Planetary Radio: Space Exploration, Astronomy and Science - A Planetary System That Looks Like Home

Episode Date: June 19, 2006

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A solar system that almost looks like home, 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. We mentioned it last week. This week we go to the source. I'm Matt Kaplan. called Habitable Zone. Not too hot and not too cold for liquid water. And perhaps life. We'll learn more in a few minutes. Later today, Bruce Betts will tell me what I'd weigh on Pluto,

but that's not nearly as important as his new space trivia contest, is it? Let's cover a few headlines before Emily drops by. It's T-minus a few days for the launch of Discovery. After an intensive two-day review, NASA has announced July 1 as the target date for the return of the space shuttle to the International Space Station. Commander Steve Lindsay and his six crewmates on the STS-121 mission will spend 12 days in orbit. Meanwhile, NASA's Genesis Mishap Investigation Board has put the blame for that mission's failed parachute exactly where we had been told. So-called G-switches had been installed upside down.

The board also faulted the better, faster, cheaper policy, which resulted in the cutting of critical corners. There's a detailed story at planetary.org on the web. Lastly, some good news for science out of Washington. The House Appropriations Subcommittee on Science, and a whole bunch of other things, has restored some of the research funding NASA wanted to cut from next year's budget. The overall recommendation was still $100 million less than the administration had requested. Again, you can read more about it at planetary.org.

Emily is thinking about what it takes to make a planet, and its metal she has on her mind. Rock on. I'll be right back with Christoph Loves. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, I've heard that our sun is a metal-rich star, and it's the metals that make up planets.

Does that mean that solar systems like ours are rare? First of all, it's necessary to define what an astronomer means by metals. You or I imagine shiny, malleable, dense substances like iron, nickel, and gold. But astronomers mean something quite different. Metal, to an astronomer, means any element heavier than helium. Hydrogen and helium were formed in the Big Bang. Metals mostly formed through thermonuclear fusion inside stars. Stars that formed very early on have low metal abundances because there weren't many metals around when they formed. But they created metals as they aged,

and when their lives ended, they scattered metals around the galaxy. Second and third generation stars, like our own, have higher amounts of metal, and metal abundance does appear to be an important factor in the size of planets observed around other stars. How does our sun match up against other stars, and what does that mean for extrasolar planets? Stay tuned to Planetary Radio to find out. With well over 100 extrasolar planets on record,

it now takes a little something extra for another discovery to make the major media. The Geneva Observatory in Switzerland delivered the goods last month. A team led by Christoph Loves announced that it had found a system with three planets, each only a few times bigger than our lovely little Earth. It's a testament to the incredible improvements we've seen in planet-finding technology and a testament to the incredible improvements we've seen in planet-finding technology, and a testament to the patience and skill of Christoph and his team. Christoph, first congratulations on this wonderful discovery of a fascinating solar system. Thank you very much. Thank you. You are the lead author of the paper that appeared about a month ago in Nature,

announcing this system at a star not very romantically called HD 69830. But I think your discovery could be described as romantic. What has made this stand out from all the discoveries of extrasolar planets in the last 10 years? Well, I would say that this system accumulates a lot of interesting stuff for us. First of all, it is the first planetary system, multiple planetary system, we discover with several low-mass planets, in this case Neptune-mass planets, and without a massive Jupiter-like planet.

So that would be the first time that we discover such a system. There are three planets in there. The third planet with a minimum mass of 18 Earth masses is located in what we call the habitable zone of the system. That's the distance from the star at which life could exist, at least physical conditions for life are present. But of course now we are not claiming that there is life on this third planet. We are just happy because this shows that we are able to detect low-mass planets in this habitable zone. And this is a very interesting point. Although in that very case, the planet itself is probably

still too massive to be considered as Earth-like. So that's another interesting point in this system. And there is yet another one. It's the fact that the Spitzer Space Telescope discovered about one year ago what could be an asteroid belt around this same star. So we end up with three planets, three low-mass planets, an asteroid belt around the star which looks like our sun. And all these properties make this system very interesting for us.

