Planetary Radio: Space Exploration, Astronomy and Science - Voyager 1 at the Edge of the Solar System, With Ed Stone

Episode Date: February 7, 2011

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Voyager 1, at the edge of the solar system, this week on Planetary Radio. Welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. A very full show this week as we bring back Voyager project scientist Ed Stone. He has had that job for 39 years. First, though, we'll jump into the big story from last week with Bill, followed by our visit with Emily Laktawalla. Hey, hey, Bill Nye the Planetary Guy here. This week, the excitement, the crazy new information is from the Kepler mission. Looking at an area of the sky about the size of a grain of salt held at the length of your arm.

And they look at stars to see if the stars get just ever so slightly dimmer. And then brighten again according to Kepler's laws if there were a planet passing between that star and us and the Kepler spacecraft. And sure enough, these guys have found over 1,200 potential planets. Now, they haven't found 1,200 planets, but what seem to be planets. And of those 1,200, 54 of them seem to be in what we like to call the habitable zone, the place near a star where the Earth is, where there might be liquid water. On top of that, five of them are small enough to be about the size of Earth. Oh, but hang on a second. Suppose there's a great big planet that has an Earth-sized moon going around. So what it means is we have discovered dozens or dozens of dozens of worlds

that might be not different from the Earth. They'd be like the Earth. This idea is so cool, everybody. So you've got this spacecraft that has a period around the sun of not 365 and a quarter days, like the Earth has, that's's our year but 371 days so it's trailing the earth as it goes around the sun and that way they can point it at these different stars without having the earth get in the way and every quarter every season they rotate the telescope a quarter of a turn and that helps block out light from the star that might be accidentally absorbed by the telescope.

It's so cool. It's so elegant. If we discover planets that might have water and then convince ourselves that we find some gases or trace gases that might be the kind of gases you'd expect if you had living things there. My friends, it would change the world. It's just a mission that NASA has been working on for a long time, and now it's coming to fruition. It's making astonishing discoveries. I've got to fly. Bill Nye the Planetary Guy. So there is Bill Nye's take on what is truly going to be, I'm sure, remembered as one of the great discoveries or great announcements of 2011. Emily, you're also covering Kepler in the blog.

Mostly I'm covering other people's quite excellent coverage of the Kepler announcements. There are actually a couple of announcements. One was of a six-planet system, and then the other one is just this huge catalog full of 1,200 planets. And that's just for a start. And so I've suggested you read Amir Alexander's write-up on our website, as well as some other people around the Internet. So check the blog for links to excellent stories. Amir has a terrific article at Planetary.org,

and you have in the blog this map of these Kepler planet candidates, which is pretty cool. It's pretty cool, especially when you consider that Kepler is only looking at a very tiny portion of the sky. So you can just imagine repeating this map across the entire sky. And there must be thousands upon thousands of planets hidden where we're not even looking for them. Let's briefly move on to Rosetta. We have a regular listener to the show who is a key member of the Rosetta team. And he was telling me about the scary moments they had just a few days ago. Yeah, this is something you don't want to wish on any mission. Rosetta was in the middle of a really important series of burns.

These weren't just rocket trim firings to sort of fine tune its trajectory. It was in the middle of five really enormous firings of its rockets to line itself up for its final approach to the comet Cherry Gary, which it's not going to get to for a couple of years now. And apparently in the middle of the second large burn, the spacecraft went into safe mode. And, you know, that's not a lot different from what happened on Akatsuki when it was passing by Venus and failed to finish its burn in time to go into orbit around Venus. The difference here is that Rosetta was not in the middle of a gravity assist burn. This was a deep space burn. And so once they recovered the spacecraft, they were also able to recover the ability to do the rocket firings they needed to do

to get back on course. I don't know yet exactly what went wrong with the spacecraft, but they say that everything's fine now and they're on course for the comet. And thank goodness, because that is one heck of a mission, something else to look forward to. And as we look forward, let's talk about your What's Up column for the month, maybe starting with a big event to take place next week. That's right. Stardust is approaching Comet Temple 1. It'll be the first time that a comet's been visited again after a passage through perihelion, which is a big deal. It'll be interesting to see what changes have happened on the comet during the six years that have passed since we last saw it. Of course, Deep Impact is the one that visited it before. And we hope we'll finally get a chance to see the crater that Deep Impact made on the comet six years ago.

