>> From the Library of Congress in Washington DC >> Stephanie Marcus: Good morning and welcome to our seventh of eight talks in our NASA lecture series this year I am Stephanie Marcus from the science technology and business division And, today I think we can say, Houston we don’t have a problem, because Houston is world champions in baseball, hooray! [ laughs ] And I did see someone from NASA from the Johnson Space Center who is in an orange space suit and had all kinds of things hung on him Go Astros! So, exoplanet Everyone seems to love them, it’s not enough to love our own planet, we have to love that which we know very little about And today we have the perfect person to tell us about exoplanets Our speaker is Dr. Padi Boyd, and she’s chief of the exoplanets and stellar astrophysics laboratory at NASA Goddard She has her B.S. in astronomy from Villanova And she was originally more of a music, artsy kind of person and then she turned towards astronomy later in high school and look her now! And then she went to Drexel and got a M.S. and PhD in physics and atmospheric science She’s been involved with exoplanets way back because she has worked with the Kepler Mission and the Hubble Space telescope And now she is also the director of the Guest Investigator Program for the Transiting Exoplanet Survey Satellite mission, which we like to call TESS And we did have a speaker in 2015, almost two years ago in October, Steven Reinhert, who talked about TESS And at that time, it was supposed to launch in 2017 but Dr. Boyd says March 2018 is the expected launch date We do have a webcast of the TESS program if you don’t learn enough about exoplanets today, but I’m sure you will So, please join me in welcoming Dr. Padi Boyd [ Applause ] >> Padi Boyd: Well, thank you very much Stephanie Can you all her me okay? It was a real pleasure to be here at the Library of Congress I am really excited to visit the building and the people and to talk to you about the very exciting field of extra solar planets, or exoplanets, as we call them Planets around other stars So I thought I was start off with a very thought invoking engraving that most people have seen in some time or another in their lives It’s from the late 1880s And it was an engraving that first appeared in a textbook about meteorology, the study of the atmosphere But it’s so thought provoking and it really has so many things going on in it that many people can read a lot into this engraving It’s someone who’s peering beyond what is known around them and the world around them The sun, the moon, the stars And they are peeking through and they are catching a glimpse of what’s going on beyond In this particular image you can see the familiar, trees on the earth, the sun setting, moon and stars in the sky And then beyond that, a picture of a mechanistic solar system So some people associate this image with the birth of the scientific revolution because human beings, ever since we’ve been able to sit around a campfire and talk to each other and share ideas, we’ve known that some stars are the same in relation to each other every night and that others were wanderers The wanderers were the planets, been known about for centuries, but it was only during the scientific revolution where scientists like Kepler and Galileo put the picture together, and Isaac Newton, of what was really going on in our solar system So that’s a moment that shows you a kind of transformation, someone seeing the world in a new way for the first time And this has happened so many times in science and I think it’s happening right now in astrophysics as we’re exploring the planets close to earth now Oops, don’t know what that musical signal was, but we’re still seeing I think this was a very transformational moment for many of us too Many of us who are old enough to remember that picture which is called Earth Rise I’m just barely old enough to remember when it first appeared and it made an impact to everyone on planet earth It was really the first time that the human race could think

about what the planet earth looks like from a distance These were the Apollo astronauts and as they were orbiting the moon one of them turned around and took that beautiful shot of the earth The sun is eliminating both the moon and the earth And you get that sense of a pale, small, blue dot that is floating in a dark, dark universe It really gave us a sense of our perspective of the solar system But, up until — even at that time, the solar system was the only set of planets that we knew for a fact existed We’d known about them for thousands of years We’d put them together in a picture of how the solar system works over the last several hundred years So we know that the planets in our solar system orbit the sun, which is a typical star compared to the other stars in the sky And the planets are on orbits that are defined by their distance from the star, the closer they are, the faster they go And we knew a lot about our solar system We could study it, we sent probes to it in the 60s and 70s and beyond We learned a lot about the planets that orbited our star, but for so long it was the only solar system that we really knew anything about And I’ve picked this picture from an Issue Asimov book, because Isaac Asimov was so amazingly talented at marrying the science and his science fiction ideas So he really brought science to humanity through his science fiction stories and he also embedded them with great science Of course, science fiction knew of many planets beyond our solar system There are so many examples of stories that are so important to all of us that really depend on this idea that planets like earth are plentiful throughout the galaxy and even in galaxies far, far away So there are many scientists who are interested in exoplanets who can tie their first moment of really thinking about planets beyond our solar system to some moments in Star Trek or Star Wars or something where they were exploring planets beyond our solar system But for so long, those were just dreams and stories When we’d look up at the night sky, this is a picture actually from Joshua Tree, of a beautiful dark sky And you can see the band of the Milky Way there The sun is one of hundreds of billions of stars in the Milky Way galaxy And some lucky nights we’re lucky to really look at a huge swath of stars And for generations all we could do is look at those stars and wonder, is the sun unique? Are we the only star out there out of hundreds of billions that have planets around them? And that was the only they we knew for sure But scientists are persistent Our technology develops and allows us to learn more and more as time goes on So one of the reasons we didn’t know about stars that had other planets was because they’re very, very hard to detect The stars light vastly outshines a planets light Planets are just little specks compared to giant stars Ten billion times brighter typically But our technology got better and better so instead of seeing our planets we could allow ourselves to detect them indirectly One method is called the radial velocity method And what this relies on are just simple Newtonian mechanics, you remember Isaac Newton put together a picture of how the solar system works and it’s based on gravity And we know that all stars are obeying these laws So if a star has a planet orbiting it, we know from Newton that they’re orbiting a common center of mass It’s not the star being completely static and the planets orbiting around the star They’re actually both in orbit The planets orbit is bigger because the center of mass, where most of the mass is, is inside the star typically for a small planet But that doesn’t mean the start doesn’t move at all If our technology gets good enough we can detect that tiny wobble from a star that’s telling us that a planet is imparting that wobble on it It’s called the Radial Velocity Method And the was really getting going in the mid 90s Of course we were looking for solar systems that looked a lot like ours We knew big planets were going to be the ones that imparted that signal strongest on the stars But the big planets in our solar system are Jupiter, Saturn, they are way, way far beyond where the earth is They take years to go around the sun, 5, 10 maybe even longer years So people were looking for signals in their data from big planets that they thought would be like Jupiter and Saturn They were so focused on what they were expecting to see from our solar system that many of the scientists who were working this area missed the first signals This is actually the discovery image It’s actually the confirmation image by a group, Jeff Marcy and Paul Butler, who confirmed a planet call 51 Peg b, orbiting the star 51 in the constellation Pegasus So what you see there is going up and down is the velocity

