Ison: The comet of the century
This amazing photo of Ison was taken by Damian Peach with a 20cm telescope on 15 November
Comet Ison, or some part of it, may have survived its encounter with the Sun, say scientists.
The giant ball of ice and dust was initially declared dead when it failed to re-emerge from behind the star with the expected brightness.
All that could be seen was a dull smudge in space telescope images - its nucleus and tail assumed destroyed.
But recent pictures have indicated a brightening of what may be a small fragment of the comet.
Astronomers admit to being surprised and delighted, but now caution that anything could happen in the coming hours and days.
This remnant of Ison could continue to brighten, or it could simply fizzle out altogether.
The European Space Agency (Esa), too, which had been among the first organisations to call the death of Ison, has had to re-assess the situation. A small part of the nucleus may be intact, its experts say.
There were early doubts when nothing was seen in pictures where Ison should have been (cross)
How much of the once 2km-wide hunk of dirty ice could have survived is impossible to say.
Passing just 1.2 million km above the surface of the Sun would have severely disrupted Ison. Its ices would have vaporized rapidly in temperatures over 2,000C. And the immense gravity of the star would also have pulled and squeezed on the object as it tumbled end over end.
Ison has come from the Oort cloud, a belt of comets on the very edge of the Solar System, where it has been for the last 4.6 billion years.
What makes Ison so special is that it is a "sungrazer". Many comets pass through the Solar System every decade, but very few go through the corona of the Sun. Ison will do just that.
Whatever happens next, comets are going to be a big feature in the news over the next year.
Compiled from various Sources
ESSS Information, Education & Communication (IEC) Committee
November 29, 2013