Emily, I think that's it for this week. Thanks again for a great report, and we'll talk to you in seven days. All right. Bye, Matt. Emily Lactual is the Science and Technology Coordinator for the Planetary Society and a contributing editor to Sky and Telescope magazine. I'll be right back in conversation with Ed Stone of the Voyager mission. After 33 years of flight, Voyager 1 is on the threshold of interstellar space. Our most distant emissary to the stars is still sending back knowledge After 33 years of flight, Voyager 1 is on the threshold of interstellar space.

Our most distant emissary to the stars is still sending back knowledge about that unexplored territory. Ed Stone has been Voyager project scientist for every one of those years, including a decade as the director of the Jet Propulsion Lab. Now he is the David Morris Rowe Professor of Physics at the California Institute of Technology, where he also serves as Vice Provost of Special Projects. One of those special projects is the TMT, or 30-meter telescope, an international effort that we also talked about in a recent Skype conversation. But we started with the mission he has worked on for nearly four decades.

Ed, I am delighted to have you back on Planetary Radio. Thanks for joining us. You're welcome. We mark another special occasion for something that has been a big part of your life for, what, 39 years now? The Voyagers? That's right, since 1972. Talk about this latest milestone by Voyager 1. Well, Voyager 1 is out at the very edge of the bubble the sun creates around itself. There's a wind, the solar atmosphere expands outward at almost a million

miles per hour, creating a bubble around the sun called the heliosphere. And of course, eventually that wind has to slow down and approach contact with interstellar wind. And what we have now found in the last six months or so is that the wind is no longer moving readily outward, but in fact has turned, because it must turn to flow down the tail of the heliosphere since it can't really invade interstellar space. And you expected this event.

Did it happen about when you expected it? Actually, this is a bit sooner than we expected because the models all tell us that the actual boundary itself where we enter interstellar space may be four years ahead yet. And so it's a little surprising that the wind is already no longer moving outward radially. So our models are clearly not completely accurate, which is not a surprise. We keep learning new things in this mission. And I don't think we yet understand fully what this means as to how much further it is before we reach interstellar space.

How was the rate of deceleration? As I read the press release about this, it sounded like it was surprisingly sudden. Actually, we've been seeing ever since we crossed the termination shock, the termination shock is where the supersonic wind becomes subsonic. It's a sonic shock. And after that, at that point, then the wind can start turning. And we've seen the radial speed of the wind decline almost linearly with time. And so it was pretty clear some months ago or a year ago that we were approaching the time when the wind would, in fact, be no longer moving out radially. And that's exactly what happened.

It's just that it's sooner than the models suggested it would happen. So now, even nearly 11 billion miles out, we still can't actually say Voyager 1 is in true interstellar space? No, it's still surrounded by the wind, which has come from the sun. And we are now in the final outer layer of that wind, where the wind is now moving more or less parallel to the boundary, which is out beyond us. And so we don't know how much further we have to go. It still may be several years ahead. What is the value to science and to our knowledge of maybe not only our solar system, but other star systems or planetary systems, of knowing the structure, how this solar wind behaves out there at the edge?

Well, most stars have spheres around them. We're called astrospheres as a general term. Ours is the heliosphere, after helios, the sun. And we are understanding the physical process by which the wind from a sun interacts with the wind which is outside, which has actually come from the explosion of supernovae five to ten million years ago. And it's that interaction which determines how large this bubble is. And the bubble itself provides some level of shielding, holding out some of the higher energy particles, galactic cosmic particles, which are outside in interstellar space and cannot really come in because of the solar wind.

So is this a bit comparable, although I know the physics are quite different, to the Van Allen belt that protects our own planet? Well, the Van Allen belt is trapped radiation trapped in the Earth's magnetic field. This is actually a mechanism, a barrier, if you like, which is a magnetic barrier created by the outward flow of the solar wind carrying the solar magnetic field with it. And that magnetic field prevents the lower energy and tense cosmic radiation

from actually coming inside the heliosphere. And, of course, the size of the heliosphere is a very important factor in how well it does that. What is the health of the spacecraft? We'll talk about Voyager 1 still for a moment or two, and then we'll get to its sister, Voyager 2. I am forever amazed that you have a spacecraft which is still sending back valuable data after all these years. It is a remarkable journey, actually. It's been launched in 1977, over 33 years ago. But it has a very robust power supply.