of the star coming towards us and moving away from us Towards and away, in a perfectly periodic way that’s telling us what the orbit of that planet was It was actually on a few days orbit, less than 5 days Much, much closer than any planet in our solar system and quite massive, almost the mass of Jupiter, to be able to impart that signal This was a watershed event It was like the earth rise image for scientists because we now had evidence that there were planets around other stars and that first planet was so surprising compared to what our solar system has that we had to rethink how we were looking for exoplanets So it’s hard to read this in the light, but this is artists impression of what 51 Peg b looks like Its orbital period is about four or so days It has a very hot temperature because it’s so, so close to the sun, 1800 degrees Fahrenheit That’s really hot you don’t want to live there We don’t think it’s a habitable planet And then as we start thinking about what that means to be habitable we start to get a sense that planets like earth, maybe Venus, maybe Mars, are in a region near our star called the Goldilocks zone, where they’re not too hot for water to exist on the surface and they’re not too cold for all the water to be frozen So we started to find planets but they were not in the habitable And exoplanet discovery started to take off There are several different methods you can use to discover exoplanets And so in 2009 NASA finally completed a mission called Kepler Kepler was actually dreamed of decades before it was built and launched by principal investigator Bill Borucki He knew theoretically, he wrote a paper, that said if you were very careful with your photometry, how you measure your light, that you could detect a tiny dip in the light as a planet passed in front of a star, that’s called a transit So finally, Kepler was launched in 2009 by NASA with one goal and one goal alone, to answer the question, how common is a planet like the earth — so a small rocky planet like we live on, how common are those planets around stars like the sun at a distance that’s in the Goldilocks zone? In other words, how common are we? Here’s a transit, many of you may have actually seen this transit It’s the transit of Venus Did you see it? Did you see it? Anyone? It was visible in the morning sky, I think that was the one that was in the morning You could get up on your roof with the right equipment and watch the transit of Venus They happen very, very rarely but they happen in pairs a few years apart Venus is about the size of the earth and that’s going right across our sun So you could see all kinds of things in that movie Let’s see if I can start it over So you see that the sun actually looks darker on the edges and gets brighter as we go in You can start to see some granulation on the surface of the sun Stars are actually pretty active, they’re not super quiet Our star is actually very quiet as stars go And you can start to see that haze around Venus, the atmosphere Venus has a very thick atmosphere Some of the suns rays are getting — they’re not passing through the atmosphere, it’s actually dimmer around there And then as it comes off you can get a sense of the size of Venus It’s covering just a little piece of the sun, so it’s light is going to dim just a bit Here’s an example of what Jupiter would look like if it passed in front of the sun It would cover up about a hundredth the size of the sun And you’d see a dip that you could measure and you could get a sense of that size if you knew the star size very well Here’s what the earth would look like That’s hard Maybe you can’t even see it but it’s there on the right side If they were a bit more high definition or darker you’d be able to see some features on the sun, sun spots, that are the same size or even bigger than the planet So it’s a real challenge to try to disentangle the signal from the stars from the signal of the transit But Kepler was meant to do this How did it do it? Well we launched Kepler into a really interesting orbit called an Earth Trailing Heliocentric Orbit So it’s almost on the same orbit as the earth but it was a little bit further out, so it lags behind us And that orbit was a very good orbit for us to stare without blinking at this patch right above the Milky Way galaxy It’s near the Cygnus and Lyra region of our Milky Way If you’re familiar with the constellations you’ll know to look out in the summer time near the summer triangle and if you were to stare there without blinking for four and a half years you would be doing what Kepler was doing [laughs] Why is it so important that it’s stared without blinking? Well a transit like I showed you of Venus, I said only occurs from where we can see every 200 years or so and it only lasts a very short while Well the same thing is true, a planet like the earth is only going to transit it’s star once a year, once every 365 days We have to be perfectly aligned in order that that planet passes

in front of the star as we’re viewing it from our vantage point in the Milky Way It turns out that we expect only about one in a hundred stars are going to be aligned with us so that we would see transits So you have to look at a lot of them So we looked at 150,000 stars, getting a brightness reading every 30 minutes for four and a half years pausing only to turn around and dump the data back to earth so that we could detect these tiny transits in 1% of those stars, if planets were plentiful Of course one of the questions Kepler wanted to answer was how plentiful are they? What I told you is that one in a hundred stars would be aligned so that we could see the planets But if only one in a hundred stars has a planetary system well then your statistics go way down You have to look at a lot to get some meaningful number if planets are rare So we didn’t know before Kepler launched what the situation was So here’s a graph that gives you our picture of exoplanets before Kepler launched, on the eve of our launch And there up at the top are several methods that we can use to detect planets There’s the radial velocity method and the transit method that we’ve just talked about You can also imagine if you’re close enough you could see the planet if you had the right technology and there’s a couple blue ones on there Eclipse timing is something where if you have some very precise way of timing a system like neutron stars that are like rock solid clocks, you could see difference in the times that you expect versus the times that you measure and you can infer that a planet is there from that No Kepler points on this yet because Kepler didn’t launch yet So what we see there are a bunch of massive planets Planets bigger than Neptune and Jupiter, up near the top And we see a whole bunch of planets that are very short orbits So at the bottom we’re look at how long is the orbit in days, and you see that pink chunk of pink ones from the transit method They’re all like on a week or shorter orbit So we see a lot of massive planets, we see a lot of planets that are very close to their stars None of those are planets like the earth orbiting in the Goldilocks zone So let me show you what the first few years of Kepler taught us >> Whoa! >> Padi Boyd: There’s another transformative moment in our understanding of what planets are like in our galaxy So remember that’s just a little patch of our galaxy, it’s