Planetary Radio: Space Exploration, Astronomy and Science - By the Light of a New World

Episode Date: April 11, 2005

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Shedding light on new worlds, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. that takes you to the final frontier. I'm Matt Kaplan. Harvard astronomer Dave Charbonneau and his colleagues used a new space telescope to detect light from a planet that's 500 light-years from Earth. That's a first.

We'll talk with him about the meaning of this discovery. Already got a stylish Planetary Radio t-shirt? Later today, Bruce Betts announces a new prize for winners of our space trivia contest. It's part of his usual What's Up report on the night sky and more. Let's start with a sampling of the news from here and then in the space-time continuum. You can now take a look at a somewhat controversial image taken by a team of European astronomers. They believe it is the first actual picture of a planet orbiting another star. Check it out at planetary.org.

Dave Charbonneau and I will also talk about this story in just a few minutes. Spirit and Opportunity have gotten a new lease on life. NASA has extended their mission on the surface of Mars by another 18 months. Both are showing signs of wear and tear, but Spirit recently got a car wash of sorts. High winds blew the dust off her solar panels, doubling the amount of electricity available to the rover. And the Japanese Space Agency has laid out plans that could put Japanese astronauts on the moon by 2025. The nation will send robotic missions as it looks at development of a vehicle that can carry humans.

Dave Charbonneau is here right after Emily serves up some of our planet's deepest dishes in this week's delicious Q&A. Back in a minute. Delicious Q&A, back in a minute. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, what is the Deep Space Network? Despite its name, the Deep Space Network is not located in space. It's right here on Earth. But it's the pipeline that brings us everything we know about space,

listening for the faint signals from every deep space satellite. The Deep Space Network, or DSN, consists of three facilities, Goldstone in Southern California, Madrid in Spain, and Canberra in Australia. These locations are roughly 120 degrees apart on the Earth's globe, so that as the Earth rotates, there is usually at least one DSN station visible to any deep space satellite. Each DSN facility has at least four radio telescopes, the largest of which is 70 meters, or 230 feet, in diameter. Why do the dishes have to be so big? Stay tuned to Planetary Radio to find out. Our regular listeners know that well over 100 extrasolar planets have been found in the last decade, but all the evidence for them has been indirect.

Not anymore. Just three weeks ago, teams announced they had detected the actual light coming from two of these bodies circling relatively nearby stars. David Charbonneau of the Harvard Smithsonian Center for Astrophysics is lead author of a paper describing one of these efforts. He had just returned to his office from delivering a lecture when I caught him on the phone. Dave Charbonneau, congratulations on the detection of that light from an extrasolar planet. Well, thank you. It's been a really interesting few months. I can imagine. You guys call it TRACE-1, T-R-E-S hyphen one. Tell us how it got that name. Well, TRACE stands for the Transatlantic Exoplanet Survey,

which is a network of three telescopes that we have, and one of them happens to be in the Canary Islands in Spain. So our Spanish colleagues like to play on the words TRACE. The other two telescopes, one is located in California at Palomar Observatory, and the third telescope is in northern Arizona at Lowell Observatory. And this was the first planet we found by the survey, so we named it Trace 1. So this planet, Trace 1, was found by these three Earth-based telescopes, but this most recent discovery that has gotten so much attention is, I guess, thanks to the Spitzer Space Telescope.

That's right. It's actually been very charming. We used this set of four-inch telescopes. Essentially, the trace network consists of three telescopes, which are each a camera lens, so very, very humble equipment. And then we went from that discovery immediately to using one of NASA's great observatories, the Spitzer Space Telescope. And so that was a very exciting leap in terms of equipment for us. Well, we should follow up on that because I know this use of fairly small telescopes,

small aperture telescopes, is something that you've kind of championed along with some of your colleagues. Really, a 4-inch telescope, or as you've said, a camera lens, I assume just sort of a telephoto lens that you might see on a single-lens reflex camera, it seems rather amazing that you could discover something as far away and as small as an extrasolar planet. Well, the trick is that, of course, we would really like to find planets around the nearest, brightest stars because they're easier to follow up and they're really our neighbors.