It's the radioactive decay of plutonium-38, which has a half-life of 88 years. So it's a very steady but decaying power supply, which means that we will have enough electrical power to continue beyond 2020. And in other words, your hope is that we actually will still be hearing from Voyager 1 when it does pass into interstellar space. That is certainly our hope, that we will, in fact, hear Voyager, we will continue to be listening to Voyager 1, and it will become our first interstellar probe. Now, not all of Voyager 1's instruments are still active, right? For example, the cameras were turned off quite a while ago? Yes, the instruments which were there for the planetary encounters of Jupiter, Saturn, Uranus, and Neptune have all been turned off. We still

have the instruments to measure the environment, that is, the solar wind. We can't measure the solar wind itself any longer on Voyager 1, but we can measure the magnetic field carried by the solar wind, and we measure the energetic particles, the cosmic ray particles, which are part of the environment out there, and we can infer what the speed is from another one of our instruments. We'll hear more from Caltech's Ed Stone about the Voyager mission and the coming TMT, or 30-meter telescope. This is Planetary Radio. I'm Sally Ride. After becoming the first American woman in space, I dedicated myself to supporting space exploration

and the education and inspiration of our youth. That's why I formed Sally Ride Science, and that's why I support the Planetary Society. The Society works with space agencies around the world and gets people directly involved with real space missions. It takes a lot to create exciting projects like the first solar sail, informative publications like an award-winning magazine, and many other outreach efforts like this radio show.

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Welcome back to Planetary Radio. I'm Matt Kaplan. Ed Stone has been the Voyager Mission Project Scientist for nearly 40 years. Voyager 1 is now near the outer edge of our sun's influence through the so-called heliosphere. Almost incredibly, the craft's feeble radio signal is still transmitting data that is picked up by some of the most sensitive receivers ever built. Well, we're pretty good at it, but that doesn't mean it's not a spatial challenge, actually. It really does require the largest antennas that we have in the deep space network, 70-meter antennas. It requires very modern, very low noise, very sensitive receivers,

because the transmitter on the spacecraft radiates only 20 watts of radio power. So it is really a remarkable achievement that we can get data back. We do that, of course, at a very low rate. 160 bits of data per second is all we can receive from such great distances, but that is certainly enough data to tell us what's out there. Another good reason, I guess, that you're not sending pictures back anymore. It would take an awfully long time to form one of those images. Yes, it would. Yes, it would. And 20 watts, I mean,

really, to put that in perspective, we're talking about not much more than the power of a citizen's band radio. That's right, exactly. And it's being transmitted from over 11 billion miles at this point. Not bad. A little better than the range of most CB radios.

How about Voyager 2, that sister craft? Not quite as far out there, but what kind of science is it doing? Well, it's following along behind. It's about 2 billion miles closer to the sun. It's making many of the same measurements in a different region of the heliosphere. Voyager 1 was deflected upward out of the plane of the planets from its Saturn encounter, and it's about 35 degrees north of the equator, the heliospheric equator. Voyager 2 is deflected downward by its flyby of Neptune in 1989,

and it's about a comparable distance below the equator. So we have one spacecraft north and one south, and it turns out that's important because the heliosphere has been distorted by what's outside. And the shock and we believe the heliopause are actually closer in the south in the direction Voyager 2 is headed than in the north. And of course, Voyager 2, though it may be losing this race, if one can call it that, of course, it's not really a race at all. It certainly can be proud of its achievements, having given us our only close-up views of Uranus and Neptune all those years ago. And I sure know some scientists like Heidi Hamel who wish that

another spacecraft was following in its tracks. Exactly. We currently have no plans to return to either Uranus and Neptune. I'm hopeful that someday a spacecraft will go into orbit about each of those planets and allow one to really explore them. So what Voyager did now over 20 years ago is still the best that there is in terms of encounter science. Is this still pretty much the case in spite of the fact that the burgeoning number of really huge telescopes, one of which you're involved with, do we have any telescopes yet on Earth or even projected or under construction that could have achieved what the Voyagers did? better than it was. And some of the images we now take with the Keck telescopes, which are 10-meter telescopes with using adaptive optics to correct for atmospheric disturbances, those images now look very much like the images taken by the Hubble telescope in Earth orbit. But still, if you really want to get close and explore things at the highest possible resolution, you really do need to have a spacecraft either flying by or even better in orbit where it

