Comet Lovejoy approaches the sun in this filtered image taken by the U.S. Naval Research Laboratory's LASCO instrument aboard NASA's SOHO satellite. (U.S. Naval Research Laboratory)

A small comet survived what astronomers figured would be a sure death when it danced uncomfortably close to the broiling sun.

Comet Lovejoy, which was only discovered a couple of weeks ago, was supposed to melt Thursday night when it came close to where temperatures hit several million degrees. Astronomers had tracked 2,000 other sun-grazing comets make the same suicidal trip. None had ever survived.

But astronomers watching live with NASA telescopes first saw the sun's corona wiggle as Lovejoy went close to the sun. They were then shocked when a bright spot emerged on the sun's other side. Lovejoy lived.

"I was delighted when I saw it go into the sun and I was astounded when I saw something re-emerge," said U.S. Navy solar researcher Karl Battams.

Lovejoy didn't exactly come out of its hellish adventure unscathed. Only 10 per cent of the comet — which was probably millions of tons — survived the encounter, said W. Dean Pesnell, project scientist for NASA's Solar Dynamics Observatory, which tracked Lovejoy's death-defying plunge.

And the comet lost something pretty important: its tail.

"It looks like the tail broke off and is stuck" in the sun's magnetic field, Pesnell said.

Comets circle the sun and sometimes get too close. Lovejoy came within 121,000 kilometres of the sun's surface, Battams said. For a small object often described as a dirty snowball comprised of ice and dust, that brush with the sun should have been fatal.

Astronomers say it probably didn't melt completely because the comet was larger than they thought.

The frozen comet was evaporating as it made the trip toward the sun, "just like you're sweating on a hot day," Pesnell said.

"It's like an ice cube going by a barbecue grill," he said.

Pesnell said the comet, although only discovered at the end of November by an Australian observer, probably is related to a comet that came by Earth on the way to the sun in 1106.

As Comet Lovejoy makes its big circle through the solar system, it will be another 800 or 900 years before it nears the sun again, astronomers say.