A near-Earth asteroid tracked since 1998 turned up far from its predicted spot in the sky, and astronomers have now confirmed why — it is secretly a comet, nudged off its path by escaping gas, with a tail too faint for ordinary telescopes to see

Object 1998 SH2 turned up 153 arcseconds from where a gravity-only orbit said it should be. A NASA-led team predicted a hidden comet from that drift alone, then photographed its faint tail with some of the largest telescopes on Earth. The object now carries both an asteroid number and a comet designation.