actually 10 degree by 10 degrees, so it’s a fairly large patch of the sky compared to something that Hubble can see But you can see what’s happening is that we’re going down to much smaller sizes and in fact, if you look at where most of those yellow dots are collecting they’re collecting near the small planets We’re not picking up those big Jupiter’s, they’re the easy ones to find, that’s why we found them when we first started looking because you can’t miss them They’re in plain sight And you can also see that we’re pushing out a little bit towards longer periods and there’s of course still some Jupiter’s up there and still some hot Jupiter’s Let me show you the newest catalog of Kepler planets You may have seen a press release related to this within the last few months The Kepler team, the Kepler mission is done now It’s on a new mission called K2 and what the team is doing is they’re compiling all their statistics and really improving their pipeline software that finds the planets to give us a sense of what Kepler found So the little yellow ones are the newest planets and you can see that the improved processing it really, really pushing us down towards those smaller planets and towards longer orbits You see where the earth is there, we’re really starting to fill in that region of planets that are on earth like orbits We’re still only talking about a couple dozen planets But remember, Kepler looked for four or so years, you’ve got to see several transits before you know you have a planet So really, finding something at around an earth or a Mars orbital period is at the limits of what Kepler can do We found that planets were everywhere This is an image that shows you that region of the sky but now plotting some of those planets down on it as a function of how big the planets were So there’s big planets and small planets, they’re everywhere in the region that we looked There’s no preferential treatment There’s no stars that have them and don’t have them But one of the really key points that we found when we found so many transiting planetary star systems was that planets are everywhere You can take what Kepler found and you can extract that to determine that pretty much every star out there should have a planetary system and that one in five probably has a planet about the size of the earth in an orbit where you could have liquid water, a habitable zone planet, one in five So when you look up at the sky next time, count ten star, two of them probably have an earth like planet in orbit Earth like is a tricky thing to say I’ll say earth size instead Here’s the distribution of planets, of the planetary candidates as of a couple of years ago So here’s some surprises So you see Jupiter sized planets and larger are actually fairly rare in the Kepler haul We’ve got a couple in our solar system

but most solar system that we interrogated with Kepler really didn’t have a huge planet like that Also, we see a bunch of earth size planets and a huge number of things that are bigger than earth, but not too much One and a half to two times the size of the earth, we call those Super Earths And then you see this big, big peak at around Neptune or so, they’re actually a little bit smaller than Neptune up to Neptune size and we call those Sub-Neptune’s And as the data got better, this is actually from that recent catalog that I was talking about before You could get much better statistical insight into the sizes of the planets, we actually see something we call the Fulton Gap What it tells us is in those small planets that are so numerous they appear to come in two separate categories, two separate populations One that we think are probably very similar to the earth like Kepler-452b And by similar, I mean a small rocky planet with just a little big of an atmosphere Because believe it or not the earth has kind of a tenuous atmosphere And then we think the other population are planets that are probably right around the same size in their core but for some reason they have attracted and retained a huge atmosphere, bigger than Venus, maybe close to Neptune The atmosphere being so big that you can’t really have life there, it would be way too dense Two populations of small planets and a gap in the middle that may be telling us about two different formation mechanisms for the same kind of planets or the similar sized planets But what’s really surprising about this type of result to me is that — remember we were learning so much about planets before by studying our solar system Now what we’re finding out from Kepler is that the two most common type of planets out there, Super Earths and Mini Neptune’s, we don’t have one in our solar system That’s interesting Were they here? Did they go somewhere? Did our solar system form in a different way? Or is it just small number statistics? Wee know a lot about one This is a really thought provoking animation that I love to show, it’s called the Kepler Digital Orrery When scientists first figured out the solar system they love to build things call orreries, where you could turn a crank, you can see it on [inaudible] cover there and the planets would start to go around They’re like little mechanical systems This is basically that idea applied to the Kepler multiplanetary systems, because something else we didn’t know for sure until Kepler launched, is whether solar systems, systems of planets with more than one planet were common or rare Now what we’re finding from Kepler is that they are incredibly common, it’s very common to find systems of planets And when you find systems of planets around a single star, it’s much more powerful because each one of those planets can tell you something about the same star And since the planets interact with each other gravitationally they can even tell you about the masses of the planets themselves So you may have seen as it zoomed out and zoomed back in, that you started to see our solar system on the same scale So again, just another graphical reminder that Kepler was really studying those tight, tight solar systems where the planets are going around weeks, months, out to a year or so Whereas our solar system, we know of things on very, very long orbits So, you may have also noticed that there is a difference in the star type, the star type then planet temperature up there Well that’s because Kepler was looking in one region of space at about 150,000 pre-selected stars We selected most of them to be very similar to the sun but it turns out that there are just a whole bunch of starts that are much, much smaller than the sun There’s a distribution of stellar sized And the sun, while it’s a normal star in some ways, the most typical star in the milky way is actually a low mass star, what we call a M star It’s just a way of categorizing stars Some of them are only 10% the mass of the sun What that means is that if an earth sized planet is transiting a much smaller, much dimmer star, then the transit signal is a lot deeper So you see on the right, a transit signal around Kepler 186, which was one of the first earth sized planet in a habitable zone announced by Kepler Compared to what the earth transiting the sun looks like Much, much easier to find those earth sized planets around the smaller stars Here’s a gallery of some of the small, hopefully earth like, but certainly close to earth sized planets the Kepler has found Showing you their size by how big the circle is There’s earth up there, sort of towards the top and the middle And giving you a sense of the habitable zone We’re sort of right smack in the middle of the habitable zone we thinking Wee could live, we could exist closer in We’d have a completely different climate, we’d probably be a different species We could also be pushed out, we would have different characteristics

