Dean chats with Dr. Lisa Kaltenegger, an astrophysicist, astrobiologist and author of, Alien Earths: The New Science of Planet Hunting in the Cosmos. Listen in to hear about the strangest exoplanets Dr. Kaltenegger has come across, and if an Earth 2.0 is out there waiting to be found.
NASA/Caltech
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EPISODE TRANSCRIPT:
Looking Up is transcribed using a combination of AI speech recognition and human editors. It may contain errors. Please check the corresponding audio before quoting in print.
Dean Regas: So we have eight planets in our solar system, right?
[Archival Audio]: Pluto was a planet.
Dean Regas: No, no, don't get me started by Pluto. Not right now. And we have hundreds of moons that circle the planets. That's not even counting Pluto's moons. Dad,
[Archival Audio]: Pluto isn't a planet.
Dean Regas: For centuries, people have looked up at the wandering planets and wondered, what was up there?
Was there life on the moon? On Mars? Jupiter even? Of course, most of these worlds have been ruled out as places to look for aliens. So They're too hot, too cold, too gaseous. What if I told you that there's a lot more places to look farther away, circling distant stars. Astronomers have already found more than 5, 000 other planets, exoplanets, and some of them are downright alien.
From the studios of Cincinnati Public Radio, I'm your host, Dean Regas. And this is Looking Up, theshow that takes you deep into the cosmos or just to the telescope in your backyard to learn more about what makes this amazing universe of ours so great. My guest today is Dr. Lisa Kaltenegger, an astrophysicist and astrobiologist and author of Alien Earths. The science for planet hunting in the cosmos.
So what is an exoplanet anyway?
[Archival Audio]: The term exoplanet means a planet outside our solar system, a planet that doesn't orbit our sun most orbit other stars, but some are just sunless wanderers out in the space between the stars.
Dean Regas: An exoplanet is a planet circling around a. Distant star. So, you know, we have our eight planets going around our sun, which is about 93 million miles away. But all the stars out there are trillions of miles away. And it's super hard to find a planet around another star. This is something we've only really been able to do in the last 20 years or so, at least very well.
And so, how do we find a teeny tiny little planet that's reflecting starlight from trillions of miles away? It's really tough. And so there's a couple methods. I'm only going to go over a few of them because there's so many of them. But, of course, the first one is, well, let's just take a picture of one. We call it direct imaging.
[Archival Audio]: In 2004, The first picture of an exoplanet was released, 2M1207b, a planet with five times the mass of Jupiter.
Dean Regas: And this is super tough, because the stars are so bright that you really can't see a little planet next to them, unless the planet is really far away from its star. And it's a really big planet, like a Jupiter sized planet.
So very, very few exoplanets have been found with direct imaging. Then there's another one called astrometry, where we basically watch for a star wobbling, like it shakes and shimmies and moves because a giant planet is going around it and its gravity affects the star enough to actually move the star just a little bit.
And if you see it move in a regular pattern, well, you got a planet moving it. But again, that's going to show you gigantic planets.
The one that's really been hot lately is called the transit method. And this is when a planet goes in front of a star and blocks out a little bit of its light. And that means we can detect a dip in the star's brightness. And so we watch for the starlight dimming. And if it dims on a regular basis and dims about the same amount, we know there's a planet that's blocking out that light.
It's like a little teeny tiny eclipse. That's the way we find most planets. And with the transit method, we can find big planets. Sure. We can also find little tiny planets like. Earth sized planets. Because those are the ones we want to find, right? We want to find the ones that look like us. Because if we find ones that look like us, what else are we going to find?
Well, I'm not going to go all the way to aliens, but you know, maybe aliens. That's what we want. We want to find Earth 2. 0. This is all exciting stuff. This is like one of the newest fields, very fast growing, and probably going better than anybody would have hoped. Because it's looking like, on average, one out of every five stars in our galaxy has a planet.
[Archival Audio]: Here's the thing about exoplanets, they are everywhere. In fact, from our observations so far, we know there are more planets than stars.
Dean Regas: And there's 300 billion stars in our galaxy. That's a lot of planets. And I can't wait to hear more from our guests today about this.
