[Music] [Music] Using archival data from NASA's decommissioned RXTE X-ray satellite, researchers have discovered a rare type of black hole lurking in M82, a galaxy about 12 million light-years away. Known as M82 X-1, the object is the galaxy's brightest X-ray source. It was long suspected of being an exceptional midsize black hole, too big to be made by a dying star, yet much smaller than the monsters found in the hearts of galaxies, but definitive evidence had never materialized. Now, through careful analysis of RXTE data, astronomers have shown that M82 X-1 weighs in at about 400 times the mass of our sun. Measured masses for black holes formed by stars reach about 25 solar masses, and those found in galaxy centers weigh at least 10,000 times more. Only a handful of black holes have been discovered with inferred masses between these extremes. Astronomers measured M82 X-1 by finding a special signature in its X-ray glow. Hot gas orbiting a black hole emits X-rays. Near the bring of the black hole, various physical effects create hot spots, which produce variations as they orbit. These signals encode important clues to the black hole's mass. One important signal comes in the form of stable pairs with a 3-to-2 relationship, meaning that one flashes three times for every two flashes of the other. In searching through six years of RXTE observations of M82 X-1, astronomers recently found this key signature. One hot spot flashes 5.1 times a second, while the other flickers 3.3 times a second-- a solid 3-to-2 relationship. These signals, combined with other previously variations, pointed to an accurate mass of about 400 suns. With that finding, M82 X-1 now joins the exclusive club of middle-mass black holes. [Music] [Beeping] [Beeping]