And so we don't need to gather a lot of light to detect them, and that's why we're able to get away with such a small camera lens. So we can do this for much cheaper than you might expect. But when it comes to really following them up and looking for their light directly, and that's what we have discussed and presented over the last few weeks, then you really do need a much more sophisticated

observatory. And really, the sort of facility that NASA can provide is the only way to go and make these detections. Well, talk about what the Spitzer enabled you to discover. So the trick, of course, is that you're trying to see this very faint planet next to this really bright star. It isn't the intrinsic faintness of the planet that's the difficulty, so much as overcoming the contrast ratio, the glare of the central star. And so you need to have some kind of trick to separate out the light of the planet from the light of the star. Of course, what we'd love to do is just take an image and you would see a faint little planet sitting next to a bright

star. We can't do that yet. We don't have the technology yet to image these planets near sun-like stars. So we have to use the trick. And the trick that we use is that for some of these systems, we have a very special, a very favorable geometry. We happen to be looking at them. Our line of sight goes right through the orbital plane of the planet. And so that means we see the planet pass in front of the star every orbit. Every time the planet comes around, it makes a little eclipse as it passes in front of the star. That's how we first detected this planet, Trace 1.

Well, if it goes in front of the star, then we know that half an orbit later, it goes behind the star. And that's a very special time. When it goes behind the star, then you're able to capture the light from the star in isolation. So you're able to see the star by itself. And that's magical, because if you can subtract that, as we did, from data gathered at other times when both the star and the planet are visible. Then you're left with just the light from the planet. You know what I thought of as a comparison to this? Weighing your dog by getting on the scale, holding your dog, and then getting off and weighing yourself, and then coming up with the difference. It's similar, except that instead of your dog, I think you should imagine maybe your pet hamster or something even smaller.

It's just a tiny little blip compared to the star, but the NASA Spitzer Observatory is so stable and so sensitive that we are able to measure that tiny difference. Talk about the Spitzer a little bit, too. It is quite an impressive instrument, much as the Hubble is, except that it works with a different range of light. That's right. The Spitzer Space Telescope, of course, observes in infrared light, in thermal emission. As you might imagine, we have first tried to do this from the ground on many different occasions. I used to plan various observing runs with colleagues, with my office mate in graduate school.

various observing runs with colleagues, with my office mate in graduate school. We would go to Hawaii. We would go to Arizona. And we would try to gather data to see precisely this little eclipse as the planet went behind the star. And we always failed. And the reason was that in the infrared, where the planet is emitting light, everything around us also emits lots of light. So the telescope is glowing in infrared light.

The atmosphere above us is glowing. And so there's so much noise from all that additional thermal emission from our environment that we could never succeed. And so we always end up not being able to see the light from the planet. The difference, of course, is that Spitzer is in outer space where it's nice and cold and stable, and so you don't have any of this difficulty. The light that you see is purely the light from the star and the planet.

And moreover, it's very, very stable. The space-based platform means that you're not contending with the changes in the Earth's atmosphere or changes in the telescope conditions. It basically is this beautifully stable platform where you can measure these very, very subtle changes. It basically is this beautifully stable platform where you can measure these very, very subtle changes. We should also mention that this discovery of this first-ever light from a planet circling another star, you're not alone in this. You have a colleague and friend, Drake Deming, who found one in very much the same way.

Oh, yes. Yeah, that was really the exciting news for everyone in the community. So these planets were first identified just about 10 years ago. Since that time, people have been trying to come up with ways to see the light from the planet directly, because that would be so precious. Well, Drake Deming's team chose to study a different planet. So we studied the planet named Trace 1. They studied a planet named HD 209458b. And yours has so much better name.

A bit of a telephone number of a name, but it's named after its star, of course, and the star has a catalog name. If there's any comfort in the long name, it's that there are many other such stars out there potentially with planets as well. They used a different instrument on the Spitzer Space Telescope, and they looked at a different planet, and they were also successful in seeing the light from the planet. So the exciting news is that Spitzer seems to be this really robust machine for pulling out this very faint signal from the planets. And so we are hopeful that over the next two years, as more of these planets in this special geometry are identified,

and that's something we're working very hard at, that we'll be able to turn Spitzer's gaze on those systems and perform similar observations, and then really be able to compare the properties, the temperatures, and the atmospheric constituents of these various planets between themselves, and then to compare them also to planets of our own solar system. We are talking with Dave Charbonneau of the Harvard-Smithsonian Center for Astrophysics, an assistant professor of astronomy at Harvard University, the lead author of a paper describing the detection of light from a planet,

a planet called Trace 1, and it happens to be a planet that does not circle our own sun, but one far away, maybe not in galactic terms, but certainly in terms of our own solar system. Dave, when we come back, there's much more I hope we can talk about regarding Trace 1, but also what else is happening in the world of searching for other worlds. And we'll be back right after this break. This is Buzz Aldrin.