Even this third planet in the so-called habitable zone is quite a bit closer to its star than the Earth is. It's less than one astronomical unit, in other words. But I guess that's made up for by the fact that this star is somewhat cooler than our sun? Exactly. That's exactly the explanation. So this third planet orbits at a distance of 0.6 AU, which means 60% of the sun-Earth distance, and orbits in about 200 days around its parent star.

So it is closer than our Earth in our solar system. But as you mentioned, the star itself is a little bit cooler and a little bit less luminous than our sun, and therefore the habitable zone would be located closer to the star compared to our solar system. Now, I feel sorry for those of us in the Northern Hemisphere, but happy for our Southern Hemisphere listeners who can actually look up in the sky and see HD 69830.

Actually, you can also see it from the Northern Hemisphere. It's located minus 12 degrees in declination, which is not too far south. So, provided you are not too close to the North Pole, you will be able to see it, even from the

Northern Hemisphere. It is located not very far away from the bright star Sirius. Of course, if you really want to spot it, even from the northern hemisphere. It is located not very far away from the bright star Sirius. Of course, if you really want to spot it, you will need a star map and good eyes to really see it, and a good night, of course, because it is just visible to the naked eye. Well, I'm glad to hear we have a shot at it, and I guess some good astronomy software might also be helpful. And even though it can be seen, apparently, from the northern hemisphere, you discovered it at the European Southern Observatory in Chile? Yes, exactly.

We used the HARPS spectrograph, which is an instrument that was built to be able to discover extraterrestrial planets. It is located in La Silla Observatory in Chile. And from there, we observe many stars in the southern hemisphere, but also some stars in the northern hemisphere. And HD 69830 was part of our search sample. And we've been monitoring this star for a few years and accumulating data on it. And we were measuring it very precisely, its radial velocity, and by analyzing the radial velocity curve we got, we were able to find these planets.

And by measuring the radial velocity, you were measuring, I assume, the tiniest red and blue shifts in the light coming from the star? Exactly. That's what we are basically doing. We measure the so-called Doppler effect. So when the star is receding from us, its light will be shifted to the red, and if the star is coming towards us, its light will be shifted to the blue

just a simple explanation like this actually we use the spectral lines in the stellar spectrum and we measure very precisely the positions of these absorption lines by measuring this position we are able to measure radial velocity differences of about one meter per second, which is the speed of a man, of a walking man, basically. And we are able to see if the star is changing its radial velocity by such a tiny amount, and that allows us to detect very small mass planets orbiting the star. Because the planets will have an effect on their star because of their gravitational attraction, and the star is going to move a little bit around the center of mass of the whole system. And this is this small movement that we can detect.

That kind of sensitivity in the HAARP spectrometer is just extraordinary. I guess it is the most sensitive instrument of its kind on our planet? Yes, yes, the most precise instrument to do this, yes. Was this also extremely useful in your ability to tease out from these tiny changes in radial velocity that this was actually a three-planet system at minimum? Yes, sure. Actually, it was a complicated system to analyze

because when you have more than one planet, you get a very complicated radial velocity signal. So you get a complicated curve that you have to interpret and you have to find out what is going on with the star. So in this case, we quickly noticed that there was not only one planet because the curve was more complicated. And so we kept measuring the star to accumulate a lot of measurements because the number of measurements is very important when you have a whole planetary system. You really need a lot of data points to be able to completely resolve the system. So we first noticed that there was a planet orbiting in about 10 days, so we got a radial velocity curve changing over 10 days, but then we also noticed that it was not completely periodic.

Then the variations, there was something more hidden behind the first planet, and so we then discovered that there was a second signal with a period of about 30 days, and so we were then pretty sure that there were at least two planets in the system. When we removed the orbits of the two first planets, there was something left. There was a signal still present in the data with a period of about 200 days, and that was the signal of the third planet. More from extrasolar planet discoverer Christoph Lovis when Planetary

Radio returns in a minute. 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. We didn't just build it. We attempted to put that first solar sail in orbit, and we're going to try again. You can read about all our exciting projects and get the latest space exploration news in depth at the Society's exciting and informative website, planetary.org. You can also preview our full-color magazine, The Planetary Report.

