Is it possible for a planet to be in orbit around a black hole?
Black holes are typically thought of as destructive forces... but could they allow a planet to orbit without causing harm?
Asked by: Ryan Sullivan, Hertfordshire
There’s no fundamental reason why not: despite their reputation for devouring anything that goes into them, black holes are really just another source of gravity – like a star. As such, they’ll cheerfully allow anything to orbit them if it travels fast enough. For a black hole with the same mass as our Sun, the required speed is the same as that needed to orbit at the same distance from our parent star.
Whether any planets really do orbit black holes is a different matter, however. That’s because black holes of solar mass are usually the remnants of huge stars that run out of nuclear fuel and detonate in a supernova explosion. The chances of any planet remaining intact through such a cataclysmic event seem pretty slim.
That said, in 1992 the very first planets ever discovered beyond our own solar system were found orbiting a pulsar, another form of supernova remnant. Quite how they survived the destruction of their parent star is something of a mystery. One possibility is that they were formed after the supernova, from the debris created by the explosion. So despite the odds, it may just be possible that there are black holes out there with planets orbiting them.
Robert is a science writer and visiting professor of science at Aston University.
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