S2’s orbit is the epitome of extreme. In 2018, the star will reach the closest part of its 16-year journey around Sagittarius A*, coming as close as 17 light-hours of the black hole’s event horizon. At this point, the star will be traveling 30 million kilometers per hour, that’s 2.5 percent the speed of light. This makes S2 the perfect tracer for astronomers using GRAVITY to measure its position to extreme precision to check whether its motion agrees with predictions set out by Einstein’s general relativity.
The GRAVITY instrument is currently undergoing commissioning at the Very Large Telescope (VLT) Interferometer at the ESO’s Paranal Observatory in Chile and it’s prime mission is to ultimately probe the region immediately surrounding Sagittarius A*, the 4 million solar mass supermassive black hole that lurks in the center of our galaxy, around 25,000 light-years from Earth. This sophisticated instrument collects light from the four main 8.2 meter diameter telescopes of the VLT Interferometer, combining it as one.
The new measurements exclude with high confidence that the central dark mass consists of a cluster of unusual stars or elementary particles, and leave little doubt of the presence of a supermassive black hole at the center of the galaxy in which we live.
The VLT, the interferometer mimics a 130 meter-wide telescope, boosting its collecting power 15 times that of a single operating VLT telescope. And now, with GRAVITY online, astronomers hope to probe the strongest gravity environment known in the universe: the very edge of a black hole’s event horizon.
ESO Press Video eso0226 was produced by the Max-Planck-Society and shows the observed motions of S2 and other stars in this area.
Inferred orbits of 6 stars around supermassive black hole candidate Sagittarius A* at the Milky Way’s center.