Astronomers are monitoring a newly discovered comet, which is expected to put on a spectacular sky show next year, becoming visible with the unaided eye.

The celestial visitor, named C/2012S1 (ISON), was detected beyond the orbit of Jupiter last week, and will make its closest approach to the Sun in late November 2013.

The comet was discovered by astronomers Vitali Nevski and Artyom Novichonok using the International Scientific Optical Network at the Kislovodsk Observatory in Russia.

Scientists have confirmed that the comet will pass about 1.1 million kilometres above the visible surface of the Sun.

Australian Astronomical Observatory astronomer Malcolm Hartley says it's impossible to tell if the comet will survive such an extremely close encounter.

"Quite often Sun-grazers or Sun-divers simply disintegrate - the head of the comet just evaporates because of the tremendous heat," says Hartley.

"Last Christmas, Comet Lovejoy was expected to be swallowed up when it got too close to the Sun, yet amazingly survived."

"This one's still an unknown, so we'll have to wait and see."

1,000 times brighter than Venus

Astronomers are speculating that C/2012S1 could be one of the brightest comets ever detected, easily visible in the northern hemisphere for several months as it approaches the Sun. Star watchers located south of the equator may only get a glimpse of its tail.

Some reports have suggested the comet could be as bright as magnitude -11 or even -16, making it more than 1000 times brighter than the planet Venus and almost as bright as a full Moon.

"It's an unknown," says Hartley. "It could be a dazzler or a complete washout, that's the problem with comets like this one."

If it survives its close encounter with the Sun, C/2012S1 will pass about 60 million kilometres from Earth on 26 December 2013.

Its orbit suggests C/2012S1 originated in the Oort Cloud, a distant comet repository a quarter of the way to the nearest star. But Hartley speculates that it could have previously passed by the Earth.

"There was a great comet in 1680 with an orbit very similar to this comet," he says. "So there's a faint possibility that it may be this comet [or part of it] coming back."