Well, Lisa, thanks so much for joining me today.
Dr. Lisa Kaltenegger: Thanks for having me.
Dean Regas: Now, am I wrong in saying that Exoplanet research is the hottest, most exciting field in astronomy right now?
Dr. Lisa Kaltenegger: Well, you know, I'm not allowed to say it, but I think you might not be that far off.
Dean Regas: What's happening? What's making this thing just take off like crazy?
Dr. Lisa Kaltenegger: I think to me personally, what is so exciting that for the first time ever, we have a telescope in space, the James Webb Space Telescope, that can now look at the small planets that could potentially be like ours. And that's a game changer. So for me personally, for me personally. This is what I love to think about, this big space telescope looking at these other worlds that could be like ours and getting us that information now.
Dean Regas: Well, and so have we found any other like solar systems like ours, you know, with multiple planets that are, some are large, some are gaseous, some are small and rocky, things like that.
Dr. Lisa Kaltenegger: Absolutely, so what we found is planetary systems out there, and we have hundreds to thousands of those because we already found more than 5, 600 planets around other stars, so that's incredible, a huge number, and we have 10, 000s of candidates, that just basically means we see a signal and we still have to make sure that it's not anything wrong with the detector that saw that signal or the telescope at that time, but so we have thousands of new worlds around other stars that we saw.
And most of them are not alone. So most of them have systems of planets and some of them even have more planets than we do. So we are just gathering the knowledge about what's normal out there, but there are planetary systems. So
Dean Regas: it's kind of like the James Webb Space Telescope can point at these candidates, the more interesting ones, I guess, to get a closer look at them.
Dr. Lisa Kaltenegger: Absolutely. And I wish we could see the vegetation and the trees and whatever kind of creatures you want to imagine jumping around on these other planets. But we are far away from that right now. We can only say what the chemical composition is of what the gases in the air are, and if some of them can only be explained by light.
Think about our own world and the oxygen we have in our air that's created by life. And so we're looking for these kinds of combinations. of gases that we need life to produce, or we don't have another explanation but for life to produce it. And then when we can get an even bigger telescope, and we are actually designing that one right now, it's called the Habitable World Observatory, By NASA, then we want to actually catch the light that reflects off a planet.
So basically then we're not just going to do shadows or jiggles, but when the telescope's big enough, we'd be able to catch the light from a small rocky world. And we can see if it's reflected off of green vegetations or blue oceans or anything else you can imagine.
Dean Regas: Well, with most of the exoplanets we found, they've been You know, a lot of them have been bigger, a few of them have been smaller, but from studying Earth and studying other exoplanets, are we rare?
Are we unique or exceptional? Or are there going to be lots of Earths out there, do you think?
Dr. Lisa Kaltenegger: That's such a great question. One thing that we already know, is from everything we've found so far, we know that there must be a potential Earth like planet, so that means a rock, not too hot, not too cold, around every fifth star out there.
So, the universe seems to be teeming with possibilities. Of course, we don't know if these planets could also become Earth like ours, and if they could also harbor life, but at least the possibility is there. A rock at the right distance, so you could have glistening water on the surface, and some of the key ingredients that we need for life, at least as we know it here on the Earth, is liquid water, carbon, and then oxygen.
We can have fingers crossed that there might be life on these other worlds too. And the way to find them would be the combination of gases in the atmosphere or the coloring of the surface. It's called bio-pigments.
Dean Regas: Well, let's leave Earth like planets and go to the weirdest, wildest ones. Like, what are some of the characteristics of exotic exoplanets?
You know, features that would boggle your mind.
Dr. Lisa Kaltenegger: Absolutely. How much time do you have?
Dean Regas: Oh, pick your, pick your favorite, pick your wildest and blow my mind.
Dr. Lisa Kaltenegger: So there are worlds that are rocks, but they actually go around their star, so a complete year on those worlds is less than an Earth's day. What that means is that they are so close, that there's so much heat hitting them from the star, that they would be covered by ocean.
of molten lava. And so we call them lava world and if you like science fiction crematoria, this whole idea is playing with it that there could be a world that when the sun hits it, it would get so hot that you would have like rocks evaporate and there would be lava oceans. And then we have planets around stellar corpses.
