“Until now, only one star orbiting Sagittarius A *: S0-2 was known, which takes 16.2 years to complete an orbit and whose study has allowed us to establish the mass of the black hole at four million solar masses,” he says. Rainer Schödel, co-author of the research, who works at the Instituto de Astrofísica de Andalucía of the CSIC. Now, thanks to this new finding, we not only know two stars with orbits very close to Sagittarius A *, but we will also be able to verify the theory of General Relativity under extreme gravity conditions “, he adds.
The detection of the star has been possible thanks to un archive of high resolution images obtained by the WM Keck observatoryin the Mauna Kea volcano (Hawaii) over the last 17 years, as well as a new image analysis method developed by Schödel that allows us to detect stars that were previously too faint and went unnoticed. “Thanks to this new technique we have been able to detect S0-102 in an image taken about ten years ago and follow it throughout its orbit”, highlights the CSIC researcher.
General Relativity suggests that the geometry of space-time is not rigid, but that the presence of matter causes it to change and, more specifically, to “bend” in the vicinity of objects. This curvature is the cause of the gravitational effects that govern the movement of bodies, both that of the planets around the Sun and that of galaxy clusters. Supermassive black holes are an ideal environment to verify this effect.
Thestars S0-2 and S0-102 draw elliptical orbits around Sagittarius A *, so that from time to time they are exceptionally close to the black hole. It is believed that, in these circumstances, its movement is affected by the intense curvature of space-time produced by Sagittarius A *, which causes, among other effects, that its orbit does not end up closing, but instead traces an open ellipse.
“Measuring the effects of gravity on stellar orbits is very interesting because gravity is the least known of the four fundamental forces,” says Schödel. The environment of Sagittarius A *, with thousands of stars and stellar remnants, was difficult because the mass of these bodies, undetectable with current telescopes, also contributes to orbit alterations. “In order to untangle the different effects, that of General Relativity and that of the mass around Sagittarius A *, at least two stars were needed with which to measure with high precision”, clarifies the CSIC researcher.
