Lawrence LeBlond for redOrbit.com – Your Universe Online
Hale-Bopp, Haley´s, McNaught. These are just a few of the more well-known modern comets that have blazed across the night sky in our lifetime. Another comet that has been recently discovered could be added to that list next year when it makes a pass by the Sun in late 2013.
The comet, named C/2012 S1 (ISON), is due to come within 1.1 million miles of the Sun on, or around, November 29, 2013. Vitali Nevski and Artyom Novichonok from Russia, made the discovery using the International Scientific Optical Network´s (ISON) telescope, capturing the images of the comet on 21 September with CCD imagery equipment.
The comet could blaze brightly across the heavens when it does arrive, experts believe. But just how brightly is difficult to determine. And there could be a chance the Sun will just boil it away as it passes, just as happened to comet Elenin last year. If it does survive the encounter, experts speculate it could outshine any comet seen in the last hundred years–perhaps even brighter than the full moon. If so, it should be easily visible to the naked eye for about two months, and could even be visible during daylight.
If the predictions hold true, Comet C/2012 S1 will likely be one of the greatest comet encounters in human history, exceedingly outshining the memorable Hale-Bopp of 1997 and Haley´s Comet in 1986. It could even be a much bigger spectacle than the long-awaited Comet Pan-STARRS, which will make a pass in March 2013.
BRIGHTNESS
The only thing that is certain at this point, is that the large cometary body was discovered just beyond the orbit of Jupiter and it´s orbital trajectory will take it close to the sun next year. The comet is currently very faint, but as it approaches the Sun, it will steadily brighten. It will be easily picked up by experienced amateur astronomers with CCD equipment in the coming months, and will be within binocular view by late summer 2013, and eventually by the naked eye in early November. Depending on brightness, the comet should remain visible to the naked eye from early November 2013 to mid-January 2014
“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,” Karl Battams, of the NASA-supported Sungrazer Comet Project, told Spaceweather.com.
However, this outcome is far from certain, noted Battams. “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,” he said.
Writing in a blog for the Planetary Society, astronomer Bill Gray pointed out that the comet´s orbit has been very well constrained, but just how bright it will be is anyone´s guess at the moment–“…estimating comet brightnesses a year ahead of time is about like asking who’s going to win the World Series next year.”
“It could be astonishingly bright, or it could fizzle. I think it was David Levy (co-discoverer of Comet Shoemaker—Levy 9) who said that comets are like cats: they have tails, and do whatever they want to do,” Gray remarked.
COMET ORIGINS
Comets originate from the outer limits of the solar system and are generally composed of icy volatiles such as water, carbon monoxide, carbon dioxide, methane and ammonia. These icy behemoths also contain dust, rocks and any other debris that just happen to be floating around when the Sun evolved. Researchers hypothesize that Comet C/2012 S1 originates from the Oort Cloud, a cloud of frozen comets located about one light year from the Sun possibly containing billions of cometary nuclei that formed during the early days of the solar system when the Sun formed.
“This is quite possibly a ‘new’ comet coming in from the Oort cloud, meaning this could be its first-ever encounter with the sun,” Battams pondered. “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.”
As comets close in on the Sun, the increased solar energy puts stress on the celestial orbiter, causing its frozen volatiles to vaporize, bypassing the liquid phase altogether. Sublimation causes the comet´s gases to erupt, sweeping them back by the solar wind, which forms the tail, the common trait of the comet. Depending on the comet´s chemical elements, the journey past the Sun could make the tail spectacularly impressive.
Of course, this will be dependent on what the exact chemical makeup is and how it formed in deep space. And it is very likely the chemical elements may be just the right mixture that it will cause the comet to erupt, fracture and break apart long before it becomes visible to the naked eye. Or, it may whiz by and release very little material, fizzling any excitement of a spectacular showing.
SUNGRAZER
Due to the comet´s scheduled close inspection of our Sun, it will be, what experts call, a sungrazer. Sungrazers are comets that typically pass within a few million miles of the Sun, with some passing even within a few thousand miles. Famous examples of sungrazers are the Kreutz sungrazers and the Great Comets of 1843 and 1882, as well as the Comet Ikeya-Seki of 1965.
Despite the likelihood of breaking up under the increased solar output of the Sun, there remains a slight chance it could become the brightest comet to scream across the skies in the last hundred years–even brighter than Ikeya-Seki, which dazzled astronomers in 1965.
If it lives up to the hype, it will be far brighter than the last bright visitor, Comet McNaught, which gave earthlings in the Southern Hemisphere a good show in January 2007. But then again, it could peter out like Elenin did in 2011, or more famously, the comet Kohoutek, which failed to live up to predictions in 1973.
“This is a very exciting discovery. The comet looks like it could become a very spectacular sight in the evening sky after sunset from the UK in late November and early December next year,” Robin Scagell, vice-president of the Society for Popular Astronomy, told the Telegraph.
“Our members will be eagerly following it as it makes its first trip around the Sun and hoping to see it shining brilliantly and displaying a magnificent tail as it releases powerful jets of gas and dust,” he added.
DOOMSDAY
The debate over the brightness should not spill over into any concerns over the comet´s projected orbit. Doomsayers often get excited when new comets are discovered and start rumors of collision courses with the Earth, such as what happened with last year´s comet Elenin.
Comet C/2012 S1 will not even come remotely close to Earth. Even on its nearest approach in January 2014, it will be 36 million miles from Earth, according to comet hunters at Remanzacco Observatory in Italy.
Gray said the best bet is to just sit back, relax and enjoy the show. “I’d give it about a 30 percent chance of being exciting, with a 60 percent chance that I’m wrong. In other words, it’ll certainly bear keeping an eye on, but I don’t think anyone can say for sure right now.”
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