People often think about archaeology happening deep in jungles or inside ancient pyramids. However, a team of astronomers has shown that they can use stars
X-ray: NASA/CXC/Technion/N. Keshet et al.; Illustration: NASA/CXC/SAO/M. Weiss and the remains they leave behind to conduct a special kind of archaeology in space. Mining data from NASA's Chandra X-ray Observatory, the team of astronomers studied the relics that one star left behind after it exploded. This "supernova archaeology" uncovered important clues about a star that self-destructed – probably more than a million years ago. Today, the system called GRO J1655-40 contains a black hole with nearly seven times the mass of the Sun and a star with about half as much mass. However, this was not always the case. Originally GRO J1655-40 had two shining stars. The more massive of the two stars, however, burned through all of its nuclear fuel and then exploded in what astronomers call a supernova. The debris from the destroyed star then rained onto the companion star in orbit around it, as shown in the artist's concept. This artist's impression shows the effects of the collapse and supernova explosion of a massive star. A black hole (right) was formed in the collapse and debris from the supernova explosion is raining down onto a companion star (left), polluting its atmosphere. CXC/SAO/M. Weiss With its outer layers expelled, including some striking its neighbor, the rest of the exploded star collapsed onto itself and formed the black hole that exists today. The separation between the black hole and its companion would have shrunk over time because of energy being lost from the system, mainly through the production of gravitational waves. When the separation became small enough, the black hole, with its strong gravitational pull, began pulling matter from its companion, wrenching back some of the material its exploded parent star originally deposited. While most of this material sank into the black hole, a small amount of it fell into a disk that orbits around the black hole. Through the…