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Pluto's New Moons

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Pluto's New Moons

Pluto's New Moons

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
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You're listening to TALK OF THE NATION Science Friday. I'm Ira Flatow. We're going to move ahead and actually move out into space because up next, the neighborhood around Pluto is getting crowded, or actually we're discovering how crowded it really is.

To make crowded is(ph), that's because the Hubble Space Telescope has found two new moons around the distant planet, bringing the total to three. A camera on the telescope got photo proof of the moons, which are creatively labeled P1 and P2. Took those pictures in May and the official announcement came last week in the journal Nature.

Richard Binzel is professor of planetary sciences and the chair of the Program in Planetary Science at MIT in Cambridge. He joins us now to talk about the new moons and a spacecraft on its way to Pluto. He is on the phone from his office in Cambridge. Welcome back to Science Friday, Dr. Binzel.

Dr. RICHARD BINZEL (Professor Planetary Sciences, Massachusetts Institute of Technology): Thank you very much. Good afternoon.

FLATOW: Those were great -- I saw the photos on the Web. That was a great photo of those moons, of Pluto.

Dr. BINZEL: Yes, they're quite astounding. It's a matter of just getting the time and being able to search carefully. And it's always amazing what you find.

FLATOW: Why has it taken us so long to find them?

Dr. BINZEL: Well, there have been searches for the satellites of Pluto from the ground for many years; in fact, going all the way back to its discovery in 1930. And it's just a matter of getting better and better instruments and better and better looks.

And finally we got the time on the Hubble. And we were able to look in close and carefully at the region around Pluto. And there they were. We call them P1 and P2.

FLATOW: And what might they some day be called? Do you have any -- who names them?

Dr. BINZEL: Yes, so these names, P1 and P2, are just their preliminary names. They will get official names from the International Astronomical Union, a governing body of astronomers. And those names might come out this summer.

FLATOW: Give us an idea of the size of those two new moons compared to the one we know about.

Dr. BINZEL: Well, Charon is about 1,200 kilometers, or about 1,000 miles -- I'm sorry, Pluto's about a 1,000 miles across and Charon's about half that. These little guys, P1 and P2, may be about 50 miles across.

FLATOW: Fifty.

Dr. BINZEL: Yes.

FLATOW: They're -- no wonder it took a while to find them.

Dr. BINZEL: Right.

FLATOW: And, you know, the debate about even our own moon, we debated for years how the moon was formed. How do we think these two moons were formed?

Dr. BINZEL: Well, what's interesting about Pluto's large moon, Charon, and these two smaller ones that we call P1 and P2 is that they're all in the same plane. So it's like the same tabletop, if you will. You could make a tabletop or a plane through the orbits of all of these satellites.

And that's probably a clue as to how they formed. You know, it's always been a problem figuring out how the earth moon formed. And the best idea we have is that right after the earth was forming a large body, maybe even the size of Mars, crashed into earth and splashed a lot of material off of the earth that formed the moon. And we're thinking that's the same way that Pluto got its large moon, Charon, that some large body left over from the early formation of the solar system smashed into Pluto and splashed some material off and we got Charon.

And because these other satellites are in the same plane or the same tabletop, orbit plane as Charon, we think that maybe they formed at the same time. That it was just additional material that also formed independent moons at the same time the big moon was formed.

FLATOW: Might there be other undiscovered moons around Pluto?

Dr. BINZEL: Well, it's possible that these guys, P1 and P2, are just the tip of the iceberg because one can always probe faster, deeper, and farther. And the fact that there's these two small guys I think suggests that there could be more.

We certainly haven't finished looking yet.

FLATOW: Why would Pluto have so many little moons? Why would it be its own little solar system there?

Dr. BINZEL: The neat thing about Pluto is that it's so far from the sun that, sort of, the gravitational perdivations(ph) or tweaks or twirks that you might get from the sun itself or from Jupiter. It's a little bit more independent and so it's possible that Pluto can have a little bit more complicated system that we might not otherwise see in close to the sun.

FLATOW: Now, there is a space probe headed on its way to Pluto, correct?

Dr. BINZEL: That's right. We have a mission called New Horizons. It was launched from Florida last January 19th. And we are on our way to Pluto. It's a nine-year flight to get from earth to Pluto, even though we're currently traveling 20 miles a second.

I mean, we're going so fast, at that speed it would take you 10 seconds to go from New York to Washington. But still, even at that kind of velocity, it's going to take us nine years to get all the way out to Pluto.

FLATOW: 1-800-989-8255. 1-800-989-TALK, if you want to dial it that way.

