Planetary Radio: Space Exploration, Astronomy and Science - The Most Earthlike Extrasolar Planet Yet -- A Conversation With Co-Discoverer Stephane Udry

Episode Date: April 30, 2007

The Most Earthlike Extrasolar Planet Yet -- A Conversation With Co-Discoverer Stephane UdryLearn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Could it be another Earth? 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. You could not have missed the announcement. A team of astronomers has found a planet that is only slightly larger than our home, and it could support liquid water. We'll talk with Stefan Udry, one of the team leaders about this discovery,

and why it shouldn't have caught anyone by surprise. Our local astronomer, Bruce Betts, will tell us where to look for the considerably more familiar planets in our own skies. And wait till you hear his impression of a well-known movie star. Space headlines now. Happy birthday, Hubble Space Telescope. It has been 17 years since the great instrument was launched into orbit. And it has given us a present for the occasion.

An awesome 50 light-year-wide image of the Carina Nebula, yet another stellar nursery, this one about 7,500 light-years away. You can see it at planetary.org, but be careful, you may not be able to tear yourself away for a while. The other story you may want to check out at the site is not even about space, strictly speaking, but you've got to love it. The world's most famous living physicist has just slipped the surly bonds of Earth, at least for a few seconds at a time. Stephen Hawking found out what it's like to be free of gravity when he flew on Zero-G's modified 727 a few days ago. By doing so, he became the first seriously disabled person to experience the joy of weightlessness. I don't know about you, but I can't wait for my turn.

Emily has been a bit under the weather, but it hasn't kept her from answering a question about what you'd see in the night sky over the red planet. Here's the first half of her extraterrestrial stargazing session. I'll be right back with Stefan Udry. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, how does Mars' night sky look different from Earth's? Because the stars that dot the night sky are so far away, the patterns made by the stars in

the sky are the same for every planet, moon, and asteroid in our solar system. An astronaut walking on Mars at night would still see familiar constellations overhead, though she might be dazzled by the number of faint stars visible through Mars' thin, cold atmosphere. However, she might suffer vertigo if she looked too long, because the stars would wheel around a different point in the sky than they do on Earth. If our astronaut were in Mars's northern hemisphere, she'd see Polaris in motion, while the constellations Cepheus and Cygnus would whirl together in a dance around Mars's north celestial pole. The different pole results from the different orientation of Mars's spin axis. Mars is slightly more tilted than Earth, and moreover, it's not pointed in quite the same direction.

What else is up in Mars' night sky? Stay tuned to Planetary Radio to find out. We are edging ever closer to discovery of another planet that looks very much like home. That's what Stéphane Noudry would tell you. The Geneva Observatory astronomer and his colleague Michel Maillard led an international team that has just announced the most Earth-like extrasolar planet yet. Gliese 581c circles close to a red dwarf star just 20 light-years from our solar system. It's still too far to be seen directly, but its influence on that star is unmistakable.

You can read a good background story about this at planetary.org. When I talked with Stefan just a couple of days ago, he had just finished a photo session, a symptom of the immense media coverage for this discovery. Stefan, thank you so much for taking time to talk to us on Planetary Radio when you have become a very popular person in the field of astronomy. Thank you very much. Things must be very busy there. This story is getting more coverage than, I think,

any coverage I've seen in the past for discovery of an extrasolar planet. Wow. I'm very happy, but also a bit surprised, because astronomers were telling to the people that we will find those planets. It's just a question of time and work. And you have no doubt, I guess, that this won't be the last of these planets discovered in the so-called habitable zone. No. All our program is designed to find those planets. To be able to find planets, small-mass planets that are rocky, more like the Earth, in the habitable zone,

you need really to improve the precision of your measurement. And we built the instrument to do that three years ago, and we are still developing new instruments that will be even better and could get to the detection of real Earth around other sun. We've actually talked about this incredibly sensitive instrument, the HARPS instrument, before on this program. Would you give our audience a quick explanation of why its exquisite sensitivity enabled you to do this? Okay. If first we just say a few words about the detection technique,