When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. We sponsor the search for life on other worlds. And we're building the first-ever solar sail. You can learn about these adventures and exciting new discoveries from space exploration in the Planetary Report. The Planetary Report is the Society's full-color magazine. It's just one

of many member benefits. You can learn more by calling 1-877-PLANETS. That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments at our exciting and informative website, PlanetarySociety.org. The Planetary Society, exploring new worlds. Our guest this week on Planetary Radio is astronomer Dave Charbonneau of Harvard University, also the Harvard-Smithsonian Center for Astrophysics, where he has taken the lead as author of a paper about discovery or detection of light from a planet called Trace 1, a lot further out there than Pluto, circling another star,

known as an extrasolar planet, or I guess the other term, Dave, is exoplanet, kind of wraps it up in one word. Yeah, that rolls off the tongue a little bit easier. Tell us a little bit more about Trace 1. You've seen this light. That sounds great in itself, but that light can tell us a lot about this little planet, or not so little planet. That's right. When you're able to detect the light emitted by the planet itself, then that, of course, is very precious information. And so the first thing we're able to measure about this planet is its temperature.

These planets are nicknamed hot Jupiters, and that's because they are big like Jupiter, but they are much, much closer to their stars than anything in our own solar system. They're about 100 times closer to their stars than our own Jupiter is from the sun. And so you can imagine that that means they are very different beasts. They're heated to a high temperature. And so that makes them a little bit brighter in the infrared, a little bit easier to detect. If you looked at our solar system for comparison, would that put them inside the orbit of Mercury? Yes, this is really unlike anything in our own solar system. It's closer to its star than even Mercury is from the sun. And the other exciting thing, of course, we measure the temperature.

We can measure that indeed they are hot, and that's a very useful piece of information because it tells us how much of the light from the star, which is the way that these planets get hot, is absorbed by the planet and how much is reflected into space. So the planet is receiving a certain amount of radiation from the star. It's going to reflect a certain amount back into space. And that's very interesting because we might want to go and observe them in visible light.

We might want to go see what they look like in the normal light in which we can see. At those wavelengths, they would shine only by the light that they reflect. So that information might help these visible light astronomers, I assume. Exactly. The other piece of information that we get, of course, is that by measuring how much light the planet emits at different colors, then that can tell us about the atmospheric constituents present in the planet's atmosphere. Spectrographic analysis.

That's right. So we expect these planets, of course, to show lots of fingerprints, signatures of certain molecules such as water, carbon monoxide, methane. Models have been produced by theoretical calculations for basically as long as these planets have been known, which is almost 10 years. But for the first time, we're getting to compare those models to actual data, and we're finding out that some of our initial guesses were correct, and as is not so surprising in this game,

often we are mistaken, and then we're going to go and think a little bit harder about really what these planets are made of, and in particular, what their atmospheres are made of. Always makes science fun. It wasn't even just the discovery of these rather large hot Jupiters so close to their star. Didn't that kind of throw off some planetary formation models 10 years ago? Oh, yeah. That was a complete surprise. Of course, when we had only our own solar system

to explain for hundreds of years, we got very good. We got very confident in those explanations about the architecture of our solar system. And as you know, in our own solar system, the big planets like Jupiter and Saturn are far from the star, and the small rocky planets are close to the star. And so there's an expectation that that would be the architecture of planets discovered around other stars. The first discovery, this first planet that was less massive than Jupiter, really was a planet, was named 51 Peg that was discovered by two Swiss astronomers in 1995. And indeed, it was one of these hot Jupiters. And so it was completely at odds with the

expectations from our own solar system. So really the message from the more than 150 planets that have been found to orbit our neighboring suns, is that there's a huge diversity of planets out there. Some of the systems look like our own solar system. Many do not. Of course, one of the big questions that we hope to answer over the next 10 years is whether our own solar system is really a commonplace throughout the galaxy or whether we're somewhat unique.

Well, certainly the list of discovered exoplanets or extrasolar planets, take your pick, is growing pretty rapidly. And there are instruments in development that we've talked about on this show that may at some point give us a direct view. For example, the Terrestrial Planet Finder now being researched by NASA. But there is this interesting claim that has come up, work by a group of European astronomers who've been studying for a lot of years a star called GQ Lupi, or Lupi, I guess.

