Finding the perfect planet with "Alien hunter" Seth Shostak

Remember how you learned the names of the planets in elementary school? There was this mnemonic device – let’s see if I remember it: "My Very Educated Mother Just Sent Us Nine Pizzas" ... or was it Pies? Whatever that P-word was, it stood for the planet Pluto. That is, until 2006.

DISCOVERY NEWS REPORTER JORGE RIBAS: Pluto, the long-embattled ninth planet in our solar system, is officially out of the club. The frozen little world got the pink slip Thursday in Prague, as the International Astronomical Union, or IAU, approved new guidelines for what it takes to be named a planet.

Pluto didn’t have what it takes. Planets come, and planets go. And last month, lo and behold – we found a new one.

Astronomers around the world rejoiced at the discovery of a new planet, lovingly called Gliese 581 g after the star that it orbits. And it’s pretty close – only 20 light years away. So let’s head there right now:

DARK HELMET [From “Spaceballs,” 1987]: Light speed is too slow. We're going to have to go right to ... ludicrous speed!

Unfortunately, we can’t travel at light speed, let alone ludicrous speed. So 20 light years might as well be a galaxy far, far away. So then, why all the fuss? Well, Gliese 581 g has a lot of Earth-like qualities, meaning it’s potentially habitable. And that means Earthlings might have a shot at a second home planet. That is, unless somebody – or something  – already calls it home...

Here in the Bay Area, the SETI Institute deals with astronomical research, and the search for extraterrestrial life. So KALW’s Hana Baba visited the SETI Institute in Mountain View and sat down with astronomer Seth Shostak to find out more about Gliese 581 g.

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HANA BABA: First, what's the significance of discovering this "new planet?" How big of a deal is this?

SETH SHOSTAK: Well, I think it's not an unexpected deal, but it is still big because we found 500 planets around other stars – that's the tally since 1995 when the first one was found around a normal, other kind of star. Almost 500 planets, but none of them are the kinds of planets that you would want to live on because they tend to be very big planets or they're planets that are in peculiar egg-shaped orbits. They'd either be too hot or too cold, mostly too hot, actually. Now, the assumption’s always been that the good planets are out there, but we hadn't found them, mostly because of the limitations of technology. But this is the first one that we've found that happens to be at the right distance from its star that it might not be very unpleasant to be on. It might have liquid oceans, it might have a thick atmosphere, so that makes it exciting.

BABA: So you say the "good planet." What's a good planet to you?

SHOSTAK: For us, a good planet is a planet that can support liquid water, preferably on the surface, not hidden underneath somewhere. And we have all these oceans, I mean two-thirds of the surface of the earth is covered with liquid water. That's where life began on earth; that's where a lot of the life on earth still lives. We think it's necessary in order to get life started to have these big, liquid environments. And in order to have that liquid ocean on the surface of our planet, we need the right temperature. In other words, we can't be too close to the sun, too far from the sun. But also, you need an atmosphere cause without an atmosphere, or we'd all just immediately vaporize into space, which wouldn't be a good thing. So indeed, that's the kind of world that we think might be the most attractive for E.T. Mind you, it's a little bit self-centered of course, but we're the only example of intelligent, or any other kind of life we know.

BABA: So they said they found this planet smack-dab in the middle of the Goldilocks Zone. What's the Goldilocks zone in outer space?

SHOSTAK: Yeah, well the Goldilocks Zone is just a perfect analogy with those three bowls of soup. One bowl of soup is too hot, and the other bit of porridge was too cold, and the other one was just right. This is a planet that's, as far as we can tell, not too hot, not too cold – just right.

Do keep in mind that the way this planet was found was simply by observing the star that it goes around, a star that's about 20 light years away. So, what is that? On the order of a hundred and ten trillion miles away from where we're sitting – that's a long way, or it sounds like a long way. It's actually pretty close.

BABA: That's close?

SHOSTAK: Yes, that's our backyard, actually. But this one happens to be going around that star and causing that star to wobble a little bit, that's how we find it. We haven't actually seen this planet, so we don't know whether it has oceans or not. This is all inferred on the basis of this slight wobble that it causes...

BABA: So nobody's seen anything yet?

SHOSTAK: Nope!

BABA: What are they celebrating?

SHOSTAK: Actually, even the discovery is slightly dicey. There's another group that's analyzed the data as well, and they say, "You know, we're not so sure we see Gliese 581 g in the data. So there's a little bit of controversy, that's not so unusual in a new discovery, right? But let's assume that it's really there. Then, all you can tell is that it's a planet that's at a certain distance from that star. And also you can tell something about the mass of that planet. We know about how big it is – it's maybe about one and a half to two times the mass of the earth, which is about the same size as the earth, really. And it's at the right distance so that the temperatures won't be way below freezing or way above boiling.

