Astronomie - Superkomet C-2012 S1 ISON im Anflug


A new comet superstar named C/2012 S1 (ISON) is heading for the spotlight starting in November 2013 — but will it perform as some hope it will, or will it be a dud of cosmic proportions?
"This is one to watch, definitely," said Karl Battams, a scientist at the Naval Research Laboratory who monitors comets for the NASA-supported Sungrazer Comet Project. "But the astronomy community in general tries not to overhype these things. Potentially it will be amazing. Potentially it will be a huge dud."
Comet ISON quickly rose to the top of the charts after its discovery, which was based on imagery collected on Friday by the International Scientific Optical Network's 16-inch (0.4-meter) Santel reflecting telescope in Russia. The comet, which was described in an IAU circular on Monday, takes its common name from the network's acronym. Since the discovery, astronomers have gone back through their files to find "pre-discovery" images and calculate the comet's orbit.
That orbit is due to bring Comet ISON incredibly close to the sun — within just 1.1 million miles (1.8 million kilometers) in late November of next year. As a result, current projections suggest it could get very bright. How bright? Various estimates have set the brightest magnitude at -10 to -16. That suggests the comet could become brighter than the full moon — which led Astronomy Magazine's Michael E. Bakich to say it "probably will become the brightest comet anyone alive has ever seen."
Over the next year, you're going to hear a lot of comparisons to stunners of the past, as long ago as the Great Comet of 1680 and as recent as the Great Comet of 2007. You'll also hear comparisons to past letdowns, ranging from Comet Kohoutek to Comet Elenin. You may also hear a fresh wave of doomsday talk, like the ridiculous rumblings that accompanied Elenin's approach.
Don't believe anything you hear about a comet catastrophe — and don't get your hopes up just yet for a comet extravaganza. But do make plans to keep an eye on the sky in late 2013.
Battams said a lot depends on Comet ISON's composition. "It could turn into a huge letdown if it's a comet that's just too fragile and dissipates as it makes its way into the inner solar system," he told me. That's basically what happened to Comet Elenin. Because ISON appears to be a "new" comet coming in from the far-flung Oort cloud, it's tough to predict how the comet will behave.
The comet is currently in the constellation Cancer, as indicated in this star chart from Astronomy Magazine. When the comet hits prime time, a year from now, it should be heading through the constellation Virgo and visible from northern latitudes before sunrise. Here's a night-sky animation from the Remanzacco Observatory that shows how things are likely to go down. 
During the months ahead, astronomers of all stripes will be keeping a watch on Comet ISON and refining their expectations. "I would imagine that by next summer, we should have a much better handle on it," Battams said.
Geschätzte Sichtbarkeitsgröße bei größter Annäherung (November 2013) und gut sichtbar mit bloßem Auge.
Raumfahrt+Astronomie-Blog von CENAP 0