Mysterious ring of stars guards Andromeda’s heart
The new observations prove conclusively that a supermassive black hole really does lurk at the heart of Andromeda, with a mass 140 million times that of our Sun (Image: R Gendler)The Milky Way's near-twin galaxy, Andromeda, harbours a supermassive black hole at its core that is surrounded by an unexpected and unexplained disc of young stars.
These new observations by the Hubble Space Telescope answer one longstanding mystery: the source of bright blue light very close to the spiral galaxy's central black hole, first spotted using Hubble a decade ago. Yet solving this mystery has immediately created another in its place.
The newly discovered disc is composed of over 400 very hot, young blue stars, orbiting like a planetary system very close to the black hole. That puzzles astronomers because the black hole's intense gravitational field should have torn apart any clouds of matter long before they could coalesce to form new stars.
The stars form a very flat disc that is only one light year across. An elliptical disc of older red stars surrounds it, spanning about five light years. Since the two discs appear to be in the same plane, they are probably related, but no one yet understands how either disc came into being. View an animation of how the two discs of stars might look, in Quicktime, or Mpeg format.
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