A Planet for Goldilocks: Kepler & the Search for Living Worlds

[Music] good evening everyone my name is andrew frak noi i was for many years the instructor of astronomy here at foothill college in Silicon Valley and in my retirement we're still continuing these Silicon Valley astronomy lectures it's a great pleasure for me to be able to introduce these lectures to you these are co-sponsored by NASA's Ames Research Center the Foothill College astronomy program here in Los Altos Hills the Astronomical Society of the Pacific and the SETI Institute tonight's speaker were delighted to welcome back dr. Natalie Battaglia she is an astrophysicist at NASA's Ames Research Center and she is the project scientist for NASA's Kepler mission searching for exoplanets for planets orbiting other stars and I think we would all agree this has been one of the most successful and scientifically rewarding missions of all time so we want to congratulate her on her success she holds a doctoral degree in astrophysics from the University of California at Santa Cruz she's been involved with the Kepler mission since the proposal stage and contributed to many different aspects of the science from studying the stars themselves to detecting and understanding the planets that they Harbor dr. Battaglia served 10 years as professor of physics and astronomy at San Jose State University before joining NASA Ames for the Kepler project in 2011 she was awarded a NASA public service medal and in 2017 Time magazine very appropriately named her to the list of the 100 most influential people in the world so ladies and gentlemen please join me in congratulating and welcoming dr. Natalie Burton hello everybody welcome thank you so much for the lovely introduction and for having me it's really a pleasure to be back it's very meaningful to me because I gave a lecture here when Kepler first was launched or right thereafter then about midway through I gave an update and now here I am just one month after the Kepler prime mission actually closed out so everything all the ribbons have been tied on the packages and the data's been delivered and my job is pretty much done and that feels really great so I'm here to tell you about the exoplanet science that we did with Kepler how many of you had heard of Kepler before coming tonight that's that's fantastic wonderful so the title of the talk is a planet for Goldilocks primarily because Kepler's reason for existence was to find planets amenable to life the just right planets and we'll see that that's not too big not too small not too hot not too cold and we want to convey the message that the results of Kepler have catalyzed the search for life or evidence of life beyond the solar system in a very tangible way so I'm going to spend the first half of the talk talking about Kepler results and then specific to exoplanets and in the second half we'll look a little bit towards the future the search for evidence of life really has three pathways and two of them are represented here on the left we've got solar system exploration we have this one ever one example of life in the solar system here on earth but that doesn't mean that there couldn't be life elsewhere the image I've chosen for this to represent this pathway is an image of the satellite of the planet Saturn this is Enceladus and what is special about this satellite is that it is seen to have geysers dating from beneath a and icy crust many kilometers thick and where there's liquid water we think that there might be life so it's very compelling to go searching there underneath the ice and see if any microbes could actually survive in the water that's there there might also be life in the subsurface cave on Mars for example we know that Mars once had water maybe it still does today and certain tiny Nisha's and and again where there's water we think there might be life so to go and explore Mars is also very compelling maybe we won't find life maybe we'll find death in the form of fossils and I think that's one of the motivations for sending humans there to go and excavate on the right hand side the second pathway is marked by the radio dishes at the Allen telescope array up in lassen near the California Oregon border these are telescopes that are listening to the universe for information or for signals that have a lot of information content that have patterned signals to patterned to regular too much information content to be explained by regular astrophysics alone the idea being that perhaps the pattern signals could be due to technology so those are two of the pathways for searching for the evidence of life beyond Earth but the third pathway was opened up in 1995 with the first discovery of a planet orbiting another star outside or in the galaxy and we call these exoplanets EXO being the root for outside of so all of the planets I'm talking about this evening are not planets in our own solar system these are planets orbiting other stars in the galaxy and this is the first an artist's rendering not an actual image but an artist's rendering of what I would consider to be the first discovery of a planet orbiting another star like our own Sun this is 51 peg B I won't go into too many details about how this planet was discovered it was it was done via the Doppler method and I can talk about more that more entering the Q&A but I want to say that this first planet discovery really surprised it wasn't like anything we have in our own solar system it's a giant planet orbiting about once every three days I think it is its parent star so that makes it ten times closer to its star than mercury is to our own our own Sun and in our own solar system you know we we grew up learning that we've got the small terrestrial planets orbiting close to the stunt to the Sun we've got the big gas and ice giants orbiting far away right so here's a cartoon that shows a graphic that shows the layout of the solar system planets where the relative sizes are about right but not the relative distances they're all brought in close just for display purposes but you can see the tiny rocky things close in and the ice and gas giants far out mercury the one that's closest to the Sun here it would be about 40 fuller diameters away from the Sun just to give you some idea so this first planet 51 peg beams 10 times closer than that so you can see that it's very hot and it was a big puzzle as to how a giant planet could form so close and this very first discovery actually taught us something really important all the theoretical models say that indeed these planets formed farther out where the temperatures are amenable to creating these gas and ice giants but that these early solar systems actually are dynamical environments they can interact with one another gravitationally they can interact with the disk of material from which they formed and those gravitational interactions can get them to move around so when we talk about potentially habitable planets we have to keep in mind that the planet that we're looking at today through this one snapshot is just a snapshot in time we have to also consider the entire evolutionary history of that planet it's part of its story so that was an important lesson but the the planet 51 peg B I think was also a huge catalyst for that that pushed technology towards finding planets that looked much more familiar to us planets like those in our own solar system we needed higher sensitivity and we really wanted to find a planet like Earth a true earth-sun analog but in order to do that well before I before I talk about that let's go back to the idea of what actually makes an earth-like planet the idea of a Goldilocks world today in terms of the technology that we have we talked about the Goldilocks planets as in terms of their size and their orbits because those are the two things that we measure we would love to have more information about these planets but for now we've got size and orbit and here i've called that size and energy now why is size important I've given an example here of Jupiter Earth and I think mercury there over on the far right or maybe that's Mars science is important because while we think all the planets in our solar system have a rocky core the gas and ice giants have a very thick envelope of hydrogen and helium rich molecules that's I mean life certainly hydrogen is important for life but the other elements that make up life on planet Earth are things like carbon nitrogen phosphorus silicates right sulfur right for in DNA and RNA so we want access to those heavy elements in order to make complexity grow right and to create life and so on a planet like Jupiter by time you get down to the rocky core where you have access to all of those heavy elements the pressures are going to be too high to create or sustain DNA and RNA any kind of complex chains of molecules so those planets are probably not amenable to life on the opposite side a planet like Mars is so tiny the surface gravity is so low it has trouble hanging on to its atmosphere and so a planet without an atmosphere is going to have a very low surface pressure and water is probably not going to be sustainable on the surface it's not going to be able to pool on the surface and stay there for very long so we're looking for kind of a sweet spot in terms of a planet about the