"The pattern we're seeing is observed in X-ray novae where the central object is a black hole. Once the X-rays fade away, we hope to measure its mass and confirm its black hole status," said Boris Sbarufatti, an astrophysicist at Brera Observatory in Milan, Italy, who currently is working with other Swift team members at Penn State in University Park, Pa.
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.
The Milky way may have quite a few black holes. A February 2012 Mail news story noted:
If the roughly 200 globular clusters in the Milky Way have indeed spawned intermediate-sized black holes, this means that hundreds of them are probably wandering invisibly around the Milky Way, waiting to engulf the nebulae, stars and planets that are unfortunate enough to cross their paths.
Fortunately, the existence of a few rogue black holes in the neighbourhood does not present a major danger.
‘These rogue black holes are extremely unlikely to do any damage to us in the lifetime of the universe,’ Holley-Bockelmann stressed. ‘Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometres. There are far more dangerous things in our neighbourhood!’
Black holes seem to be quite ubiquitous these days, though I never want to see one in our neighborhood.
