SPEAKER 1: Good evening, and welcome to the second of the summer series. Our speaker tonight is not Steve Squyres. It's someone who's even better.
First of all, I have to tell you the legal things. The exits are there and there in the event of an emergency, but we don't expect one tonight.
And I also want to thank the College of Agriculture and Life Sciences for loaning us this auditorium. We appreciate it, and we thank them.
On Valentine's Day, 1990, NASA's Voyager I on its journey to interstellar space looked back from its unique vantage point, then beyond Neptune, at our solar system and snapped the first ever pictures of the planets from that distance-- Neptune, Uranus, Saturn, Jupiter, Earth, and Venus.
Three didn't make those photos. Mars had too little sunlight. Mercury was too close to the sun. And dwarf planet Pluto was too dim.
These photos were not part of the original plan. But Carl Sagan, a member of the Voyager imaging team, had the idea of pointing the spacecraft back towards its home for one last look before its camera was turned off forever.
The Earth appeared as a pale blue dot. And Carl Sagan would use that phrase as the title of a 1994 book in which he wrote, and I quote, "That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was lived out their lives. There's no better demonstration of the folly of human conceits then this distant image of our tiny world."
Tonight's speaker, Dr. Lisa-- I'm going to mispronounce your name. Say it for me.
LISA KALTENEGGER: Kaltenegger.
SPEAKER 1: OK-- is an associate professor in Cornell's depart-- I don't do German very well-- in Cornell's Department of Astronomy, and the founder and director of the Carl Sagan Institute, The Pale Blue Dot and Beyond, inaugurated in May, to further the search for habitable planets and moons inside and outside our solar system.
The Institute has built an entirely new disciplinary research group of 22 faculty-- did you just say?
LISA KALTENEGGER: [INAUDIBLE].
SPEAKER 1: So far, focused on the characterization of planets and moons, and the instruments to search for signs of life in the universe.
Lisa earned her doctorate in astrophysics. And she comes to Cornell from appointments in the Max Planck Institute, the Harvard Smithsonian Center for Astrophysics, and the Harvard astronomy department.
Her research focuses on rocky planets and super Earths' atmospheres in the habitable zone, as well as the spectral fingerprint of exoplanets that can be detected with the next generation of telescopes. And I would invite someone to ask in the Q&A period what those things mean. Super Earths, for example.
In addition to having an asteroid named after her, Lisa has been the recipient of a number of prestigious honors and awards, including being named one of America's young innovators of 2007 by Smithsonian magazine, being selected as one of the 2012 European Commission's role models for women in science and research, and in that same year, receiving the Heinz Meier-Leibnitz Prize for physics, awarded annually to only six young researchers in Germany.
Lisa, "A Thousand New Worlds."
LISA KALTENEGGER: Thank you all so much for coming and joining me on this small journey of discovery tonight. I will not tell Steve that you said I was even better, but luckily he's in Japan and really far away. So I hope I'm not going to get into trouble. Steve is the person who is still running the Mars Rover, just in case you get to hear him another time.
So what I'm going to talk to you about tonight is going to be a fascinating new array of thousands of worlds that we already discovered.
But we don't get to touch it yet, like the ones in the solar system. We can fly to Mars. We can fly to the moon. We can fly-- hopeful, in the future-- to other planets.
But what I'm going to show you today is that even without having the capability to go and visit these other worlds, we can catch their light that gets sent through the universe in our telescope. And through that, we can characterize worlds that are light years away, far in the distance. And in a way, if you want, maybe on our next discovery horizon.
And what I want to do today is I want to give you a little bit of the flavor of the recent results, what has been going on. And some of this you will find in the scientific literature. We published a couple of things just a month or two ago. Some of those you won't find yet, so you'll have to wait if you want to read the article.
But I think what I wanted to do is just take you along for the fascinating puzzle that right now is the discovery of other worlds.
And so, as was so kindly introduced, what we are building up here at Cornell is the Carl Sagan Institute-- The Pale Blue Dot, Our Own Earth and Beyond. And I'll talk a couple of minutes at the end about this real interdisciplinary endeavour that brings together the spirit of collegial work together from different departments at Cornell that I really enjoy, and is a key point of trying to understand worlds that are not our own.
But first, let me orient you a little bit. So you are here, where you see the sun. And what you see here is our galaxy. And really, it's not our galaxy. But it is like our galaxy would look like if we could take a picture of it, because to take a picture of something, you have to be far enough away to look back and take a picture.
And as Bud just said, the satellite that has gone the furthest away to date is Voyager I. And that has just reached the outer parts of our own solar system. So we have nothing that has ever flown that far away from our own galaxy to take a picture of it.
And a good friend of mine usually says, well, you know, if you salami piece in a pizza, you don't know how the pizza looks like. So in a way-- but what the salami piece cannot do, but what we can do, is we can have a look at the stars around us. We can see how they move.
And then we look up at the sky and at other galaxies, and say ooh, so from all the movement of the stars that we can measure in our galaxy, we, our galaxy, our Milky Way, looks like that galaxy over there. And then we take that picture and say, look, this is, if we could fly that far away, a picture of our home galaxy, our Milky Way.
And you see that we are roughly half out from the center. And half out from the center is our own sun. How far is really far out? Because you have a galaxy. And you know that light is the fastest thing there is. Light travels incredibly fast. But even light needs 100,000 years to go from one side of our galaxy to the other side. Light needs eight minutes to get from the sun to us. But it needs 100,000 years to get from one side of our galaxy to the other.
And so this is a vast, huge space that we're in. But by catching the light, again, of these objects, these other stars, we can already understand or explore what's going on there and which of those are suns that have planets just like our own sun.
When you look up at the star at night, at the sky at night, the stars that you see are other suns. They are suns like our own sun. Our own sun is just so much brighter because it's close to us. So during the day, it over shines all the other suns in the sky. During the night, when it's on our backside, so we don't see own sun, we can see the other suns in the sky.
In the beginning, when we didn't know there was the same, we called those suns stars. And our own sun has a special name, the sun. But really, all the stars you see out there are suns.
