Both astronomers and the general public have gone abuzz over Comet ISON thanks to a prediction released last October by NASA’s Jet Propulsion Laboratory (JPL) that stated that the comet could reach magnitude -11.6, or about as bright as the Full Moon. Additionally, besides being shadow-casting bright at night, the comet would be bright enough to easily be spotted during broad daylight. Needless to say, this would be the astronomical event of the year should the JPL’s prediction come true.
Problem: the comet has stopped brightening.
Now, even though close approach is still 6 months away and the brighter than the Full Moon prediction is just a prediction, astronomers are preparing for this potentially spellbinding event by keeping a close eye on the comet as it approaches the Sun. Unfortunately, as is being reported by space.com, some astronomers are rather pessimistic about the comet.
If that weren’t enough, writing about the ISON in March, famed comet hunter John Bortle is also very pessimistic about the comet, writing that:
“The much hyped Comet ISON is not evolving in the fashion we had earlier anticipated. Rather than slowly but steadily gaining in brightness it has stagnated at basically near 16th magnitude for a couple of months now. After experiencing an interval where the coma’s degree of condensation grew quite strong, the object threw out an unexpected strong but short tail that has persists right down to today. However, following this episode the coma subsequently faded, became less condensed and smaller, all bad signs regarding the “health” of the comet’s nucleus. Whether ISON becomes a Great Comet next fall, or just another in a long string of Great Flops, is now much more a question than ever before.”
Repeat: Comet ISON is 6 months away and comets are famously unpredictable, which means that things could change at any time. One thing, though, is certain: there is no exact science to forecasting what comets will do, so let’s collectively take this one day at a time.
For an intriguing afterthought, last fall, Bortle, writing for Spaceweather.com (go to the September 25, 2012 archived page), noted that Comet ISON’s path closely parallels that of the great comet of 1680, which was bright enough to be seen during the day, thus implying that he, at the time, thought that ISON could be spectacular so, who knows, things could change again!
When it comes to seeing the comet (if it does get bright), one should start paying attention to the sky in October as Comet ISON nears Earth. By month’s end, it may be a naked eye object. However, the real show will start in November, when the comet makes its closest pass to the Sun, which will take place on November 28 when the comet will pass a mere (in astronomical terms) 732,000 miles from the Sun. Is is this close pass to the Sun, and the resultant melting of the comet that, according to optimistic estimates, push Comet ISON to magnitude -11, or about as bright as the Full Moon.
Okay, comet hunters, here are some key dates to consider:
October 14/15: Comet ISON will pass very near Regulus in Leo
November 18: Comet ISON will be within a degree of Spica
November 23: Comet ISON will pass very near a planetary pair of Mercury and Saturn
November 28: Comet ISON’s closest approach to the Sun, hopefully it will survive and if it does, a spectacular tail (McNaught on steroids) is a very real possibility
Early December: Comet ISON will be visible on both evening and morning skies for mid-Northern observers arnd circumpolar for the far North
December 26: Comet ISOM makes its closest approach to Earth at 39.6 million miles
Even right at discovery, there was wide consensus that the comet would be visible to the naked eye. However, the consensus was not universal, which left the comet with room to be a spectacular cosmic sword like the Great Comet McNaught of 2006-7 or be a barely-visible, tiny, hazy patch of sky. Now, with more time elapsed since discovery, many are predicting that Comet ISON could be the cosmic sight of the decade.
Unfortunately, comets, especially ones making their first solar approach, are famously hard to predict. Making things even harder is the fact that ISON is still 6 months away, which complicates predictions even more.
Some for certain news: for once, this will be a Northern Hemisphere comet!
In the end, thought, the only way we’ll be able to know what Comet ISON will do is to wait and watch..
As the last part of the puzzle, if you plan to do any stargazing, be sure to keep an eye on the Cleveland weather forecast and, for hour-by-hour cloud predictions, the Cleveland Clear Sky Clock. The bad news: at least in the Cleveland area, things are always iffy when it comes to clear skies this time of year. Live somewhere else? Find a clock and see if it will be clear near you.
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