While you’re shopping, eating, napping, or having to work this holiday season, cast your eyes upward over the next few weeks and you might catch sight of a bonafide deep space dweller. It’s Comet C/2012 S1, better know as ISON. You won’t get another chance to see this visitor, if ISON survives a close pass by the sun on Thanksgiving Day, it’ll streak by earth close enough to see with the naked eye or a small pair of binoculars, on its way to the stars:
Some comets are on long, elliptical orbits dropping them in to the inner solar system before sailing them back out to the depths of space. There, they slow, stop, then fall once again back into the warmth and light. Comet Halley, for example, is on a 75-year orbit that takes it out past Neptune.
But some are more extreme. If they get an extra kick on their way in — perhaps from a collision, or a boost by a planet’s gravity — their elliptical orbit gets turned into an open-ended hyperbola: they have more than enough energy to leave the solar system forever. Once they’re gone, they’re gone.
At it’s peak velocity during its closest dip to the fiery sun’s surface, ISON or its remains will be traveling at a sizzling 225 miles per second. That’s 0.1% of c, where c denotes the speed of light, for you physics fans and wonder junkies.