It's just one of our many member benefits. Want to learn more? Call us at 1-877-PLANETS. That's toll-free, 1-877-752-6387. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Christoph Loves of the Geneva Observatory is our guest. He led the team that recently announced discovery of a three-planet system just 41 light-years from Earth. A system that may also have an

asteroid belt and other similarities to our own solar neighborhood. Could that system have even more planets awaiting discovery? Are you limited now by the sensitivity of the HARPS spectrometer, incredibly sensitive as it is? Is it possible there are more planets or smaller planets in this system? Or does the data tell you, no, this is probably a view of this entire system? Well, actually, it is very possible that there are other planets in this system. At the moment, we cannot exclude, for example, very low-mass planets between the second and third planets or beyond the third planet. planets between the second and third planets or beyond the third planet. If there was, for example,

an Earth-like planet there, then we wouldn't have detected it because its signal would have been too small. And of course, what we cannot exclude are more massive planets farther away outside, because we need good time coverage, which has to be long enough to detect planets on wider orbits. We now continue to monitor this star and if there are other planets, massive planets further away, we are going to detect them in the coming years by continuing to accumulate data points. As far as the precision is concerned, we think that it will still be possible to detect even smaller planets with HARPS, but of course we will need very precise measurements, a lot of measurements, but there is good hope that we will be able to detect even smaller signals in the future. How long have you been collecting this data on this system?

About two years or two and a half years, I'm not sure. By the way, we should let our listeners know that they can see these radial velocity curves in an excellent article by my colleague, Amir Alexander of the Planetary Society. That's at planetary.org, where we will also, right where you can hear this show, put up the link to the Geneva Observatory, where Christophe Levis works and led the team and is the lead author of the paper that appeared in Nature about a month ago about this system. Christophe, talk a little bit about the significance of this Spitzer telescope finding of a probable asteroid belt.

Yes, sure. This is indeed very interesting. It's the first time, to my knowledge, that we have a complete planetary system together with a probable asteroid belt. Well, at the moment, there are still quite a lot of uncertainties on this system because the Spitzer observations, Spitzer actually observed a nexus in infrared light is interpreted as being caused by dust emission, and this dust would be caused by the collision between asteroids in this asteroid belt. So this is quite an indirect detection, and there are maybe more than one explanation, one possible explanation for this dust, but the most prevalent one seems indeed to be the presence of an asteroid belt,

which could be situated between the second and the third planet, or beyond the third planet. Probably we'll need more observation from Spitzer to be able to decide between both possibilities. And now we are convinced that in the near future, with all the Spitzer observations of disk of debris around stars and also the detection of extrasolar planets, we'll be able to get a more complete picture of how

do the planetary system form and what's the relation between the presence of asteroids and of dust and the presence of planets, other interactions between these and so on. And how do this systems evolve in time? Is it possible that asteroid belts remain stable for very long times? Obviously, yes, because there is one in our solar system, but we have no idea if it is normal or if it is exceptional. So all these questions are still open, and we really hope that the Spitzer observations,

together with the extra-terrestrial planet detection, will help us to better understand the conditions of formation of planetary systems and also better understand the formation of our own solar system and to see if it is typical or if it is special and so on. Christophe, we're almost out of time. Let's return to that third planet in the habitable zone for a moment. With the incredible advances in astronomical capabilities in recent years, which have led to the discovery of all of these exoplanets,

can you take a guess at when we might be able to, if not resolve that planet as a disk, at least be able to tell if indeed there is water on a planet 40 or 41 light years away. Yeah, of course, that's the big question that everyone would like to be able to answer. So there is a lot of effort presently being done in astronomy to develop new instruments and new technologies to be able to study all these extrasolar planets more closely. Because, of course, at the moment it's a little bit frustrating that we can only learn a few information about those planets. We can obtain the mass, we can obtain the orbital periods, orbital characteristics.