size of Earth a range of sizes that encapsulate terrestrial sized planets and of course is this idea that if it's too hot the water will all be vaporized if it's too cold the water will all be locked up in its frozen state and we need water in its liquid form because liquid water is the solvent that facilitates all of the important chemical reactions for life on planet Earth no matter how diverse it is things like cell transport metabolisms so so that's what we're looking for our Goldilocks world is a planet that is just the right size not too big not too small not too hot not too cold now in order to find an earth-sun analog we had to find a new methodology for detecting planets this first planet 51 peg B was detected through this thing called the Doppler method which is basically looking at a motion of the central star and as the planet and star orbiting one another and that motion for a planet like 51 peg B is about the velocity of a car hurtling down the highway the best our technology can detect is a velocity that's about a walking speed about one meter one one meter per second or so maybe a couple one two three but a true earth-sun analog is going to produce induce an orbital motion on its star of something like the speed of a ladybug crawling on the ground it's very tiny it's like centimeters per second our technology today can't yet do that so we needed a new technique and that technique was first proposed in the early 1980s and it was the transit method of Planet detection basically the idea is that is really simple actually we're measuring the brightness of stars and we're going to do that very precisely and what we're looking for our Eclipse events or dimming of light that happened when a planet in orbit about the star happens to pass directly between the disk of the star and the telescope right the planet casts a shadow out into the galaxy that shadow sweeps across the face of the telescope and we perceive that or measure that as a momentary dimming of light it lasts a few hours it comes back every orbit and so in this cartoon use the the the cartoon on the top and then on the bottom the green trace is actually the brightness measurement as a function of time that was proposed as a space-based mission four times each time rejected it was proposed in 92 94 96 and 98 and was not accepted as a viable mission for detecting an earth-sun analog until the year 2000 actually 2001 but it did become NASA's Kepler mission that was launched from Cape Canaveral on March 7 2009 here you've got a picture on the left of the spacecraft of the cleanroom at Ball Aerospace it's a Space Telescope the mirror is about 1 metre in diameter it focuses all of the light directly onto a set of instruments that are very similar to the device you have in your cellphone for taking pictures without the color capability it turns brightness or photons into a voltage you measure the voltage you get out of brightness it's a very simple design and what makes it what makes it complicated is the exquisite precision that's required and I'll get to that in just one moment the mission is the telescope is actually still up there flying and it's still taking data but it's science has been divided into two parts the first for years was the Kepler prime mission and that's the time period for which we collected data to do one very simple experiment the prime objective of Kepler was to determine the fraction of stars that Harbor potentially habitable earth-sized planets that is planets that are the size of Earth and orbiting in the Goldilocks zone so it's a statistical mission it was not a mission to go out and find earth 2.0 it wasn't a mission to find on earth analogue it was a mission to take a census of sorts or maybe a pole is a better analogy you know like you call up a thousand people and ask them what cereal they eat for breakfast you apply your observational bias Corrections and you try and come up with a number that represents the general population that's basically what we're doing we're polling about two hundred thousand stars near the plane of the Milky Way in that yellow funny shape that's tucked underneath the wing of Cygnus the Swan and we observed just those stars for a period of four years more or less without blinking okay as I said these dimming zuv light only lasts a few hours and they're only going to repeat once every year for example if for a planet like Earth so if you blink you can visit you want to to take that data continuously and you have to observe a large number of stars because not all of your orbital planes will be aligned so that you get this nice transit geometry so that you can see these dimming Zoar have these Eclipse events so all of the science I'm going to be talking about are from the prime mission there are a bunch of other gray footprints if you will going along the sky that represent the other fields of view that have been observed after that first four years during what's called the k2 mission and I just want to distinguish those two and this is an example of what the data looks like this is just like the green trace in the animation we've got brightness measurements on the y-axis versus time on the x-axis every white point you see every white circle is a brightness measurement you notice a few things that oh and this is for a period of about 300 days you'll notice for first of all there are some black gaps where there are no white circles and so what I said before about the spacecraft not blinking that's not exactly true there were some moments in time when the spacecraft stopped taking data momentarily mostly due to safemode events so that's what explains the the gaps you also notice that the white points are kind of scattered up and down that's measurement uncertainty to some degree we don't measure the brightness as perfectly the stars themselves can also have some intrinsic brightness variability but what I want to draw your Gentoo is a sequence of dippings of light that are periodic over the course of this 300 days do you see them I'll mark them in cyan here for you there they are so those dimming x' of light occur about once every 45 days I think it is and it's due to a planet that's about 2.4 times the size of Earth so now we're going to zoom in on one of those here marked in green so you'll see one dimming of light due to a 2.4 earth radius planet orbiting at 45 days there you see it there just to the left and if you look carefully perhaps you'll see another sequence of periodic dimming of light as well in this actual Kepler data if not let me help you with the red lines here we are so those dimming of light you see are much shallower that's because the occulting object that is eclipsing the star is much tinier this object is about the size of an earth and it's orbiting once every 20 hours or 0.8 4 days which means it's very close to its parent star so in these two graphics on the left these are meant to represent stars just like our Sun on the left I put a black disc that corresponds to a planet the size of a Jupiter a jupiter-sized planet removes about one part per 100 of the light so imagine 100 light bulbs you take away one that's the dimming of light you get from a Jupiter on the right hand side the black disc that you can just barely see is due to a planet like Earth an earth-like planet is only going to take out one part per 10,000 of the light and so the analogy we like to use is to imagine the tallest skyscraper in New York City or downtown San Francisco maybe it's got 80 some odd stories if it's in San Francisco certainly all the lights are on it's nighttime all the windows are open and one person goes to the window and lowers the blinds by about two centimeters the change in brightness that you have to be able to see and that's what makes Kepler so technically challenging you have to demonstrate that the detector technology and the engineering of the telescope is stable enough to give you part per million precision on the brightness measurements otherwise those dimming zuv light you saw so clearly with your own eye without any fancy software would be obscured by the measurement uncertainty so just to summarize how much the Starlight dims tells us the size of the planet and how frequently the dimming zyk er how long it takes to come around once tells us the orbital period and the orbital period according to Johannes Kepler in the 1600s he taught us that the orbital period is directly related between the separation between the star and the planet and that's what tells you if it's in the Goldilocks zone or not okay all right so in one graphic I'm going to summarize Kepler's discoveries these are this is a scatter plot with the two measurables that we just talked about planet radius on the y axis and planet orbital period on the x axis every dot in the graphic represents a planet discovery and the planet discoveries that you're looking at right now we're all made before Kepler launched out into space there are some horizontal lines to guide you for for relative to oh I'm seeing my numbers are getting cut off sorry about that there's a horizontal line for Jupiter one for Neptune and one for Earth just to guide your eye you can see that most of the discoveries of planets before Kepler launched were about the size of Jupiter indeed 85% of them were larger than