Comet ISON — once touted as the “comet of the century” — fizzled out during its swing around the sun, leaving behind what scientists said was a trail of dust that continued rolling through space.
“It does seem that Comet ISON probably hasn’t survived this journey,” Karl Battams, an astrophysicist at the Naval Research Laboratory, acknowledged at the end of a NASA-sponsored Google+ Hangout SaveFrom.net that attracted more than 27,000 viewers at its peak.
Battams’ assessment dashed the hopes of millions who were looking forward to a celestial Yuletide treat. Satellite images appeared to show ISON’s remnants spreading out in an arc around the sun — a phenomenon known as a “headless tail.”
It’s still possible that the initial reports of ISON’s demise were exaggerated. “It is now clear that Comet ISON either survived or did not survive, or… maybe both,” Bruce Betts, director of projects for the Planetary Society, said in a Twitter update. “Hope that clarifies things.”
In a follow-up tweet, Battams said he and his colleagues have observed a couple of thousand sungrazer comets, but “we’ve never seen one behave like ISON.”
Highs and lows
Over the past few days, ISON’s condition had sparked waves of up-and-down speculation: Was it brightening? Fading? Resurging? On Thursday morning, astronomers saw clear signs that the sungrazing comet was getting dimmer as it headed toward peak heating, at an expected minimum distance of 730,000 miles (1.2 million kilometers) and maximum velocity of 850,000 mph (380 kilometers per second).
That suggested that ISON’s nucleus, estimated to have a radius of roughly a kilometer (half a mile), was rapidly shedding ice and dust to feed its multimillion-mile-long tail. Scientists hoped there would still be something left after its closest approach to the sun, known as perihelion — but nothing was detected by NASA’s Solar Dynamics Observatory.
“I’d like to know what happened to our half a mile of material that was going around the sun,” SDO project scientist W. Dean Pesnell of NASA’s Goddard Space Flight Center, said during Thursday’s Hangout. “Now it’s broken up, and I didn’t see anything.”
It was an inglorious and inconclusive end for a “dirty snowball” that scientists say was a fossil relic of the solar system’s formation 4.5 billion years ago. ISON spent much of that time on the solar system’s farthest reaches, in a haze of comets known as the Oort Cloud. A passing star probably perturbed the comet’s orbit enough to send it on a 5.5 million-year journey toward the sun.
For More: http://www.nbcnews.com/science/comet-ison-vanishes-puff-mystery-it-goes-around-sun-2D11670914