as well but we believe liquid water could have formed and existed on the surface and life could have flourished And we can set that Goldilocks zone, or habitable zone by how much radiation planets are receiving from their stars So on the top axis there you’re getting a sense of what type of star Are these planets round? And how much sunlight they’re getting from their star How is that habitable zone defined So you see we’ve got a lot of smaller planets around the smaller stars for the reason we talked about before and even in the earths region there are a number of planets there So they are still very hard to detect but we are finding them, dozens of habitable zone planets found by Kepler This is again an update from that latest catalog The yellow ones are the new ones So you can see that last run of the Kepler data found habitable zone planets and small planets that were getting closer to earth analogs which is exactly what we were expecting would happen with Kepler That as the data came down and we got more data and we refined our methods that we would be able to really push down into habitable zone around a star like the sun So I mentioned that the M stars are abundant in our galaxy Seven out of ten stars in the milky way are thought to be M stars and the stars closest to us are small stars So they’re important They’re becoming increasingly important as we think about finding planets, because what Kepler told us is that planets are everywhere and we saw that a lot of M stars seem to have a lot of smaller planets around them That it’s common to make smaller planets around smaller stars And the other thing that’s really exciting about them is that the habitable zone is really crunched in around these small stars and that means that that transit that you’re looking for, or anything that you’re looking for on that periodic signal, happens much more often Weeks typically So if you want to observe something over and over again for a planet, a small planet around an M star is going to give you a lot more opportunities in a given say, observing season at a telescope, than something like earth around the sun So a lot of our attention is being turned towards the smaller M stars in the galaxy now when we think about how we’re going to take the next steps from Kepler and find those really earth like planets But there are some problems and some challenges with M stars It turns out that M stars are incredibly active So sometimes you’re probably hearing about solar flares that they’re predicting are going to perhaps impact your cable signal or maybe the GPS for a little while Or maybe you’re going to be able to see an aurora down here in southern latitudes because of the suns activity Remember I told you the sun is a very calm, low activity star M stars are hundreds of times more active They give out huge flares that dwarf solar flares and they do it much more typical So much more often This means that any planet that’s really close to that M star and going around really quickly, could be bombarded, probably is bombarded with high energy radiation all the time So even if they’re in that habitable zone it could be a trick for it to really be something where you could get habitability happening Also, planets that are close to stars tend to synchronize their orbit and their spin, just like the moon has synchronized its orbit and spin with respect to the earth So we always see the same face of the moon facing the earth A planet would always see the same part of the sun I should say it the other way around If you’re on a planet that’s in one of these M star orbits you’re quick likely to have got tidally locked and you could either be on that side of the planet that always faces the sun or maybe on the side that never faces the sun Or maybe lucky enough to be on that Terminator area Maybe the planet would wobble a little bit and you would get something like a day/night cycle But typically we expect these to be tidally locked which gives you all kinds of habitability issues But we’re still working hard to study these phenomena and figure out what could really be going on in these systems that are so different from ours And the thing that I think is really exciting about this particular area of research is it really joins together all the areas of astrophysics So you have to understand our sun very well, the flare dynamics and time variability, to have some sense of other stars that are like it and to be able to compare what’s happening on other stars as far as their flares go with what we know so well about the sun The sun is very well studied We have reams of data about the sun Also, we’re learning about what happens to these planets around other stars by studying the planets in our own system Getting better refinements of how our own solar system formed Why is there water in some places and not others? Was there water that escaped, for example in Mars? And we have a lot of information about the atmospheres on the other planets in our solar systems because we’ve sent probes and we keep sending probes and the probes get better and better all the time So we’re able to take the earths scientists ability to model the earths atmosphere

and apply it to planetary atmospheric modeling and then tying that with the suns variability, getting a picture or a model of what the exoplanet atmospheres could really be like So it’s just a very exciting time to be in any area of astrophysics because anything that you do has some tie in to understanding the atmosphere’s around these planets So we know the planets are there and our next step is how are we going to find out about the atmospheres of these planets? What’s in the atmosphere? How big is the atmosphere? Do they even have an atmosphere? I’m going to take a little bit of a detour now to a system that got a lot of attention earlier this year And this is called the Trapeus system Has anybody heard of the Trappist system before? Yeah! It was very exciting, it was one of NASA’s biggest days as far as like communicating a message goes A lot of people heard about the Trappist result, downloaded the images and watched the press conference and read articles online What’s Trappist? Trappist is a really small star, like we were talking about, that was discovered with a ground based telescope to transit And the team that discovered it convinced the Spitzer Space Telescope to stare at it for a very, very long time This is 500 hours of Spitzer data, again uninterrupted Because they knew that there were a couple of systems that were transiting and if they looked for a long time maybe they’d find more So this is the discovery image of many of the planets in the Trappist system There are actually seven earth sized planets — earth size-is planets in this system They’re small planets around a small star and they’re about 40 light years away It’s actually really close in the milky way It would take us about 800,000 years to get there if we were going at the new horizon speed, the fastest thing we’ve ever sent away from earth But it’s still close Relatively speaking it’s close Some people actually think of the Trappist system as more analogous to Jupiter and it’s moons Jupiter has moons that are about the size of the earth too And Trappist is a really small star You could fit the Trappist system well within our solar systems Those planets orbit Trappist on orbits of days, weeks and months So they’re transiting all the time Sometimes you can see two of them transiting at the same time and if they’re really a lot alike you can boost the signal of what you’re detecting by looking at the two planets passing in front of the sun instead of one So there’s a lot of interest in Trappist That we know that they’re small, we saw them interacting with each other gravitationally so we can measure their masses They are so close that it’s a fairly bright target even though it’s a dim star absolutely, it’s still close enough that we can observe it very well It’s going to be observed for decades, it’s going to be a touchstone system in our exoplanet studies This is just another example of the Trappist planets on top compared to some of the smaller bodies in our solar system, the terrestrial bodies And you can see where it says planet radius there, the third down, that they’re all pretty darn close to one earth radius So they’re a really good size And some of them are in the habitable zone They should have formed in a