what we are doing is to measure the radial velocity of the star. Because if there is a planet, it will pull a little bit the star, and the star is moving. It's orbiting the center of gravity of the star. Because if there is a planet, it will pull a little bit the star, and the star is moving. It's orbiting the center of gravity of the system. And the more massive the planet, the larger the amplitude of variation of the velocity of the star. So you have to be able to detect small variation of the velocity of stars if you want to detect Earth-mass planets. And in the present case, we are kind of a bit lucky because the star is a very small star. Even a small-mass planet will do noticeable effect on the star. And

it's why we were able to find that kind of small-mass planet around these what we call red dwarf small stars. So the question was how we do it, because the shift on the detector of the signal that is giving you the velocity is very small. It's about a few atoms. So you have to be really precise, like kind of a Swiss clock watch. And to do that, we put everything in vacuum. When you talk about a small variation in velocity, you're not kidding. I mean, we're talking two or three meters per second, roughly the speed at which someone walks.

That's the shift in velocity of this small red star? That's the peak-to-peak velocity, as we call it. That's the total variation, yes. And the precision we get with the instrument is below one meter per second. So it's really something like three kilometers per second. So it's someone who is walking. You were also, I suppose, not surprised to be able to find this first smaller planet, what, about five times the mass of our Earth.

It's not surprising that it was first found, or one of these was first found, close to one of these small, fairly dull red stars. Yes, exactly, because we were looking first for giant planets around those small stars. And those are not that numerous, much less than for some type of stars. And probably it's because the disk in which the planets are forming scales with the mass of the stars. So for small stars, you may rather have small disks. And so less material, less gas, and then you're rather forming small mass planets.

And that's good also because the smaller the mass of the star, the easier it is to find the planet. So both features go towards the detection of terrestrial planets around those small stars. But this does not mean in any way that we won't eventually find Earth-class planets around stars, yellow stars like our own Sun. Exactly. And this is actually the main goal of the whole program. But the effect of the Earth on the Sun is only 8 centimeters per second. So it's roughly 20, 30 times smaller. So you need to build a new generation of instruments with still higher precision to do that.

And we are now developing those instruments to be installed on the future big telescopes that are also planned, like 30- or 40-meter telescopes that the big organizations are now developing. I think there may be some misunderstanding by some of the popular media, at least here in the United States. I talked to a couple of people last night who insisted to me that you have found water on this little planet, and that's not at all true, is it? No. What we really measure is the separation between the star and the planet, because with Kepler-Liske--Second Law, the period of the variation is related to the separation.

Then you know the star, so you know the quantity of energy that the star is emitting, and so you know what kind of energy the planet is getting, where it is. And part of that energy is used to heat the planet, and part of the energy is reflected by the planet and part of the energy is reflected by the planet. So if you do the calculation, the temperature at the planet position could be around 20 degrees Celsius. But then there are lots of unknowns because we don't know anything about the possible atmosphere of the planet. Is the atmosphere reflecting most of the light or is it taking all the energy to heat up the planet

and have a huge greenhouse effect, for example? We don't know that. So we can hope that this is not just another superheated Venus down on the surface, but we really don't know. Exactly. But on the other hand, there is another very interesting point, is that in that system we also detected a third planet a bit further out. The mass of it is 8 Earth mass, and it's just on the other side of the so-called habitable zone. And there, if there is a greenhouse effect, like in Venus,

then even if it's in a more colder part of the system, the temperature could be just right at the surface. Ah. You know, I was going to ask you about the other planets in this, well, so far we know about a three-planet system. Is there any indication that the location of these two larger planets that bracket the small one, 581 C, that they might provide some protection for this smaller planet. The way we have learned Jupiter apparently has helped life to develop on Earth just by clearing the neighborhood of asteroids. It looks very difficult because the outer planet is only eight Earth mass.

So its shielding power is not that big. Jupiter is much bigger and attracting everything around. But for that planet, I don't think, or I don't really know, but I don't think the shielding effects will be very large. Geneva Observatory astronomer Stéphane Oudry on the discovery of Gliese 581c, the most Earth-like extrasolar planet yet. He'll be back in a minute. This is Planetary Radio. Hey, hey, Bill Nye the Science Guy here. I hope you're enjoying Planetary Radio.

