A MARTÍNEZ, HOST:
One morning - a morning just like this one, actually - Bryce Bolin was studying the sky. I mean, it's his job, after all. He is one of the astronomers who discovered something new.
BRYCE BOLIN: We made a detection in the morning during the morning twilight, just before the sun rises, of an object that appeared to be an asteroid. But as time went on, it became apparent that it was a comet and coming from a very far, very distant place in the solar system.
STEVE INSKEEP, HOST:
A comet is a giant rock that hurtles through space. It differs from an asteroid because it gives off what seems like a tail, shedding dust and ice that reflect the light of the sun. Bolin says nobody had ever recorded this comet before. Astronomers think it only passes by Earth every 50,000 years. So the last time it passed, nobody would have had a telescope or a piece of paper to take a note.
MARTÍNEZ: It's nicknamed the green comet because of its verdant glow. And you may be able to see it while it's in the neighborhood-ish. I mean, it's getting to within 26 million miles from Earth.
MIKE KELLEY: It's a frozen leftover from the early solar system.
INSKEEP: Mike Kelley is an astronomer at the University of Maryland.
KELLEY: It's made out of ices and dust, and they formed with the planets and with the early sun. They're time capsules from that period of time, which is 4 1/2 billion years ago. So they give us a great opportunity to understand what our solar system was made out of.
MARTÍNEZ: Now, the best way to see the comet will be to get away from the city lights and look north. Kelley recommends using binoculars or a telescope, although you may be able to see it with the naked eye.
KELLEY: It's one thing to see a picture on the internet, but to see it for yourself, however impressive or unimpressive it may be, it's still its - it's its own experience.
INSKEEP: If you see it, you will glimpse something that has not come this close to Earth since the Stone Age. I got a kid asking to go out of town and see it. They heard about this ancient rock through a post on Instagram, which also was not available the last time it passed. Transcript provided by NPR, Copyright NPR.