place around that star where they had ice and water and as they migrated in kept some of that water on their surface So they’re also excellent candidates for looking for life signs or at least water signs How are we going to do this and how are we going to find more systems like Trappist? Well, we’re going to launch something called TESS; Transiting Exoplanet Survey Satellite as Stephanie mentioned earlier It’s actually a fairly small telescope, it’s four cameras that are pointed in a row And it’s going to launch in 2018 March and it has one purpose It’s going to do an all sky survey of the stars near us to look for planets transiting nearby bright stars So Kepler wanted a statistical answer and it looked at stars that were very far away TESS is going to look for those transiting planets now around our nearest neighbors We know they’re out there, we’re going to find them Here’s an overview of the mission It’s what we call a NASA Explorer mission NASA has big missions like Hubble and medium missions like Explorers where you launch balloons and sounding rockets as well It’s managed at Goddard The lead institution and science team is led by George Ricker at MIT Being built down in Virginia at Orbital Now The beautiful picture of it all coming together It’s going to take two years to survey the sky It’s going to do the southern hemisphere first for one year and then it’s going to turn over and do the northern hemisphere And they’ve designed it so that they can detect enough exoplanets this way that they can then go to the ground based follow up observatories to confirm them and measure their masses; fifty small planets at the end of this These cameras are really wide field compared even to Kepler So one camera, you could actually put the entire Orion constellation into Go out some night when it’s clear and look at Orion,

it is a huge constellation That’s one of four cameras So it’s really looking at a huge swath of the nearby stellar neighborhood Here’s a comparison of the Kepler search space So Kepler was looking at one region, basically a cone where the average distance of the stars was 3,000 light years And it only looked at less than 1% of the sky That is TESS’s search space Going to look at virtually the entire sky There are definitely some gaps, but those stars are more like 200 light years near us Lots, lots, closer They’re going to be brighter and they’re going to be all over the sky There it is It’s taken a long time to take a picture like this of TESS But that’s the solar array test that the space craft is all put together That’s the antenna you’re seeing looking at you, that’s going to beam our data down every 13.7 days once we go around that orbit You can’t really see the cameras but they’re on top So we’re really excited for TESS We know it’s going to find transiting planets We can’t wait to get to the telescopes and find out what their masses are and maybe have another few Trappist like systems where we can really start to figure out what’s going on in the atmospheres But all of these missions I’ve been talking about so far, really what they’re doing is discovering exoplanets They’re collecting where the exoplanets are And we’re learning about the sizes of the exoplanets, that there’s a wide variety of sizes but we don’t know very much more There’s more than 4,000 exoplanets known right now, more than 4,000 just from Kepler alone as candidates We’re not sure what any of them really look like the way that our own solar system planets are known So how are we going to get there? Well we have to turn to the most powerful telescopes that exist today and that we’re launching soon and that we’re planning for the future in order to really get these answers, we’ve got enough data now that we can really design these experiments well to take these next steps So I’m going to take a few minutes to just talk at what direction — one of the directions that we’re going in This is an artist’s concept of some work that’s being done with the Hubble Space Telescope right now It’s been going on for the last few years and there are several large programs that are devoting Hubble space telescope time to measuring the spectra of what we call those “Hot Jupiter’s”, those very massive planets To look for spectral signatures, little parts of the light that are missing, where elements have been absorbed by the light So what we see here is a signature of methane in a planet’s atmosphere Methane is one of the gases that we think could be a biosignature A lot of biological material makes methane It’s not easy to keep methane in an atmosphere if there’s no source for it in certain conditions So methane is exciting We can actually see it in a Hubble spectrum These are just really the baby steps that we’re taking here That doesn’t tell you where the methane came from It doesn’t tell you a lot about the atmosphere other than that you’ve seen a methane line in absorption But we do know that the James Webb Space Telescope is going to be able to take the next step So James Webb Space Telescope is launching in 2019 You can see it’s quite a bit bigger than the Hubble Space Telescope Hubble Space Telescope mirrors 2.4 mirrors, JWST dwarfs it It has hexagonal mirrors that come together and can reposition themselves It has a sun shield there at the bottom that’s the size of a tennis court that’s going to keep it very cold because it’s going to make measurements in the infrared, so beyond the red part of the visible spectrum That’s where a lot of exciting stuff happens in astrophysics both for exoplanets and for the distant universe That’s actually a picture of the James Webb Space Telescope It was put together at Goddard in a clean room and that was one of the days that it was facing the window So it really is huge It really is ready to roll They’re down testing it in Johnson It’s actually out of testing now, they’re warming it up in the big chamber where they did a lot of the Apollo testing Next it’ll go off to get the sun should mated to it and it’ll launch from French Guiana in 2019 We’re so excited about what it’s going to find And there’s also been a lot of interesting work done in our own solar system studying the earth There are a lot of planetary missions that you can turn around and have them look at the earth The picture on the left is actually an image that was taken I believe from Cassini You see that little blue dot in there is the earth from the distance of Saturn And that’s better than we’re going to see exoplanets around other stars, but it’s still so tiny But there were efforts made to tease out the spectrum of the earth, both in the light that’s coming right towards you and also as a transmission spectrum so that when we’re looking at a lunar eclipse, where the sun is behind the earth and we’re looking at the moon that’s red because the earth is blocking the light on the moon, but some of the light is passing through the atmosphere and bouncing off the moon so you can get some spectral signatures

