Hope still for 'dead' Comet Ison

Comet Ison swept in from the bottom-right in this image, and then something brightened just above the Sun

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.

"We've been following this comet for a year now and all the way it has been surprising us and confusing us," said astrophysicist Karl Battams, who operates the US space agency-funded Sungrazing Comets Project.

"It's just typical that right at the end, when we said, 'yes, it has faded out, it's died, we've lost it in the Sun', that a couple of hours later it should pop right back up again," he told BBC News.

The European Space Agency, 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.