newtonian Gravitation, but that they move in the direction of the plane of movement. This effect – observed for the first time in the orbit that the planet Mercury describes around the Sun became known as the first evidence in favor of General Relativity.
A century later, the dance led by S2 around Sagitrio A *, registered by the VLT, appears after almost 30 years of observation, so that the complexity of its orbital movement could be fully revealed.
The analysis of the measurements reveals that the S2 moves towards the black hole reaching a proximity of 20 billion km (which corresponds to one hundred and twenty times the distance between the Sun and the Earth), being thus one of the most important stars found in orbit of the massive giant.
At its maximum approach to the black hole, S2 travels through space at a speed of almost 3% of the speed of light, completing one orbit every 16 years, concluded the international team of scientists led by the Max Planck Institute for Extraterrestrial Physics (MPE ), in Germany, which includes collaborators from Germany, France, Portugal – such as Paulo Garcia, researcher at the Center for Astrophysics and Gravitation, in Porto – and ESO, who constitute the GRAVITY project.
According to the analysis, published in the specialty magazineAstronomy & Astrophysics.with this Thursday, most stars and planets have a non-circular orbit and therefore their displacement moves them away and closer to the object they orbit. S2's orbit precesses, which means that the location of the closest point to the supermassive black hole changes with each orbit, such that the next orbit is rotated relatively anteriorly, thus making its path follow the shape of a rosette. General Relativity gives us an accurate forecast of how much the orbit changes and the most recent measurements correspond exactly to theory. This effect, called the Schwarzchild process, had never been measured before in a star orbiting a supermassive black hole.
The study carried out with the help of ESO's VLT also helps scientists better understand what is happening in the vicinity of the supermassive black hole located in the center of the Galaxy, as well as the formation and evolution of supermassive black holes.
With ESO's future Extremely Large Telescope (ELT), the team believes it can observe much more subdued stars in orbits even closer to the supermassive black hole. With ELT, we may be able to capture stars close enough to the black hole to actually feel the rotation, the spin, of this supermassive object, says Andreas Eckart of the University of Cologne, Germany, another of the scientists leading the project. If this happens, astronomers will be able to measure the two quantities, spin and mass, that characterize Sagittarius A * and define the space-time that surrounds it. This would correspond, once again, to testing Relativity but at a completely different level, concludes Eckart.
