Comet Ison Tracker, (Update: Showtime for Comet ISON comes Thanksgiving night, when it makes its closest approach to the sun and will flare brightly-or not. It all depends on how well the comet has survived its inward trip through the solar system, and a slight dimming in its light yesterday has astronomers worried that it might have already begun to break up. ISON is moving fast-in excess of 150,000 mph [240,000 k/h]-but these matters still can’t be rushed. Tonight, we’ll know for sure.)
Every comet that’s ever been spotted is a fugitive on the lam. Comets really have no business visiting the inner solar system at all. They don’t remotely respect the orderly wheels of the orbiting planets – coming in at crazy inclinations and extended ellipses, colliding with any world that gets in their way and sometimes making suicide plunges into the fires of the sun. Where they really belong is out in the Kuiper Belt, a ring of icy, rocky objects that circle the solar system at a maximum distance of 4.6 billion miles (7.4 billion km), or in the vastly larger Oort Cloud, which stretches more than 5 trillion miles (8 trillion km) into deep space.
But now and again a comet gets jostled or gravitationally perturbed, breaks free and begins the long dive inward. Sometimes it embarks on a permanent, predictable path, sometimes it’s on a one-way trip and sometimes we just can’t tell – which is one of the things putting a recently discovered comet named ISON in the news.
It was only last year that Russian astronomers Vitali Nevski and Artyom Novichonok spotted the incoming rock, though they were denied the privilege of giving it their name because they were working as part of the International Scientific Optical Network, and the astronomical rules give the name – or acronym – of an umbrella organization precedence. Still, that makes Comet ISON no less real, and made it no less sensational when astronomers announced that it could be what some were describing as “the comet of the century.” What started that kind of buzz is the fact that ISON is a so-called sungrazer, in this case making a close approach to the solar fires of just 1.15 million miles (1.85 million km) on Nov. 28, 2013, and – if it survives that – swinging back out and passing earth at about 40 million miles (64 million km) on Dec. 26.