And by looking at them, and I'll show you how we do that, what we found is that every star up there actually hosts planets. Planets seem to be everywhere. And what we're trying to figure out now which of those could be like our own and could potentially harbor life.
So I said this is 100,000 light years. And really, where we're looking for planets is in our own solar neighborhood, and about 1,000 light years away from us-- because the furthest things are away from us, the less light makes it to us. It's like if you have a candle and the person walks away from you, you see less and less and less until it becomes so dim that you can't spot it anymore.
So we're really concentrating on the closest other suns around our own sun in the search. And what you see here, this part, that's a [INAUDIBLE] direction, or that's the direction that a very famous recent NASA mission called Kepler takes to look at the sky. And it monitored 150,000 stars, 150,000 other suns at the same time, to figure out how many of those host planets. And this is how we know that every other star out there, or every star out there, hosts planets just like our sun does.
So if you look up at the star at night, what you see is, if it's really nice and dark, this band in the sky, in addition to the individual stars. And that band is, of course, our Milky Way-- because if you are in this disk of our Milky Way, compare it to really a CD. Our Milky Way is as flat as a CD, or the pizza from before, if you want.
So if you look into the plane of the pizza, then the stars are so dense, there are so many just behind each other, that you can tell them apart anymore. And it appears like a bright band on the sky. So the Milky Way that you see on the sky, the bright band, is really you looking into the dense parts of our own galaxy.
And I like this picture because this person is reaching. And as I told you, we cannot go there yet. But even without going there yet, what we're doing is we're mapping our own neighborhood. We're already putting the first dots in this uncharted map to say ooh, once we can build a ship-- it's going to be quite in the future, and I hope a lot of you guys are working on getting us there-- but then this is a place that'd be interesting to look at. That will be another one. And that will be another one.
And so in a way, if you want, think about it as being a sailor-- a sailor before Columbus really went to find America. You're just there and have this amazing sea in front of you. But instead of it being water, it is now space. And the question is when are we going to get to venture out for the first time?
But this is our night sky. And I told you that there's so many other suns out there. Well, if you have a look at it differently-- so you see here our Milky Way. And this is really of the night sky in the northern hemisphere, so what we would see, and in the southern hemisphere. All these bright dots here are stars where we know that they host planets. We know they have other worlds circling them.
And this is a graph that was just done today, or yesterday, by one of my high school students who is the summer college here at Cornell. So Jack is in the audience, I think. Even if he's not, great work. And then on the third day.
But basically what you see here is that whether you're in the northern part of the sky or you're in somewhere in Australia, you look up at night and the majority of the stars that you can see, or all of the stars that you can see, will host other planets. We don't know all of them yet because we haven't looked at all them yet.
But we have looked at one piece of the sky here. This is the piece that Kepler looked at, and that the mission, the telescope, stared at this one tiny piece of the sky for three years to not miss any planets in that piece. And I tell you in a little bit how that worked. And that tells us how many stars have planets.
And so even if I don't know that this star has a planet because I haven't looked at it closely enough, if I look closely enough, it very likely will reveal that it also hosts another world. So next time you all go out and look at the sky, just remember one of those-- or really, from scientific data, every fifth of those-- just do one, two, three, four, five-- has not only a planet, but has a planet at the right distance, so that it's not too hot, and that it's not too cold, and is small enough so it could potentially be another world like ours.
And this is what we're at the verge of discovering. And that's where the next scientific breakthroughs, I think, are because finding other worlds like ours will also let us understand our own planet so much better-- because currently we know the Earth's, our own pale blue dot, from all the measurements we can make.
But putting that into the future is incredibly hard because there are so many unknown factors in these models. How are we going to develop what's going to happen? And now just imagine if we could see a couple of worlds like ours that are further along in their evolution. That could give us a potential first glimpse into our future-- what hopefully will be very exciting and not disastrous.
But these are all the stars that we found. But if you go out at night, in most areas, you won't be able to see all the stars. You will see a couple of thousands, really. And those couple of thousand stars, we haven't looked at all of them yet.
We have a new mission that was just approved by NASA and that we're building, and that's called TESS, that in 2017, so in two years from now, will actually go up and scan all the closest, brightest stars in the sky to tell us which ones of those host planets that could be like ours. But for now, we know statistically from what Kepler told us about this one patch of sky that every planet, that every sun out there, every star should host at least a planet-- because it's incredibly hard to find the tiny ones. So this is what I'm saying at least. So it can really only get better.
But if you look at this now, right? So there's nice stars, and this is the Milky Way. And then you see these dark patches in the sky. And you're like, well, you know. What I also should have said, this Milky Way, or this galaxy, a galaxy has billions of stars. It has billions of suns. And now you know it also has billions of planets in our galaxy alone.
But if you look here at some of the dark patches in the sky, you're like, well, doesn't look like there's anything else. And so what we did, or what scientists did, is they took Hubble, our best space telescope, and looked at some of these dark patches in the sky. And they just kept the shutter open. Like for the camera, you just basically increase the exposure time because a lot of things you won't see because they're just not bright enough.
And so when they did that and looked at this dark batch in the sky, after about 100 hours, this is what they saw. And so in every dark patch of the sky-- and this really is about a sand core beak, if I stretch out my arm. That's what Hubble looked at. This is the part of the sky they looked at.
You know, we are not looking at the whole sky. We'd like to, but, you know, it takes a while.
But so in this sand core, big piece, we found a couple of thousand galaxies. So we have billions of stars in our galaxy, with billions of planets. There's no reason to believe that these billions of other galaxies shouldn't also host billions of planets. So we probably have our work cut out for us.
Let me get back to this beautiful image that Bud actually described already. So this is an image of Voyager. And as he told you, as Voyager looked back at our own planetary system-- and this is the image that it took of the Earth. This tiny dot here is us.
And the other part of the story is if you now shrink our own solar system to the size of a cookie, the sun is not even as big as a sugar grain in that comparison. But if our own solar system is this big, then the next star is two cosmic football fields away. And this is an image that we took, or that Voyager took, within this cookie.
But with new technology, we're starting to take images, not of planets that are small as the Earth, but of planets about as big as Jupiter-- a little bit bigger-- around other suns that are cosmic football fields away.
