Astronomers are crossing their fingers that recently-discovered comet could put on a celestial show of the ages later this year.

If all goes right, Comet ISON could be so bright, it would rival a full moon at night and could even be visible during daylight.

But that is a big "if".

The comet was discovered in September by Russian astronomers Vitali Nevski and Artyom Novichonok, according to NASA. They gave the comet the acronymed-name of their night-sky survey program, the International Scientific Optical Network.

Right now, the comet is near Jupiter but the fact that it is visible to astronomers that far away indicates it's a rather large comet, and it's trajectory indicates when its orbit reaches the sun this autumn, it will graze the sun's outer edges, giving it an extremely bright glow.

Those two factors are what are giving astronomers great hope it will put on a dazzling display as the comet begins its return trip back into outer space.

Even better -- it's on a safe course that will miss Earth, but will pass essentially over Earth's head, meaning it will be above the horizon all night long in the northern hemisphere, NASA said.

A somewhat reasonable comparison of what we could see might be to look at photos of Comet McNaught in 2007 -- you never saw it because it was only in the Southern Hemisphere.

But comets are unpredictable as they are dazzling. Sometimes when comets graze the sun, they explode and break up -- as has happened with a few recent comets that showed some promise. Other times they're predicted brightness turns out to be...less than bright.

Think of it as the astronomical equivalent of a Portland meteorologist looking at a long range forecast model noting a potential arctic outbreak and major snowstorm 5-7 days away. Looks great on paper, but many times, it doesn't pan out as planned.

And those who have been around for a while might remember 40 years ago was a similar comet tagged the "Comet of the Century" in Kohoutek that had been trumpeted with great fanfare, only to fizzle and was barely visible, if at all.

"The actual apparition was such a let-down that Johnny Carson made jokes about it on the Tonight Show," said Don Yeomans with the NASA Near-Earth Object Program. "It fizzled. Comets are notoriously unpredictable."

But at this point, ISON seems to have the size and trajectory that astronomers are at least giving good odds it'll survive its sun encounter.

If all goes according to plan, the comet will begin to be visible in late October, peaking around November 28 when it makes its closest approach to the sun. The comet would remain spectacularly visible through December and into early January 2014.

Of course, here in the Northwest, that is the worst possible time for a comet to make a visit. Had ISON been a year earlier, there was -- get this -- zero officially clear nights reported in all of last November and December at PDX (although 17 of the 61 days had some partial clearing). Maybe we'll get lucky and sneak in a few clear days this next late autumn. Or just head over the other side of the Cascades. It just might be worth the trip if it all pans out.

Here is more information from NASA: