Moment of truth on Thanksgiving: Will icy comet survive close encounter with sun?
NASA, Aaron Kingery, Associated Press
CAPE CANAVERAL, Fla. — For months, all eyes in the sky have pointed at the comet that's zooming toward a blisteringly close encounter with the sun.
The moment of truth comes Thursday — Thanksgiving Day.
The sun-grazing Comet ISON, now thought to be less than a mile wide, will either fry and shatter, victim of the sun's incredible power, or endure and quite possibly put on one fabulous celestial show.
Talk about an astronomical cliffhanger.
Even the smartest scientists are reluctant to lay odds.
Should it survive, ISON, pronounced EYE'-sahn, would be visible with the naked eye through December, at least from the Northern Hemisphere. Discernible at times in November with ordinary binoculars and occasionally even just the naked eye, it already has dazzled observers and is considered the most scrutinized comet ever by NASA. But the best is, potentially, yet to come.
Detected just over a year ago, the comet is passing through the inner solar system for the first time. Still fresh, this comet is thought to bear the pristine matter of the beginning of our solar system.
It's believed to be straight from the Oort cloud on the fringes of the solar system, home to countless icy bodies, most notably the frozen balls of dust and gas in orbit around the sun known as comets. For whatever reason, ISON was propelled out of this cloud and drawn toward the heart of the solar system by the sun's intense gravitational pull.
The closer the comet gets to the sun, the faster it gets.
In January, it was clocked at 40,000 mph.
By last Thursday, with just a week to go, it had accelerated to 150,000 mph.
Right around the time many Americans will be feasting on turkey, the comet will zip within 730,000 miles of the sun, less than the actual solar diameter. In other words, another sun wouldn't fit in the missed distance.
By the time ISON slingshots around the sun, it will be moving at a mind-boggling 828,000 mph.
Whether it survives or is torn apart, earthlings have nothing to fear.
The comet will venture no closer to us than about 40 million miles, less than half the distance between Earth and the sun. That closest approach to Earth will occur Dec. 26. Then it will head away in the opposite direction forever, given its anticipated trajectory once it flies by the sun.
ISON is named after the International Scientific Optical Network, used by a pair of Russian astronomers to detect the comet in September last year. But it officially is known as C/2012 S1, a designation indicating when it was discovered.
Take heart: The "C'' means it is not expected here again.
NASA wasted no time jumping on ISON. The space agency's Deep Impact spacecraft observed ISON back in January from a distance of about 500 million miles.
Since then, the observations have stacked up.
Among NASA's space telescopes taking a look: Swift, Hubble, Spitzer, Mars Reconnaissance Orbiter, Solar and Heliospheric Observatory or SOHO, Chandra, Mercury-orbiting Messenger, and the Stereo twin spacecraft.
"Every spacecraft that has a camera, we're turning on it," said John Grunsfeld, NASA's science mission director.
The newly launched Maven spacecraft en route to Mars will gaze at ISON the second week of December, once its ultraviolet instrument is up and running.
"That's well after closest approach to the sun, so we don't whether we'll see a comet, comet bits or the last wisps of comet vapor," the University of Colorado's Nick Schneider, who's in charge of the instrument, said in an email.
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