Comet ISON probably did not survive Sun skirmish
WASHINGTON - Agence France-Presse
Comet ISON is pictured in this November 19, 2013 handout photo by NASA, taken using a 14-inch telescope located at the Marshall Space Flight Center at 6:10 a.m. EST with a three-minue exposure. REUTERS/Aaron Kingery/MSFCComet ISON seems to have perished in a much too-close encounter with the Sun, leaving only a dust trail that will disappear over time, astronomers said on Friday.
The evidence, however, is not yet confirmed, and some stargazers are holding on to hopes that a small streak satellite images have shown emerging from the flyby may point to an against-the-odds survival.
"We will have to wait a bit to see how this thing behaves in the next couple of days and weeks," according to European Space Agency (ESA) comet expert Gerhard Schwehm, who told AFP it was "not impossible" that a part of the comet's nucleus survived the fiery encounter, but also not likely.
"It looks like the nucleus disintegrated and what you see is basically the... remains," he said.
Dubbed the "Christmas Comet", the icy giant likened to a massive, dirty snowball, skimmed past the Sun at a distance of just 730,000 miles (1.17 million kilometers) around 1830 GMT on Thursday.
It had been estimated that ISON would undergo temperatures of 4,900 degrees Fahrenheit (2,700 Celsius)and lose three million tonnes of its mass per second as it made its journey around the sun.
Most astronomers had predicted the comet, with an estimated diameter of some 0.75 miles (1.2 kilometers), would not survive the flypast.
Several solar observatories watched ISON during its closest approach to the sun, known as perihelion.
The comet became faint while within view of NASA's Solar Terrestrial Relations Observatory, and the joint European Space Agency and NASA's joint Solar and Heliospheric Observatory. NASA's Solar Dynamics Observatory could not see it at all.
"It does seem that comet ISON probably has not survived its journey," Naval Research Laboratory comet scientist Karl Battams said after studying the initial space images.
"I am not seeing anything that emerges from behind the solar disk and that I think could be the nail in the coffin," he told a roundtable organised by the US space agency NASA.
Hours later, images distributed by the American and European space agencies appeared to show a small streak emerging from behind the Sun, along the same trajectory by which the comet had entered.
But astronomers were quick to point out this did not necessarily mean the comet, or even a part of it, had survived.
"I am believing it is a lot of dust, because when it comes out (from behind the Sun), you see the tail and... it is much wider, it's like a fan opening," Schwehm said of the images.
Jacques Crovisier, an astronomer at the Paris Observatory, agreed.
"It is hard to comment without having all the facts. Yes, there is still something there, but in my opinion they are remains -- the tail of the comet that hasn't yet disappeared," he said.
"There doesn't appear to be any cometary activity any more, no more ejection of gas." The tail of a comet is formed when the core of dust and ice heats up and sheds molten material.
ISON has fascinated astronomers since its discovery by a Russian team in September 2012 because it traces its origins to the start of the solar system some 4.5 billion years ago.
Several million years ago, ISON escaped from the Oort cloud, a grouping of debris halfway between the sun and the next closest star.
It had initially been expected to provide one of the greatest celestial shows of the century, streaking brilliantly through the sky towards the end of the year -- hence it's informal name.