But still, I would say this is one of the most inspirational astronomy pictures I've ever seen because it depicts, to me, how exciting and how fragile our own planet is suspended in this huge vastness of space.
But let's get you to what we actually do. So this point, if you could zoom in, if you could look a little bit deeper, then of course you would see this beautiful Earth with continents, with clouds, with oceans. The problem is, you now move this Earth cosmic football fields away, there is really no way that you get enough light to actually resolve these continents, these oceans.
And so what you do is you just take the light that this one tiny dot brings, that's going to be even dimmer in another solar system because it so far away, and you do something different. You split it up in its colors, because if you look at the colors of another world, that actually shows you-- and I'll show you indeed how that works-- what the compensation of the air in that other world is like.
And so this one pixel, even if it can't make an image, has a very characteristic light fingerprint that we can read over cosmic football fields away to figure out if that planet is similar to ours or very, very different.
And of course, this spectral fingerprint is something, if we look at the Earth, that shows us that there's life on our own planet. And what it actually shows us is oxygen or ozone-- really doesn't matter, both of those-- in combination with the gas that oxygen or ozone reacts with. Methane, in this case, so reducing gas.
So if you find both of them in a planetary atmosphere, in this light fingerprint, then something is producing this oxygen in huge amounts-- because if not, oxygen with this other gas, reducing gas, would react and would form water and CO2, so it would go out of your atmosphere.
And so by seeing them together at the same time, that tells you that something is producing oxygen in vast amounts, and we have no other way to do that on a planet If it's warm, then by biology. And so this is our spectral fingerprint of life.
And of course, you would also like to see some water just because we think water is something that life needs. So that's an add-on that we'd really like to have.
And this is how it looks like. If you split up the light-- this is the light. is This is the infrared. But you can think about it as just being light from the blue part to the red part. So basically, the individual colors of light.
And what you see is that things are missing, right? So this is the curve, but they are basically big bites taken out of the curve. And these big bites is energy that's missing because light is energy.
And the energy that's missing here is used by molecules in the infrared to actually swing or rotate. And it's characteristic for each individual molecules. And that allows us, if you know which energy is missing, which color is missing in the light of a planet, that allows you to say I know that that planet has water vapor in its atmosphere. I know that planet has oxygen. This is how it works.
And so let's get back to our own planet. But of course, this planet could be completely different. It could have a completely different biology. It could have a completely different composition. It could be completely made out of water. It could be a water world-- or it could have algae all over the ocean. So we are basically envisioning and working out how different kind of life would actually show in this spectral fingerprint in our telescopes, and if we can tell them apart.
And here, as another comparison that I wanted to show you, this is, of course, Venus. This is a [INAUDIBLE]. This is the Earth, and this is Venus. I want to bring this up because the first question that you should be asking is, OK, I really like your story. So you're telling me I find oxygen, and methane, and water and then there's life. So first point you're saying, now prove it.
It's pretty hard to prove. But what you should want to do is you're just going to look at the other rocky planets in our own solar system and test that hypothesis in the first place. So Venus is another rocky planet in our solar system. Mass and radius roughly the same as the Earth.
It's a little bit closer to the sun, so it gets much more heat. They say Venus lost all its water initially because it just got so hot that the water evaporated and then made it all the way up to the top of the atmosphere. And there it basically got plastered, so that it split into hydrogen and oxygen, and then got lost into space. This is what we think happened to Venus. So Venus could have been exactly like the Earth initially.
But so if we look at the Earth, this is what I said the spectrum, the light fingerprint, looks like. But now, if you compare it to Venus here and to Mars here, you see that it is different. Mars and Venus show you CO2, but only the Earth shows you water, methane, and oxygen.
But let's get back to our own galaxy and how we find these planets. We actually can spot them. We only have a couple of planets that we could take a picture of, the really hot ones, but we can find a lot of these planets without really seeing them.
And we do it this way. We have a look at the star. And because the planet goes around the star, the planet talks at the star. You can think about it as like you're holding something seriously heavy, and now you rotate. And so when you do that, need to lean back to just hold that weight. And that's what gravity does. The gravity of the planet grabs onto the star and reverse.
So the star itself also makes a movement countering the movement of the planet around it. And this is what we can pick up in the stellar light. We can see the star wobble. So if you have a tiny planet, the star will wobble a little bit. If you have a big planet, the star will wobble quite a bit. And so you can see that much easier.
And the way that we can do this is if we look at it, and then this is a by chance geometrical alignment, if we look at it, and by chance, the planet actually goes from our point of view in front of the star, so between our line of sight and the star, then it blocks out some of the really hot stellar surface.
A star is hot. This is white in its light. If you block out part of the surface because something cold, like a planet is in front of it-- basically, you don't see that part of the light of the surface of the sun-- therefore, the start actually appears to regularly dim. It becomes regularly a little bit less bright. And this is how we also find planets. This is what you see here.
So we look at the star. And then, when the planet goes in front of it, we don't see the planet, really. But we see that the star gets dimmer. And because the planet goes periodically around the star, so the Earth does this once a year around the sun, we can actually tell how far away the planet is from the sun and how big it is by how much of the like it actually blocks from our view.
And by doing that, we found a couple of hundred planets. And by doing that, especially with the Kepler mission-- this is how the Kepler mission finds planets-- we found several thousand of new worlds.
And now I told you that as the star wobbles, if there's a more massive planet, it wobbles more. And also, if there's a bigger planet going in front of the star, it blocks more of the stellar surface.
So now I want a show of hands. Who thinks we found more big planets? OK. Who thinks we found more small planets? Why would you think that? Once again, it's easier to find the big ones. Who thinks we found more big planets? Who thinks we found more small planets? And what does the other 70% of the room think?
It's much easier to find the big ones. It's much, much easier. So if there's the same amount of big planets and small planets, what you'll get is you found much, much more big planets, right? Because you just find 90% of the big planets, but only 10% of the small ones.
