X-shaped radio galaxies may harbour black holes that have 鈥渇lipped鈥� after gobbling up another smaller black hole, according to a new mathematical model.
If the new model is correct, then such black hole mergers may occur as frequently as once a year somewhere in the Universe. This is great news for astronomers hoping to detect the gravity waves that ought to be produced by these titanic events.
Radio galaxies typically produce two jets of radio frequency emissions spewing into space in opposite directions. These are though to emanate from the spin axis of a black hole. But about seven per cent of radio galaxies produce more irregular 鈥渨inged鈥�, or X-shaped, jets.
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David Merritt of Rutgers University realised that a merger between two black holes might explain how some black holes become reoriented. 鈥淚t occurred to me that a fairly easy way to flip a black hole would be a collision with another black hole,鈥� he told 快猫短视频.
Thunderous waves
Merritt calculated the effect of such a merger on the spin of the combined black hole. Together with Ron Ekers of the Australia Telescope National Facility, he found that the modelled transformation matched the distinctive winged emissions of some X-shaped galaxies.
Merritt鈥檚 calculations show that, no matter how rapidly the bigger black hole is spinning initially, its orientation should be substantially changed. And this would hold true even if the smaller black hole has only 20 percent of its mass.
Einstein鈥檚 general theory of relativity predicts that colliding black holes should produce the most thunderous gravity waves. 快猫短视频s hope to detect these with instruments designed to measure the minute changes in the distance between objects caused by the passing of a gravity wave.
鈥淚t is very exciting indeed,鈥� says James Hough, an astrophysicist at Glasgow University, Scotland. 鈥淚t will make detection essentially guaranteed over a timescale of a few years.鈥�
Merritt and Ekers work is not the only new tool to aid astronomers searching for gravity waves. A computer simulation of two black holes merging into one created recently by scientists at the University of Texas and the Theoretical Astrophysics Centre in Copenhagen should provide them with a detailed idea of what type of gravity waves to expect.
Journal reference: Science (DOI:10.1126/science.1074688)