Astronomers have used NASA's Chandra X-ray Observatory to conduct "supernova archaeology" on the GRO J1655-40 system, which contains a black hole and a companion star. By analyzing X-ray data, scientists have reconstructed the history of a supernova explosion that occurred over a million years ago in this system. This groundbreaking research provides critical insights into the types of stars that collapse to form black holes.
The GRO J1655-40 system initially consisted of two bright stars. The more massive star exhausted its nuclear fuel and exploded as a supernova, leaving behind a black hole. The black hole then began drawing matter from its companion star, forming a rotating disk around it. Some of this material was ejected in powerful winds.
In 2005, Chandra detected specific chemical elements within these winds. By analyzing the X-ray spectra, the team identified 18 different elements. Comparing this data with supernova models, they determined that the exploded star was approximately 25 times the mass of the Sun and contained a significant amount of heavy elements. This "supernova archaeology" offers a rare glimpse into the life and death of massive stars and the formation of black holes.