And so it was a real big surprise when we just counted them. And this is what you get. This is Jupiter, and this is the Earth, and this is roughly how many we found. These are small ones. And here this is shaded because I told you before that the really small ones are incredibly hard to pick out, right? Our telescopes are just not good enough to find all of them. We only find a fraction of them.
But if there were the same amount of big planets than small planets, this curve must look like this because it's just easier to find the big ones. But it doesn't. And what that tells you is that there must be so many more small planets out there than big ones-- what, of course, for me is super exciting because now on these billions of planets, I get quite a big fraction. There might be really interesting places to look at, right? Could have been that all these billions of planets were Jupiters. Then it would've been a little less interesting for me.
So just to give you a number from today, we have 1,930-- actually, 31-- planets confirmed. And there's a couple of thousands that we're still working on because, of course, once you find a planet, you have to run every potentially imaginable test to rule out that it's something else, like a mistaken instrument and mistaken observations.
So we're already in this beautiful, beautiful place where we actually have thousands of worlds at our disposal. And in case you want to do grad school, you can pick a couple of worlds. You don't have to fight over one, right? This is enough for everybody. We don't have that many grad students yet.
Let me run you through this in terms of numbers. So in 1989 was the first object that people thought could potentially be a planet, but they were really not sure. 1995 was the first time that actually they found the planet around another sun like ours, and they stuck their necks out. They said no, it is a planet, right?
And people were like, no, no no, no, no, no no. No, no, no-- because the planet they found was a Jupiter planet, bigger than Jupiter. And it was orbiting its sun. Jupiter needs 11 years to orbit the sun, right? Now the planet they found, like Jupiter, needed four days.
So anybody they asked, it was really funny. And you can actually see, if you want, the talk at the inauguration. It's actually the person who found it was a PhD student at the time. I was saying it was super interesting because they were like, so, what do you think if I told you there was a planet in a four-day orbit? And I was like, no, no, no. No, no, no. And they were like, but-- but.
It took an incredible long amount of time for people to actually realize that our own solar system, even so you know that our own solar system is probably not the norm, right? It's not everything that it can be. But we were so used to our own solar system that we figured Jupiter had to be at 11 years orbit.
We were actually so confident then, it was very funny, that they finished the instrument to look in this wobble technique for other planets. And then the professor went for a sabbatical to Hawaii and told the student go ahead and start measuring, because they figured they'd need 11 years to find the thing.
And then [INAUDIBLE] gave a talk at the inauguration that's really worth listening to was just sitting there. After four days, he was like, um, um, something's not working here, yeah? I found a planet that's in a four-day orbit. And so that is kind of how our vision of what we know as scientists sometimes can a little bit cloud your judgment of what you suspect to find.
But science is this beautiful endeavor that when the data tells you different, we will change our mind. And we'll take a while. The Earth was flat for a long time. We were in the center of the universe. We knew that giant planets had to be far out. It takes a little while, but we're actually getting a little bit better at the speed of what we actually agree that things don't have to be like we expect them to. And for me personally, that's one of the fascinating parts of science. You find out new things all the time.
But I digress. So what I wanted to show you is first we found couple of planets, the 95, to first around the sun. And then a little bit more, and a little bit more, and a little bit more. This was all before we built a custom-built telescope, the Kepler Telescope that Bill Borucki talks about in the inauguration-- he was also here-- that was rejected by NASA four times until finally, he just got it through. He didn't give up. He just said we need to make this, and he gave a very fun talk about this.
But if we wouldn't have had the space telescope, this is our view of what the distribution of planets out there is. And what you see here is the radius of the planets. So this is Jupiter, and bigger, and this is Earth. And yes, we had two small planets, but these small planets are actually orbiting a dead star, a star that already exploded. So yes, they are small, but there's really no way that we can actually come up with how they could potentially be anything like the Earth.
And so it was actually very interesting because people said, ooh, so by looking at the data, what you see is that most planets out there are Jupiter, are bigger, and a lot of them-- this is the orbital period-- so that means small numbers here are incredibly hot. The Earth is at 300 days number here. Earth would be here. So they were saying, oh, so most of the stars have hot Jupiters, and so the Earth seems to be really unique.
And this is, again, what the data tells you. But the problem is you don't have the whole picture. And so once we started Kepler and got the information from Kepler back, what we got is this view-- because, as I told you before, it's much easier to pick up the big things. The big planets in very small orbits are much faster and better to find, because if you look for four days, and the planet needs four days to go around the star, you found it.
If you look for an Earth in four days, you probably didn't find it because it needs 365 days to make it around the sun, right? But by having a dedicated instrument they looked at those stars and, in a way, didn't blink, but just stared at them to catch every transit, every darkening of the stars, our picture changed.
And what you see here is that there's many, many more small planets. And these are really the planetary candidates, right? So there is still the bias on here that we find the big things better and easier. If you now take that we only found about 10% of the really small things, this picture would change completely again because you would have more and more planets in the small bracket.
And also here, that part where you get further away from the star, that is very hard for us to actually pick up, especially for the small planets, because we just have to look longer, and longer, and longer. And for small, small planets, you don't want to just see it once. Generally what we do, we see it once. Could be an object that flies by your star. So you wait until you see it a second time. And then you calculate when it has to come back. And so you wait three transits before you call it a planetary candidate. And then you do all tests on it.
So for the Earth, that's more than 3 and 1/2 years that you do that. And for small planets, you really have a hard time seeing them each one time, so you want to add up the information that you get from the telescope. So you really want to have more than three transits to find it.
This is why this part of the diagram is not yet filled in. But with every day and with every announcement that you get, we get a little bit further this way because we have a little bit more data.
And what I also wanted to mention is what we're already doing is also having a look at these giant planets, right? I said that there's these giant planets that only take four days to go around their star. Jupiter in a four-day orbit is incredibly hot. Jupiter is a gas ball, so heated up, the atmosphere expands, and it's incredibly nice and fluffy. So when it goes in front of the star, part of the stellar light gets filtered through this expanded atmosphere, and therefore leaves its fingerprint on the light of the star that we see, the spectral fingerprint.
And this is just a model for one of these hot planets. And it has things like CO2, water, but it does not have the combination that we're looking for. And also, we know, because it only needs four days to go around the star, it's way too hot.
