London, August 4 : Astrophysicists have determined that bright flares emitted by a retinue of captured stars could detect a black hole ejected from its host galaxy.
When two supermassive black holes collide, one or both may be hurled from the centre of the galaxy. Some such "recoiling" black holes can be detected by their accretion discs of swirling, glowing hot gas.
However, most black holes are stripped of their accretion discs as they are thrown into exile.
Even if they keep their discs, the black holes can consume them within tens of millions of years, leaving nothing behind but a naked, invisible black hole.
According to a report in New Scientist, new calculations by David Merritt at the Rochester Institute of Technology in New York and colleagues show that all recoiling black holes should be followed by a swarm of captured stars, and that some of these stellar escorts will be torn apart by the gravity of the black hole.
These mangled stars should emit bright flares, mainly at X-ray wavelengths but also as ultraviolet and visible light.
These beacons could be used to locate the black holes.