of the earth in these ways that are not directly looking at the earth And we know that we can see some signs in those earth spectra that tell us that biosignatures are on the earth So that’s a really exciting prospect for the future If we can do this same kind of thing with nearby exoplanets can we see evidence of water, evidence of clouds, evidence of tectonic activity We also know that it’s possible if you were to say be looking at the solar system and you had a really good telescope in your alien universe or galaxy, if you could see the earth and mars and Venus we know that you could tell those spectra apart They’re all small planets They’re all class to the habitable zone, but they have specific features in their atmosphere that differentiate them and particularly as you go out towards the right of that curve that’s a spectrum and it’s going into the infrared, we can see that the carbon dioxide feature is so strong in the earth compared to Mars, other features in Venus, all that carbon dioxide in the Venus atmosphere causing those deep lines So this is again exciting evidence that we may be able to disentangle features of planets that tell us if they’re earth like or maybe more like Venus There’s some really exciting work going on now as we plan the telescope that is going to be the next generation JWST So while we’re excited about launching this huge JWST telescope in two years we’re also thinking about what have we learned from building JWST that will let us take the next step? Let us build an even larger mirror Let us take even more sensitive measurements This is a really exciting simulation that has just come out recently by a group at Goddard led by Aki Roberge She’s a scientist that’s working on a mission concept called LUVOIR, the Large Ultraviolet Optical Infrared telescope One of the things they need to know to build LUVOIR correctly is what could you expect to see if you were looking at the solar system from about 12 parsecs away? Could you even be able to disentangle all that stuff around the sun? We know there’s a lot of dust in the solar system, we know that when you’re looking at a star there’s all kinds of stuff in the background Background stars, even background galaxies This group has put together an extremely sophisticated simulation to help us understand what we would see if we could look at the earth from a distance with something called a coronagraph And the coronagraph is being designed again to be optimized for LUVOIR There’s the Hubble mirror, there’s the JWST mirror, look at LUVOIR, it’s going to get yet again huge but achievable now We know we can do something like this Let me show you a little movie of what a coronagraph does [ Music ] >> A distant star is orbited by two planets One looks similar to the earth, the other is a gas giant When viewed from a distance the two planets disappear into the glare of their sun How could we ever find these planets all the way from the earth? By using a space telescope with the coronagraph to separate star light from planet light As the stars light passes through the telescopes large mirrors, it picks up small distortions Diffraction adds concentric rings to the image we see To reveal the planets, first a coronagraph uses a mask to block much of the stars light and redirect the remaining light to the outer edges A washer shaped device can now block most of the rest of the stars light Because the planets light comes in at an angle, it misses the mask and passes through the center of the washer But when we turn up the image signal by collecting more light, we can see that the planets are still hidden under blobs of leftover star light To remove these blobs the coronagraph has a special deformable mirror that can change shape by using hundreds of tiny pistons This can correct distortions in the light beam As the mirror deforms, the blobs of light as seen in the monitor slowly begin disappearing, finally revealing the brighter of the two planets Afterwards, the fainter planet also comes into view We can now see objects more than a billion times fainter than the star And if the light from these planets is passed through a prism we can spread it out into rainbows of color But some colors are missing They were absorbed by gases in each planet’s atmosphere, giving us important clues about their composition The search for life in the universe has taken a new step forward

[ Music ] >> Padi Boyd: So that’s hopefully a pretty good explanation of what a coronagraph does, it’s really exciting engineering and math and science and software and we believe is going to be able to cut down so much of the stars light that we would be able to differentiate earth, Venus and certainly Jupiter if we had a telescope like LUVOIR at the right distance So this is extremely exciting, it’s definitely our next steps that we would like to take LUVOIR is just one of many large missions that NASA is studying There’s four large mission studies happening right now There are two that are focused on exoplanets LUVOIR is one and another one that is called HAB-X for Habitable Exoplanets They share a lot of similar characteristics They want to have a big mirror, they want to have a coronagraph on board so that you can block out that star light and start to see the planets light and take spectra of it and find out what’s in the atmosphere But they just have slightly different mission characteristics LUVOIR is meant to do as much in the distant universe as it is to do in exoplanets whereas HAB-X is a bit more focused in it’s science case But it can also of course do lots of astrophysics as well And we’re waiting to see what the community directs NASA to do Every 10 years the country takes part in a decadal survey of astrophysics and this directs the government science centers about what they should focus on in the next 10 years So we’re gearing up for the next decadal survey, it’ll be happening in 2019 and 2020 Those four mission studies I was talking about, they will be going into the decadal survey We’re waiting to hear what the community of scientists that are involved in that recommend We’re certainly hoping LUVOIR and HAB-X are very highly ranked so that we can start to really tease out these exoplanet atmospheric signatures This sort of just does the sweep of NASA and ground based astrophysics missions that are focused on exoplanets right now I showed you some Hubble results, some Spitzer results, we talked about some ground based results We looked at a lot of Kepler data here I told you how excited we are for TESS to find those nearby transiting exoplanets we know we’re going to find and be able to follow up with Hubble and the James Webb Space Telescope I didn’t even get a chance to talk about the wide field infrared survey telescope and I can’t because I don’t have time, but it’s going to launch as well And then that last mission around the bottom there is this future mission that the decadal survey will tell us what it will be like So I hope I have convinced you that we really are standing on the edge here of our knowledge of what we know about our solar system and extra solar systems and that we’ve started to peer back that vail and put together a much bigger picture of how planets exist around stars and we’ll take the next step to determine how they formed around stars and around our sun and we are soon to take the next steps in determining what those atmospheres around those planets look like And whether or not they have elements in them that we can tie to biospheres life or compatible with life So I hope that the next time you look up in the sky at the milky way, instead of seeing something that shows you that there are billions of stars in just our galaxy and so any galaxies out there, that you’ll also think about the planets that are there that you can’t see The ones that we didn’t know about when I was a kid and that we know now are everywhere and think about what we’re going to find out when your kids are my age It’s a great explosive time So this is a picture of Galileo’s telescope It’s a scale model And it was brought up on the Hubble Space Telescope servicing mission, the last one, by astronaut John Grunsfeld, who’s also an astrophysicist He is known as the Hubble repairman He is the last person to teach the Hubble Space Telescope in orbit If you can squint your eyes you can see both telescopes there Galileo’s telescope and the Hubble Space Telescope, 408 years between the two And I think we’re just at a very exciting time where knowledge is explosive in this area So, buckle up and please keep reading about it Thank you [ Applause ] >> Stephanie Marcus: Thank you so much And if anyone has questions we’ll take them now and repeat them >> Padi Boyd: Okay Let’s start in the front and go around >> So, just maybe two questions if I can cheat Can we not get a pretty good idea of the composition of — particularly the smaller planets? Or is that what we’re most interested in perhaps If we know their density and we know the mass, we know the size, can’t we tell if there’s perhaps water there from the density of the planet? And are we at a point sometime in the near future where we might be able to in fact move around these larger gas planets that we’ve been finding?