But we're already using the telescopes we have right now to practice for when we're going to have bigger telescopes that can then actually tell us about small planets like the Earth.
And this is one of the telescopes. It's a 40-meter telescope that we building in Chile that's going to look at this. And the other one is the follow-up of Hubble. Hubble's going to come down in 2017. And the next telescope, the James Webb Space Telescope, is actually going to go up hopefully in 2017. 17 It has, for the first time, the capability to collect enough light to look at the spectral fingerprints also for small planets.
So this is now, and this is what's next. And NASA actually already put out travel alerts for some of these planets. I would take it a little bit with a grain of salt, because really, what we know, as I told you before, we know the wobble, so we know the mass of the planet. If it goes in front of the sun, we know how big it is. So really what we know is the density.
So if you think about it, if you had a big bathtub of water, you could tell the difference between a Saturn that actually swims if you throw it into a big bathtub of water, and the Earth, that actually sinks because the density of the Earth is bigger than water, and the density of Saturn is smaller than water.
But what we're doing is we're preparing for the time that these big telescopes will become available. And we also need to tell them what the instruments will have to be able to do, and how long you have to stare to not miss signatures of life of other worlds that might not just be like our Earth. It might be bigger, a bit colder, a bit smaller, or it might be younger or older. Younger is easier. Older is very hard to model.
But so I'll give you younger. We know the history of life on Earth. We know if this is a 24-hour clock, that life started pretty early on, about 4 billion years ago, give or take. The oldest traces for life are around 3.5 that we find. Oxygen started to build up about 2.3 in big amounts, but 2.7 billion years ago at 5 o'clock. And we are really latecomers on this cosmic scene.
But these difference also reflects in the atmosphere of the planet. So the spectral fingerprint of the planet, of our own planet, through its geological history will change. And so if you had, if you want, an alien astronomer that actually looked at the Earth, they would be able to tell about 2 billion years ago, like for half of the history of the Earth, whether or not there's life on it, because oxygen and the reducing gas methane, is together in the spectral fingerprint.
And then, of course, these environments led to biology. And if you want, the biology then influenced the environments we're seeing. So initially, there was very simple life, single cellular. Then there were more advanced life. And hopefully, currently, we're living in the intelligent life kind of period.
What we also do now is that our sun, like all other stars, brighten through its lifetime. It brightens when it gets older. And so what we know is that if our air wouldn't have changed, we would have been frozen for 2 billion years, because it would have just been too cold, because the sun was 30% less hot than it is currently.
So that tells us that there must've been a lot more CO2 in the atmosphere of our own planet. And if you plotted-- this is 4.5 billion years ago, this is now-- you see that there was a lot more carbon dioxide to keep us warm when the sun was so dim, and oxygen started somewhere to build up in big amounts due to biology someone about 2.3 billion years ago.
And all that is captured in the light fingerprint, because the light fingerprint of this one dot actually reflects the environment of the planet. And this light fingerprint is what we're looking for. And we are modeling for, as I said, different kind of situations.
The last point that I wanted to mention is what we talk about when we talk about the habitable zone, because a lot of times you'll hear scientists found the first Earth. Scientists found the first Earth. And kind of it repeats. There seems to be a certain amount of time when we always find the first Earth again and again. It's kind of great. I just wonder how often we're actually allowed to find the first Earth without knowing much more than the density of the thing.
But what we do, and what is very hard, I think, sometimes for the press to get, is what we know is the distance, right? We know how bright the sun is and we know where the planet is that we found. And then we can say, OK, if it's like the Earth, then it would be warm there. And we know if it's too close in, it would be way too hot. If it was too far out, it would be frozen over if you put the Earth there. That's basically what we do.
And this is how we come up with this concept of a habitable zone. That doesn't mean that if you freeze the planet over you can't have life. Of course you can have life. There could be a subsurface ocean. That's why we want to go to Europa or Enceladus to actually look at that ocean. But we have to go there. We have to drill a hole in the ice and go down and look.
And so cosmic football fields away. It takes us a couple of months to get to Mars, right? I don't want to know how long it's going to take us to get to the next star and make a hole in the ice somewhere there. So this is why we limit ourselves to the region where you don't have ice covering the planet, and thus the gases of life could easily come to the atmosphere and create this spectral fingerprint.
And so in our own solar system, Venus is inside. It's too hot. Mars is actually within the habitable zone, but it's so small that it doesn't have enough atmosphere to keep it warm. So the habitable zone is defined for the Earth, for a planet like the Earth.
And then when you have a smaller sun, you need to be actually closer to the sun. It's like a bonfire. If it's small, you want to stay closer for it to be warm. And further out is too cold. Further in is too hot. But all of this, the different sun or your movement within this nice region, actually influences, again, this spectral fingerprint of the planet and the signs of life we can pick up.
And that was work by one of my graduate students, Sarah. And she basically got the cover of one of the big astrobiology magazines just for that work. So if you want to go into grad school or you want to do astronomy, there's a lot of unanswered questions that are highly exciting, I think.
And also, I said the sun brightened through time, right? So our sun gets brighter as it ages, like every star does. So if you now go back in time, Venus probably initially was another Earth, right? It was nice. It could have had water. It could have had life. Now it's not anymore.
And if you go further in time, at one point it's going to get way too hot on the Earth. And at that point in time, we definitely need to figure out how to get off this planet or it's not going to be very pretty.
But what's interesting is Jupiter and Saturn will actually flop into this habitable zone, right? And so for a small amount of time, Europa, for example, could de-freeze. Well, it will be interesting, because then we could actually pick up signs of life. Unfortunately at that point, we have to have left Earth to pick up signs of life on Europa.
And so this is what I just wanted to tell you about all of this. So once you see hear the next we found the first Earth, one of the first things to ask is, OK, how far is it away? That's usually what they get right. And the next thing to ask is, how big is it? Because if it's bigger than two times the size of the Earth, then it's a gas ball. If it's more massive to 10 times the mass of the Earth, it's a gas ball.
