If astronomers' early predictions hold true, the holidays next year may hold a glowing gift for stargazers—a superbright comet, just discovered streaking near Saturn.
Even with powerful telescopes, comet 2012 S1 (ISON) is now just a faint glow in the constellation Cancer. But the ball of ice and rocks might become visible to the naked eye for a few months in late 2013 and early 2014—perhaps outshining the moon, astronomers say.
The comet is already remarkably bright, given how far it is from the sun, astronomer Raminder Singh Samra said. What's more, 2012 S1 seems to be following the path of the Great Comet of 1680, considered one of the most spectacular ever seen from Earth.
"If it lives up to expectations, this comet may be one of the brightest in history," said Samra, of the H.R. MacMillan Space Centre in Vancouver, Canada.
So what makes a comet a showstopper? A lot depends on how much gas and dust is blasted off the central core of ice and rocks. The bigger the resulting cloud and tail, the more reflective the body may be.
Because 2012 S1 appears to be fairly large—possibly approaching two miles (three kilometers) wide—and will fly very close to the sun, astronomers have calculated that the comet may shine brighter, though not bigger, than the full moon in the evening sky.
- The comet is larger than most, which gives it the potential to be quite spectacular come next November. Some projections have shown that Comet ISON could reach between -10 to -16magnitude brightness, which has the potential to outshine the full moon (magnitude -13). Its size also gives it the potential to generate very long tails.
- Its orbit will take it very close to the Sun. It should be just 1.8 million kilometres away from the Sun as of November 28 next year, as it swings under the Sun's south pole. If its as bright as predicted, and it maintains its integrity as it approaches, it may end up being visible during the day.
- ISON's orbit is very close to that of The Great Comet of 1680 (C/1680 V1), and ISON will pass by Earth at a distance of 60 million kilometres, just a bit closer than C/1680 V1 (63 million kms). C/1680 V1 is about 4 billion kms away from the Sun right now, so Comet ISON is definitely not the same comet. However, the two comets may very well have been parts of the same larger object at some time in the distant past, which would account for their similar orbits.
- On September 30 next year, Comet ISON's orbital path looks to be lined up straight over Mars' north pole. However, it will miss that direct pass over the red planet by just a matter of a few days, because it doesn't cross over Mars' orbit until October 3. Still, the Curiosity and Opportunity rovers should get a spectacular view of the comet as it passes.
- Comet ISON's orbit is angled to the north of the ecliptic, or 'invariable plane' of the solar system. If you were to view the solar system from the outside, you would see that all the planets orbit in the same plane (or very close to it). The only time Comet ISON is south of this plane of the solar system is from just before it crosses Venus' orbit, until it swings around the sun.
- When Comet ISON first crosses Earth's orbit, on November 1 or 2 next year, it will be 'ahead' of Earth, but after it swings around the Sun and starts to head out again, its path will take it almost directly over the Earth on December 30 or 31, hopefully giving us a rather impressive New Years 2014 display.
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