Neptune so most of the planets discoveries before Kepler were larger than neptune they're color-coded the blue points were discoveries through the Doppler method and the pink points were discoveries from ground-based mostly ground-based transit surveys like what we plan to do in space but done from ground-based telescopes and in fact we ourselves here in the Bay Area built such a robotic observatory right here at Lincoln separatory on top of Mount Hamilton we had a very tiny four inch telescope that we robota sized to do this kind of thing and to learn how to do this before Kepler even lunched so that's what the scene looked like before Kepler and now I'm going to add the yellow points that correspond to Kepler's discoveries over the first four years Kepler discovered over four thousand transiting planet candidates I'll call them there that catalog is about 90 percent reliable so there are Astrophysical signals in nature that can mimic a planet transit that corresponds roughly to about ten percent of the sample and in many regions of parameter space can be even smaller but of those four thousand well over two thousand almost two thousand five hundred kepler planets have now been confirmed to greater than 99.9 percent confidence levels and that's done through other follow-up observations that happen either from the ground or other space-based telescopes or other analyses with the data that allow us to really nail down the exact characteristics of the planet and and know that that is due to to a planet so you you can already see some patterns in this diagram remember Kepler is taking a poll right so we're doing statistics we're trying to understand the exoplanet demographics and that's really what distinguishes this lecture tonight from my previous two lectures where we focus mostly on individual discoveries tonight I really get to take a look at the statistics and what they taught us but you see some patterns the first most obvious one to me is that the yellow points are mostly below the Neptune line now over ninety percent of the planets well in Kepler sample are smaller than Neptune so we put a new piece of technology out into space and literally lifted the blinders that we're preventing us from seeing the small planets that populate the galaxy now we see that they're there in spades but there are still places where there are no planets for example the bottom right hand corner is pretty much devoid of planets and that's yet another observational bias before we couldn't see the planets smaller than Neptune now we can't see the planets in the very bottom right hand corner of the diagram and that's just because Kepler itself has finite sensitivity but there are other places where you don't see planets for example on the left there's a little desert where there's very few points between Neptune and Jupiter and that's real planets don't like to form their planets with those characteristics are extraordinarily rare if they exist at all and there are physical reasons for that and our theoreticians are learning from this information and putting that information into their theoretical models in order to fine tune them okay so we'll come back to this idea of statistics and a bit before I go there though I'd like to make one point that has been extremely meaningful to me or at least surprising and informative what I've learned from Kepler is that the diversity of exoplanets in the galaxy far exceeds the diversity of planets in our own solar system this has been a surprise to me and I'd like to just give you a flavor of that I can't go through all of these discoveries in detail but what I've done has made a collection of thumbnails of artist renderings that represent very specific planet discoveries so just to give you a flavor of the kind of diversity I'm talking about we'll start in the upper left we have found planets orbiting not normal stars but dead stars like white dwarfs for example other teams have also found planets orbiting neutron stars for example that's represented in the upper left we have found planets called lava worlds these are rocky planets that are orbiting 30 times closer to their star than mercury is to our own Sun these planets have a star facing side with temperatures in excess of that required to melt iron so they've got an entire hemisphere larger than the Pacific ocean that is an ocean but it's not an ocean of water it's an ocean of molten rock and hence the name lava worlds you can take that to an even more extreme and you can put them even closer to their stars and they begin to literally photo disintegrates and they show behavior of having a cometary tail and so you see in the third thumbnail this triangular or cone-shaped darkness that's emanating from the point just like a comet tail does as a comet approaches the Sun except here you know that in the case of a comet you're talking about a dirty snowball this is a ball of rock that is doing the same thing it's being photo evaporated and we see this because the dimming of light is not perfectly symmetric it starts off very sharp and then it comes up very slowly because you've got this asymmetric shape due to the tail so we see many of those down at the bottom and the blue orb that you're looking at is meant to represent ocean worlds there is a class of planets that have this very low density but they're smaller than Neptune kind of between an earth-sized planet and a Neptune sized planet so they most likely are covered in an hydrogen and helium rich envelope like the gas and ice giants but they're tinier moreover instead of being out at the orbit of Neptune Jupiter Saturn Uranus you take one of these tiny worlds and you plunk it down at an orbit of like Venus for example whereas receiving a lot more energy from its parent star and so then the big question becomes what do these worlds do what are their hydrogen and helium envelopes like could it be possible to have a true ocean world where you've got this hydrogen and helium envelope that is partly at least in liquid form completely envelope aplanet and we really don't know what these worlds are like at all next we've got worlds that are orbiting not one but two stars so if you were to be on one of these worlds and you look over in the east you would see not one star rising in the east and setting in the West but two and they are gravitationally bound and orbiting one another continuously switching places doing a pas de deux across the sky and taking that to more of an extreme we find planets orbiting stars in star clusters these are gravitationally bound conglomerations of hundreds of stars thousands of stars so you've got a high density neighborhood of stars so if you were living on one of those planets you would look up and see a bejeweled sky much different than the Milky Way or the-the-the the starry sky scape overhead I could go on there are planets for example that are the age of the galaxy itself that formed around our galaxy's very first stars that means that the raw materials to build planets were there at the very beginning and it's that that really fascinates me because I think about worlds where life could get a toehold and have you know ten billion years to evolve as opposed to four-and-a-half billion and that to me opens up a lot of possibility okay so that's exoplanet diversity and just to drive home the point one more time about these weird ocean like worlds this is a histogram just a bar chart of all of Kepler's discoveries orbiting certain kinds of stars and out to about an earth's orbit or 400 day orbital period so there's that little caveat there on the right-hand side so on the x-axis we've just got the planets size where earth size would be one the number one would be the size of Earth so we've got the brown bars corresponding roughly to terrestrial sized planets like Mars and Earth for example then on the right-hand side you've got the blue bars that correspond to sizes that are roughly like the gas and ice giants Uranus Neptune Jupiter Saturn but the most common planet in the Kepler sample is a kind of planet we don't have in our own solar system these super Earths slash sub neptune planets at short orbital periods we don't have one in our own solar system or at least we think we don't maybe the study of the Kuiper belt objects will tell us otherwise but for now we have nothing in that size range on the top I've ordered the planets in terms of size just to show you this gap in the radius distribution and yet that's where most of these most of our discoveries lie so that that's me is very interesting okay but what I've told you already is that this is that we're taking a poll right so we've called up 200,000 stars and ask them what planets they have at least orbiting from an Earth's orbit and inward and we got our discovery space back that's what you see here in these histograms but now I need to transform that into the intrinsic population of planets that's actually out there in the galaxy and to do that I need to correct from all my observational biases in the case of our cereal analogy maybe I made all of our phone calls mostly around 3:30 when all the teams get home and that biased my results so so I have to think about the kinds of things that bias our statistics and and we have to quantify all of them one of the biggest biases that we