So, you know, this is how you can find the first earth over and over again. And now it's actually a new connotation. It's very funny. Now it's a little bit more Earth-like, right? The one Earth, first Earth, was 40% bigger than the Earth. The new best Earth is 30% bigger than the Earth. The next best Earth is 20% bigger than the Earth.
I really wonder what happens when we hit the same size because I don't know if [INAUDIBLE] 90% the size of the Earth is going to be better, or worse, or-- I don't know. The trend says it's going to be better, but I really don't know.
And there are other life that can live in different conditions. And that's another part of what we investigate. Could other planets host life as we already know it, but as it's not dominant on our own world?
And of course, you also have completely different chemistry that could happen. And all of that could show itself in the colors of another world, in addition to in the spectral fingerprint. And here at Cornell, at the Carl Sagan Institute, one of the other things we also do is we host a catalog. We host a catalog for the colors of potential of the worlds, where we [INAUDIBLE].
One of my PhD students, [INAUDIBLE], that's with us at this center called Sagan Center, he basically went out and measured a lot of these extreme forms of life, and measured what they would reflect, how they would look like, how their color would look like, and then modeled if the whole planet were covered with that. Could you tell the difference by looking at it with a telescope? And these are just some of the parts that we're working on here.
The last thing-- the real last thing-- that I do want to do today is I would like to show you what we're trying to do with this Carl Sagan Institute. That is, an interdisciplinary endeavor where biologists, talk to chemists, talk to astronomers, talk to engineers who built the different instruments that we're going to be using.
And I think in a way, how I would like to do is to show you where our logo came from. That was, in a beautiful, beautiful ceremony revealed by Andrew [INAUDIBLE] at the inauguration of our institute. And so this is just going to be my last hooray and taking you with me out there among the stars to think about different worlds.
And what I wanted to draw your attention to, this graph that looks like a beautiful video-- and it really is because we got the team that animated the Avenger movies to be super excited about our logo and animate this. So, you know, Hollywood connections. They do want to go to the next stars.
But what I wanted to draw your attention to, this is our world. And so our world also has-- it has the spectral fingerprint, but the spectral fingerprint is in the form of a human fingerprint. The other worlds that we see here on the horizon don't have any spectral fingerprint yet because for the small ones, we are just on the verge of being able to do that.
And I would like to end with a quote. There was an essay competition. And somebody said, what does the cosmic shore mean to you? And one of the most beautiful entries for me was a young girl who wrote, "and the next time we will arrive at the shore, we will look back, and the ocean will be made out of stars."
So with that, any questions? Thank you. Please go ahead.
SPEAKER 3: [INAUDIBLE].
LISA KALTENEGGER: I do not know anybody from another planet. I would love to actually do know somebody from another planet. That would be, as a scientist, for me one of the best proofs that there's life on another world.
And having said that, what I would love to happen is that person not have the DNA, not be carbon based, because at that point, the question is-- for example, if you find life on Mars, it would be super exciting. Did we bring it there if it looks like us?
What I want is somebody to walk up to me, be made out of silicate or anything else, look completely different than me, and say I'm from another planet. And then it's going to be a super exciting endeavor. So far I haven't met anybody, unfortunately.
SPEAKER 4: Does Pluto count? [INAUDIBLE] hear some more about that.
LISA KALTENEGGER: Pluto is super exciting. So one of the questions, Pluto definitely counts. Pluto is a dwarf planet. And the interesting thing about Pluto in a nutshell is that Pluto is a ball of ice, right? It's basically a dirty snowball, but it's really non-dirty snowball. So when you have a small telescope and you look at Pluto, then the light that Pluto reflects is like if you go out with fresh snow, and then it's really bright outside, right?
Unfortunately-- or fortunately, with better telescopes, we found a lot of other objects like Pluto that are even bigger than Pluto, but they're just a little bit more dirty at the same distance. And so with the small telescopes, we couldn't see them because they just wasn't reflective enough.
But in all of this-- and this is why it's now a dwarf planet, but it has a family of dwarf plants. So it's actually tens and dozens and dozens of objects like Pluto out there, which is super exciting because they're going to be more initial parts of our own solar system, and hopefully less contaminated, if you want, to tell us about the initial formation of planets.
But it's going to be super exciting. Next week, July 14, so we're going to fly by Pluto, so it's the big next picture show there, the dwarf planet that we haven't seen. And then we're going to fly to some of the other dwarf planets. And that's definitely going to teach us more about these small, cold worlds.
And then we take everything we can get. We'll learn from all the plants and moon in our own solar system because every little piece that we can put to the puzzle lets us prepare for the next observation and make them better. And then use that data efficiently to make our models better and better and better.
SPEAKER 5: [INAUDIBLE].
LISA KALTENEGGER: That's a very good question too. So Fermi paradox. So apparently, Fermi said, where is everybody? And I just got told by somebody who's very vehement about this that it's not a paradox, and it's not Fermi's-- because apparently, Fermi didn't say what he's accredited to saying. Fermi just basically said, where is everybody apparently because he said, well, you know, space travel seems to be incredibly hard.
And if really, speed of light is the fastest speed there is, everything's really far away. These two cosmic football fields that I was talking about are four light years. So if you can go about 10% of the speed of light, you really, really, really need to want to go there, right? And that's just our next star.
Personally, my answer to that is a question to you, in a way. I give you two planets. One is further advanced than we are, and one is a bit more backwards. Let's say 100 years back. I can go to one of those two. Which one do you pick? Do you want to go to the one that's actually advanced and has made the jump into space, or do you want to go and look to the people that are in Neanderthal age and haven't figured out how to use fire yet?
SPEAKER 5: [INAUDIBLE] the last one.
LISA KALTENEGGER: And so in a way, if that's OK, that's my personal answer to the Fermi paradox [INAUDIBLE] because, you know, I wouldn't visit us either. We are not terribly interesting yet. I love our planet and everything, but I don't think we're that terribly interesting.
SPEAKER 6: [INAUDIBLE] light years away [INAUDIBLE] probably be a little less frozen now [INAUDIBLE]?