We're talking with Richard Binzel, professor of planetary sciences and chair of the program in planetary science at MIT.

If you want to, I know I'm going to approach this gingerly Dr. Binzel, about this whole debate about Pluto, because a lot of people think, oh this is just something that, you know, is trivial. I mean, does the fact that Pluto has two more moons than we knew about make is any less trivial or add to the fact that maybe we should put it in the camp of being a planet, or does it not matter?

Dr. BINZEL: Well, first of all, I think that the moons make Pluto an even more interesting place than it was before. It's telling us that there's a lot of interesting things that are going around in the whole Pluto system. So I think Pluto's just gotten a lot more exciting and interesting. And I've always thought it was interesting in the first place.

The second thing is Pluto doesn't care what we call it. Pluto's an interesting place no matter what we call it. It's a body that has an atmosphere. It has these moons. We believe it has polar caps. We believe it has seasons. In fact all of the science questions that we're addressing with our spacecraft mission that we're calling New Horizons, all of the science that we're doing on Pluto and the scientific questions that we're asking are the same kinds of scientific questions that we ask about missions that go to Mars, for example. So they're planet questions and its planet science regardless of what you call Pluto.

FLATOW: Speaking of planet science, are you fearful that the budget cuts at NASA, which are happening to the science, the space science programs because of the money that is being funneled towards going, returning to the moon and mars and the space station, are you fearful for those other science projects?

Professor BINZEL: Well it's a, it's always a question of balance. And in my view, the robotic program of NASA has been an outstanding success in terms of the science and the excitement per dollar that comes back. Now that's not to say that we don't need visions in other areas, but I think that one has to make sure that the overall program remains in balance. And I think what's currently proposed, my personal opinion, is that its tweaking the whole system out of balance.

FLATOW: Because then the jewel, you know, right now the jewels of the system are the planetary probes and the Hubbell's and things like that.

Dr. BINZEL: That's right. And its all about the vision and exploration. And its, you have to imagine that the robotic and the human space flight program go hand in hand, that the robotic program lead the way and the human program can eventually follow. And so, we've got to have this be a partnership and a thing that moves forward together, and not be in a situation where we're trying to do one at the expense of the other. This should all move together in a very smooth, uniform way.

FLATOW: Let's see if we can get a phone call or two in here. Kenneth in Cottonwood, Arizona.

Hi Kenneth.

KENNETH (Caller): Hi.

FLATOW: Hi. Go ahead.

KENNETH: Oh yeah, and thanks for taking my call.

Dr. BINZEL: Yes. Hi Kenneth. What can I do for you?

KENNETH: I wanted to talk to you about naming these two moons of Pluto.

Dr. BINZEL: Okay.

KENNETH: I've sent in a few emails to that IAU, but I haven't had any success in getting a return from them.

Dr. BINZEL: Well keep sending or...I'm sure they've been received. The prerogative of the name goes to the discoverers. And while, the way it works is that the discoverers get to choose what names they would like to propose and the IAU is the body that makes the decision. So, you know, so they, it's a process, and I'm sure that getting suggestions into the system are welcome.

But it's the discoverers who will make the formal suggestion to the, or the formal proposals to the IAU, and the IAU will be making its decision. And it can choose what the discoverer's proposed or it can choose whatever they deem is appropriate.

FLATOW: Kenneth, can you share with us what names you proposed?

KENNETH: Yes, the two names I was proposing were Tarterus(ph) and Arabus(ph). And those two are the sections of the underworld in Greek mythology. And since Pluto is already named after Hades(ph) and all that, and Charon(ph), the boatman on the river Styx, I thought that would be, well, for them. Because it's just the two, there.

FLATOW: A natural fit.

Dr. BINZEL: Yes, those are great suggestions.

FLATOW: And Kenneth...

Dr. BINZEL: You're definitely up on your mythology.

KENNETH: Thank you.

FLATOW: (Laughs) Thank you. Have a good weekend.

What, do we know the names that the discoverers proposed for these?

Dr. BINZEL: No, they haven't divulged what they're thinking.

FLATOW: So, we might actually have a winner here?

Dr. BINZEL: I don't know.

FLATOW: (Laughs) 800-989-8255.

Let's go to Ed in Berkeley. Hi Ed.

ED (Caller): Hi! Boy I am so impressed by your last caller! My gosh (laughs). Anyway, I don't want to forget my...

FLATOW: It's a tough, you've got a tough phone call to follow with!

ED: (Laughs) Indeed! But (unintelligible) succeeded. Um, can the moons have moons? I mean, I know they probably don't, but what governs that? How many generations can it go? If our solar, could our solar go around a hugely big sun? I know it goes around the sun in the Milky Way, but how many, you know, there's the center of the Milky Way, then there's our sun, then its our, then it's the moon, could that moon have moons?