So those are great questions The first question is about whether the density gives you everything that you would need to know about the planet and the second question is whether we can see exomoons, moons around exoplanets So the first one you’re exactly right, you’ve hit the nail on the head And that’s why when I was talking about TESS I focused on the fact that we are going to detect a lot of exoplanets but that we’re expecting that 50 of those we’ll be able to follow up with ground based measurements to measure the masses So they Kepler and the transit method in general do, just gives you the size of the planet, the radius We don’t know the mass until we’ve measured it through a different method usually radial velocity And the test targets are going to be so close and so bright that we’re expecting several dozen will be amenable to really accurately measuring the mass And so that if you know the star very well, the size of the star, then you know the size of the planet from the transit And once you’ve got its mass, you’ve got its density And that gives you a huge amount of information about the composition of the planet, it’s bulk composition But there’s a whole bunch of ways that you can make an average density out of, you know, either a differentiated planet like the earth where we’ve got a lot of iron in the center and then the crust is a different density and a slight atmosphere You can imagine putting that together in a slightly different way where you would still have the same common density So it’s a really important step but it’s not enough to tell you everything Yes. Oh, there’s a second question Exomoons, sorry And yes, we do think that the Kepler telescope was precise enough that it could have measured exomoons It’s a little bit trickier to do that because it’s not — so the pipeline for Kepler is just meant to find transiting planets Finding transiting exomoons around a planet requires another level of effort in the pipeline There’s a huge amount of data in the archive I wouldn’t be surprised if someone were to try to attack that problem in the next few years but to the best of my knowledge they have not announced any exomoons yet They have announced some exotrojan asteroids So we have the trojan asteroids in our solar system that are in very special orbits compared to the planets So they make a triangle, for example, with the sun, Jupiter and an equilateral triangle There’s two areas where asteroids can be stable and collect and coagulate So if you scale a lot of the Kepler planetary systems onto the same scale you can start to see signs that look very consistent with trojan asteroids, which is exactly what you’d expect because gravity is the same everywhere Yes >> You talk a little bit about the time factor, Kepler looked at one point and stays there for a long time and collects data, but doesn’t make a decision on its own The data comes back and decisions are made once the data is collected Is there something that’s coming in like a hound dog idea? Where you talked about you’re pointing back at the earth and collecting data [inaudible] that Goldilocks type of scenario would be for the earth and then speeding up the process of changing sectors and saying, alright, we were in this area, we decided this was long enough to determine the transits, move to the next area and look for that type of Goldilocks prospective of an earth, of whatever that is from perspective of oxygen or water or whatever consideration we’re looking for that we would consider for life Is there something like that? Versus, you don’t want to miss anything but so much time is spending on the majority of things not being the right thing >> Padi Boyd: Right So the question is to talk a little bit about how the time axis impacts your ability to detect planets and Kepler pointing in one direction meant that while we were really interrogating one patch of the sky very intensely, we were missing almost all of the sky during that time I think that was the point, right? And so for TESS, so no, nothing so sophisticated is in the near term plans like that But you can imagine putting together two simpler missions to get where you’re going So, TESS’s main difference from Kepler is that it stares in one region of the sky with those four cameras for 27 days only And then it’s going to rotate to like a next slice of the sky The camera that’s at the bottom or top is basically just rotating but looking at the same stars So those stars would be monitored continuously for about a year, whereas the other parts of the sky we’re only going to have 27 days worth of data on those stars So we’re going to be — it’s a preferentially red filter so we’re going to be preferentially finding transits around those dim, low mass stars where you can see habitable zone planets in a short amount of time But, currently there’s no effort to dynamically change your time length based on what you’ve found so far You can use the TESS results to then go to telescopes and do the more sophisticated stuff Yes >> When you [inaudible] biosignatures of the [inaudible] that you will What’s the degree of certainty will you have that you’ve found something that might signify life? >> Padi Boyd: Oh that’s a really great question And there’s actually a lot of people that are working

on that particular question As I was talking about earlier, exoplanets has become extremely multidisciplinary So you know the astrophysicists are capable of developing these amazing telescopes with the ability, you know, to really detect signatures in a spectra But we also need atmospheric scientists to do modeling that tells us what are the possible sources of that feature in an atmosphere What could be tricking us? You know, what could look like a biosignature that isn’t? And so we’re using all kinds of information that we have from earth science and from planetary science and just from modeling to start to answer those questions So I think it’s going to be very similar to the answer about like, once you’ve got the mass does that nail down everything that the planet is made of? If we’re going to have a similar answer for spectral lines and potential biosignatures I think when we find something we’ll know it as a potential biosignature, they we’re going to have to do an awful lot of work modeling theory and just measuring many other systems before we have a sense of how secure we are in that >> Just a follow up, and then what would be the next step in what’s [inaudible] on that modeling What would be the hope like you said when our kids at your age? Or each generations >> Padi Boyd: So I actually — so I have a seven year old and I am fairly confident that when he’s my age he’s going to be able to go outside with his kids and point to a couple stars in the sky and say, that one right over there has a planet a lot like earth We know it’s about the right size, we know that liquid water does exist there and we think that there could be life because we know of these things The next step is not up to my generation Keep going this way and then come back Yes >> I know there was an earlier mission proposed that hasn’t been launched yet or planned