LISA KALTENEGGER: So if I understood this right-- let me rephrase it. So you were just saying if we saw a frozen world, but because it's actually that far away, light needs time to get to us. So could it be better there already than the information we have? Is that the question?
SPEAKER 6: Yeah.
LISA KALTENEGGER: OK. So yes, absolutely. What I was telling is we are looking within about 1,000 light years. So the sun actual needs-- our sun lives about 10 billion years. We are 4.6 billion through, so we have a little bit more time. To thaw something, you would need quite some time, so a lot more than about 1,000 years, to actually make it better. But it could already be a little bit better.
And the flip side of that question that some people are saying is, well, if we find the civilization that's 500 years away, they could have blown themselves up. I'm like, yes, they could. This is why we're looking at a lot of planets, because chances that everybody blows themselves up is hopefully a little lower.
Sorry. Yes. You had a question?
SPEAKER 7: So [INAUDIBLE] to be able to make inferences about the location [INAUDIBLE]?
LISA KALTENEGGER: So what we can do-- I was telling you that for these big, giant planets, we can actually already probe the atmosphere because they're so expanded and the light of the star that filters through is intense enough for us to basically see the planetary atmosphere, if you want.
And so what we can do for these giant hot planets-- we're talking about 2,000 degrees, right? It's nothing for life. Not anything for life. But what's really interesting is-- what you can actually do is you can even see the movement of the gas.
And so what they did is they actually measured for one planet-- it's close by, it's incredibly hot-- the wind speed, if you want. So the movement of this part of the atmosphere versus that part of the atmosphere, because the planet rotates. And so we could do this for one planet, and it's incredibly fast.
Now, caveats. We only have one measurement on each side, so we could be actually seeing down further on one side than on the other one and we wouldn't know, you know? And that would make sense, that something rotates faster on the side than the other side. And also for a gas giant, the rotation of the atmosphere has nothing to do with the rotation of the surface, like the planet of the Earth.
And what's going to be really hard to do for finding out the rotation of a planet like the Earth is clouds are really bright, and they do not rotate with the rotation speed of the ground, right? Clouds go their own frequency. And so this is why it's going to be really hard initially to figure out if another planet has a 24-hour day, or a 48-hour hour days, or a five-month day.
And Venus, for example, has a day that's more than 200 days long, right? So the day on Venus is just incredibly long.
We also don't know if that makes any difference for life. It's just basically the day/night cycle will be different, but you probably easily can adapt to it. Or if you're under water, underground, that should be fine, if that's--
SPEAKER 7: So I hadn't even thought about those, but what I was wondering [INAUDIBLE] tidally locked [INAUDIBLE].
LISA KALTENEGGER: So actually, yes. So tidally locked planets is like the moon to the sun to the Earth. So we always see one side of the moon. And it can happen if that planet is close to its sun, where it would be for very cool suns, that the planet also gets tightly locked. So only one part of it would actually get permanent daylight.
But if a planet like the Earth would happen to be in that stage, actually the temperature, because it has air, it has an atmosphere, would be easily distributed everywhere because for us, day and night is really not that difference in temperature.
And the other thing that's also really interesting is a planet never starts out like this. So if you have a planet, and it now starts, with tidal interaction, it starts to rotate slower, and slower, and slower to get tightly locked to its planet, the moon starts to rotate slower and slower-- if a planet does that that has an atmosphere, or a moon that has air, the air just nudges it a little bit over that and a little bit under that.
So there's really interesting results from research right now that show that if you have an air, you actually have incredible trouble getting locked in a synchronous rotation when you only would have one side. But even if you did, it shouldn't be a problem.
Sorry. Short answers. Lots of questions. Questions. Sorry, yes. And then-- sorry. Yeah. Sorry. Yeah.
SPEAKER 8: [INAUDIBLE].
LISA KALTENEGGER: Yeah.
SPEAKER 8: Venus [INAUDIBLE].
LISA KALTENEGGER: Yes and no. So Venus is the most interesting planet in terms of it being the size and the mass roughly of the Earth. But the problem with Venus is that the pressure is 90 times as high as on Earth, so trying to make it. And the best things that we've ever built for the Venus environment, because it's just so hot-- it's more than 400 degrees Celsius-- or Fahrenheit. It's just incredibly hot.
The best things were the Russia Venera missions. And they basically lived from 23 minutes to about two hours, is the max. Then everything we can build dies because it's just not built-- we cannot built anything for those conditions because it's incredibly dense, it's sulfuric acid, and it's incredibly hot. So everything melts or dies and all the electronic frizzles.
So Venus would be really interesting. And in a way, the interesting thing is Venus could be like a future-- it's basically a really long, long, long future Earth. So we look at Venus more like, yeah, we should really get the space program going.
SPEAKER 9: I have a question about the signature. [INAUDIBLE] the signature and thus [INAUDIBLE]? So are you buying stories [INAUDIBLE] here? Or [INAUDIBLE] photosynthesis?
LISA KALTENEGGER: Absolutely. There are definitely other ways that you could have life without photosynthesis. So this is why we've also explored these extreme forms of life that, for example, live under surfaces or underwater and are basically chemo [INAUDIBLE] instead of being photo organisms, so they don't need light. They get their energy from chemistry. And so we're looking at all of these different kinds of life.
The only problem is that-- and I'll borrow a quote from Sagan here-- extraordinary discoveries need extraordinary evidence. Life can introduce CO2. It did initially when our planet was young. It produced CH4, methane. But there is no way for me to tell you whether that CO2 that I see is made by life or by geology alone. And so I cannot claim that I found life even so I'd say, ooh, that planet is interesting.
So our way of looking for life is an incredible conservative way because we will basically miss a lot of life that just didn't do oxygen. But having said that, if you talk to biologists, they argue that if life advances significantly-- and this is an astronomer, so if there's any biologists in the audience, feel free to correct me. They said that if life advances significantly, oxygen is a really great energy source, so life would actually start to use oxygen and, in terms, in symbiosis, produce oxygen.