Dr. BINZEL: Right. Well it's very interesting, the, maybe the most well known analogy are multiple star systems, where you can have a primary star and then a secondary star, which, where the second one is actually double. And so you can get these multiple systems.

It's probably difficult in the case of Pluto and Charon because, what you need is to have the system be stable against gravitational tugs or perturbations(ph) from other things. And the fact that Charon is so large it probably disturbs, it probably would disturb anything in orbit around P1 and P2.

And in fact, even Charon, in fact I think, even is responsible for placing P1 and P2 where they are because P1, for example, is in an orbit that goes around exactly one time for every six times that Charon goes around. P2 is in an orbit that goes around one time for exactly every four ties that Charon goes around. Charon's closer in, so it goes faster. And these are these little ratios are called resonances. So, it may even be that Charon is driving that the, was even driving the formation or at least maybe nudging these orbits so that when they finally got to these perfect resonance locations that they stayed still and stopped in enabled (unintelligible) sense.

FLATOW: Ed, I hope we made your day.

ED: Well I, I--that is beautiful. And the fact that there is these resonances, that is just, just, just amazing. On what basis would it be? How many generations, like five generations, or could you have twenty generations? I mean, how do you do the, it's the mass of each of these objects?

FLATOW: Yeah, it's amazing. Thank you.

Dr. BINZEL: Yeah, you have, you just to look and see whose gravity dominates and whether something can be stable against all the nudges and tweaks and pulls or perturbations that other things can pull on you. And it, it is indeed a complicated problem, but I think in the case of P1 and P2 they're probably there as solo bodies in this system.

FLATOW: We're talking about Pluto this hour on TALK OF THE NATION Science Friday, from NPR News, with Richard Binzel.

It reminds of that old three-body problem in math and physics.

Dr. BINZEL: That's right, but it...

FLATOW: It made my hair hurt (laughs).

Dr. BINZEL: (Laughs) And once you get more than three bodies in the universe it gets much more complicated. And in the case of the Pluto system we've got four.

FLATOW: Uh, four. Let's see if we can get a quick, last phone call in, from Saundi(ph), in Massachusetts.

Hi Saundi.

SAUNDI (Caller): Hi Professor. I was wondering if you could talk a little bit about Pluto itself and whether it has an atmosphere or not.

Dr. BINZEL: Well Pluto, we think, has an atmosphere of nitrogen and maybe methane, and, you know, it's interesting, Pluto was just closest to the sun in 1989 it reached its closest point called perihelion. And now it's, in another century, Pluto will be at its farthest point. And we think when Pluto warms up that the ices on its surface go into the gas phase and we get this thin atmosphere.

So we have in fact detected an atmosphere on Pluto, we know it s there. And a big question we have that we're hoping to find out when New Horizons gets there in 2015 is whether the atmosphere is still present or whether or whether it is frozen entirely out onto the surface.

FLATOW: We can always hope there is still intelligent life on this planet by the time it gets there, 90 years from now.

Will New Horizons be taking measurements of the solar system as it goes, or does it shut down and wait until it gets to Pluto?

Dr. BINZEL: Well in just about a year, in fact, just under a year from now, we will be arriving at Jupiter, and we're going to use Jupiter as a gravitational boost or a gravitational assist to get us out to Pluto in a little bit faster fashion. And we're going to take science data on Jupiter during our fly-by, and then after Jupiter we're going to go into more or less a quiet phase for the spacecraft. We'll have routine checkouts of the spacecraft, make sure it's happy and healthy, but we'll go into a quiet phase so that we've got everything functioning with the, you know, at full capacity, full capability when we get to our main target; which is of course, the Pluto system.

FLATOW: And what, in the last minute and a half left, what is the thing you want to know most about Pluto, that has to be answered?

Dr. BINZEL: Yep. I think we want to know what it's made of and how its there. It's an entirely different region of the solar system and the ices and all the material that Pluto is made up of, Pluto is the basic building blocks of what formed all of the planets including the earth. And even the very stuff of life. It's all preserved out thee in the outer solar system, and we just want to go out and see what it is firsthand.

FLATOW: Well I want to thank you for taking time to be with us, and good luck to you. We'll be following that mission, I hope, on Science Friday for the next nine years.

Dr. BINZEL: All right. Call us anytime.

FLATOW: Take care. Richard Binzel is professor of planetary sciences, the Margaret McVicar Faculty Fellow Chair, Program in Planetary Science at MIT, in Cambridge.

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