have is that of all the 200,000 stars that we looked at only a very small fraction will have the right geometric alignment for an eclipse to occur at all and in fact the probability of that happening is really small it can be as small as a tenth of one percent at most maybe ten percent so what that means is for every one planet we did discover there are something like 10 to 200 others out there that that just didn't have the right geometry so we make those kinds of Corrections and so when we make those Corrections I can transform a bar graph like this which is showing the fraction of observed discoveries into an intrinsic population in the galaxy and the way I'm going to express that is in the at is the average number of planets per star so that's what's going to be on the y-axis and my histogram then looks like this and I just I calculated this yesterday this is with the latest final catalog that was just livered in june and with all of our most advanced bells and whistles in order to get the best most robust measurements so this is not yet published so you're seeing it for the first time but what we've got here again is planted size on the x-axis the average number of planets per star on the y-axis and so what you see is that the brown bars and I've dropped the two to the far left just because I'm not confident about this to the error bars for Mars size planets are really large so I'm limiting us to earth sized planets up to about twice the size of Jupiter but what we see is that the brown bars came up a lot relative to the blue bars the blue bars went down the brown bars came up that's because my bias Corrections inflated those numbers because the earth sized planets are the hardest to find I had very low sensitivity of the earth sized planets relative to the Jupiter sized planets so I had to make that adjustment okay so this graphic tells me a lot of really interesting things first it tells me right off the bat that nature makes small planets more efficiently than large planets at least inside of an Earth's orbit or the inner parts of a solar system that's true the other interesting thing I think about this diagram is that if I add up all of the numbers for example the brown bar is roughly 0.4 the grey bar next one over both of them are around point 3.3 and you keep going and you add up all those numbers you end up with a number that's something like 1.3 to 1.5 so what that tells me is that every star on average every star has at least one planet keep in mind that we're only talking here about planets orbiting within 400 days in 400 day orbital periods or smaller and we're excluding all of the Mars and Mercury and Pluto's objects out there I didn't say planets dwarf planets so at least one so when you look up in the sky at night and I hope that you don't see these pinpoints of light this just stars anymore you should see them as planetary systems because every sun-like star every every normal star has at least one planet now we can take this diagram and actually ground-based observers have been using the world's best most powerful telescopes like the Keck 10-meter telescope to study all of the stars that Kepler has been observing especially those that are known to have planets and they've been doing that in order to pin down their star properties very accurately so that we could know the planet properties with very high accuracy and if you fold in that information you get a diagram or a histogram now that looks something like this so our our bar graph now has more bins so if you follow the orange line from the right hand side it starts out very low around Jupiter sizes just like our previous bar graph did and it starts to grow and grow as you get to the Neptune size planets around four and you work your way into the super Earths down around two and a half but then it takes a dive and it comes down before going back up and in fact we did see this in this graphic as well you see a little dip there in the first gray bar but now that we update when we update our star properties that actually gets more extreme and what it tells us is that the small planets actually come in two different sizes they seem to bifurcate into two different pile up into two different groups so I just I wanted to communicate that as as an example of the kind of detailed information that exists in that period radius diagram that you saw with those four thousand points there are a lot of patterns there and this kind of information can now be folded into a scenario for developing theoretical models about how planets form from tiny attesa Milles little pebbles on the left to rocky cores that then accrete on hydrogen and helium envelopes and that are sculpted and exposed to radiation from their parent star and eventually end up into these kind of two regimes of sizes that we call roughly the super Earths and mini Neptune's so we're just beginning to learn what this actually means and what the implications are I will come back to that in a minute but what about the Goldilocks worlds after all this is Kepler's reason for existence Kepler did find Goldilocks planets this is one example kepler 452b one of the exoplanets most like Earth that Kepler discovered and it's shown quite clearly in this infographic this split screen on the right-hand side or on the left-hand side I should say we've got the Sun in the middle the half disc is the Sun and the earth and it's 365 day orbital period with its its size their relative to the other planet kepler 452b on the right you see that its central host star is very similar to our Sun it's only 10% larger same temperature pretty much the same age a little bit older it's about 6 billion years instead of four and a half the planet kepler 452b is about 60% larger than the earth and our what we know about planet masses and sizes and densities and compositions tells us that at 60% the size of the earth or one-point-six 60% larger than the size of the earth we do expect to have roughly a rocky composition so we believe this is most likely to be a rocky world it's orbiting its star once every 385 days very similar to the earth which means it's receiving about the same amount of energy so it makes it a very interesting Goldilocks world and in fact kepler found about fifty Goldilocks worlds and they're represented in this scatter plot which is a little different than the period radius diagram I showed you before now we're plotting on the x axis the energy that's received by the planet how did its orbit from its central star how warm it is the green band corresponds roughly to the Goldilocks zone but you see it's tilted over that's because the exact numbers for the Goldilocks zone depend on the kind of star that it's orbiting and so on the y-axis I've got different kinds of stars on the top so as indicated by the temperature of the star our Sun has a temperature of about 5800 degrees Kelvin so that corresponds to the biggest circle on the top you've got the K type stars and the tiny m-type stars at the bottom the details aren't as important is the message here which is that the 50 Goldilocks worlds that Kepler identified are orbiting a variety of stars from the tiny m-type stars all the way up to the solar like stars and so this offers us a nice sample for which with which we can do statistics again that the point here is to take the discovery space apply our bias Corrections and turn it into the intrinsic population of planets that's in the galaxy so to tell you what those results are I'd like to do a thought experiment we're gonna take the Milky Way galaxy and we're going to shrink it down to the size of the continental United States okay and we're here in California on the coast with our backs to the Pacific Ocean looking out across the continent and we're going to ask ourselves the question based on these 50 discoveries how far out would I need to look in order to find the nearest potentially habitable earth-sized planet okay and the answer it turns out to be if you're here where we are in this theater and you're looking across the continent where is the nearest potentially habitable exoplanet likely to be it's right over there on the other side of campus at the foothill Observatory it's about a quarter of a mile away which is a stone's throw in galactic terms that's about 10 light-years compared to the hundred thousand light-years across of the Milky Way galaxy so I said at the beginning of this talk that the results that Kepler found have catalyzed the search for life on exoplanets this is why we set out to find out if nature makes earth-like planets efficiently or not are they common are they rare we've now found out through Kepler discoveries that there are over 10 billion such planets in our galaxy alone and the nearest one is a should be a stone's throw away and indeed in 2016 astronomers identified one orbiting not just within ten lightyears but orbiting the very nearest star to the Sun a star called Proxima Centauri that's in the Alpha Centauri system which is actually three stars a g-type star like our Sun a k-type star like the middle one in your habitable zone graphic and a little m-type star and it's that little m-type star Proxima which has a planet that we think is about roughly earth size and orbiting in its Goldilocks zone okay so that's a look at the Kepler results I