Magnifying Light by 100 Billion Times with the Solar Gravity Lens to Image an Exoplanet

so this is my great pleasure tonight to introduce the two speakers which are co-leading kiss workshop on the solar gravity lands telescope and one of the founding principles of the Keck Institute for Space Studies is to think outside the box and I think it's fair to say that is way outside the box so again this is my great pleasure to introduce dr. Slava to reshef and dr. Louie Friedman Slava is a research physicist at JPL who the real research includes gravitational and fundamental physics research in astronomy planetary science astrophysics is an expert in spacecraft navigation sort of system dynamics and many other things and in particular this topic on which he has been working for the past 15 years Slava is also known for having worked on the pioneer anomaly so it's really extra qualified to think way outside the box again the second speaker tonight is a dr. Lou Friedman who co-founded the Planetary Society with Marc with Carl Sagan and Bruce Marais it was also the executive director of the Planetary Society for 30 years before that it was JPS advanced program manager and at various programs including the post Viking Mars program so lower ceilings and the International Ailey watch he has written a few books one on SolarCity another one on human spaceflight from Mars to the Stars is also on the breakthrough starshot Advisory Committee and shared NASA's innovative advanced concepts external console so Lou Slava the stage is yours [Applause] Thank You Dmitry you didn't mention that you are also the co-lead of our workshop which is listed here so and it's a pleasure working with you and Slava on this exciting topic which we used to think was a very tough and difficult one but now that we're working on it we realize how easy it's going to be to get out to 550 2008 you and we also have some people who are working on the interstellar flight idea with star shot and compared to them you know we're one third of a percent of what they're trying to do so we we know with it that we have it easy um how I got into this was with this chart that we produce in a previous Keck Institute for Space Studies workshop activity that we had on the exploration of the interstellar medium and this is a chart basically the geography of the interstellar medium for those of you need a little help in recognizing where we are on the left is the solar system and on the right is the nearest star now this is a log scale and it's really important to understand this is a log scale which means that all the perspectives are kind of different and I need to show in particular yeah so the solar system is here the Voyager spacecraft has gotten out to about here that's the furthest that we've ever sent anything anywhere and that's about 130 au astronomical unit systems from the Sun 130 times the distance of the earth to the Sun and then our goal here is to get out to 550 plus au das as you'll hear more the solar gravity lens focus is not a point it's a line that begins at 558 you and extend straight out from there and so that's five times further so that's quite an achievement if we can actually do this this mission to get to there but to put this scale into perspective and we showed it linear all of this region would be down you know right down there and the and this distance out here to the nearest star is 260,000 astronomical units 550 au is where we want to go this is 260,000 astronomical units and that's not all we want to observe we may have target planets that we want to observe with this mission that are out at a million astronomical units or more so one compelling thing I need to to say which is pretty evident your space is big and and then the other thing is it's empty and that's what led me into this whole study unlike slava was the scientist who'll give you the rationale of why we should do it I'm just going to tell you what motivated me was I knew people were interested in this and I knew it was very tough and I was looking for something to do on the way out there that would be an intermediate goal and it's empty there's nothing there and you know Pluto's already been done then Kuiper belt objects are small and they're minor planets and they're they're dwarf planets and we don't want to go there or at least okay it's some people do and I'm kind of looking for a destination and there weren't any and then I learned from Slava and others that there's a point called the solar gravity lens focus which as far as we know there's nothing actually physically there but it's a fantastic place and maybe the only place where we'll ever be able to get high-resolution imaging of an extrasolar planet the idea that we can use the Sun's gravity lens to image an extrasolar planet so that became a mission target which is what I'm which is motivated me now this is the solo gravity lens Sunda bends light rays Bend and then you put something at the full I have to focus like a telescope and you'll see an image created in the ring and I won't explain any more about that slot that's lava stoic and and and it'll go into a lot more detail so therefore I'm not going to explain it and furthermore I don't really understand the physics okay but what motivated me is trying to get there and that's what is my interest in mission interesting and there are several ways of getting