STEVE INSKEEP, HOST:
This week, while most of us are sitting down to a Thanksgiving meal, astronomers around the world will be working, looking up at an unusual comet passing near the sun. NPR's Geoff Brumfiel has the story of what some are calling the comet of the century.
GEOFF BRUMFIEL, BYLINE: The story of comet ISON started in September of last year, when a pair of astronomers in Russia spotted it out beyond the orbit of Jupiter. Two things stood out right away: First, ISON was really bright. Second, it was going to pass close to the sun and the Earth. That's led to a lot of excitement. The Science Channel even has a documentary in the works.
(SOUNDBITE OF SCIENCE CHANNEL DOCUMENTARY)
UNIDENTIFIED NARRATOR: ISON has arrived. But where does it go from here?
KARL BATTAMS: The media caught wind of it before reasonable astronomers could catch wind of it. And so suddenly, everyone started talking about "the comet of the century."
BRUMFIEL: Karl Battams is a reasonable astrophysicist as the Naval Research Laboratory. Despite the hype, the comet isn't easily visible to most of us. Only a few amateur astronomers have seen it. But for the pros, ISON is interesting on a couple of fronts: It's a chunk of ice and rock from the Oort cloud, a huge field of debris beyond Pluto, filled with leftovers from the solar system's formation.
BATTAMS: It has never been into our solar system before. It's a 4-and-a-half-billion-year-old, frozen chunk of what our solar system was made of. Comet ISON is also a sun-grazing comet, which means it's on an orbit that's going to take it extremely close to the sun and go through the sun's atmosphere.
BRUMFIEL: Using solar-observing spacecraft, Battams hopes to see the comet boil as it passes the sun.
BATTAMS: The surface is going to be vaporizing furiously, and that's going to release a lot of interesting material that hopefully, we can study.
BRUMFIEL: It could yield clues about how our solar system formed. It's all happening on Thanksgiving Day.
BATTAMS: We're going to be roasting a ball of ice while people are roasting their turkeys.
BRUMFIEL: If the comet survives its roasting, it could become easily visible in the December sky. But that's a big if.
BATTAMS: The next week is really, really critical for the comet. The surface is going to be vaporizing furiously. And that's going to release a lot of interesting material that hopefully, we can study.
BRUMFIEL: Even if it can stand the heat, the sun's gravity could rip it to shreds. But Battams is staying positive.
BATTAMS: This morning, my gut is telling me that it's actually going to survive past the sun, in some appreciable form.
BRUMFIEL: It could be a small smudge, or a dramatic streak of fiery ice. For now, Battams is staying away from the comet of the century.
BATTAMS: Comet of the decade - we'd be definitely more comfortable with comet of the decade. And comet of the year, it's nailed it, at this point. (Laughter)
BRUMFIEL: It's anyone's guess just how cool it will be. Battams says comets are like cats: They have tails, and do whatever they want.
Geoff Brumfiel, NPR News.