Comet ISON was burned to death on its maiden voyage around the Sun, scientists say.
The comet, which excited astronomers and the media as it zipped within 730,000 miles of the sun on Thanksgiving Day, was pronounced dead at a scientific conference Tuesday.
Naval Research Lab astronomer Karl Battams, who headed the observing campaign for the comet, said ISON was stretched and pulled by the sun’s powerful gravity. It was also hit with solar radiation. And the icy snowball just fell apart.
Comet ISON was burned to death on its maiden voyage around the Sun
“At this point it seems like there is nothing left,” Karl Battams said at the American Geophysical Union conference in San Francisco.
“Sorry, everyone, Comet ISON is dead. But its memory will live on.”
Astronomers had hoped it would survive because some comets make it past close approaches with the sun. Last year, Comet Lovejoy did.
According to some specialists, Comet ISON appears to have survived a close encounter with the Sun that had threatened to vaporize it.
The remnant could now go on to be visible from Earth in December, but astronomers do not know how bright it might become.
Travelling at more than 200 miles per second, ISON passed 730,000 miles above the sun’s 6,000C surface on Thursday evening. This would have heated the comet to almost 3,000°C, enough to vaporize rock as well as ice.
The hope was that the comet would remain sufficiently bright to be visible with the unaided eye throughout December. However, as ISON sped towards the sun, it faded dramatically from view. This led some experts to assume it had disintegrated.
“I’m not seeing anything that emerged from behind the solar disc. That could be the nail in the coffin,” said astrophysicist Karl Battams, from the Naval Research Laboratory in Washington, during a live broadcast on NASA TV.
Yet, rumors of the comet’s demise may have been greatly exaggerated. Overnight, something following ISON’s orbit re-emerged on the opposite side of the sun. Now it is brightening as it plunges back into deep space.
Comet ISON appears to have survived a close encounter with the Sun that had threatened to vaporize it
“To all intents and purposes it looked like it had gone, and then amazingly this thing appears out the other side,” said Professor Tim O’Brien, associate director of the University of Manchester’s Jodrell Bank observatory.
“What we don’t know is whether the whole thing fell apart and whether the dust that was embedded within the ice is just basically in a big cloud and that is continuing to orbit,” he explained.
“The question is, is it just a cloud of dust … or is there still either one or more remnants of the nucleus.”
The nucleus, a huge lump of rock and ice, was several miles wide on its approach to the sun, and brightened as the sun heated it to create an atmosphere, or coma, of ice and dust which was blown away from the sun to form a tail.
But radiation pressure, extreme heat and gravitational forces could have ripped the comet apart.
If the remnant is a cloud of dust it will rapidly dissipate. If it is solid the sunlight will continue to vaporize its ice, creating a tail that may be visible from Earth.
Astronomers are waiting to see if Comet ISON survives its encounter with the Sun.
Comet ISON will reach its closest approach to the Sun at approximately 18:35 GMT on Thursday.
It has been billed as a potential “comet of the century”, but the Sun’s heat and gravitational tug could destroy it before it has a chance to light up the skies.
Comet ISON came from the Oort Cloud, a mysterious, icy region at the furthest reaches of our Solar System.
It has been hurtling towards the Earth, travelling at more than a million kilometres an hour.
Comet ISON makes final approach to go around the Sun on Thanksgiving Day
Now it is entering the most perilous stage of its epic journey.
ISON will pass the Sun at a distance of just 1.2 million km, effectively grazing its surface.
The Sun’s intense gravitational field produces tidal forces that will also have a major effect on the comet.
Scientists fear it could follow the path of Comet Lovejoy, which broke apart after it passed near the Sun in 2011. Or it could run out of fuel and fizzle out. It is hoped Ison’s large size could protect it.
Astronomers estimate that its nucleus could be several kilometres in diameter, helping it to withstand the solar assault.
If it does remain largely intact, the heat from the Sun will excite the dust and gas in its core, allowing it to blaze a trail across the night skies. But whether it really will be a “comet of the century” is unclear.
There has been some debate already about whether Comet ISON is starting to break up, and telescopes such as the ESA/NASA SOHO Sun-observing satellite will be trained on the star during the approach.