BABA: They say they found this planet after 11 years of searching. And they're hailing this as a really short time to be finding a planet. So how do astronomists go about searching for planets? What are you looking for?

SHOSTAK: Well, it indeed requires mostly three things: a big telescope; what's called a spectroscope, which is just a piece of instrumentation that's used to break up any starlight that you're looking at into its colors; and third, a lot of patience.

But the way they do it is they just look at a bunch of nearby stars. They have a big list of hundreds and hundreds of nearby stars, and you just look at them and you see from their light whether they're moving towards you or away from you. You just watch all these planets dance. Well, the ones that do dance! And it turns out that we found about 400-500 dancing stars in the sky so far in the last 15-16 years. And those dances are because they've got partners, little planetary partners, that they're whirling around and doing their do-si-dos with.

BABA: This planet is supposed to be the most earth-like planet yet discovered. So if it does have habitable qualities, what does that mean for us in terms of going there? Is it too far?

SHOSTAK: Well, in a word: yes. Our rockets go out about ... well, the best NASA rockets move at about seven, eight miles a second. Which is, you know, great if you're going to Stockton! But if you were going to the moon at that speed, it'd take a couple of days, that's how long it took the astronuats to get to the moon. If you were going to Mars, it'd take you a couple of months. If you're going to Pluto, if for some reason you wanted to go to Pluto, it might take you ten years, five years, something like that.

But if you were going to Gliese 581 g at that speed, well, it's going to take you on the order of ... maybe a half a million years or something like that.

Now, of course, anybody listening to this will be saying, "Ah well, yes. But of course our rockets are too slow, but we'll build better rockets! We'll invent warp drive or something like that!" Well, who's to say that warp drive can even exist, but you know, maybe in some not-so-near future, we might be able to go to the stars, but at the moment, that's not really on for us. We're not going to go visit. Mind you, we can build bigger telescopes, and we might be able to find some evidence that there's life on this planet.

BABA: If there was to be life on this planet, what would it take the form of?

SHOSTAK: Well, we don't know that! Most life on this planet is single-celled. It's microscopic. I mean earth, up until 500 million years ago – there was nothing on earth that you could see with your eyes. A lot of life had been here for billions of years, but it was all in a soup! You needed a microscope as they say. So, you know, it could be that this planet has a lot of life, but it's all of interest to people who have good optics with them.

On the other hand, it's not at all impossible that it's proceeded to something a little more interesting. Maybe our equivalent of plants and animals, maybe they have something there. We just don't know.

BABA: They've discovered it; they've identified this planet. What happens next?

SHOSTAK: Well, I'm sure that there will be a lot more observations of this particular system, just to begin with to confirm that 581 g is really there. But also, you can learn more about it the longer you make observations.

And also, what I think is really exciting is the fact that in two years' time, NASA's Kepler telescope, which is just a big telescope up in space, it's not very far from the earth, it's just staring at about 150,000 stars. It has the ability to find planets that are small. That is, the size of the earth, maybe the size of Mars, maybe even a little bit smaller than that. And it will in two years' time, it will be able to answer this very big question. That question being: what fraction of stars in the entire universe – because it will answer for the entire universe – what fraction of stars have planets that are somewhat like the earth?

BABA: In the entire universe?

SHOSTAK: Well, because you look at 150,000 stars that are nearby, and one thing we know about the universe is that it's not very different when you go from place to place. It's generally speaking, the same. We're typical. And nobody likes to think they're typical, but we are! We're just another duck in the row! It will know. Within two years, you will know. All you have to do is keep reading the news for the next two years, and we will know, we will be able to say that 1% of all stars have planets like the Earth, or 10%, or .001%...

BABA: And might some be closer than Gliese 581 g?

SHOSTAK: Could very well be. Nobody knows what the answer's going to be, of course, because we don't have the answer yet. But the smart money, which is to say the people that are doing the experiment, figure that maybe a few percent of all stars have planets like the earth. Now if that's true, if it's two or three percent, that means that they're on the order of a few tens of billions of earths just in our galaxy. And keep in mind, there a hundred billion other galaxies...

BABA: I just can't wrap my head around that.

SHOSTAK: These are huge numbers! That's part of the excitement, of course. When you have ten billion other earths, just in the Milky Way, it's hard to imagine that they're all sterile.

BABA: E.T.'s somewhere!

SHOSTAK: I think so!

You can hear more from Seth Shostak on the weekly radio program “Are We Alone.” That show airs on Tuesday’s at 1 p.m. at KALW 91.7 FM. You can also listen online at kalw.org.