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TINY black holes could be eating stars alive and in the process causing gamma-ray bursts, the most violent explosions in the Universe.

Some physicists believe there may be hidden space dimensions that subtly affect gravity’s behaviour. If those dimensions are big enough, it would allow mini black holes to be born when high-energy cosmic rays or neutrinos slam into matter. In theory this could happen in particle accelerators on Earth, such as CERN’s Large Hadron Collider, due to start smashing particles in 2006. The black holes won’t have time to swallow us up though, as they would “evaporate” almost as quickly as they formed, in a hail of energy called Hawking radiation.

However, if a microscopic black hole was formed in a “quark star”, it would grow into a monster, says Peter Gorham of the University of Hawaii in Honolulu. A quark star forms if a star goes supernova and its collapsing core crushes the atomic nuclei so violently that they dissolve into their constituent free quarks. Astronomers finally spotted one of these ultradense objects last month (91av, 20 April, p 12).

If a high-energy cosmic ray or neutrino crashed into such a dense object, the tiny black hole it created would suck in mass much faster than it could lose it as Hawking radiation. The black hole would grow rapidly until it had swallowed the whole star. “It’s a very novel way of making a stellar-mass black hole,” says astronomer David Hough of Trinity University in San Antonio, Texas. The resulting explosion would release a tremendous quantity of energy—easily enough to generate a gamma-ray burst, says Gorham. He and his colleagues have submitted their paper to Physical Review Letters.