would like to now look a little bit towards the future and before doing that you know at this point in the lecture you you you have this new knowledge that there are over ten billion earth-sized planets in the galaxy there are usually two responses to that when we start to talk about life you've got the philosophical camp that says well there are over 10 billion planets in our galaxy alone surely there must be life that would be a huge waste of real estate if there was not life on one of them but then you've got the other camp that's way over on the other side of the spectrum that says well but wait a second life is not just about liquid water and in fact we've already talked about some of the things that are required for life like the right materials we want rocky planets and it turns out that you can even take these arguments even further well yeah you need you need surface liquid water but you also need the right kind of this fear and a magnetic field to protect us from harmful particles and you need plate tectonics because plate tectonics recycles carbon dioxide which provides us with this great thermostat for keeping the climate stable and speaking of climate we need a really stable star we don't want a star that has a lot of intrinsic variability and we don't want a lot of a large eccentricity in our orbit either because that could make season so extreme that it wouldn't be amenable to life and we need a moon to shield us or to stabilize our spin axis and we need Jupiter out there to protect us from asteroid collisions and you could go on and on and on and this is the philosophical camp I'd call the rare earth errs and so when we talk about the prevalence of life in the galaxy the the reality is that we don't have an answer the answer could be anywhere between these two extremes and we won't know until we go out and actually measure and look and so that brings me to the future here is NASA's arc of exoplanet missions that are that are in the works that have flown are just finishing like Kepler are almost about to launch like tests and web or are on the designing the the in the design phase like W first or are kind of in in our minds as ideas like our future exoplanet missions there on the right now what I'd like to say I want to spend a little bit of time talking about tests and web and look forward to our future exoplanet missions because we're moving now you know we've had 20 years of exoplanet discovery we had the first ten years finding planets for the first time kind of like stamp collecting we went out and we found worlds and we knew their names there was tau ceti and 51 peg and HD 180 973 3 HD 2 or 9 4 5 8 we were we were stamp collecting in the second 10 years we moved from stamp collecting to doing a census or a poll doing a statistical study in order to understand demographics and that was the era of Kepler and now we're moving into another phase of exoplanet research which I want to call atmospheric characterization we now want to start to learn about the atmospheres of planets so what I'm showing here is a rainbow it's a rainbow that stretches so long that I actually have to chop it up and make like an accordion and stack pieces one on top of the other but it's a spectrum or a rainbow of a star the spectrum is another word for rainbow so you see all the colors that this star emits from red all the way down to indigo you see some black places little holes where light is missing these are absorption lines these are colors where the atmosphere actually removes light that's emanating from the core of the star so the atmosphere is taking away those colors so that they don't reach our eye and it does so in a very systematic way so that these absorption lines these this absence of light acts as a chemical fingerprint for whatever elements were there in the atmosphere and what temperatures they had and what pressures so by collecting light from the stars spreading it out into this rainbow and looking at which colors are missing we can start to ascertain what's in the atmosphere you know what what its temperature is what its pressure profile is etc so this is the same thing this is also a spectrum but it's represented graphically not pictorially so at every color now instead of showing it pictorially for every color here I translate that to a number that's related to an amount of energy that's emitted from That star at that particular color and I plot those energies as a function of color represented by wavelength and so here I've got these energy measurements and you can see the blue trace sometimes dips down that would be equivalent to a black hole where light is missing and in this case these black absences of light are due to particles or molecules like carbon dioxide or methane or water vapor but that's because this is not the spectrum only of a star this is the spectrum of starlight that has passed through the atmosphere of a planet this is a scenario called transmission spectroscopy these transiting planets are very special because when they happen to pass directly in front of their stars some of the Starlight is going to filter through the limb of that atmosphere as depicted in this cartoon now this atmosphere is quite exaggerated this is an actual picture of a planet it's the only actual picture of a planet that I'm showing tonight can you see its atmosphere it's very difficult to see its atmosphere I can only see it if I look at the blackness of space on the limb of the Sun this is actually Venus transiting the Sun and if I look there at the limb I can see a very faint thin yellow band that's the atmosphere of Venus it's only about five kilometers thick so you've got this light that's headed your way towards your telescope from the star a deluge of light and only one part per 10,000 and 1/2 hundredth of that is going to actually have this chemical fingerprint of the of the planet's atmosphere but it's exactly that chemical fingerprint that we want to collect so that we can find these kinds of greenhouse gases maybe even one day indications of a biology that saw the surface and putting metabolic products into the atmosphere in order to do this because it's very hard because it's one two hundredth of one ten-thousandth we have to find all the planets that are closest to the solar system Kepler did a survey it looked three thousand light-years out into the galaxy this one yellow cone out into the galaxy looking at 200,000 stars near the plane of the Milky Way galaxy and surveyed those stars so so as I said they stretch all the way out to 3,000 light-years and the ones orbiting the nearest stars were completely missed the there's a future mission called test which is due to launch hopefully next spring of 2018 that's going to survey the entire sky and look for planets orbiting than very nearest systems out to about 200 lightyears once we find those nearby transit well here's a cartoon an animation of the test instrument as you can see in the barrel of the of the instrument you've got four black squares representing four different cameras four different telescopes and they're each pointed in a slightly different direction so tests at any given moment in time can take an image of the sky from the pole almost all the way down to the equator and it will observe a patch of sky like that for about 28 days or so then it's going to clock over and do another longitude strip etc it's going to cover first the southern hemisphere sky and then during the first year and then it's going to flip and it's going to cover the Northern Hemisphere sky and in doing so it will provide us with targets that have planets orbiting in the transit geometry and are very close to the solar system and we want the nearby ones just because the stars are brighter and we get better accuracy of measurements on them we have a better hope of seeing those atmospheric characteristic characteristics so we want to do that now we were going to pass these targets on to telescopes like the James Webb Space Telescope this is the successor to that to the Hubble Space Telescope it's going to launch in well it was just too late something like late summer early fall of 2019 or they're about to know maybe it's early summer let's say summer of 2019 the date is still uncertain and it was just slipped by about six months but that's the here on the left is a mock-up of the James Webb Space Telescope it's a six and a half metre aperture mirror here's a picture of it in the cleanroom at Ball Aerospace there is a human being there that's at about 11 o'clock you can see him in his white bunny suit the floor is also white so he's kind of hard to see but just to give you a sense of scale the mirror itself is a segmented mirror made out of beryllium that's very light mined in Ohio and coated with a very thin layer of gold which is highly reflective in the infrared the telescope was completely assembled and it was packaged up and it was shipped to the Johnson Space Center in Houston in the summer and the reason that it was shipped to Johnson in the summer is because they have there a very large cryovac chamber and the telescope was inserted into this gigantic chamber with only about five inches clearance so I've been told in order to simulate space like conditions and that means extract all the air to create a vacuum and lower