Planetary Radio: Space Exploration, Astronomy and Science - Billions of Earths?

Episode Date: September 6, 2004

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A galaxy full of planets on Planetary Radio. Hi everyone, I'm Matt Kaplan, back with Public Radio's weekly trip around the solar system and beyond. Way beyond this week, as we welcome back Jeff Marcy of UC Berkeley. He and his colleagues have been in the news lately, thanks to their discovery of planets that are much closer in size to our own Earth. Later, of course, we'll be joined by Bruce Betts with this week's What's Up and his latest space trivia contest. Here's a taste of what's happening around our universe.

Recent reports of a phone call from E.T. are sadly highly exaggerated, says SETI at home chief scientist Dan Wertheimer. He and others with the project believe the so-called signal is almost certain to be explained by a natural phenomenon. Scientists in Georgia have found more evidence of a deep impact almost 36 million years old. The 50-mile-wide Chesapeake crater was first discovered in 1994. Now grains of quartz formed in the heat of that meteor strike have been dug up. And the man who first proposed that comets are dirty snowballs has passed away. At 97, Fred Whipple was the oldest living astronomer. He made many other important contributions to science in his long career. You can fill in the details of these and other stories at the Planetary Society's website, planetary.org. I'll be back with Jeff Marcy, professional planet hunter, right after this high-impact visit with Emily.

Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, what's the difference between a meteor, a meteorite, and a meteoroid? The word meteor was originally used to describe any phenomenon that occurred in the sky, but now its definition has narrowed to the fiery trails that streak across the sky during meteor showers. These showers of fiery trails were once thought to have an earthly origin. During the 19th century, people began to associate these fiery meteors with rocks that fell to the earth. These rocks became known as meteorites. Once people began to understand that the meteorites didn't come from earth but actually

came from space, they needed a word to name the population of objects out in space that supply meteor showers, and the term meteoroid was born. So there are meteoroids out in space which can enter the earth's atmosphere, leaving meteor trails. And if they survive to hit the surface, they are meteorites. But wait, what makes a meteoroid different from an asteroid or a comet? Stay tuned to Planetary Radio to find out. Dr. Ann Kinney has one of the world's greatest job titles. She is director of NASA's Universe Division in Washington, D.C. This was her reaction to the announcements made by planet-hunting astronomers just a few days ago.

I think that what you've heard is an astounding amount of progress for nine years of research. I mean, ten years ago, this field barely existed. And now, I myself never dreamt that we would be making announcements about Neptune-class planets at this stage. Our guest this week was with Ann Kinney at that NASA press briefing. Jeff Marcy was on this show just three months ago, but we knew we had to get him back for you. He joined us from UC Berkeley to talk about that astounding progress Dr. Kinney mentioned and where he and his team will go from here. Jeff Marcy, congratulations.

Thank you so much. You told us last May that you get paid by the planet. From my viewpoint, you guys deserve quite a bonus last week. Well, when you're paid on a commission basis, you have to work extra hard. And the other sort of bonus that I heard about that was suggested by Alan Boss of the Carnegie Institution, he's the author of Looking for Earths, during the NASA press briefing that you did a few days ago, he said that you really deserve an Olympic gold medal. Well, of course, I don't know about that.

My team works very hard, and we have fantastic people at the observatory. Gold medal doesn't quite apply because this is such a large team effort. Probably six or seven of my collaborators have been working day and night, seven days a week, and then there's all the technical staff that make the optics and the computers and the telescopes work. So it's really more of a relay effort when there's a lot of team members. If somebody had said to you nine years ago, as you and others were just beginning to discover extrasolar planets, that by now you would be discovering ones that are only a few times as big as our Earth. What would you have said?

Well, it was clearly impossible. I mean, most people back in the 1990s thought that even finding the largest of the planets, the Jupiters, would be impossible. People literally laughed at me. I asked some experts, do you think we really will be able to find planets by looking for the wobble of a star due to the planet yanking on it gravitationally? And, you know, people said, of course, probably not. It's such a tiny effect. And so even finding the biggest planets was thought to be ridiculous. And I remember, I was going to say as a kid, but it's more recent than that, people saying, well, we'll probably never be able to detect planets, just like we'll never be able to resolve a star as a disk, except, of course, for our own star and the planets circling our own sun.