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You can become part of the action, helping us fly solar sails, discover new planets, and search for extraterrestrial intelligence and life elsewhere in the universe. Here's how to find out more. You can learn more about the Planetary Society at our website, planetary.org slash radio, Transcription by CastingWords That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. We're talking with Geneva Observatory astronomer Stéphane Oudry, one of the leaders of the team that has announced discovery of an extrasolar planet that is just slightly larger than Earth and orbits at just the right distance for liquid water,

the so-called habitable zone. The search hardly stops with Gliese 581c. Since you are very confident that this is only the first of these roughly Earth-sized planets, I assume that your team is busy looking for these elsewhere in our neighborhood. Yes, we have something like 2,000 stars in our program that we are following regularly. And we already have candidates, indications of the possible presence of small mass planets around several of them.

But if the star is not that quiet, for young stars, for example, you have intrinsic variation related to the star is not that quiet, for young stars, for example, you have intrinsic variation related to the star that is spoiling your measurement. And you really have to be very careful before saying, oh, that's a planet. It could just be motion of the surface of the star. So we have to work hard, gathering lots of observation and characterizing the stars very well before announcing the planets. But actually we do have more candidates, and we are sure that there are those planets, because planet formation models are predicting these small mass planets all over the place,

at all separations, around all kinds of stars. So we just have to find them in the sense of having the instrumentation to find them and being sure that our modeling is correct. Would you like to take a guess? I'm sure you're aware of the other instruments that are in development or at least being discussed. I wonder if you've thought about how soon we might be able to observe a planet like this directly. We are part of a project in Europe called SPHERE that is an extreme adaptive optic project, the aim of which is to correct for the atmosphere effect, disturbing the image,

and then putting a mask in front of the star and looking what's around. So in that way, we will be able to see the big planets, the giant Jupiters, in a few years from now. But if you want to see these very small-mass planets, the terrestrial planets, you have to go to space and have big telescopes. And there are several projects, but only projects at this stage. And the agencies have to push a little bit now for the development of those projects in order in maybe 20 years from now being able to go to space, hide the light coming from the star, and see light coming from the planet nearby. And if we can do that, then we can start to analyze the chemical composition in the atmosphere of those planets.

That's the Terrestrial Planet Finder project by NASA or the Darwin project at ESA in Europe. Something to look forward to. Let me bring us back to where we started with only a couple of minutes left, and that is the enormous attention that this is receiving worldwide. You sounded like you might have been a bit surprised at how much coverage it's getting in the United States, but I'm sure that your telephone is ringing continuously. Indeed it is, and not only from the U.S., also in Europe, the coverage is great for us. the US, also in Europe, the coverage is great for us. But the absence of surprise is more

because we are seeing it as a, we have a view of the project as a whole. So we knew that we would find one, we know that we will find future such candidates, and we are sure that we will also find these low mass planets around sun like stars. So we are just in the middle of the road going step by step, slowly but in a very safe way. So okay, we are just surprised because we are deep in our work. And now we are starting to realize that for the public it's a big deal because they don't see the path from the beginning to the end. We have our eyes already watching the aim at the end, the goal. Right. Eyes on the prize, we say. And obviously, though, this has captured the imagination not just of the media but of the public.

And it is exciting to confirm confirm that yes there really are planets out there that if many other conditions are correct they might support life i would imagine even as a good scientist you must be in your off hours dreaming of uh perhaps uh i mean i won't go as far as saying somebody on this little planet looking back at us and wondering if anyone lives here, but certainly this thought that perhaps there is a biosphere circling that little red star. Oh, yes, and I'm a lover of science fiction, so I'm good public for that. So all the time we think about it. Each time you look at the sky, you think about other creatures maybe existing on the other side.

And by the way, I'm quite convinced that life exists outside the solar system because all the main building blocks of life, the carbon, oxygen, nitrogen, chemical components are all made in stars. So they should be all over the place. And now we are finding places like these small planets where life could develop. So for me, the conditions for the development of life are present in many, many places in the universe. So I have no doubt that life exists elsewhere. Well, I'm sure you're familiar with the Drake equation. Sure.

Well, thank you very much for adding just a bit more reality to that equation, filling in a little bit more of one of the variables there as we edge closer to finding that life that you and many others have confidence is out there waiting for us to find it. Okay, thank you. And congratulations, by the way, to you and your entire team on this discovery, and we wish you continued success. Thanks a lot. We appreciate it.

