Light Behaves Really Strangely Around a Black Hole
Black holes are famous for being inescapable. Within the event horizon of these celestial objects, matter and even light enter and then disappear forever. However, beyond the event horizon, black holes are known to form accretion disks from which light can escape. In fact, this is how astronomers are able to confirm the presence of black holes and determine their properties (i.e. mass, spin rate, etc.) However, according to a recent NASA-funded study led by researchers from the California Institute of Technology (Caltech), there is evidence that not all light emanating from a black hole’s disk simply escapes. According to their observations, some of the light escaping from the disk is pulled back in by the black hole’s gravity and reflected off the disk again. These observations confirm something astronomers have theorized for about forty years. For the sake of their study, which recently appeared in The Astrophysical Journal, the team consulted archival data from NASA’s now-defunct Rossi X-ray Timing Explorer (RXTE) satellite. Specifically, the researchers examined X-ray data from a binary object designated XTE J1550-564, a black hole orbited by a Sun-like star located about 17,000 light-years from Earth. This black hole feeds off material pulled from the star, drawing it into a flat accretion disk that surrounds it and slowly deposits material onto the face of the black hole over time. This material is accelerated by the black hole’s gravity and, in the case of black holes that are actively growing, results in bright X-ray emissions. By examining the X-ray light coming from the black hole’s disk, the team found that as light spiralled in towards the black hole, there were imprints that indicated that some of it was bent back towards the disk and then reflected off of it.