can fly within a few hundred kilometers of the surface. Let me continue that segue to talking about really big telescopes because I happen to know that you are the vice chair of the board of directors for one of the biggest, the TMT or 30 meter telescope. How is that project coming along? We are well along in our design, and we are now in the process of putting together an international team to begin construction in about another year. And it's about, we hope that by 10 years from now, we will have first light with a telescope with a mirror 30 meters in diameter. The Kecks, currently the world's largest ground-based telescopes, are 10-meter mirrors. And we use the same revolutionary technology that made the Keck's possible. That is

the mirror, the main mirror is actually made of a collection of hexagonal segments. In the case of the Keck telescopes, 36 such segments. In the case of the 30 meter telescope, there'll be 492 segments, all controlled by a computer, to maintain their alignment so that they behave as though they're a single, single piece of glass. I was on the TMT website just before we started this conversation, and there are some new renderings of this mighty observatory as, I guess, people begin to figure out from engineering studies how it might actually look.

That aperture is pretty stunning. Yes, it is. It is really quite remarkable. And, of course, the reason we need such large apertures is to look back to see the very first stars. We now know that the age of the universe is about 13.7 billion years, that the first stars probably started, there were enough atoms collected into large enough bodies for starlight to be generated about 400 million years after the beginning of the universe. But that's very far back in time.

It's very far out. And one needs the collecting power of a 30-meter telescope in order to really analyze and understand what kinds of stars were there at the beginning of starlight in the universe. Ed, I read on your Caltech bio that the very first space-borne instrument that you had something to do with was in 1961, and I should be wishing you a happy 50th anniversary in space. You're absolutely right. December 1961, I flew my first experiment looking at energetic particles coming from the sun. Is it as exciting as ever? It's even more exciting. It's really quite remarkable that the Voyager mission, for instance,

continues to explore things which no one has explored before. And as we do it, as usual, we find that although we had some good ideas, the nature was even better. Ed, thanks so much. It is always a pleasure to talk with you. You're welcome. Thank you. Ed Stone, Edward C. Stone, is the David Morisot Professor of Physics at the California Institute of Technology, better known as Caltech. He's also Vice Provost of Special Projects there.

He was the director of the Jet Propulsion Lab not far away. It's operated by Caltech, of course, for about 10 years, 1991 to 2001. And he remains project scientist for the Voyager mission, that is Voyagers 1 and 2. We'll be back for a visit with Bruce Betts and take a look at the night sky in just a few moments.

We are in the office of Bruce Betts, the Director of Projects at the Planetary Society, and it's time for What's Up on Planetary Radio. Welcome, or you should be welcoming me. Welcome, Matt. We're so glad to have you here today. What do you got for us? We got Venus in the pre-dawn, dominating, super bright. Up above it, you can see Antares, the brightest star in Scorpius, but still much dimmer than Venus.

High above in the pre-dawn is Saturn. And in the evening sky, we've got Jupiter still dominating in the west in the early evening, looking like a super bright star. Let's go on to this week in space history. 1984, the first untethered spacewalk. Was that with the man maneuvering unit? It was indeed, the man maneuvering unit. The cool I'm flying free of the space shuttle thing

that then didn't really get used a lot, but made some really cool pictures. Yeah, I want one of those. I'll look into it 2001 we had an orbiter land on an asteroid eros landed on i'm sorry no it depends on how you look at it but shoemaker near spacecraft landed on eros though it was an orbiter they cleverly got it down to the surface and did some great science as a result that was fun i remember it well all right i want to mention one other thing before i forget a contest unrelated to the surface and did some great science as a result. That was fun. I remember it well. All right. I want to mention one other thing.

Before I forget, a contest unrelated to the show, but deeply related to the Planetary Society. We've launched contest. Guess the distance Stardust has traveled. Stardust next we'll encounter on February 14th. Don't miss it. It will return to Temple 1, the spacecraft that Deep Impact slammed its impactor into a few years ago.

And they'll fly by and check it out. So the contest is guess how far it has traveled. You can find details at planetary.org. Got some good prizes? We've got prizes. We've got a spiffy Stardust Next Planetary Society produced t-shirt and a goodie bag from the project and there'll be ten. Ten. Ten winners. Goodies. That's a Rocky and Bullwinkle reference. You can go on. Moose and squirrel. So have we got anything weird and special?

