An international team has discovered S301, a star that is breaking all records in its orbit around Sagittarius A*, the supermassive black hole at the centre of our Galaxy. It travels at 25,000 km/s – 8 per cent of the speed of light – and comes within just 12 astronomical units of the black hole, roughly the distance between the Sun and Saturn.
This exceptional proximity makes S301 a new laboratory for general relativity. Its orbit could enable the detection of the effect of the black hole’s rotation on space-time and, ultimately, allow for a direct measurement of the rotation of Sagittarius A*. It could then provide a new test of general relativity in one of the most extreme environments in our Galaxy.
This discovery is the result of several decades of technical progress to which LIRA has actively contributed : adaptive optics systems, the development of GRAVITY and subsequently GRAVITY+, new methods of data analysis, and numerical tools for comparing observations with theoretical predictions. These advances now make it possible to detect stars that are ever fainter and ever closer to the black hole.
