Comet ISON: Viewing guide for the comet of a lifetime (maybe)
Potential "comet of the century" will be visiting the sun for Thanksgiving Day. There's one last chance to catch this week before it fizzles or makes history.
As always, this Thanksgiving (and Hanukkah) holiday week will be all about food, friends, family, Black Friday shopping -- and one large space snowball's existential journey around the sun that will either annihilate the comet or turn it into a majestic and luminous celestial body for a brief period of time.
On second thought, I don't recall one of those things from last year. That's becauseis on target to make a once-in-a-lifetime trip around the sun on Thanksgiving afternoon. Basically a rock from deep space covered with tons of ice and snow, Comet ISON has been winging its way past Earth and our neighboring planets in recent weeks on a "sungrazing" course with our nearest star.
It will reach its point of "perihelion," where it comes closest to the surface of the sun (within only 730,000 miles) on Thanksgiving afternoon and then whip around the other side of the star and head back in our direction. If ISON survives this closest encounter with the sun, it could become one of the brightest comets seen in recent decades or longer as it passes by on its way back out of the solar system in December.
Or it will be turned to less than smithereens by the awesome amounts of energy being radiated by the sun and never be heard from again, kind of like the Spin Doctors, or Palm.
Either way, it's a good idea to get your Comet ISON viewing plan in order now.
First and last chance?
If you haven't yet seen ISON, which has been visible under the right conditions with a good telescope or set of binoculars for a few weeks now, the last chance to catch a glimpse of it before its solar encounter is probably the morning of November 26 in the predawn sky. NASA says the nucleus of the comet will be below the southeastern horizon (to the right of Saturn and Mercury), but you should be able to spot its tail.
If the comet does break up before it has a chance to make a round trip, this could be your last chance to see what has already been a brilliant comet.
Don't go blind on Turkey Day
After Tuesday, as ISON makes its final approach on the sun, you're going to want to take a holiday break from the sungrazing comet-gazing unless you're a professional astronomer or have always wanted to go blind by starting directly into the sun.
A better plan for Thanksgiving is to gather the family around some sort of connected screen and join NASA's Google+ Hangout "Fire vs. Ison" for live coverage of perihelion and the comet's potential breakup. Sure, football players are fast and strong and also fun to watch, but none of them are near as speedy as ISON, which will reach a top speed of around 845,000 miles per hour on Thursday.
A new light in the holiday sky?
If Comet ISON survives what could be a violent Thanksgiving meeting with the sun, it should reemerge from its shadow and begin to become visible in December. The weeks leading up to Christmas and New Year's Eve could show ISON at its brightest. In the best-case scenario, it could be luminous enough to be seen in daylight skies, rivaling even the Great Comet of 1680, which reportedly had a tail that took up a significant part of the daytime sky in Europe.
By Christmas Day, ISON could be visible above the horizon in North America's nighttime skies all night long before beginning to fade away in January.
All of this is still a lot of educated guesswork, however. Comets are unpredictable by their nature, and this particular sungrazing comet, a newbie direct from the Oort Cloud, is unlike anything seen or studied so close to home in recent decades.