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Comet ISON ComethComet ISON will barrel past Mars next week on its way toward a close encounter with the sun that has had scientists and skywatchers buzzing for a year.
Comet ISON will fly by Mars on Tuesday (Oct. 1), then gear up for a close solar approach that will bring the icy wanderer within 724,000 miles (1.16 million kilometers) of the sun's surface on Nov. 28. If ISON manages to stay in one piece, it could put on a memorable sky show around that time, experts say.
Here's the lowdown on Comet ISON and its journey through the inner solar system, which scientists are already observing with a phalanx of instruments on the ground and in space. [Photos of Comet ISON: A Potentially Great Comet]
FIRST STOP: Comet of the Century? Maybe Not...
'Comet of the century?' Probably notSlide 2 of 17
'Comet of the century?' Probably notISON was tagged as a "comet of the century" candidate almost immediately after its discovery in September 2012, with some forecasts suggesting it could shine as brightly as the full moon in late November and early December.
A spectacular show is certainly possible, experts say. But Comet ISON probably won't live up to the most breathless hype.
"More likely, ISON will be one of the brightest comets in the past several years and, thanks to the global astronomy community, we hope one of the most broadly observed comets in history!" researchers with the NASA-organized Comet ISON Observation Campaign (CIOC) wrote in a recent status update.
NEXT: Comet ISON Isn't HugeSlide 3 of 17
Comet ISON Isn't HugeSlide 4 of 17
Comet ISON Isn't HugeBased on how much dust ISON is shedding, the comet's core is likely between 0.12 miles and 1.2 miles across (0.2 to 2 km), CIOC team members say. Other estimates have placed ISON's nucleus somewhere in the neighborhood of 3 miles (5 km).
So ISON appears to be an average-size comet, or perhaps a bit smaller than average. It's certainly a far cry from giant icy wanderers like the 19-mile-wide (30 km) Comet Hale-Bopp, which lit up Earth's night skies during its pass by the sun in 1997. [Amazing Comet Photos of 2013 by Stargazers]
NEXT: An Inner Solar System NewbieSlide 5 of 17
Newcomer to the Inner Solar SystemSlide 6 of 17
Newcomer to the Inner Solar SystemScientists think ISON is making its first trip to the inner solar system from the huge comet repository known as the Oort Cloud, which lies about 1 light-year from the sun.
This explains some of the uncertainty in the forecasts of ISON's performance. It's difficult to predict how any comet will behave during a close solar passage, experts say, and especially tough to do so for "dynamically new" comets like ISON.
NEXT: Many Eyes Watch Comet ISONSlide 7 of 17
Many Eyes Watch Comet ISONSlide 8 of 17