ROBERT SIEGEL, HOST:
If you get up early tomorrow morning, bundle up and look at the still, dark sky, you might think that the stars are aligned. Well, actually, it's the planets that are aligned. As long as you're willing to set your alarm for an early start through February 20, you can see five planets in the sky - Jupiter, Mars, Saturn, Venus and Mercury. No telescope required.
JACKIE FAHERTY: I like to think of it as the Academy Awards showing of the planets in the sky. All of them are there, the five that you are able to see with the unaided eye.
SIEGEL: Astronomer Jackie Faherty is a Hubble Fellow at the Carnegie Institution of Washington. Assuming millions of people do this tomorrow morning, which direction should they look in?
FAHERTY: Look to the east - so rising in the east, setting in the west. Jupiter will be high in your sky because Jupiter rises first. Mars will also be pretty high in your sky. Venus and Mercury will be low. Mercury is going to be the hard one to find. It'll be the last one to rise and it'll be closest to the horizon in the east.
SIEGEL: I used the word aligned. I guess alignment really doesn't describe what's happening here.
FAHERTY: I like to think of it as a planetary lineup rather than an alignment because they're not aligned in the sense that you could stick your finger out and along that line of sight, you'd see all of the planets. But you do see them lined up in the sky, meaning you could draw a line between Jupiter and Venus. And that is awesome because that is a leftover of how the solar system formed. It's showing you that the planets are all on the same plane so that they formed in a disk around the sun. So it's actually not just an awesome thing to look in the night sky, but it's also a signature of the formation of the solar system.
SIEGEL: And what is actually happening that we get to see it for this one month?
FAHERTY: All of the planets are orbiting the sun at a different rate. And at this point in time, they're in the same quadrant of the sky. I mean, think about it - there's a lot of sky out there. And this whole event actually begins at 9 p.m. So you've got many hours before sunrise. So on the order of 10, 11, 12 - now I have to do the math.
SIEGEL: That's about eight hours or nine hours.
FAHERTY: Eight hours or so before you get to see Mercury. So it's a slow event with each one of the planets arriving at a separate time. But by the end, what you've got is all of them in a quadrant of the sky that you can see from your point on earth.
SIEGEL: How rare is this?
FAHERTY: Relatively rare. So the last time this happened for us was in 2005. But the next time is going to be in August of this year. And then after that, it's 2018, I think. So it varies because the planets, as they move around the sun, they move at very different rates.
SIEGEL: They'll be up there in the sky before sunrise, but with the moon up there...
FAHERTY: The moon is actually going to be a little guide because often times people are confused which planet is which. But you can use the moon. You can look up when the moon will be passing by your planet. I believe around February 1, it's going to pass Mars. So that if you weren't sure which one Mars was, it's the red one. That's actually the biggest clue. It's quite red.
SIEGEL: (Laughter) Yes, I think we've heard of that.
FAHERTY: OK, the red planet, right. But the moon will pass it.
SIEGEL: How many mornings this month will you be out there early?
FAHERTY: Every morning.
SIEGEL: Every morning.
FAHERTY: I will get up early and go for a run just before sunrise so that I can see a planetary lineup.
SIEGEL: Well, thanks for telling us all what to do early in the morning for the next several weeks.
FAHERTY: Are you going to go see it, Robert?
SIEGEL: Absolutely, my dog and I will be looking for this planetary lineup.
FAHERTY: Make sure you point out to your dog...
SIEGEL: I will.
FAHERTY: ...Which planets are which.
SIEGEL: (Laughter) OK. That's Jackie Faherty, a Hubble Postdoctoral Fellow at the Carnegie Institution of Washington. Thanks for talking with us about the planetary lineup.
FAHERTY: You're welcome. Transcript provided by NPR, Copyright NPR.