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Jimmy Westlake: Super comet coming next year?

Many people recall spectacular Comet Hale-Bopp from the spring of 1997, shown in this image taken from Georgia. It is the brightest comet most of us have seen in our lives. If newly discovered Comet ISON lives up to some of the optimistic expectations, it could exceed the brightness of Hale-Bopp by a factor of 4,000, or it could fizzle out as it rounds the sun in November 2013.

This week I have some really exciting celestial news to share. Astronomers have announced the discovery of a new comet that might — and I emphasize might — become the brightest comet seen from the Northern Hemisphere in many decades, if not centuries. It might even be visible in broad daylight. Remember the name: Comet ISON.

The brightest comet that most people alive today likely can remember is Comet Hale-Bopp, which graced our skies in the spring of 1997. It was an amazing naked-eye spectacle that hung in our early evening sky for several weeks before returning to the outer solar system. It won't be back for 25 centuries. Comet ISON might outshine Hale-Bopp by a factor of 4,000.

The Northern Hemisphere missed out on the brightest comet in the past 40 years when Comet McNaught turned south after rounding the sun and gave Southern Hemisphere observers the view of a lifetime in January 2007. Even so, a few wispy tendrils of Comet McNaught's enormous tail managed to extend over our horizon after sunset for a few nights that month. I glimpsed it in the daytime sky beside the noontime sun when it was at its brightest. Comet ISON could outshine Comet McNaught by a factor of 100.

Before that, we have to go back to 1965, when sungrazing Comet Ikeya-Seki became visible next to the sun in broad daylight. It was one of the brightest comets in the past 1,000 years. Comet ISON has the potential to equal or even outshine Comet Ikeya-Seki.

Comet ISON is named for the automated telescope that first photographed it, the International Scientific Optical Network. The humans who first recognized the comet on the robotic telescope's images were Russian amateur astronomers Vital Nevski and Artyom Novichonok. According to the rules of the International Astronomical Union (IAU), which has the authority for naming all things celestial, the comet is named after the automated telescope that first photographed it rather than the two humans who first spotted it in the images. So, we have Comet ISON instead of Comet Nevski-Novichonok. It certainly rolls off the tongue more easily.

Excitement about this discovery grew last week when it became clear that Comet ISON would pass exceptionally close to the sun Nov. 28, 2013, and then swing by the Earth just a few weeks later. As it makes its scorching, hairpin turn around the sun, the icy comet could be visible in daytime skies next to the sun. It will fade somewhat as it recedes from the sun, but it will approach within 4 million miles of Earth shortly thereafter. The potential for an amazing comet spectacle is great, but not certain.

I was a freshman in college when the much-heralded "comet of the century," Comet Kohoutek, was supposed to dazzle sky watchers in January 1974. It failed to live up to the high expectations and its name has become synonymous with the word "dud." Astronomers have been very cautious about hyping new comets ever since.

Here's part of the problem: Comets that approach the sun for the first time apparently are coated with a layer of very volatile ice that quickly boils away while the comet still is far from the sun. This sudden brightening alerts astronomers to the approaching snowball, but as soon as this layer of volatile ice is gone, the comet settles down and sometimes does not become very active. Some do, but some don't. Predicting the behavior of a comet months before it arrives in the inner solar system is dangerous territory. Still, when you consider that this snowball is going to pass a mere 725,000 miles above the solar furnace, you know something wild is going to happen.

We're more than a year away from Comet ISON's visit to the inner solar system. That's a long time to wait to see if it will become the next super comet — or the next Kohoutek. I will try to remain cautiously optimistic and patient during the interim — at least as patient as one can be while awaiting what could be the celestial event of a lifetime.

Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake's astrophotography website at http://www.jwestlake.com.