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 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.
Karl Banttam wrote on the Nasa Comet Ison Observing Campaign blog: "It does appear that a least some small fraction of Ison has remained in one piece and is actively releasing material.
"We have no idea how big this nucleus is, if there is indeed one. If there is a nucleus, it is still too soon to tell how long it will survive.
"If it does survive for more than a few days, it is too soon to tell if the comet will be visible in the night sky."
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.
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.
Whatever happens next, comets are going to be a big feature in the news over the next year.
In 11 months' time, Comet Siding Spring will breeze past Mars at a distance of little more than 100,000km. And then in November 2014, the European Space Agency's Rosetta mission will attempt to place a probe on the nucleus of Comet 67P/Churyumov-Gerasimenko.
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 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.
Karl Banttam wrote on the Nasa Comet Ison Observing Campaign blog: "It does appear that a least some small fraction of Ison has remained in one piece and is actively releasing material.
"We have no idea how big this nucleus is, if there is indeed one. If there is a nucleus, it is still too soon to tell how long it will survive.
"If it does survive for more than a few days, it is too soon to tell if the comet will be visible in the night sky."
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.
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.
Whatever happens next, comets are going to be a big feature in the news over the next year.
In 11 months' time, Comet Siding Spring will breeze past Mars at a distance of little more than 100,000km. And then in November 2014, the European Space Agency's Rosetta mission will attempt to place a probe on the nucleus of Comet 67P/Churyumov-Gerasimenko.
