'Great Comet' could dazzle or could fizzle on Nov. 29


6 photos
Save Story
Leer en español

Estimated read time: 3-4 minutes

This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.

SALT LAKE CITY — A much-anticipated and potentially spectacular comet is nearing the sun, and it's possible all Utahns will have a chance to see it on the morning after Thanksgiving.

The latest observations, however, suggest it may not live up to its promises.

A few months ago, some optimists labeled Comet ISON "the Comet of the Century" or, in the wildest prediction, the most brilliant in human history. But now the question is: Will the "Great Comet" dazzle or simply fizzle?

Not so long ago, some experts predicted it would be brighter than the full moon — so bright it might be visible in the daytime.

Astronomers started backing off those predictions a few months ago as Comet ISON continued its long journey inward to the sun.

"Its brightness was not increasing the way it should be if it was going to be spectacular," said Seth Jarvis, director of Clark Planetarium. "But, nor was it a complete dud."

The icy visitor from the outer Solar System has been an astronomical celebrity for months. It's been featured on the cover of science-oriented publications such as Discover magazine. Space buffs have been drooling over the possibility that the sunrise on the day after Thanksgiving will look like a huge exclamation point. A long comet tail might be bright enough to be visible shooting vertically high into the sky above the rising sun.


Comets are like cats. They have tails. And they do precisely what they want.

–David Levy


That scenario now seems unlikely, at best, as the duller-than-expected comet approaches its rendezvous with the sun.

Comet ISON raised high expectations because it's on its first trip to the sun and thus is bringing plenty of unspoiled ice to the party. It has spent most of its life in the distant Oort Cloud nearly a light year away from the sun, about six trillion miles beyond the orbits of the planets. It's a giant chunk of ice left over from the birth of the Solar System.

"It's been hanging out there, just minding its own business, for 4 and a half billion years," Jarvis said.

ISON Fun Facts
Provided by Seth Jarvis, Clark Planetarium

ISON was discovered in Sept., 2012 by Russia's International Scientific Optical Network (ISON).

Comet ISON's closest passage to the sun will occur on November 28 when it will pass a little more than 700,000 miles above the sun's surface.

Between the sun's heat and gravitational forces, it is still unclear whether or not ISON will survive its encounter with the sun on November 28.

ISON will pass 40 million miles from Earth on December 26. It's the closest we will ever get to this comet.

Comet ISON is not expected to reach naked-eye brightness until around November 6 at the earliest, and may not be observable by the general public until mid-month. Assuming it survives its passage by the sun, it may be visible to the naked eye into early January 2014.

Recent observations indicate that ISON is only expected to reach a maximum brightness of magnitude -3 to -5, roughly as bright as the planet Venus.

If ISON survives its ultra-close passage to the sun, it might put on a show for observers — either as a bright tail rising out of the east that disappears into the dawn, or even, if we're lucky, as a white smudge against the blue sky next to the sun not long after sunrise. Don't look at the sun!

Something knocked the comet loose thousands of years ago. It may have taken a gravitational punch from some passing object or it might have been buffeted by unknown forces. Whatever the cause, ISON has been falling ever since in an extreme elongated orbit that will take it around the sun at a strikingly close distance. In astronomer parlance, it's what's known as a "sungrazer."

"It's not (just) going to pass near the sun," Jarvis said, "It's going to almost hit it."

As it swings around the sun on Thanksgiving Day, the heat of the sun is expected to boil enormous amounts of ice off the comet.

"As all of this ice vaporizes, that's going to release an enormous cloud of gas into space," Jarvis said. "It could be really, really bright. But we don't know right now."

Many will wake up the morning after Thanksgiving with hopes of seeing a spectacular sunrise. Even if the astronomical extravaganza fails to develop, Jarvis says he won't be disappointed because he's still thrilled by Comet ISON's incredible journey.

Jarvis resurrected a famous quote from astronomer David Levy. "Comets are like cats," the famed comet expert once said. "They have tails. And they do precisely what they want."

"We know where the comet will be," Jarvis added, "but we won't know what it's going to do until it's doing it."

Photos

Related stories

Most recent Utah stories

Related topics

Utah
John Hollenhorst

    STAY IN THE KNOW

    Get informative articles and interesting stories delivered to your inbox weekly. Subscribe to the KSL.com Trending 5.
    By subscribing, you acknowledge and agree to KSL.com's Terms of Use and Privacy Policy.

    KSL Weather Forecast