In a very near future, the interesting thing is that if we can observe transits of these low-mass planets, so when these low-mass planets transit in front of their star, then we'll be able to measure their radius. And that's a major step forward, because if we get the radius and the mass, then we can get the density of the planet, and we can say if it is made of rocks, ice, water maybe, or hydrogen. And maybe that's the first thing that is going to happen in the near future,

is the observation of a low-mass planet, Neptune mass or even lower maybe, probably thanks to the future space missions like CORO or Kepler that are going to be launched in the next years. And these satellites will be able to observe these planetary transits. So we have good hope that we'll be able to measure some of the properties of these extrasolar planets. Now, to understand more precisely your question about if we can resolve the disk of these planets or see the composition of the atmosphere or the surface and so on.

That's for the farther future, maybe in 20 years or something like this. But as I said before, there are a lot of space missions in preparation, like TPF Darwin. TPF, the Terrestrial Planet Finder? Exactly, yes, and also the Darwin mission that aims at being able to investigate the chemical composition and the physical properties of these individual planets. Christophe, we are out of time. It is a delight to talk to you, as it is whenever we speak to explorers and discoverers on Planetary Radio. Good luck with your continuing observations of HD 69830 and its family of planets.

Thank you very much. Christoph Loves is at the Geneva Observatory in Switzerland. He was the lead author of the paper appearing just about a month ago in Nature, revealing the discovery of three Neptune mass planets, one in the habitable zone, circling a star just 40 or 41 light years away from Earth. We're even closer to a visit with Bruce Betts. This week's edition of What's Up? That'll be right after a return visit from Emily.

I'm Emily Lakdawalla, back with Q&A. If our sun is more metal-rich than other stars, does that mean that it has bigger planets than most other stars? In brief, yes, on average. But the sun isn't very much more metal-rich than average. Stars that are close to us and being studied for planets are about 60% as metal-rich as our sun. That's still plenty of metal to form planets with.

It may be that solar systems containing a Jupiter-sized body are not so common, but there's certainly enough metal in these systems to build Neptunes. These solar systems wouldn't look all that different from our own. And Earth-sized planets require a puny quantity of metals compared to Jupiter's. So even if we don't see solar systems just like ours, there are enough metals available to build planets like ours. But we only have to look as far as Venus to see that Earth-sized planets may not look like Earth at all.

Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Live and in person, it's What's Up with Bruce Betts, the Director of Projects for the Planetary Society, joining us every week to tell us what's up in the night sky. I just was so excited because we're in person again. You're sitting right across from me. It's just great to be here.

And I did shower. I know. I can tell. Anyway, yes, it's good to be live, alive, and in person. Yep. Bruce, what's up? Well, we've got Mars and Saturn just nuzzling each other in the evening sky, fairly low in the west after sunset.

Exactly. When people are hearing this, we've already passed their closest approach, their conjunction. We've been telling you about, but they're still very close together, Saturn being the brighter of the two and Mars, not surprisingly, being the redder of the two. All right, sing it with me now. Strangers in the night, exchanging declination. So anyway, these two planets walk into the night sky. Now, we've also got Mercury.

Mercury is going to be tough, tough, tough, but still might catch a glimpse of it. Low, as always, whenever you see it see it it's low somewhere either in the sunset or sunrise this time it's a little bit after sunset uh low in the west but jupiter getting pretty darn high up there in the sky in the early evening and the brightest starlike object in the early evening whereas in the pre-dawn sky still got venus brightest starlike object up there you gotta just keep going i'm still trying trying to control myself over exchanging declinations. Pondering asteroid Sinatra. Okay, this week in space history, in 1978, Pluto's moon Charon was discovered.

Of course, recently we've had more Pluto moons discovered. Someday we'll do a This Week in Space History about them, especially once they get names, like, you know, real names. Let us move on to... Rainbow Space Fact! Matt. Bruce.

I enjoy, once in a while, returning us to the old concept of how much would you weigh on another planet? So you weigh what, about 100 pounds? A little more. A little more, yeah. A little bit more. Yeah, you want to know for real?

No, not really. Good. Let's just say you weigh 100 pounds. Yeah. Which is why you went into radio. Yeah. Yeah. If you weighed 100 pounds here on Earth, many people know on Mars you'd weigh about 38 pounds.