They claim to have an actual image of an extrasolar planet. I mean, what do you think of this work? Yes, I've just read that paper, and I think it's a beautiful image. I hope your listeners all get a chance to see it. The trick there, of course, is that they want to go and image a planet next to a star, and so they're surveying a lot of very young stars. The reason they are looking at young stars is that the planets presumably are also young, and the planets, therefore, are brighter because they're hotter when they're young,

and then planets cool off over time. Indeed, for this one star, they are able to see this faint point of light next to the star, and when they compare that brightness ratio to theoretical models, then they think it's most reasonable to explain this second point of light as really being something that's sort of the mass of Jupiter, maybe a few times the mass of Jupiter. There is a critical difference, though, which is that in our case, we are studying planets for which we have very precisely measured the mass directly, because we can measure the wobble of the star. And we've measured their size because we can measure when they eclipse the star. And we know that they're really like Jupiter, and they are

definitely planets. The trick with this other discovery is that they don't know the mass of the object directly. And so some of the models say it could be about two times the mass of Jupiter, which would definitely make it a planet. Some of the other models say it could be about 50 times the mass of Jupiter, and then it's really not a planet.

It would be a brown dwarf. But it's very exciting. And so what will be really exciting over the next few years is to see future observations of the system. Dave, we have only about a minute left. I want to follow up on something that we talked about right at the beginning of the conversation. Is it really conceivable that some of the backyard astronomers listening to this program could join the search for extrasolar planets? Oh, absolutely.

We ourselves, of course, found a planet using only a 4-inch telescope. Only three days later, after we announced the discovery, three days later, a team of amateurs followed up that same system and detected an additional eclipse when the planet went in front of the star. And I guess I have to say that I wasn't so surprised because they had a 10-inch telescope, so that was much bigger than our research telescope. But still something you can go to a good store and buy.

Yes, absolutely. So if any amateur astronomers are interested in getting involved, please visit transitsearch.org. Transitsearch.org is a website developed by professional astronomers that predicts when planets that are known to exist would pass in front of their stars and instructs amateur astronomers how to make the observations that would tell us about whether indeed the planet is passing in front of the star and what its size is, and therefore you could maybe figure out its composition.

So it's very, very exciting, and indeed amateurs can certainly make a significant contribution to the science. Indeed, amateurs can certainly make a significant contribution to the science. TransitSearch.org. We will put that link on the website, Planetary.org, right alongside the listing for this radio program, along with the Spitzer Space Telescope site. And, Dave, if you don't mind, your own website, which has a lot more information about your work,

and this detection of light from Trace 1, an extrasolar planet. We're out of time. Thanks so much, Dave. I hope we can check back with you as you continue to learn more about these faraway worlds. Oh, it's going to be a very exciting year ahead. Dave Charbonneau is with the Harvard-Smithsonian Center for Astrophysics. He is in the astronomy department, assistant professor of astronomy at Harvard, and is the lead author of the paper about the detection of light from TRACE-1. We'll be back with the easily detected Dr. Bruce Betts and what's up, right after this return visit from Emily.

I'm Emily Lakdawalla, back with Q&A. The largest radio dishes at the three deep space network stations are 70 meters in diameter. They have to be so big because of the vast distances involved in communication between space missions and the Earth. A typical radio transmitter on a deep space satellite, such as Cassini, broadcasts with 20 watts of power. But Cassini is orbiting Saturn over a billion kilometers from the Earth. By the time that Cassini's broadcasts reach Earth, that 20 watts of power has spread out into a cone more than a thousand Earth diameters across,

and the signal strength intercepted at the DSN antennas amounts to less than a millionth of a billionth of a watt. In order to detect these signals, the DSN dishes must be very large, and their highly sensitive detectors must be cooled to within a few degrees above absolute zero so that they generate no background noise. Of course, deep space satellites cannot have 70-meter dishes. In order to transmit signals that the satellites can hear, DSN antennas have transmitters that broadcast at nearly half a million watts. The three DSN stations at Goldstone, Madrid, and Canberra are the narrow pipeline through which we speak to and hear from our explorers out there in space. Without them, we could hardly see beyond

the Earth. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Well, we've got the Director of Projects for the Planetary Society, Dr. Bruce Betts, on the phone. He's ready to do what's up, but Bruce, what's up with you? You're not feeling well. Yeah, yeah. Not my health being up there, Matt, but it's doing okay. Could be a lot worse. I know you've been a little under the weather, too. It's just sicky time in the