So a star explodes, and then what's left over is about the size of the earth and incredibly dense. But even there, after this explosion of a star at the end of its lifetime that nothing should survive, we already found plants that orbit this dead stellar husks. And then of course another one that is kind of really interesting and very weird are these lonely wanderers where we find planets that are not attached to any star out there that are forever flying or wandering alone through the dark cold space out there.
How am I doing? blowing your mind yet?
Dean Regas: Uh, yeah, my imagination is going crazy. Like, I'm just trying to picture what it'd be like living on these places. I always see these, uh, media reports about the discovery of Earth 2. 0. Like, we found another copy of Earth out there circling around another star. And I got to say my eyes start rolling because I know we can't exactly see our twin out there in space yet.
Is that changing? Are we, are we to the point where maybe in our lifetime we're going to be able to see a comparable Earth like planet in all of its glory?
Dr. Lisa Kaltenegger: I think the word comparable is exactly where you get to, and this is also one of the reasons the eye rolling, I completely agree, why I wrote the book Alien Earth, to put all that information in so, you know, you don't have to just eye roll, but you can say, Ooh, let's see, so is it at the right distance?
Is it small enough to be a rock? Because the chance we have right now for the first time is not an Earth analog, so not an Earth around a yellow sun. But an Earth around a much smaller star, a red star.
And so, all the planets, and we know about 40 of those, that could potentially be like ours in terms of temperature, and maybe having liquid water, and maybe, big big maybe, even the potential for life, all of those worlds have a red sun in their sky. And so, how Earth analog is that? But for those rocky worlds that are not too hot and not too cold around the smallest stars out there these red suns we have for the first time ever a shot at exploring their atmosphere and this is at the edge of technical possibilities it's by no means easy but we're learning every day how to do this and so if life is everywhere it could be Then, we have a chance to do this within our lifetime, because we're already using the James Webb Space Telescope to look at worlds around these small red stars.
And they are specially one system called the TRAPPIST-1 system that you might have heard about. It's a red sun with seven earth sized planets, and three of those within what we call the habitable zone, so not too hot and not too cold. And we have no idea if those planets could harbor life. But with the James Webb Space Telescope for the first time ever, we can investigate what the area is made of.
Dean Regas: Well, you definitely have my imagination going. Uh, Lisa, thanks so much. This has been a lot of fun.
Dr. Lisa Kaltenegger: Thanks so much for having me and hopefully when you go out at night do me a favor and count to five stars because one out of five could have a planet that could potentially be like ours and with 200 billion stars in our galaxy alone, I like our odds.
Dean Regas: Well, this conversation really got me thinking about life on earth. And you know, the question I always ask myself is what Is our situation unusual? I mean, how rare are we? When we look at all those other planets out there, those other exoplanets, is there another Earth like us out there? We have these cycles in our lives that we kind of don't really even think about very much.
We hardly ever think about this, but our day is 24 hours long. What if you're on a planet where a day is different, like Venus? If you lived on Venus, your day is longer than your year. So it's 200 and some days long is your day, and then you take our year, our year is 365 days long. What if your seasons were longer?
What if you lived on a planet with no seasons? Or super extreme seasons? Some deep stuff. So just some things to think about as we prepare to send people back to the moon and maybe on to Mars. Those astronauts who may live there for short periods of time or long periods of time will find these truly alien worlds and have to figure out the new rules.
Looking Up with Dean Regas is a production of Cincinnati Public Radio. Kevin Reynolds and I created the podcast back in 2017. Ella Rowen and Marshall Verbsky produce and edit our show, and they really like the Earth way better than that, you know, water planet from Interstellar. You know that movie? I don't blame you. I like land, too. Jenell Walton is our vice president of content, and Ronny Salerno is our digital platforms manager. Our theme song is Possible Light by Ziv Moran, and our cover art is by Nicole Tiffany. I'm Dean Regas. Keep looking up!