Well, you know, people compared a few years ago, nine years ago, people compared hunting for planets to the search for UFOs and maybe pyramid power and that sort of thing. Of course, you know, you can see there's sort of a connection between them all. Indeed, we wonder if the extraterrestrials are hovering around watching us from afar. But in the case of planets, it really worked out, and it didn't have to be that way. I mean, we could be sitting here today in 2004, 2005, still wondering where the planets are. Are there planets? Is our solar system special? And yet, here we are nine years later,

and I'm proud to be part of the media conspiracy that's keeping you from doing any science this week. You really have been busy, haven't you? Well, personally, it's been a little crazy. I have to say, I mean, on Tuesday, when we were at NASA headquarters announcing the first Neptunes ever found, I think I did 25 television interviews with TV stations from Beijing and Hungary,

and there was one from South America. And so that's the lovely thing about these planets is that everybody is interested. Children of six, seven years old point up at the night sky and wonder the same profound questions that we professionals are asking. Are there other Earths out there, and are we alone? Clearly, our audience, me included, were pretty thrilled and very happy to have you back on. Didn't realize that we'd be having you back on quite so soon. What, if anything, that you can pin down, what led to this more than an order of magnitude improvement in your ability to discover planets? Well, we're very lucky to have access here in the United States, anyway, to the world's largest telescope, the Keck telescope, located on the big island of Hawaii, high atop a hopefully dormant volcano called Mauna Kea.

Hawaii, high atop a hopefully dormant volcano called Mauna Kea. And with that world's largest telescope, we can gather enough photons, which is really the key, from these stars to spread them out into all of their wavelengths of light, blue, green, yellow, and red, and look for this tiny Doppler shift of the light from the star as the stars yanked around by the planet. So really, without the world's largest telescope, we couldn't do it. And then to be a little more recent, in the last few years, we've improved the optics of the spectrometer that spreads the light out into a rainbow of colors. We've gotten much faster computers to analyze those spectra.

And frankly, my collaborators, Paul Butler, Deborah Fisher, Steve Vogt, and I, have rewritten all of our software that we use to analyze the data. So it's a combination of a lot of improvements that have led to the discovery of Neptune-like, maybe rocky planets. And in fact, you said during that NASA press briefing just a few days ago that you really have to look now at everything, all of your plans, and how you conduct this search, because it suddenly now seems to be within the realm of possibility that even before these amazing new planet-finding NASA missions are launched,

you guys might be able to find another Earth? Well, I hate to sound too optimistic, but if you don't dream, you probably won't get anywhere. What we're hoping here is that we can improve yet further this so-called Doppler wobble technique for finding planets. Here we've found planets that are about 15 times the mass of the Earth, and with another factor of two or three improvement, maybe we can get down to five Earth masses. That's starting to get interesting, because a planet five times the mass of the Earth, well, it would just be a little bit bigger than the Earth. It would have a rocky surface,

maybe lukewarm temperatures if it's the right distance from the star, and it could harbor liquid water that would serve as the solvent for biochemistry. Alan Boss also gave you lots of kudos, because this planet that you found, Circuline, I hope I pronounced it correctly, Gliese 436. Exactly.

It's an M-class red dwarf. There are an awful lot of them around, aren't there? Well, you know, our Milky Way galaxy contains 200 billion stars. Many of them are pretty average stars, like our sun, but most of the stars are, in fact, these low-mass little runts of stars, the so-called M dwarfs, M-type stars. So something like 70% of the stars in our galaxy are of this type, and now, finally, we've found not only a planet around one of them, but, in fact, a rocky one.

And that clearly suggests that our galaxy almost certainly harbors billions, indeed, I have to say, 10 or 20 billion planetary systems. As exciting as the announcements were that you made about the discovery of these new planets, that quote that you gave during the press briefing, which you've just almost repeated, that you believe there may be now as many as 20 billion planetary systems in our galaxy alone, that gave me chills. You know, I have to say, I'm a conservative guy when it comes to science anyway, and that's a conservative number because you see our galaxy with 20 billion planetary systems,

that's got to be a lower limit with 200 billion stars. I'm only imagining at at the very least, one out of ten of them has a planetary system. And frankly, it's pretty hard to imagine that it's so few. We're probably just filled to the brim with planets of all sorts, all sizes, all types of orbits, some of them with just the right temperature for biology. Wow. Jeff Marcy of UC Berkeley is our guest.

