The more they are understood, the more mysterious they become
THE black holes that get the most press these days are the microscopic sort expected to pop out of the Large Hadron Collider in Geneva and, some misguidedly fear, gobble up the Earth in the process. But not every black-hole buff’s gaze has turned to the collider. Plenty of physicists still look to the skies in search for clues to the nature of what is now believed to be as humdrum a cosmic occurrence as stars and planets. Some of what they see poses more questions than it answers.
Apart from the as-yet-unobserved microscopic variety, physicists have spotted numerous telltale signs of black holes that weigh several times the mass of the sun. These are believed to be the remnants of stars that have run out of nuclear fuel and thus collapsed through the pull of their own gravity. There are also signs of the even-more-massive brethren of these star-sized black holes—monsters which are thought to weigh between 100,000 and 50 billion solar masses and found at the centres of galaxies. …