So they're saying in that respect, looking for oxygen as one of the component, oxygen alone won't do it. Oxygen plus a gas it reacts with is actually a solid, as far as we know, way of looking for life. But there's a lot of life that we'll miss that way because we just can't tell the difference if it's biology or not. And for the oxygen-methane combination, we have no other way to get that much oxygen than there being life if the planet is within this habitable zone that we defined. So it's conservative.
But, you know, it'd be good if we say, wow, there is life. That we actually are pretty sure that there is life being one of the nice things.
SPEAKER 9: Thank you.
LISA KALTENEGGER: Sorry. Any other questions? Yes. Go. Sorry. Yeah. No, no. I just saw a hand over there too. OK. Go.
SPEAKER 10: What should a person do in high school to prepare for a career in space science [INAUDIBLE] specifically [INAUDIBLE]?
LISA KALTENEGGER: So what can you do in high school to actually prepare for for a career in space science or if you want to become the next explorer of other worlds. So once you can come and work with me like Jack did. No, that's fine. Yeah.
What I see as the language of science is math, right? So yes, a lot of times you think, like, oh, math. Maybe you think some of it is boring and so on. But it's really the language we speak. It's the language that we describe the universe in. And physics and math go hand in hand.
And so I would say if it becomes boring, dive through that part of saying, oh, why would I need to just study math now? Because it's like any language. If you learn Spanish, initially it's like, oh god, I really don't care about this verb or that word, right? And then you go to Mexico or to Spain, and all of a sudden, it's fun.
And so as a young person, what I would do is I would learn the language of science that happens to be math. And once you're fluent in it, there's a lot of things you can do.
Was there a question over there? Sorry, yes.
SPEAKER 11: I was wondering if you talked to people [INAUDIBLE] space telescope is hopefully going to be replacing the Hubble Telescope [INAUDIBLE].
LISA KALTENEGGER: Yeah.
SPEAKER 11: I was wondering what [INAUDIBLE] you're hoping to do [INAUDIBLE] with the new telescope [INAUDIBLE] technologies [INAUDIBLE].
LISA KALTENEGGER: Yeah. So basically, Hubble is a little bit bigger than me. And the new one, the James Webb Space Telescope, is going to be me over there, like [AUDIO OUT] 6.5 meter. And what that does is it allows you to collect enough light to see those really, really dim sources. It also allows you to get better resolution on the bright things because you collect more light. And so you can split it up into more thinner pieces. So you can basically, if you have a blurry picture before because you just didn't get enough light, with more light catching, you can get a very detailed image of something.
But you can also, for the first time, collect enough light to actually see very dim objects. [INAUDIBLE] are very, very dim objects because they don't shine. Planets only reflect the light from their host star. So the host star is really their sun are really, really bright. But the planets are tiny. The Earth goes 100 times next to each other into the diameter of the sun. That's what we're talking about.
So having a really big capability, a really big light pocket-- that's really what a telescope is-- is actually for the first time going to give us access to very dim objects, and among those are going to be planets. And we're going to try our best to get as much time as humanly possible to look at these dim objects that could potentially be other Earth.
SPEAKER 12: Coming back to the Carl Sagan quotes. So [INAUDIBLE] question, but Carl Sagan was saying at the end of Cosmos says that we all went to the cosmos [INAUDIBLE] we sprung from to continue on and discover and explore it. But earlier on in Cosmos, he gets very existentialist. He starts [INAUDIBLE] saying that the universe is very indifferent and the universe could care less.
So therefore we have a paradox. How do we justify this morality that we owe it to the universe, to the cosmos, to explore it when at the same time, the cosmos is indifferent to us.
LISA KALTENEGGER: I think I actually like that the cosmos is indifferent to us. And I like that we, as the only species we know, currently, have this inquisitiveness, this curiosity about the world around us-- because as a species or as we all are, we could just live out our life on this planet, right? We could have never figured out that the sun brightens. You have to observe things around you to figure that out.
But by actually having this curiosity about everything around us, we figure out that at one point, our planet will become too hot, right? We figured out how we potentially could actually reach for the stars, if you want.
So I feel more like as an opportunity to explore. And I would say in [INAUDIBLE], if you go back to Columbus, for example, America at that point in time was indifferent whether Columbus were exploring it or not, you know? If they would have had a choice, the people there would have had a different saying. But generally, America the continent did not care.
And so I think it's the new frontier. And it's up to us to grasp onto the opportunity to explore it or not. Last question. Sorry. I think you all have to go home at one point.
SPEAKER 13: So I suppose this is another [INAUDIBLE] philosophical question. I heard you say how often you think the spark of life occurs. So we don't know [INAUDIBLE] right now here on Earth. And we obviously are looking for other Earths or other planets out there that can be like Earth. But how often do you think life occurs?
LISA KALTENEGGER: That is a great question. And I have no idea. And the good thing is, I have no idea because I am a scientist. I have no data except the one point that it actually started on Earth.
And part of the Fermi paradox-- or the equation, I'll say, like the Drake equation, how many lives or how many civilizations would be out there, is that part that says, OK, how many stars have planets that could support life. Check. Really good at that.
Then, how many of these planets could actually start life? Biologist, no check. We have no clue how many of those are. And then, how many of those could become advanced?
But what I find fascinating is that this is such a basic questions, right? We would like to know if life starts like this everywhere if the conditions are right, or if life is incredibly hard, or if life just started once. And we don't. And the search, where we're now at the cusp of discovering other worlds and looking for the spectral fingerprint-- once we have that light, once we have the first sign of light on another planet, I can tell you it's easier than we saw.
Once we look at hundreds, and they all have signs of life, I can say, oh my god, it's seriously easy. Once we find it only on hot planets, we can say, well, it probably needs warmth. Once we find it only on cold planets-- all of this is a completely open field, and such a basic question, in a way, that I think living at the time where we actually have the tools to answer it is one of the coolest things.
And with that, thank you very much for your attention.
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Lisa Kaltenegger, director of the Carl Sagan Institute and associate professor of astronomy at Cornell, has been examining alien worlds for biosignatures--the pre-conditions and indications of life. Here she shares her research on potentially habitable planets beyond our solar system. Recorded July 8, 2015 as part of the School of Continuing Education and Summer Sessions summer lecture series.