Comet brightens mysteriously by a factor of a million 22:04 25 October 2007 NewScientist.com news service Maggie McKee A comet usually too faint to be seen with the naked eye has brightened by a factor of a million since Tuesday, suggesting its surface may have cracked open and expelled clouds of dust and gas. Astronomers are scrambling to observe the strange object, which is likely to fade in the coming days and weeks. Comet 17P/Holmes, which orbits the Sun every seven years on a path that takes it from the distance of Jupiter's orbit to about twice that of Earth's,...