Nasa has discovered a new black hole in our own galaxy.
The Swift satellite made the find after a rare burst of X-rays from a source near the centre of the Milky Way.
The outburst, known as an X-ray nova, appears suddenly when a massive store of gas suddenly rushes towards a black hole or heavy neutron star, and is swallowed up by its gravitational pull.
It is thought that the stunning burst is so powerful that it could only be the result of a black hole - though this has not been confirmed yet.
"Bright X-ray novae are so rare that they're essentially once-a-mission events and this is the first one Swift has seen," said Neil Gehrels, the mission's principal investigator, at Nasa's Goddard Space Flight Centre.
"This is really something we've been waiting for."
It is thought that the black hole is located about 20-30,000 light years away from our solar system, in the inner regions of the galaxy.
In the night sky it is located close to the constellation Sagittarius and is named Swift J1745-26 after its coordinates.
The black hole must be a member of a low-mass X-ray binary (LMXB) system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.
But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions -- a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.
This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae - where the central object is a white dwarf star - and even bright emission from supermassive black holes in the hearts of distant galaxies.
Swift, launched in November 2004, is managed by scientists at the Goddard Space Flight Centre as well as others in the UK, Italy, Germany and Japan.
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