No, it's up to you. So much pressure after barbershop quartets. Humorous concoctions? All right, I'll give it a try. La, la, la, la, la, la, la. Random Space Fact. Did you notice I had to back the microphone off about four feet? All right, so I have a little issue with volume control.

Random space fact. I am so pleased as punch with the random space. You said you had something really special. You've put a lot of time into this. I really enjoy, as long-time listeners will know, the scale model solar system concept. But now I've taken it to a human scale. So if the sun were the size of a small flake of dandruff on the top of your head and Pluto were at the soles of your feet, then the distances to

the entire inner solar system would be contained within your head. Jupiter would be about where your chin is. Saturn would be about the middle of your chest. And that's right. Uranus would be exactly where you would expect it to be. Dare I ask? I kid you not. Let us just say your posterior. Are you me? Totally serious. Scale model are you me totally serious scale model of the solar system on the scale of the human body uranus is well right there uranus it's pronounced uranus sorry i lost track and neptune is somewhere slightly below your kneecap i that is just mind-boggling is what that is.

Finally, we have a reason for that name. Finally. All right. I'm speechless. We move on to the trivia contest. Asked you kind of a challenging one here. Asked you what the tallest rocket that had successfully gotten to space that was not American, Soviet, or Russian.

How'd we do, Matt? A great deal of controversy. And the odds were good with this one, because a lot of people, one, had it wrong, and a lot of other people just chose not to enter, because it was tough. It really took some research. We got a lot of people who came up with the wrong answer. One that they proposed was Ariane 4, which is not even being flown anymore. But it was beaten out by one that I guess you know something about, the Ukrainian Zenit 3SL, except it's not really so much Ukrainian? It's a complicated hybrid. The design originates from the Soviet era, which might disqualify it. The bulk of it is Ukrainian, but it uses a Russian component, which might disqualify it. And it uses a U.S. Boeing-produced component

and is launched by Sea Launch. And so it's just overall messy. Now, we might have given that to you, except there's another contender that in one of its configurations is taller than the Zenit 3SL in any case. And that is the Chinese Long March 2F, winning by a couple meters at 62 meters in height at its largest configuration. And we did get that from a number of people, including Christopher Farrow in Melbourne, Florida. Christopher Farrow, a first-time winner, I believe,

he won himself a 2011 Year in Space calendar. So congratulations, Christopher, and thank you, everybody else, for entering. I do have one other that I have to tell you about. This came from Craig Jernay. You know, you did say rocket, right? It just couldn't be Russian or American, so on and so forth. He says it was Yao from China who plays for the Houston Rockets.

He is 2.26 meters tall. He is the tallest rocket, not from the U.S. or Russia. Thank you, Craig. Yeah, I suppose that's accurate. That's funny. All right, another trivia contest for you. And for this one, tell us the names of Neptune's rings. The names of Neptune's rings. Go to planetary.org slash radio. Find out how to enter and what are they competing for and when do they have until to get that entry in. And these are the rings around Neptune, not the rings around Uranus. We want to make sure we get that right.

You have until the 14th of February, 2011, the 14th, Monday, 2 p.m. Pacific time. And what are we giving away? I'm glad you reminded me because we have a terrific prize this week. We have a regular listener, Marcus. Marcus Chown, I think is how it's pronounced. And Marcus was involved with the writing of something called Solar System for iPad. And it actually is a fully interactive digital book on the iPad. It's not just your run-of-the-mill

app. It comes from TouchPress. And TouchPress and Marcus have donated several copies of this to us. Now, it is an app for the iPad, so you've got to have one or have some loved one that you might want to donate this to. But let me tell you, it's a terrific app. It's really fun to play with and chock full of beautiful photos and information. It is very cool. My kids were having fun with it the other day. All right, everybody, go out there, look up at the night sky and think about your favorite scale model solar system. Thank you. Good night. I think we all have a new favorite scale model of the solar system now, and be sure to tell your friends that you heard it first here on What's Up.

I'll be at the Space Up Unconference in San Diego, California, Saturday and Sunday, February 12 and 13. Planetary Radio is produced by the Planetary Society in Pasadena, California, and made possible in part by a grant from the Kenneth T. and Eileen L. Norris Foundation. Clear skies. Редактор субтитров А.Семкин Корректор А.Егорова