NOEL KING, HOST:
If you go outside and look up at the sky this month, you're going to see something pretty special.
EMILY LAKDAWALLA: You cannot help but notice these incredibly bright stars. And every night, you can go outside, and you can see them getting closer and closer. And just a couple days before Christmas, they'll kiss. And then they'll wander apart again.
KING: That's planetary geologist Emily Lakdawalla. She's describing a phenomenon that's known as the Christmas star.
DAVID GREENE, HOST:
The Christmas star, even though we're not talking about a star or two stars, it's actually two planets, Jupiter and Saturn, closely aligning in the sky. Astronomers call this a conjunction. And this year, its peak will come on December 21st. Jupiter and Saturn will appear to be right on top of each other.
KING: Now, this is space we're talking about. It is spacious up there. And so Derrick Pitts, the chief astronomer at the Franklin Institute, put it into perspective for us.
DERRICK PITTS: They are nowhere near each other. The separation between the two is something on the order of 400 million miles.
KING: More than four times the distance between the Earth and the sun.
GREENE: Yeah, just that. The two planets have not appeared this close in almost 800 years. The next big conjunction will be a lot sooner, relatively speaking. We'll have another shot at seeing the planets align in March of 2080.
PITTS: That brings up this really interesting awareness of my time in the universe. You have this once-in-a-lifetime chance to see this thing, so you should see it.
KING: So how do you see it? Well, there is some great news.
PITTS: It's, like, dead easy to see this. You don't need binoculars. You'll be astounded how bright this is.
KING: You can start tonight. When the sun goes down, go outside, and look to the southwest.
GREENE: And here's what you'll be seeing. The big, bright light there is Jupiter next to the slightly dimmer Saturn. While you're out there, it might be a good time to reflect.
LAKDAWALLA: I hope that it reminds people that Earth is just one among many planets and that, for better or for worse, all of our problems are confined to this one spot in the universe (laughter). And above our heads, the things just happen without us needing to be responsible for any of it. It just goes on and on.
KING: Emily Lakdawalla - she's a planetary geologist, and she will be watching out for the Christmas star.
(SOUNDBITE OF 369'S "JUST LOOK AT YOU") Transcript provided by NPR, Copyright NPR.