Pretty much every major telescope in the world is gearing up to witness a meeting that has been scheduled since long before humans walked the Earth. Around Thanksgiving, Comet ISON, a mountain-sized chunk of primordial solar system, will approach within 2 million kilometers of the sun and either fall apart or slingshot back into deep space. Astronomers aren’t sure yet how much of a spectacle ISON will be for earthbound observers, but from their vantage point the comet is already providing a brief, unprecedented glimpse into what the solar system was like in its infancy.
“It’s the sort of thing I’ve been waiting for my whole career,” says Matthew Knight, a comet researcher with the Lowell Observatory in Flagstaff, Ariz.