ISON: Icarus revisited?

At roughly 4.5 billion years of age, it's perhaps unfair to liken the comet ISON to the world's first overambitious mythical pilot, Icarus.

Still, it seemed the ancient orb had met a similar fate to Daedalus' foolish young son on Thursday evening - albeit without having a choice in the matter - as its flight path took it perilously close to the sun.

"Like Icarus, #comet #ISON may have flown too close to the sun," NASA said on Twitter, albeit also saying "we will continue to learn."

According to the European Space Agency, ISON was to fly within 1.2 million kilometers (750,000 miles) of the sun, a distance so small by space's standards that it's referred to as "grazing" our nearest star. To put the distance in perspective, it would have taken light from the sun bewteen 4 and 5 seconds to reach ISON, while sunlight takes around 8 minutes and 20 seconds to reach Earth.

'Something' re-emerges

Astronomer Phil Plait, who pens the Bad Astronomy blog for Slate, later said that NASA's Solar and Heliospheric Observatory (SOHO) - a sun-obseving spacecraft - captured images showing that "something" had survived the solar flyover.

"So comet C/2012 S1 (ISON) has passed the sun, but not without cost," Plait's late-night post began. "At some point previous to the rendezvous something happened to the nucleus (the solid part) of the comet, and by the time it made its final approached it clearly was not doing well. The normally compact head of the comet got smeared out, a pretty good sign the nucleus has disintegrated."

Plait said that on first analysis of the images after ISON passed the sun, what remained visible "looks like debris to me, or at best a very small and pale reflection of the splendor of what ISON was."

Similarly, the European Space Agency wrote on Twitter that "Our #SOHO scientists have confirmed, comet #ISON is gone."

The news of ISON's apparent demise was liable to disappoint many around the world, as the comet was scheduled to become visible from earth this coming Sunday.

First spotted in 2012, the comet grazed the sun after some 5 million years of flight through the inner solar system. It's named after the Russian International Scientific Optical Network telescope through which it was first observed.

It hailed from a family of comets that usually reside in the Oort Cloud - a vast area outside the inner solar system thought to contain billions, if not trillions, of icy comets. Computer models suggested that ISON was on its first trip to the inner solar system after an event - possibly a collision - changed its course.

The ball of ice, dust and dirt was far larger than the last sun-grazing comet, called "Lovejoy," which fell apart shortly after a similar fly-by two years ago. ISON's size had prompted hopes it might survive the close encounter. Nevertheless, the astronomers' work continued even after Thursday's apparent disappointment.

"Still, there's more observing to do, and of course much more data over which to pore" Phil Plait wrote on his Bad Astronomy site. "We'll learn a lot from this event, I have no doubt."

msh/jm (AP, dpa, Reuters)