Feedback
Science

Skywatchers excited as Comet ISON approaches its big day in the sun

As Comet ISON approaches its climactic Thanksgiving swing around the sun, astronomers are getting increasingly excited about the prospects for a memorable show when it comes around the other side.

"It's looking pretty wonderful, to be honest," Naval Research Laboratory astrophysicist Karl Battams, who's part of the NASA Comet ISON Observing Campaign, told NBC News. "It's behaving in terms of its brightness pretty much how we thought it would back in February."

Comet ISON has been sparking stellar expectations ever since its discovery by Russian astronomers in September 2012. But unlike some comet fans, Battams has shied away from predicting it would turn into the "comet of the century." Instead, he favors the saying attributed to veteran comet hunter David Levy: "Comets are like cats; they have tails, and they do precisely what they want."

So far, Comet ISON appears to be doing what Battams and his colleagues want: It's hanging together, and not breaking up as feared. Fresh imagery from NASA's STEREO-A probe shows the comet in one piece — with Comet Encke's tail waving in the solar wind as it approaches its own close encounter.

"There are some really, really nice tail dynamics going on," Battams said.

Even as he gushes over the latest pictures, Battams is keeping that catlike unpredictability of comets in mind — particularly considering that ISON is due to come within only 730,000 miles (1.2 million kilometers) of the sun on Nov. 28. "My opinion this morning is, I'm starting to feel like it's going to survive," Battams said on Friday. "It might actually make it."

If ISON does survive, "I'm feeling comfortable saying that we're going to have a nice night-sky object in December," he said. 

How nice? "It was never going to be the 'comet of the century,'" Battams said. "It'd have to be pretty good to out-comet Comet McNaught."

Comet Lovejoy (formally designated C/2011 W3), which wowed Southern Hemisphere observers in 2011, might be a "good analog" if ISON lives up to Battams' expectations. "It's an educated guess," he said.

ISON is on the verge of being too close to the sun for casual observers to make out in dawn's skies, but seasoned skywatchers are still getting some good shots, as evidenced by the pictures submitted to SpaceWeather.com's comet gallery.

A view from Oregon photographer Richard Lighthill shows ISON as a fuzzy speck with an upturned tail. "The comet had barely cleared the horizon when dawn began to lighten the eastern sky and battle with the moon's light ... so there was little time to do much better than this," Lighthill wrote.

Image: Looking for Comet ISON
It's getting harder to detect Comet ISON as it approaches the sun, but if you have a clear view to a flat eastern horizon, it's worth a try. Start with Saturn and Mercury to locate the comet, preferably using binoculars or a wide-field telescope. On the morning of Nov. 23, ISON is directly to the right of the two planets. It's even closer to the horizon on Nov. 24. For scale, this scene is two or three times as wide as your fist held at arm's length. The size of the comet symbol is exaggerated. Check out SkyandTelescope.com for more finder charts.

Spanish photographer Juan Carlos Casado got more impressive results from his vantage point at the Teide Observatory in the Canary Islands. "ISON was at the limit of naked-eye visibility, but it was an easy target for my SLR camera with a small telephoto lens (85 mm focal length) on a static tripod and 6 seconds of exposure," he told SpaceWeather.com.

"What's really impressing me is how skilled a lot of these observers are getting," Battams said. "I would say probably for a couple of days more there's going to be someone on top of a mountain somewhere who is going to be able to catch images of the comet in dawn skies. But I've got to imagine that on Monday it's probably done."

Then it'll be up to sun-watching satellites to track the comet's progress. At about 12:45 p.m. ET on Thanksgiving Day, the team behind NASA's Solar Dynamics Observatory expects to begin posting near-real-time images and movies of ISON's solar encounter. Those pictures might show the comet crumbling from the gravitational stresses, or flaring up due to the heat.

As a comet-watcher, Battams is hoping for a spectacular sky show after Thanksgiving. But as an astrophysicist, he'll be satisfied whether ISON goes boom or bust.

The Comet ISON Observing Campaign was organized primarily to take advantage of the opportunities afforded by the comet's first visit to the inner solar system. Battams said he's already seeing some unusual behavior in the comet's tail, and the fact that Comets ISON and Encke are rounding the sun during the same time frame adds to the interest. Scientists will be closely watching how the two comets respond differently to solar events over the next few days.

"That's valuable information for building up a 3-D picture of the heliosphere and solar wind structure," Battams said. "For solar physicists, that's a really big deal."

Update for 5 p.m. ET Nov. 22: Here's Battam's updated blog post and animated image showing Comet Encke and Comet ISON as they make their way through the solar wind. Is there a coronal mass ejection heading for the comets? Stay tuned!

Update for 5 p.m. ET Nov. 23: NASA is planning a Google+ Hangout titled "Fire vs. ISON" to monitor the comet's swing around the sun from 1 to 3:30 p.m. ET Nov. 28. See you there?

More about Comet ISON:

For updates on Comet ISON, keep tabs on Space.com, the Comet ISON Observing Campaign, Hubblesite's ISONblog, SpaceWeather.com and the websites for Astronomy Magazine and Sky & Telescope. On Twitter, follow @ISONUpdates, @CometISONnews, @CometISON2013, @SungrazerComets and @Cosmos4u.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.