He's part of the team that just announced a couple of planets which are closer in size to our own Earth than any found before, especially if you consider them along with one found by a European team. And maybe we'll mention that work after the break. But I also hope, Jeff, that we can talk a little bit more about where you go from here after we do take this quick break. about where you go from here after we do take this quick 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.

Jeff Marcy of UC Berkeley, professional planet finder, is our guest on Planetary Radio. We had him on just a few months ago, but now he goes off and finds a few more. And they are, in many ways at least, more interesting than any found before, in large part because they're not so large. They're only a few times as large as our own planet Earth. large. They're only a few times as large as our own planet Earth. And as you heard him say in the first part of our conversation, the search continues and becomes ever more refined. Jeff, you are certainly not alone in this. Talk about your colleagues around the world, maybe beginning with Barbara MacArthur, as she put it, the middle of West Texas. There's a wonderful planet hunting team there in Austin, Texas, based at the University of Texas.

Barbara MacArthur was leading the search for planets around this very nearby solar-type star, 55 Cancri. And what she found with her colleagues Bill Cochran and Fritz Benedict was a Neptune around this solar-type star, the first Neptune found around a solar-type star, which is interesting in two ways. First, it's probably small and maybe rocky, which makes it a possible abode for life. But also, that star harbors three other planets. One of them, the outermost, orbits as far from the star, 55 Cancri, as our own Jupiter orbits the sun. So that system has not only a Jupiter analog, but now a possibly rocky planet in close. So you can begin to see that the architecture of other planetary systems in some ways is similar to and in other ways different from our own solar system.

How about that team in Switzerland, which made their announcement of a Neptune-class planet just maybe a week before yours. Well, they're doing beautiful work in Geneva. It's led by a venerable, wonderful astronomer, Michel Mayor. He's built his own spectrometer to do this. It's called HARPS. And you've got to give them credit for building a spectrometer specifically designed to hunt for planets.

It sits in the Atacama Desert on a modest-sized telescope there in Chile. And with it, they're surveying 100 nights a year for extrasolar planets. And as you said, the more sensitive the spectrometer, the smaller a wobble in the orbit of that star that you can detect. Yeah, that's right. In the planet hunting game, little is better. And finding the littler planets means you're finding planets more and more like the Earth. And the problem is, technically, that a little planet can't be detected directly, nor can the bigger planets.

They can only be detected by how they gravitationally yank on their host star. And so little planets are hard to find because they don't pull very hard. We'll mention that there's much more, a lot more detail about all of these planet searches on the Planetary Society website at planetary.org. And we will also have a link on the website where you can hear this radio show at planetary.org slash radio to websites that have a lot to do with NASA and Jeff's work. Jeff, I said we wanted to talk a little bit more about where you go from here and how these most recent discoveries are affecting your work.

You've already expressed that optimism, well placed we hope, that we might find a real Earth-like or perhaps a super-Earth, a little bit bigger-than-Earth-sized planet, sooner than anybody thought? Well, I'll tell you something that I don't think anybody knows, and that is we've only learned in the last month or so that stars are more quiescent than we thought they were, making them more amenable to precise Doppler shift measurements and hence allowing us to find these even smaller planets. So the future is ridiculously bright. I'm just almost giddy about it. We should be able to find planets that are only a few times bigger than the Earth,

and we have to gear up with the Keck telescope now to survey stars even more intensely than we had before to get enough photons to observe the stars often enough to find these Earth-like planets. So obviously you feel that you're not at the limits of what the Keck is capable of doing. Well, that's right. We're not really at the limit yet. We just installed a new digital camera, a CCD detector, which, by the way, costs a little bit more than the one that you might have in your drawer in your house. The CCD digital camera was $950,000.

But we just installed it. It's going to be designed and geared up to hunt for planets of the lowest mass. So we're really opening up a new window here into a new era of planet hunting. In how you analyze this data, is that changing as you refine your techniques? You know, that's really where we spend our time. People often ask, well, what do you do? You go to the telescope, you take data, then what? And the answer is we come back with the data,

and then we write algorithms, software, that is used to analyze the spectra, the colors that come from the stars. And that's really the bread-and-but butter activity that allows us to find ever smaller planets. Let's look out then over maybe the next five years, because I guess if we get out much further than that, we're talking about these NASA missions that everyone hopes will make it into space. If you wanted a hazard of prediction, how far do you think we might get in the next five or so? Here's what's going to happen. This is pretty exciting.

