© Painting by Atlas van StolkThe Great Comet of 1680 - Rotterdam
Astronomy forums are buzzing with speculation about
newly-discovered Comet C/2012 S1 (ISON). Currently
located beyond the orbit of Jupiter, Comet ISON is heading for a
very close encounter with the sun next year. In Nov. 2013, it will pass less than 0.012 AU (1.8 million km) from the solar surface. The fierce heating it experiences then could turn the comet into a bright naked-eye object
Much about this comet--and its ultimate fate--remains unknown. "At this stage we're just throwing darts at the board," says Karl Battams of the NASA-supported
Sungrazer Comet Project, who lays out two possibilities:
"In the best case, the comet is big, bright, and skirts the sun next November. It would be extremely bright -- negative magnitudes maybe -- and naked-eye visible for observers in the Northern Hemisphere for at least a couple of months."
"Alternately, comets can and often do fizzle out!
Comet Elenin springs to mind as a recent example, but there are more famous examples of comets that got the astronomy community seriously worked up, only to fizzle. This is quite possibly a 'new' comet coming in from the
Oort cloud, meaning this could be its first-ever encounter with the Sun. If so, with all those
icy volatiles intact and never having been truly stressed (thermally and gravitationally), the comet could well disrupt and dissipate weeks or months before reaching the sun."
"Either of the above scenarios is possible, as is anything in between," Battams says. "There's no doubt that Comet ISON will be closely watched. Because the comet is so far away, however, our knowledge probably won't develop much for at least a few more months."
Meanwhile, noted comet researcher John Bortle has
pointed out a
curious similarity between the orbit of Comet ISON and that of the Great Comet of 1680. "Purely as speculation," he says, "perhaps the two bodies could have been one a few revolutions ago."
This is file-it-away-for-future-reference info:
Comet designations are complex. P/ means a periodic comet, C/ is an unknown periodic or aperiodic comet, X/ are historical where that can't be determined, and D/ are comets that have been lost or were observed to disintegrate. The next four numbers are the year of discovery, after that, a letter indicating what half-month the discovery was (so A is the first half of January, C the first of February, you skip I, and Y is the last half of December) and then a sequence number.
Now, about this particular comet:
Around October 1, the comet is expected to pass close to Mars, and it is possible that one or more of the craft orbiting Mars might catch sight of it. Given the small mass of Mars, the comet's path is not expected to be much perturbed.
There is a lot of speculation about the comet's future, As one might expect, it is all coming from the "dirty snowball" crowd.