the temperature to make it really really cold like in space so they did this they got it there in the spring of this year and they had this very complicated timeline for for testing the instrument and you don't need to read all of these words or even understand them what I wanted to show you though is that there are eight days at the beginning seven point nine days to create a mostly a vacuum inside the cryovac then you've got a 33 day period just to get it to cool down to temperature all right so that takes already about 40 days total and then you've got a period of 22 days where the cryovac chamber and the telescope inside is stable enough to do your your tests of the instruments inside and exactly when that period started around July hurricane Harvey made landfall on the coast of Texas where the Johnson Space Center is located there in Houston so that was a pins and needles and of course the major concern was losing power that would have shot the whole experiment you'd have to all 40 days would have been lost luckily they had good generators but of course many other concerns not just for the safety of the employees and their families their ability to get to work and once they got to work the ability to keep them there and to be fed if they were going to actually do their job and probably not be able to get home multiple multiple concerns what ended up happening is that the tests they did not lose power the tests went forward but you can see that they had to be a little creative they had to put tents over the equipment the roof was leaking on the right hand side you can see those roof tiles like we have a universities and offices and they were literally peeling off of the ceiling and dripping onto the floor so they worked under large duress but they got everything done and the schedule I think in the end they only ended up losing about 24 hours of time and all of the instruments checked out beautifully so that was a huge success and at the end of it they were even able to rally and make a hurricane relief crew and go out and help their community so I think that this is a just a wonderful story and when you see the James Webb Space Telescope launched in 2019 and you start to see the amazing data that comes back from it I hope you will remember this story about the human element of the people that made it all possible and the kind of duress that they were under during the stressful time okay now some people say that the James Webb Space Telescope might be able to even detect the atmosphere of an earth-like planet I personally think that that's going to be very difficult simulations show that we'd have to get very very lucky in order to do that we'd have to find an earth-sized planet orbiting a very very nearby m-type star like Proxima Centauri but one that is actually transiting Proxima Centauri does not appear to be transiting or in that right transit geometry so we would have to get really lucky James Webb is going to characterize the atmospheres of many planets and I actually think that one of its greatest contributions is going to be to figure out what these that gray area in between was between the brown bars and the blue bars those super Earths slash sub Neptune's that we have no example of in our own solar system I think we're going to totally understand what those planets are by observing their atmospheres and seeing what their outgassing products are we're going to be able to understand their compositions more accurately but if we really want to find an earth-sun analog and look at its atmosphere and see what it's made out of we're going to do atmospheric characterization in a slightly different way instead of focusing on just that thin thin yellow band that's hugging the planet that band that's only five kilometers thick and is one two hundredth of the total area of the occulting planet we want to catch all the photons that are actually bouncing off of the planet as shown in this diagram when starlight bounces off of a planet just as it does when you look up at the full moon that starlight is also passing through the atmosphere of the planet and just like in the spectrum of the star that I showed you the gases in the atmosphere of the planet are going to eat away some of the colors and produce the same kinds of patterns but now you've got the entire disk of the planet to work with not just the thin layer so you have the possibility of detecting more light that way it makes it easier the problem is that planets are literally lost in the glare of their host stars it's like trying to see a mosquito next to a searchlight the ratio and brightness between an earth-like planet and a star like the Sun is 10 billion to 1 so in order to make that happen we have to invent new technologies to suppress the star light to see the faint things that are nearby so there are a couple of ways to do this what's called star suppression technology the idea is really simple just like trying to see the features on the ceiling I can't see them because this spotlight here is in my but if I put up my thumb I can block the light and I can see the fainter features nearby so you can do that by either inserting an occulting disk inside the optical path of your telescope or you can make a giant occulting disk as another spacecraft that you fly independently of your space telescope both ways are being investigated and I wanted to show you a video though of one in particular just to give you a flavor for what's involved and how difficult it is because the things that we're trying to see are so exquisitely faint 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 a coronagraph to separate starlight from planet light as the star's light passes through the telescope's large mirrors it picks up small distortions diffraction adds concentric rings to the image we see to reveal the planets first a chronograph uses a mask to block much of the star's light and redirect the remaining light to the outer edges a washer shaped device can now block most of the rest of the star's 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 starlight to remove these blobs the chronograph 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 to superior 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] there is a few ideas that are that are introduced there but one in particular is the idea that light bends around obstacles so when I hold my thumb up to the light I can't block it out perfectly because some of the light is always going to bend around so the idea is to shape these masks very very carefully and to control the the wavefront that's coming in very very carefully in order to be able to really tease out these signals but this has already been done from ground-based telescopes a handful of planets have already been identified this way not earth-like planets not earth analogs but planets more like Jupiter very young Jupiter's that are very bright and orbiting at very large distances where the glare of the star doesn't interfere as much but the point is that technological precursors are already exist on ground-based telescopes and now the idea is to put one into space so we know what to do we know how to do it technology is almost catching up and at the right readiness levels there is a 30-year roadmap for NASA there's a sentence in there which I think is very telling says that is there life on other worlds for the first time in human history we have finally been able to embark on the systematic scientific pursuit of an answer and I think that this statement is largely motivated by Kepler's results I think it's caught the imagination not just at the scientific community but also the public our stakeholders and our legislators so much so that in the last space act agreement for NASA the agency as a whole had a tenth objective added to its reason for existence its purpose up until that point it only had nine and as you can imagine a lot of those are dealing with the International Space Station manned exploration etc but a tenth objective was added and that is the search for evidence of life beyond Earth I think that this is achievable within the next 30 ish years maybe not in my lifetime but so only in the lifetime of my of my children and their children we're going to be able to point up at a star and say that star has a planet that is a living world not just a Goldilocks planet not just a habitable environment but truly a living world I look forward to that day I hope to be alive when it happens and I hope that in our search for worlds like Earth we come to appreciate the habitability of our own planet and understand that it's precious and that creating a sustainable future right here on earth is worth doing because life is precious living worlds are precious with that all I'll end on that note and happy to take your questions [Applause] so for the kind of the kepler-452b which is kind of a super-earth what what what is the kind of probability that you know there would be a lot of these roads how do we kind of measure at with the current technology without some of the atmospheric kind of light that you're getting to what's kind of the way of figuring out if they have water or is there a way today the kind of mass and stuff yeah that's that's a great question so how do we figure out I mean right now we just know the size