Stéphane Oudry is one of the leaders of the team at the University of Geneva and elsewhere that have used this massive telescope in Chile and the incredibly sensitive spectrographic instrument attached to it, the HARPS instrument, to discover the first of what will clearly be many planets that are in the class of our own, just five times the mass of our Earth and traveling rather close to a red star, but within what is known as the habitable zone. Stefan is at the University of Geneva and headed toward, and we'll congratulate you

for this as well, full professorship coming this summer. Thanks a lot. We'll be right back with Bruce Betts for this week's edition of What's Up, and that includes this new planet 20 light years away from us, but that'll be right after a return visit from us. But that will be right after a return visit from Emily. I'm Emily Lakdawalla, back with Q&A. Mars and Earth have different pole stars, but their ecliptic planes are pretty much the same.

So Mars and Earth astronomers can both watch the sun and planets march through the same zodiacal constellations. However, the different orientation of the spin axes means that the seasonal changes in the night sky are different for Mars and Earth. For example, when spring comes to Earth's northern hemisphere, the Sun is in Pisces, and Gemini and Cancer are overhead at sunset. But when spring comes to Mars' north, the sun enters Scorpius instead, and Pisces is actually up in the night sky. The sun doesn't get to Pisces on Mars until the northern summer solstice. These seasonal changes happen much more slowly on Mars because of a year that's nearly twice as long. For Earth, the constellations change with the seasons at a

pretty steady pace because Earth's orbit is almost circular. But Mars's orbit is so elliptical that it moves one and a half times more slowly at aphelion than at perihelion. Mars just happens to be at aphelion near northern summer solstice. So future Mars sky watchers will get one and a half times as many warm summer nights as cold winter ones, as long as they've got observing sites in the northern hemisphere. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Time for What's Up on Planetary Radio.

Bruce Betts is here, the director of projects for the Planetary Society. Ace Astronomer comes in each week to tell us what's going on. And what's wrong? I like that. I like that title. Okay. You've got little planets scratched on the side of your telescope, don't you? Yes, I do.

What's up? Well, hey, if you want to go scratch some planets on the side of your telescope. Stenciled. I should have said stenciled. Stenciled. Okay. You can pick some up. Of course, it's hard to miss Venus in the early evening, dominating out there.

Bright, star-like object. And not that there's any problem finding Venus, but it will make for a pretty pair on May 19th. It will be right next to the crescent moon. So we should look for Venus sort of inside the crescent, right? Yes, just like it's always erroneously drawn and gives me like quivers and shivers of annoyance. Because you're an ace astronomer. I am.

They draw stars in the middle of the crescent. The moon is there. Just because it's not lit by the sun doesn't mean it doesn't exist. Although if no one can hear it because they're in space, does that mean it doesn't exist? Yeah, well, no one can hear you scream either. That's true. That's true. Same in Hilbert space.

We also have Saturn up in the early evening as well. It's actually going to be pushing closer to Venus over the coming weeks, and we'll keep you posted on that. In the sky, not in reality. Well, I mean, that kind of is reality. Anyway, I digress. In the pre-dawn sky, you can see Jupiter high overhead. It's actually rising fairly early now, meaning 11 p.m. or so. You can catch it in the east looking like another bright star-like object. And you can see Mars is just going to continue to be dim and hanging out in the pre-dawn sky, low down for a few months, and then it'll start to perk up and get bright again. This week in space history, a lot of amazing things. Of course, 230 years ago,

Carl Frederick Gauss was born. Now, what does that have to do with astronomy? Because I mostly know him for magnets. I'm so glad you asked. Well, have you ever noticed that many planets have magnetic fields? Oh, that's true, isn't it? And in fact, I didn't even prompt you, but because of this, it's going to be perfect. I'm going to give you a little tutorial of magnetic fields through the solar system. Oh, goody. Throughout the rest of the show. Get excited.

But in the meantime, let's not forget to mention 1961, Alan Shepard becomes first American in space. time, let's not forget to mention 1961, Alan Shepard becomes first American in space. 2002, NASA's Aqua satellite was launched five years ago, taking lots of cool, spiffy Earth observing data. And we've got 1968, and you, I mentioned also this for you, being a fan of old, cool videos, Neil Armstrong successfully ejects from the Lunar Landing research vehicle before it crashes. Do you remember seeing that? Oh, my goodness. Right. Yeah. That spindly thing they did to simulate the rover and it.