planetary world, apparently. I guess so. Well, inspire us. Look up at the sky. Tell us what's up. I will try. Well, we've got three lovely planets to take a look at easily in the night, pre-dawn sky, in the evening sky. If you look a look at easily in the night, pre-dawn sky. In the evening sky, if you look anywhere towards the east, the brightest star-like object you see up there is Jupiter. And at the same time, in the early evening, you can look high in the west, southwest, and you will see Saturn looking kind of yellowish near Castor and Pollux, the Gemini stars. And in the pre-dawn sky, you can pick up Mars,

looking yellowish-reddish off there on the horizon. And right now, Mercury and Venus are playing with the sun, kind of lined up with the sun, so we're not seeing them in the evening or pre-dawn skies. But you can see the other three. Let's go on to this week in space history. On April 12, 1961, Yuri Gagarin became the first human to go into space and the first human to orbit the Earth. A big day in space history. Yuri's night, or Yuri's

day, I guess. You know, there's people who still celebrate this and call it Yuri's night. Anyway, on to, I know, random space facts! They're these subatomic particles that come flying out from the sun. They come from other places, too. They're called neutrinos. My random space fact has to do with these guys. They do not get absorbed very easily by much of anything. For example, you, Matt, will probably absorb, on average, if you're an average human, you'll absorb one of these in your lifetime.

Is that right? That is true. And yet there are, what, trillions of them running through me as I speak? I don't know about trillions, but there are a lot. Three different kinds. But enough about neutrinos. Let's move on and talk about our trivia question. Last time around, we asked you, what was the name of the lunar module on

Apollo 10, which I couldn't resist because I'm a big fan of this character that it was named after. How'd we do, Matt? What was the answer? What did people say? Did they like it? They liked it. They liked it. They liked, in fact, also that we had two dog contests

in a row, a lot of them. And many of them got the right answer. One of those many was Adrian Castellanos of Hoboken, New Jersey. Hoboken, the birthplace of Frank Sinatra, who said that module was called Snoopy. Wait, I'm sorry. Frank Sinatra said it was called Snoopy? No, no, no. Adrian did, but I'm sure they're close personal friends, he and Frank, when Frank was still around.

Anyway, Snoopy. Yeah, Snoopy. Sorry, I was going to start singing. Yes, the lunar module on Apollo 10, which was the dry run for the first landing on the moon, got down to within 50,000 feet of the surface of the moon with the lunar module Snoopy. The command module was, of course, called Charlie Brown. And you know what Charlie Brown said when he got back to Earth after the mission? No, what?

I got a rock. So anyway, let's give you your trivia question for next time around, and you two can win a beautiful prize from us. In fact, we are going to change the prize these days. Yay. We've been giving away Planetary Radio t-shirts for quite a long time. We are right now, for the next little while, getting giveaway solar sail posters. Beautiful artwork, large poster of the Planetary Society's

solar sail mission, Cosmos 1, which is scheduled to launch within the next month or so, the next couple of months. And that prize will be going out to you if you enter our contest and get it right. I ask you, how many wheels did Lunokhod 1 have? This was a robotic rover that the Soviets sent to the surface of the moon,

drove around on the surface of the moon. How many wheels did Lunokhod 1 have? Go to planetary.org slash radio, find out how to email your answer to us, and win a beautiful solar sail poster. So nice to have a new prize. And so all of you who've won in the past, you are going to want to get in on this one, right? You've been sitting back because you're enjoying your T-shirt. Well, now here's an opportunity to pick up that poster. If you

get your entry into us with the correct answer, by the 18th of April, April 18, Monday the 18th at 2pm Pacific Time. Alright, everybody, go out there, look up in the night sky and think about why dogs circle before they lie down.

Thank you, and good night. He's Bruce Betts, the Director of Projects for the Planetary Society, and if you have your tried-and-true cure for a chest cold, you can send that to us, too, at planetaryradio at planetary.org, and if it works, I'm sure you'll have Bruce's undying gratitude. That's for sure. Come on back to Planetary Radio next time for a great conversation

with America's first woman in space. Sally Rye will tell us what she's up to nowadays and reflect on the role of women in science, in engineering, and in spacesuits. Our show is produced by the Planetary Society. Have a great week, everyone.