Researchers at the University of New Hampshire have found evidence of the existence of an elusive type of black hole.UNH researchers used data from three orbiting X-ray telescopes to observe a star in a distant galaxy that was apparently being consumed by a black hole. They were able to measure the mass of the black hole and determined that it was an intermediate-mass black hole, something that has been theorized but not proven to exist. Black holes typically form when very massive stars, several times more massive than the sun, run out of fuel and collapse. The collapsing matter is so dense that nothing, not even light, can escape its gravity, and it becomes a stellar-mass black hole. Small black holes can collide and form larger black holes, which can eventually form supermassive black holes that are millions of times more massive than the sun. Scientists believe supermassive black holes are in the centers of most galaxies, including the Milky Way. Astronomers can see evidence of stellar-mass black holes by observing jets of X-rays being emitted by matter rapidly circling the object. Scientists have also detected gravitational waves created by the collisions of black holes using the Laser Interferometer Gravitational-Wave Observatory, or LIGO. Supermassive black holes can be detected by the way they alter the orbits of nearby stars. The black hole at the center of the Milky Way galaxy has a mass of about 4.3 million times the mass of the sun. But black holes with in-between masses have been difficult to detect. Dacheng Lin, the lead researcher on the UNH study, said observations from NASA's Chandra X-ray Observatory and Swift satellite, along with the European Space Agency's XMM-Newton, provided evidence of this type of black hole. "We feel very lucky to have spotted this object with a significant amount of high-quality data, which helps pinpoint the mass of the black hole and understand the nature of this spectacular event," Lin said. "Earlier research, including our own work, saw similar events, but they were either caught too late or were too far away." In the study, which was published in the journal Nature Astronomy, the researchers with UNH's Space Science Center said the telescopes detected an enormous multiwavelength radiation flare from the outskirts of a distant galaxy. The brightness of the flare decayed over time just like it would if it were a star being devoured by a black hole. Lin said the star was observed being disrupted in October 2003, and the radiation that was created decayed over the course of a decade. The observations were consistent with an intermediate-mass black hole, Lin said. "From the theory of galaxy formation, we expect a lot of wandering intermediate-mass black holes in star clusters," Lin said. "But there are very, very few that we know of, because they are normally unbelievably quiet and very hard to detect, and energy bursts from encountering stars being shredded happen so rarely." The researchers believe that their discovery implies that there could be many intermediate-mass black holes in nearby galaxies that have gone undetected because they aren't in the process of consuming nearby stars.