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 on Thursday.
The sun-grazing Comet ISON, now thought to be less than 1.6km 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 scrutinised 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 64,000km/h.
By last Thursday, with just a week to go, it had accelerated to 240,000km/h.
On Thursday, the comet will zip within 1,175,000km 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 1,332,000km/h.
Whether it survives or is torn apart, earthlings have nothing to fear.
The comet will venture no closer to us than about 64 million kilometres, less than half the distance between Earth and the sun.
That closest approach to Earth will occur December 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 2012. 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.
Share