This, by the way, and I love this, it's an old random space fact thing, the gravity on the surface of Mercury, almost exactly the same as on Mars, you'd weigh about 38 pounds. This, by the way, and I love this, it's a little random space fact thing, the gravity on the surface of Mercury, almost exactly the same as on Mars. So you'd weigh 38 pounds there because even though it's smaller, it's the whole gravity, density, all those things trade off. But what about Pluto? That's what you've been asking yourself. How much would you weigh on Pluto? I need to know.

Less than six pounds, Matt. Oh, that's incredible. Talk about a diet. That's great. I need to know. Less than six pounds, Matt. Oh, that's incredible. Talk about a diet. That's great. I can take more luggage. You sure can. Well, why is that? Do they know Pluto is just not terribly dense? Yeah. Well, it's just, it's small. And it's small. It doesn't have a lot of mass and has kind of your run of the mill, rocky icy density. So then it becomes largely, it's a mass and radius. This is purely rhetorical because certainly you don't know, but what would escape velocity be from a body where 100 pounds on Earth weighs 6 pounds?

A buck 25. That's cheap. That's great. I'm going today. We'll get back to you with the exact number. Next week. Next week. After we spend a buck25 to get the answer.

Let's go on to the trivia question, Matt. We asked you, who was the second Soviet in space? Of course, Yuri Gagarin, the first. Who was the second? How'd we do, Matt? Well, I wish we could have given it to one of our Russian listeners, like Georgi Petsrov,

who did get the answer correct, But you know what? It's random. What can we tell you, folks? David Weatherholt. David from Newport News, Virginia, came in with the answer. German Titov, who was 25 years old, apparently still the youngest person ever to go into space. 25, his only trip into space. German Titov, not to be confused with later Titov, like Vladimir Titov, who flew much later on in the Soviet and Russian space programs. And only spent a day. I guess he got a little sick to his stomach. And I don't know if that meant they brought him home early or, you know, because the day was pretty good.

It was pretty much a day. He was the second person to orbit the Earth. He beat out John Glenn. John Glenn being the third to do a complete orbit around the Earth. He beat out John Glenn. John Glenn being the third to do a complete orbit around the Earth. Yes, I got sick to the stomach. Didn't help his reputation, but that was before they knew

it was fairly common and not easily predictable who would do such things. Couldn't have been too surprising. Now moving from Soviet cosmonauts to NASA astronauts, here's our random trivia question of the day, which is, what NASA astronaut selection group was Buzz Aldrin in?

What NASA astronaut selection group? Which astronaut class, basically, was Buzz Aldrin in? I think I know, and I almost, as I sometimes do, yes, I almost blurted it out. Okay, how do they enter? Go to planetary.org slash radio and find out how to send us your email and try to win your fabulous uniform as a Planetary Radio listener. A Planetary Radio t-shirt.

Better get it to us, though, by the 26th of June. June 26th at 2 p.m. Pacific time to be a part of this newest, latest, and almost greatest space trivia contest from Planetary Radio. We've got to get around to doing a really big contest with a really big prize. Can we do that sometime maybe over the summer? Yes. Let's do a big contest with a big prize as soon as our listeners send us one.

No, we actually will. We'll come up with some bigger and wilder contests, like, ooh, we could give them a Planetary Radio t-shirt that's signed by us. That'd be huge! Yeah, you think? Well, no, but maybe we can come up with something else. Yeah.

We done? We are. We are done. Go out there, look up the night sky, and think about something new and creative to do with a magnet. Thank you, and good night. I love magnets.

I have this really cool one that came out of a hard disk drive. I think it'll take your finger off. Well, that is something new and creative. So do you have a metal finger? I should have wondered about that, shouldn't I? I guess it's Ferris, whatever it is. Probably.

There's iron in the blood, as X-Men has taught us. Save Ferris. Okay, now we really got to go. He's Bruce Fetz. He's the-R. B-O-R. He's Bruce Betts. He's the director of projects for the Planetary Society. He joins us every week here for What's Up. B-O-R. Planetary Radio is produced by the Planetary Society in Pasadena, California.

Have a great week, everyone. Thank you.