to track terrestrial planet finder Is there an upcoming mission that’s analogous to that or how far off will the terrestrial planet finder type mission be in the [inaudible]? >> Padi Boyd: So, some elements of the terrestrial planet finder the LUVOIR concept But you can think of LUVOIR as a reengineered version of the terrestrial planet finder So the question was, how soon will something like the terrestrial planet finder be realized? So, LUVOIR takes some of the best ideas of the terrestrial planet finder and it takes all the information that we have right now about the exoplanet populations we know of to design a mission that can really tell us something about what we know we’re going to see When the terrestrial planet finder was first being designed we didn’t really know that much about the exoplanet population out there and then some of the other things that might have made it very challenging to visually see planets like how much dust was in the system But we’re taking what we’re learning now about systems to make LUVOIR even stronger and better There’s always a next step though and there’s people that are thinking about what do we do even beyond the LUVOIR? And so there are some ideas about building super large mirrors in space using astronauts or robots near the space station, where you could launch pieces of it and put it together like a Lego And then of course, very much more sophisticated coronagraph technology The movie that I showed you about where we’re going in coronagraphs now, we’ve made huge strides there in the past decade but we’ve got a long way to go there too and you can see some kind of transformative technology there for direct imaging that you’d want to fold into the next mission as well Yes >> Ages ago I remember reading that we shouldn’t get too excited about exoplanets because there’s so many double stars out there and double stars were less likely to have planets I didn’t hear you mention double stars at all >> Padi Boyd: You are right, I didn’t have time to mention them at all So you may remember that scene in Star Wars where Luke Skywalker goes back to his childhood home and he sees something terrible and he goes out on a hill and he watches the sunset and it’s two stars that are setting, not one And people said at the time George Lucas, that was fantastical You’re not going to have any stable planets around binary star systems There are actually planets around binary star systems when we found them with Kepler The first concubinary planets were found just a few years after the mission launched and there’s quite a collection of them So that opens up a whole new set of questions about the stability of planetary systems Where did they form? Do they form somewhere else and migrate in? Do they form around one star or did the whole system form, you know, as one? And have they interacted, have then been around one star for a while and the other? It’s fun, it’s a lot of fun dynamics in that one Yes? >> Actually yeah, my question was sort of based on that How does binary or even tertiary that has ever been in the situation, how does it affect the means for Kepler and maybe future tests to elaborate on these exoplanet findings? Have they impeded or have they, I guess, lead to more fascinating [inaudible]

>> Padi Boyd: So the question is, how does the binarity of many stars impact the results that we’re talking about with Kepler and TESS? So we know that about half the stars in our galaxy are found in binaries and half are single And lots of what I talked about was sort of implicitly suggesting that they are single stars And in fact we know that about half of them aren’t So there’s a great effort that goes into taking a Kepler planet candidate and turning it into a Kepler confirmed planet And one of the things we have to watch out for the most is whether a binary star is tricking us Because if you see a planet that’s going around one star you’re going to get a certain size estimate But if it’s actually two stars that are giving you the flux from the star, then the transits going to look much smaller and you’re going to make the mistake that the planet is smaller than it really is So there are efforts that go into like direct imaging of these systems to see if we can get very high resolution imaging and look for binary pairs If they’re very far away that’s also very challenging So there’s also some statistical arguments about whether this is a single star or a binary and then also we can look at the data itself and see how the light moves on the detector to determine if there’s something fooling us Yes? Should I take one more question? It’s 12:31 >> Stephanie Marcus: Yeah >> Padi Boyd: Okay >> Can you speak at all — you didn’t mention if there was any significance to the location of where these missions were looking Like Kepler seemed like it was kind of a somewhat arbitrary area This spot and this distance away And then the next mission is looking 200 light years away >> Padi Boyd: Mmm-hmm >> They’re both, with Kepler the location but also the distance of the two of those Is there a reason why they matter? >> Padi Boyd: Sure So the question is say something a little bit about, basically the mission design Why was Kepler chosen to look where it looked? And why is TESS looking at the 200 light year sphere around the earth? So, yes, there are good reasons And there was a lot of debate and discussion and collaboration that went into deciding what the final Kepler field would be We knew in order to do the mission it has to be staring, so it had to be somewhere where it could look for four years straight We wanted to have lots and lots of stars like the sun, so you needed a relatively dense patch of the sky But you didn’t want to be so close to the milky way that you had a lot of crowding That your typical star would have other stars nearby that would dilute the signal So you wanted to get far enough off the milky way plane that you would have about 150,000 sun like stars that you could put little postage stamp patches to get the light curves And another reason that that position was chosen was because there were a lot of ground based telescopes that could get on the part of the sky pretty quickly to confirm the planets For TESS, once TESS was being finalized we of course knew from Kepler that planets were everywhere and so that made the choice of looking close, looking nearby, much, much better You know, we know they’re going to be there So now you can design TESS in a way that’s a lot different than we designed most astrophysics missions where we’re trying to look at really dim things TESS is really meant to look at bright stars Most telescopes saturate when you look at bright stars But TESS won’t So, it was intentionally designed to be shallow so that it’s only going out to 200 light years because we know there are more than enough stars in that area that it is sensitive to that we expect thousands of planets and hundreds to be with measured masses >> Stephanie Marcus: Well, thank you very much >> Padi Boyd: Thank you Thanks for all your good questions >> This has been a presentation of the Library of Congress Visit us at loc.gov