We probably will find, if you just want to guess reasonably, we in the astronomical community will probably find another dozen or two of these rocky planets of, say, 10 or 20 Earth masses, maybe some down as low as five Earth masses. But here's the interesting point. We will then collaborate with our theoretical companions, that is to say, colleagues who work on the theoretical formation of planetary systems, and ask them to build new theories for the formation of planets based on our observations, albeit only of these larger Earths.

And they may well be able to extrapolate and tell us what fraction of stars have Earth-like planets and what those Earth-like planets are like. Yeah, I think actually one of the most exciting things about your work is that you're giving us some real numbers to fill into Dr. Drake's equation. Well, that's a whole other realm. I mean, the search for extraterrestrial intelligence and the prospects for life, both primitive and intelligent, we have much more reason to be optimistic about life in the universe. We didn't really know as of two weeks ago. We didn't know for sure if there were lots of rocky planets out

there. Now I think it's a certainty. And so those rocky planets can serve as the petri dishes within which biochemistry experiments can occur, replicating molecules, maybe can spring up and voila, you have primitive life. My fingers are crossed. We've got maybe a minute left, Jeff. Just review what is out there a few years in NASA's plans. And are you any less excited about those planet-finding missions since you seem to be doing so well from down here on the surface? There are three NASA missions, not just on the drawing boards, but actually in the engineering shops and even the machine shops.

The first is called Kepler. Kepler is a mission to survey stars to see if any of them dim, dim due to an Earth-like planet crossing in front of the star, blocking the starlight, making the star dim in a repeated way as the planets go around and around. And that will give us the first measure of what fraction of stars have Earth. And then the next mission that NASA is doing is called the Space Interferometry Mission. It, too, will find Earth closer to us, 10, 20 light years away. And then the big granddaddy is called the Terrestrial Planet Finder.

And that one NASA is hoping will take the first pictures of a pale blue dot orbiting a yellow star, reminding us of home. And we love that phrase, pale blue dot. Jeff Marcy, we are out of time. I guess people can watch for, those who really want the nitty-gritty, can watch for the December issue of the Astrophysical Journal, the publishing of the work done by you and your colleagues. My pleasure being here. Jeff Marcy is with UC Berkeley, and he is in the business of finding planets

and seems to be awfully good at it, along with his colleagues and his team at Berkeley and, as you heard him say, elsewhere around the world. Lots more in store, and so, Jeff, I hope that we'll have you back on once again, sooner than we thought we would. It would be my pleasure. I'll be back with Bruce Betts and this week's edition of What's Up right after this return visit from Emily. I'm Emily Lakdawalla back with Q&A.

What makes meteoroids different from asteroids and comets? The commonly accepted difference is size. Meteoroids are small. Asteroids and comets are big. The reason size is important is that we can see asteroids and comets with telescopes, but we can't see meteoroids. We can guess that meteoroids are made of the same stuff as asteroids and comets because there are annual meteor showers that take place when the Earth passes through the wake of a passing comet. But until our telescopes get sensitive enough to see meteoroids, we won't be able to compare meteoroids and asteroids directly. One day, though, our telescopes may well be that sensitive, in which case we'll have ourselves a terminology problem. We're running into that problem with the word moon already.

The Cassini spacecraft just discovered two bodies only three kilometers across orbiting Saturn. Are these moons, or just big ring particles? Let the semantic arguments begin. And that's just a warm-up for the question of whether Pluto is really a planet. 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 once again for What's Up on Planetary Radio

with the Director of Projects for the Planetary Society, Dr. Bruce Betts. Dr. Betts, new planets, new Neptune-sized planets. Is this exciting or what? This is so exciting. I mean, we're the Planetary Society. Don't we get a bonus when this happens? Hey, you're right. We should. I i mean after all it

was clearly uh founded with vision there were only nine when we started they're like 125 now yeah more i think yeah and we've grown by a hundred and you know i don't know anyway let's talk about what's up the night sky shall we yeah planets let's talk about that ones you can actually see with your naked eye instead of through crazed spectroscopic techniques on gigantic telescopes. And it's good to know with 20 billion planetary systems in the galaxy that we hold our own

right here in the solar system. Darn straight, Tootin' stuff. Anyway, if you're going to see planets, you need to look before dawn, but you've got great planets to look at. If you do, Venus, brightest star-like object up there. Look in the east. You can't miss it before dawn.