and the orbital period so we can get a measure of how much energy is being radiated onto the surface of the planet but we don't have any idea of what the atmosphere is actually made out of and until we know that we can't ascertain whether or not liquid water could actually pool on the surface I think that well I don't know what we're gonna find certainly if the pressure and temperature is right and if there's water vapor in the atmosphere you can pretty much be certain that there's going to be water vapor on the surface or water pooling on the surface in the form of an ocean or links or something on the surface barring I mean that that's how we want to find out if a planet is a truly a habitable environment whether it has liquid water on the surface I mean there are other there are a couple of other ways some people have suggested that you might be able to perceive the glint of starlight as it's reflecting off of a sheer water surface like an ocean you can also look at the reflectivity of light for example light reflects differently off water than it does off of rock or a desert or forest or ice this is a property called the albedo and if you look as a planet rotates and it presents different faces to you you might be able to see different amounts of reflected light coming back to your telescope and maybe that will be another way to disentangle whether or not there's surface liquid water over here yes thank you for your wonderful talk and wonderful research that makes it seem more likely than ever that there are like and that brings up with my mind the Fermi paradox and I just wondered a few thoughts on our resolution to that for those aren't familiar with it it's basically like there's a funny echo in here oh I'm sorry did you hear what I said I didn't catch it did you okay well I just said thanks for your research that suggests there are lots of extra you know earth-like worlds out there and that brings up in my mind the Fermi paradox which you know where are they if there are say people out there intelligent extraterrestrial life I just finished you your thoughts on the resolution for that well I don't have an answer to the family paradox but to me the fairy paradox says that maybe space interstellar travel was difficult it doesn't necessarily speak to whether or not living worlds are common or rare so I don't know we we won't know the answer until we go out and search I mean the Fermi paradox is as he said where is everybody if life is indeed very common how come we haven't seen in the indication of other life in the universe to me that presupposes that life was would somehow come here or make itself known to us we'd have started these systematic surveys of like the SETI surveys have gone out and listened but if so far probe to just a tiny part of the parameter space that's out there so we haven't done a complete survey so it's not fair to say where is everybody until you've actually done a systematic look telescope is essentially built at this point can you give us a sense of what work is left in the next year a year and a half two years two years to launch I'm not sure I understood the question so the telescope is almost ready it's almost ready so I'm curious what else is left what else is left yeah it's so underneath the telescope is a tennis court sized structure that insulates the telescope and keeps it protected from heat and so that is what's being assembled now at Northrop Grumman in Southern California that process is taking a little more time than they thought it would that's the sunshield so that's I think what was responsible for the delay but the spacecraft was actually the launch was probably going to be delayed anyway because of a European mission called Pepe Colombo which is a solar system exploration mission to mercury and that was also how also had a launch window of October 2018 which was the initial JWST launch window so unless that mission changed its timeline drastically we would have had to move anyway so I think now so is just pre-emptive and said uh we'll just go ahead and say over here yes I'm really having trouble making out the words I what happens when you find a Goldilocks planet what happens when we find an earth-like planet so one that we know has life on it well that's a really good question what do we do I think that we're going to want to find not just one but a lot of them we're gonna want to understand the diversity of planets out there and we're gonna need to learn a lot before we think about actually going to these places but but I do think that once we have the Stars if you can point to a star and you say that star has a living world I think that humans in their creativity and and and sheer will are gonna figure out a way to get there and a little bit of that is already happening they're trying to build very very tiny postage dyes stamped and postage stamp-sized spacecraft to go to Alpha Centauri for example so I think that we'll eventually want to go there but I think humans have a lot to learn before we go and mess up other planets so I'm hoping it kind of takes a long time I think that we should do that carefully you know and in the past when we went exploring we made a big mess of things and I think that we can learn from our mistakes and maybe may not make such a mess of things next time yes hi um thank you for your lecture today this stuff is just utterly fascinating and it's just so inspirational to me and I would love to be a part of the mission and this question isn't about the science or the talk today but I want to know I'm a student here in a chemical engineering major and I would love to know what would be my educational plan will be my career path in order to be a part of this yeah that's a great question I you know for everything from art to science and engineering these missions employ people that run the gamut with we have artists who do the artist renderings who get all of the information about these worlds everything that the scientist knows and makes them come to life writers we've got writers the the search for life is interdisciplinary so it requires planetary scientists geologists atmospheric scientists biologists to understand the biology and astronomers and then you've got the all the engineers so I think that there's so many different ways that you can contribute and be a part of it just to study what you love to do it to expose yourself to lots of different things and to always have an open mind and take risks and and just just do it you know I mean that was that's what I did take a lot of math and science do well at it excel at it but you know even if you don't do well at it keep at it because nobody is good at it at the beginning it takes it's a it's a new way of thinking you have to train your brain to think in that new way I certainly wasn't good at it at first but you keep at it and your persistence because that's what it needs to make these kinds of things happen is just sheer persistence and you're in a great place for all of this [Applause] yes thanks for your very informative presentation I really loved it so this is real this question is related to the starshot technology solicited by Stephen Hawkins well you a particular Nanosat liked using laser towards a particular star so do you think propelling them towards Proxima Centauri or Alpha Centauri will actually bring in some information and we could actually find an exoplanet like well we already know that there's one orbiting Proxima Centauri so the question is you know you you if you're going to send just one object out there you're gonna have to choose between them I think that the fact that Alpha Centauri is a triple star system the statistics for the potentially habitable planets basically is turning out to be about 25% so that means one out of every four stars is expected to have a potentially habitable earth-sized planet so the Alpha Centauri system has three so you have pretty good pretty decent odds in fact the 25% is for a narrower range of the habitable zone if you look at the full habitable zone it's actually probably more like 30% well and if you go down to planets that are smaller than Earth that number is probably more like 50% so that gives you a pretty good chance that you're gonna find something interesting yeah you know there there are other missions that are proposed to do this kind of direct imaging star suppression technology using a small telescope only pointed at Alpha Centauri alpha and beta Centauri that has not though it was proposed once to NASA already and it was not selected and I think NASA and general sees it as being too risky because you don't have a guarantee of a scientific result I personally think that's short-sighted because even if Alpha Centauri the Alpha Centauri system does not have a potentially habitable earth-sized planet around a and B I think that's a sign result in and of itself so I don't know I don't understand that rationale but your question is specific to star shot not exactly sure what you're asking is it a good idea or I do you have a more specific question about star shot I mean could you actually do science with star shot I mean star shot is this postage stamp-sized spacecraft that I was mentioning earlier in order to study atmospheres you would need to have the capability to detect light to