Unless you’ve been living in the Oort Cloud you’ve probably heard about the current travels of comet C/2012 S1 (aka ISON) through the inner solar system. Although this soon-to-be “sungrazing” comet was first spotted by astronomers Vitali Nevski (from Belarus) and Artyom Novichonok (Russia) on Sept. 21, 2012, it’s actually been on its way toward the Sun for much, much longer — possibly for the past several million years or so. But on November 28 at 1:38 p.m. EST, as many Americans are sitting down for their Thanksgiving Day dinners here in the U.S., ISON will make its closest pass around the Sun (called perihelion) and, while you won’t be able to see it in the sky at that point (it’s much too close to the Sun right now) our many eyes in the sky will be watching.
There’s been a lot of misinformation passed around the ‘net recently regarding ISON (as seems to be de rigueur whenever something astronomical is occurring) and I can’t stress enough that there’s no reason to be concerned about this comet’s visit. If anything, ISON should be the one worried — there’s still a chance that it won’t survive perihelion intact! In fact, some reports are suggesting that it already has broken up (which as yet has not been confirmed). So to answer some of the most common questions people have been asking about ISON, NASA has shared some video interviews with experts on the subject. Watch them below:
Don Yeomans is a senior research scientist and near-Earth object expert at NASA’s Jet Propulsion Laboratory. (Source)
In another Q&A video, solar physicist Alex Young (check out his website TheSunToday.org) from NASA’s Goddard Space Flight Center talks about ISON and what we can learn from its once-in-a-lifetime visit:
“This is just all-in-all a very exciting and a very unique object.”
– C. Alex Young, Ph. D.
Also, here’s the latest view of ISON as seen by NASA’s STEREO-A , one of two solar-observing spacecraft orbiting the Sun on nearly the opposite side of Earth:
The movie from the spacecraft’s Heliospheric Imager (HI) shows comet ISON, Mercury, the periodic comet Encke (which reached perihelion on Nov. 21) and Earth over a five-day period from Nov. 20 to Nov. 25. The Sun is off frame to the right.
Comets have always been a source of fascination to humans. Once seen to portend inauspicious events, and then thought to be fiery “exhalations” of the atmosphere, they are now known to be icy visitors from the furthest reaches of the solar system… leftovers from the time of planetary formation and containing the same stuff that made up the original protoplanetary disk that once surrounded our Sun. It’s a rare event to have an object like ISON — a large, pristine comet that has never been “heat-treated” by the Sun’s corona — come so near and regardless of whether it becomes a dazzling night-sky object or not, scientists around the world are going to get a great chance to learn more about the history of our solar system.
It will be interesting to see if ISON “pulls a Lovejoy” and reappears from around the Sun! You can have your football games — I’ll be rooting for team ISON on Thursday! 🙂
(Of course, it could also drop an Elenin on us. We’ll just have to wait and see. As the well-known comet hunter David Levy famously said, “Comets are like cats; they have tails, and they do precisely what they want.”)
NASA’s Solar Dynamics Observatory (SDO) will be watching ISON’s pass on Nov. 28 and sharing the images in near-realtime here (which will give you a much better — and safer — view than going outside and trying to look at the Sun yourself) and ESA’s SOHO spacecraft should be getting ISON in view of its LASCO imagers in just a couple of hours.
Spaceweather.com also has a great library of the latest visitor-submitted photos of ISON and other comets taken from all around the world. It’s also a good source for the most recent info. There’s also a Flickr group just for ISON photos.
Check out an infographic of ISON’s visit timeline below, and read more about ISON’s visibility on my friend David Dickinson’s article on Universe Today here.
And as far as after perihelion, the gif below will tell you where in the sky to look for ISON as it (or whatever is left of it) heads back out into space, most likely never again to return. Oh, and sorry, southern hemisphere… ISON is a northern sky object. (Source: Troy Dunham/Huffington Post)
Dave Dickinson also has a detailed viewing guide for after perihelion up on Universe Today as well. (Pending ISON’s survival, of course!)
UPDATE 11/27: as of this morning, ISON has appeared in the field of view of the SOHO spacecraft. Karl Battams of the Naval Research Lab and member of the ISON observing campaign, currently watching the comet from the Kitt Peak Observatory, has posted some answers to common questions regarding ISON and its chances of surviving perihelion. Read more here.
“Comet ISON has started to act like a Sungrazing comet. What does this mean? Well it means that ISON is now in a very near-Sun region of the solar system and is experiencing levels of solar radiation that your average comet is never going to have to deal with. Accordingly, its surface is boiling away furiously, releasing tremendous amounts of ice, dust and gas and brightening up enormously.”
– Karl Battams
Lights in the Dark 
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