The lander. Sorry. Not the rover. The lander. He was the rover. With nothing over the top of it. Yeah. Yeah.

Retro rockets. Retro rockets. And there's this great video of him ejecting as the thing is completely out of control. Yeah, it made them really happy they had the budget for that ejection. He was, he was. Or we'd be celebrating someone else as the first astronaut on the moon. Let us move on to random space facts. Okay, we're getting back to magnets.

You got it. Magnetic fields. Okay, we're getting back to magnets? You got it. Magnetic fields. Earth's magnetic field, measured at its equator, is about 0.3 Gauss. You see, it all comes back together. Frederick Gauss, a unit of magnetic field named after him, and all the planets at their surfaces, not that far off from one Gauss within an order of magnitude.

Even Jupiter. I'm glad you asked. Once again. People think we script this stuff. Well, they know the times you stumped me that we don't. But this time I'm ready for you. Jupiter at its equator, about 4.3 gauss. So more than 10 times stronger than Earth's.

But, of course, it would be even stronger if it weren't for Jupiter so darn huge. This is a measurement out at its upper atmosphere level. It's sort of kind of surface. Yeah. So it's actually a much, much stronger magnetic field in general. But a magnetic field, of course, drops off with distance, square of distance. So that's enough for that tutorial. Let's go to the trivia contest.

Yeah. And maybe we'll even come back to magnetic fields. Oh, we might. Well, you remember what we were doing? Oh, I do. It wasn't magnetic fields. Oh, we might. Well, you remember what we were doing? Oh, I do. It wasn't magnetic fields. It was asteroids. Yeah.

The Rosetta spacecraft is scheduled to visit two asteroids on its way to a comet. What are their names? How did we do? This was relatively easy, I guess, for people to find. And find they did, lots and lots of them. But it was Georgi, who is sure that we can't pronounce his name properly. I'm sure he's right. But Giorgi Petrov, who is from Dallas.

He's a past winner. Giorgi, your name came up. And sure enough, he said it is scheduled to visit 2867 Steins on the 5th of September 2008 and 21 Lutetia on July 10, 2010, not quite two years later. Steins and Lutetia, you remember the show they used to do? No, it was great. They were great. They were like the best since Martin and Lewis, I think.

It's true, but it just wasn't the same once they split and tried to have their solo careers. No, no, they never equaled it. Especially Lutetia, just whew. Really, she went downhill fast. Yeah, I felt badly for her. I mean, they never equaled it. Especially the Tessia. Really, she went downhill fast. Yeah, I felt badly for her. I mean, they were great together. But anyway, let's move on to the next trivia contest. And surprisingly enough, we'll come back to our random theme of the day, magnetic fields.

Which planet in our solar system has the second highest magnetic field at its equator? Clearly, Jupiter has the highest. I mentioned that. Which planet has the second highest at its equator. Clearly Jupiter has the highest. I mentioned that. Which planet has the second highest at its equator? Go to planetary.org slash radio. Find out how to enter and compete for a Planetary Radio t-shirt. We hope you win a shirt. Okay.

All right, everybody. Go out there. Look up in the night sky and think about ducks in a row. Thank you and good night. I thought for sure you were going to say something about like repels and opposite attracts. After this show, people will undoubtedly be thinking about magnetic fields, so I thought I'd give them something else. Did you know that ducks actually are attracted by magnetic?

Okay, maybe not. If you place a magnet inside a piece of bread, the duck will be attracted to the magnet. I see. I guarantee it. Okay. Yeah, good night, Bruce. And, you know, I was quacking up the wrong tree there, but still magnets. So there you have it.

Bruce Betts, don't call him Donald. He joins us every week. Here for What's Up. You'll probably want to know that the deadline for this week's new trivia contest is Monday, May 6th at 2 p.m. Pacific time. We hope to hear from you. Next time, a Cassini update. Planetary Radio is produced by the Planetary Society in Pasadena, California.

Have a great week, everyone. Thank you.