measure it actually to spread it out into a spectrum and to measure those energies at all those different colors with very high precision then you have to be able to transmit that data back to earth so that's a lot of instrumentation and spectrographs tend to be very large instruments you're not going to fit it on a postage stamp-sized object but it should the idea is that it would be capable of taking pictures you know send a cell phone out into space or I mean the star shot is even tinier but the idea is just to go out and take pictures and so yeah you should be able to at least be able to detect its presence I am having it's the echo I can't understand the questions I mean did you find out you ate basically planets you already exactly yeah okay can you make a prediction about whether or not a star is going to have a planet based on the statistics I mean you can only make a probabilistic with the statistics with the demographic survey you can make a probabilistic argument you know for example around Alpha Centauri a and B based on the cap of results I can I can guess I can quantify the probability of about 75% that we would find potentially have a bowler sized planet around those two stars one of those two stars so I can make a probabilistic argument but I don't know of a way to make a definitive argument that would be a yes or no gate that's very clear so he's asking if there's a similarity between the architectures of the planetary systems that would help us to make predictive predictions that's a great idea what we've learned from architectures of planetary systems that they too are more diverse they're not all like the solar system for example one of the reasons why Kepler found four thousand planet candidates is because we've got a lot of multiple planet systems but more specifically these systems can have six planets orbiting all interior to what would be Venus in our own solar system we call these come dynamically compact systems six planets orbiting interior to what would be Venus in our own and they tend to have very specific characteristics we know that our own solar system planets orbit along a disk for example you can think of that like a pancake these systems the con that dynamically come compact systems are so exquisitely coplanar that they're more like crepes as opposed to pancakes they're just really exquisitely coplanar so there is some physical characteristic about them that distinguishes them from the solar system architecture all that tells me is that the architectures are diverse so I'm not sure that there's predictive power there but who knows yeah that's a great question so our numbers of detections of exact earth-sun analog really really tiny and we have more detections above 1.4 so on the period radius diagram that I showed that scatter plot both axes were logarithmic so it tends to exaggerate the effect if you go up quite a bit off of the earth radius line you're still kind of in the regime of a rocky planet so it's a little misleading but you're absolutely right the numbers of discoveries there are really really small and that's because those are the planets that are hardest to detect we're right on the envelope of what Kepler is capable of to the bottom right hand side of that mind we have the zero detection that's because that's where a sensitivity falls off so we didn't over design the engineering of this instrument to be able to do sufficiently beyond what actually ended up happening is if Kepler observed stars that behaved exactly like our Sun we would have detected about ten such planets that are kind of Earth Sun analogues about one earth radius but it turned out that the Sun was quieter than the average g-type star that we observed so there's a little more intrinsic variability of the Stars compared to our Sun and that just added a slight noise component that made it more difficult than we thought it was going to be to detect those planets and part of the diagram so what we wanted to do was to continue observing those stars for another four years but then one of Kepler's reaction wheels failed and we couldn't do that we had to move to different parts of the galaxy but so we kind of thought that we were only going to be sensitive to planets that were about twice the size of the earth in that 365-day orbital period range but the very innovative brite engineers that designed the software found ways to improve the pipeline to be more sensitive so we ended up recovering a little bit of the sensitivity that we lost because the stars were more noisy than we thought they were going to be so I'm very very happy with what we accomplished in that we found these fifty Goldilocks worlds and some of them albeit small numbers are orbiting even the sun-like stars three okay we were told three more and I see six people standing okay well we're back on this side thank you have a question about current and they'd be some announcements about examples discovery and are we close to be able to discover actually if they are core between together and if they are transiting to see the two dips and basically detect a larger examples of exoplanet yeah so the idea is that and I should mention we found 50 Goldilocks worlds that have roughly terrestrial sized diameters but there are hundreds of Goldilocks worlds that are larger planets and the idea is well what if those larger may be gas and ice giant planets have satellites that are roughly earth size kind of like the Pandora scenario in the movie Avatar so there are researchers who've been combing Kepler data quite carefully in order to look for other dips of light nearby a primary transit to see if there's evidence of a satellite and so far it hasn't returned anything definitive however a statistical look at the data has shown that there is there does seem to be some transits that have a slightly perturbed shape that could be indicative of something those objects are being observed with the Hubble Space Telescope like pretty much right now so it's not a done deal Kepler might yet yield the discovery of an EXO moon we'll have to wait and see let's see one over here and then we've got a child over here that would like to ask a question yes [Music] based on current current age of the solar system but I guess solar system is also evolving so maybe in previous couple of billion years ago we have so do you take the evolution of the solar system and the star systems yeah yeah absolutely this is a really important point because our atmosphere right now looks the way has has had this oxygen content for a relatively short amount of time if we look at a planet in its first two billion years of evolution we would probably conclude and if it were like Earth we would probably conclude that it was a lifeless world because the kinds of creatures that populated early Earth didn't create sizable quantities of auction I mean they were putting oxygen into the atmosphere but abbath the oxygen was being leached out of the atmosphere at a at a relatively constant rate and so it took a long time for the oxygen to accumulate in the atmosphere to reach a saturation level and then continue to grow so we recognize that that's a problem and it's going to factor into the detectability of living worlds we have to take that into consideration I don't know what we're gonna find we have to you know there's a lot of arguments for when when we do design right now people are in behind closed doors deciding how big the telescope is going to be to find life to find living worlds and I'm arguing that that telescope should be at least 16 meters in aperture it's about the biggest thing that we can fit into it rocket fairing and and honestly I think that we could assemble telescopes in space if we had to I would not argue for going smaller for exactly these reasons right that there's a lot of things that could actually make it difficult to find life and I don't want to be in a position where we have a null result and we don't know how to interpret it so I would like to be able to find least thirty three dozen nearby potentially habitable planets in the Goldilocks zone and image them and look statistically at their atmospheres in order to get a better feeling for how they differ yes so if the Kepler is orbiting there how does it keep looking at one point in the sky all the time I you're gonna be an engineer right it doesn't orbit the Earth it's actually orbiting the Sun so what that means is you've got the spacecraft here and it's always got a look at the same part of sky right and so it's orbiting not the earth but the Sun so sometimes it's going to be pointed kind of over the Sun and that was one of the constraints for where we could look in the sky because we couldn't look at a place in the sky where once in orbit the telescope would be pointed towards the Sun we had to be pointed away from the Sun but yeah it's it's because it's not orbiting the Earth that's orbiting the Sun [Applause]

Channel: SVAstronomyLectures

Views: 77,630

Rating: 4.622951 out of 5

Keywords: astronomy, science, astrophysics, science news, exoplanets, Natalie Batalha, Kepler mission, hot Jupiters, Earth 2.0, earth-like planets, habitable zone, planets around other stars, solar systems, SETI, life elswhere, space

Id: e2Q1iBgEKbU

Length: 89min 5sec (5345 seconds)

Published: Wed Dec 06 2017