And you'll see Saturn, also looking like a bright star, but not nearly as bright, just above Venus, growing slightly farther away, as seen in our sky over the coming weeks. To their upper left, you can see the stars Castor and Pollux, the twins. coming weeks. To their upper left, you can see the stars Castor and Pollux, the twins. You can also check the moon out as its crescent goes passing by Saturn, then Venus on September 9th to the 11th. And then it visits with Mercury, which is far to the lower left of Saturn and Venus. Really good time to see Mercury right now. It's always going to be low on the horizon, but it's a good time. It's actually bright brightened up it's actually a little brighter than saturn is looks like a very bright star and again far to the lower left of venus and saturn and it'll be near the moon on the 12th and 13th of september and and september 10th don't miss this mac go out there mercury really close to the star regulus

not actually really close to it but it's seen in our sky very, very close. Tenths of a degree apart in the night sky, particularly on the 10th, but you'll also see it on like the 9th and 11th. On to this week in space history. September 11, 1997, Mars Global Surveyor arrived at Mars. It's been up there working constantly for seven years now, returning unbelievable data about Mars that's revolutionized our understanding of the planet. This mapper that's given us not only fantastic images, but topographic data, magnetic data, all sorts of stuff still cranking seven years later.

Unbelievable. On to random space. Of the 22,000 or so meteorites that have been discovered on the Earth, approximately 32 have now been identified as originating from the planet Mars. And how is it that they know that for a fact? They have a little message on them. Made on Mars. Yeah, it's stamped. It's some type of international legal agreement.

Made in Meridiani Planet. No, it's actually interesting. It's some type of international legal agreement. Made in Meridiani Planum. No, it's actually interesting. The original ones was determined from gas that had been trapped inside these rocks. And that was compared to the Viking lander observations of the Martian atmosphere, which has very different isotopic compositions. So different, like nitrogen 15 to 14 ratios. And so a unique atmosphere compared to the Earth or other planets in the solar system.

They compared the trapped gases, saw, hey, they look just like Mars. And so that was the real killer evidence that told us they were from there. Now, based on composition and comparisons, they've been able to identify more, and a lot more discovered and identified as Martian in the last two or three years, actually. Fascinating. Probably many more to be found. Indeedy-do. On to the trivia contest. Our previous trivia contest was,

what was the first lander to return images from the surface of Venus? How'd we do? The listeners did well. They always do. We got, I think, only one answer that wasn't correct this time. You know, what we do is try to select randomly from all those that are submitted with the correct answer. And it turns out that this time we head for Scandinavia. Our winner this week is Bjorn Getta. Bjorn Getta of Sweden had the correct answer.

And it was, of course, Venera 9. The Venera 9 lander put up there by the Soviets. Touchdown on the surface of Venus, October 22, 1975. So, Bjorn, congratulations. Congratulations to you. Let's go on to the new trivia contest. Those Martian meteorites I talked about originally were referred to as, and still are, as SNCs, sometimes pronounced SNICs, the SNIC meteorites. What does S-N-N-C stand for in the SNIC meteorites?

Good one. Thank you. Thank you, Matt. How do they enter? Go to planetary.org slash radio and you'll find out how to enter. Basically email your answers to us for your chance to win the fabulous planetary radio t-shirt just as bjorn ghetto will soon be receiving at his home in sweden he'll probably have to wear it under a heavy coat but what the heck summer will

come around again and there it'll be a planetary radio t-shirt get yours by entering the contest by here's the deadline for this one, Wednesday, September 15 at noon Pacific. Wednesday, September 15 at noon Pacific. Give us your T-shirt size. It'll save a little bit of trouble there. We've still got to get Bjorns, I'm afraid. Are we done, Bruce? Yes, we are, Matt.

Everyone go out, look up in the night sky, and think about health and happiness. Thank you. Good night. And that's a particularly sweet health and happiness. Thank you. Good night. And that's a particularly sweet contribution from Dr. Betts, Bruce Betts, the Director of Projects from the Planetary Society, who does join us right here every week on Planetary Radio with What's Up. And we'll be back with much more next time.

I hope you'll join us again. Have a great week, everyone.