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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]
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