there we first thought about the chemical propulsion and in the first-kiss study that we did on exploring the interstellar medium we came up with a mission design that use chemical propulsion but it really does tax all the limits of that and it's still not adequate to get out there in the 20 or 30 or even 40 years that we want to accomplish this mission if you're willing to wait I mean Voyager is going out there now but boy as your has already been what inflate about 35 40 or 41 years and it's only a third of the way out there so so we want to go out there faster then my interest in solar sails was always driven by the fact that the only thing that solar sails are uniquely capable of is they're on the path to interstellar flight anything you want to do in the solar system there's always a competition but on the path to interstellar flight you do you need the only way to accomplish that is with light sails and and in the case of getting out to interstellar flight you have to use beamed energy can use just sunlight because we run out of that but the solar sail is always to me on the critical path to thinking about an interstellar flight and that's the high motivation and here's the perfect mission because it can be used as an interstellar precursor to get out to to but it to the solar gravity lens focus but it requires something else again just be done on propulsion alone the other I claim most important propulsion invention is small spacecraft if you can get the spacecraft small enough you can get a high enough acceleration in order to do the mission quickly then there are other techniques that are being studied the solar thermal and nuclear electric nuclear thermal these are also candidates they would evolve much bigger spacecraft they involve engines and I'm opposed to engines but these may turn out to be the technology that that we trade off and we still in our workshop that we're conducting this week are going to end up trading off these technologies there are various proponents of various advantages to each and and that's part of the trade off of the study and I'll talk more about that and then there are a couple of items which I call below the line because really they're a little way out they're not ready yet for prime time an electric sail concept has come up which is a rather innovative it has the advantage of the power loss it's still you it uses the solar wind instead of solar pressure and and the power and the effect of the solar wind on this create a plasma around electric wires basically instead of falling off is 1 over R squared it falls off as 1 over R to the 7/6 power and then there's a a really way out idea which is innovated by John Brophy at JPL which takes an external laser beam and uses it as the power source for an electric propulsion vehicle and he can get out to distances traveling at 40 au per year but it takes a giant Elektra laser basically a laser station in orbit around the moon or some place in space in order to accomplish so it's not within our current line of thinking so I put what we consider the basic mission trade-offs here is a controversial chart I have my opinions about what what do you trade off here and there very well-educated opinions and there right but nonetheless not everybody in the workshop agrees with me yet and so but I think they'll agree that at least at this column I call off the kind of main questions we have which is what kind of propulsion do we use and unless the main ones we're considering the what's the basic mass of the spacecraft okay do we have to do this with a 500 or more kilogram spacecraft that has these that it can accommodate the nuclear electric or the solar thermal design or can we get it into the realm of small sets that maybe with a large a large enough sail could also achieve that speed and interplanetary cube sets were a subject that had had no subject matter up until about two weeks ago but now with the launch of Marco on the insight mission we actually have interplanetary cubes as and maybe they're an oppressive the way for small sets into the solar system and beyond and then there's how does it operate out there very complicated problem because you have to it's not just a question of getting there and making measurements as you'll hear from Slava the the it's a common it's a complex problem to capture the image and maneuver around out there and finally how do we communicate the data back from those large distances and so these are the trade-offs involved I won't spend any more time on that the way we get to Delta V is either with the chemical propulsion this is a plot of velocity applied with a solid rocket motor as a function of solar radius where you apply the moment this is a so-called Oberth maneuver or a maneuver at very low perihelion where you get the maximum if you give it a large maneuver at perihelion you can stretch out the aphelion of the orbit to infinity which makes it a hyperbola which makes it escape the solar system and so if you can get very close to the Sun and and apply at Delta V this these are contours of how fast you can go out of the sources as you can see there's a big payoff and going close trouble is going close it's very hot and so it's a challenge of the spacecraft design the other way is with the solar sail there the relevant parameters are how large an area you can have and how small a mass you can have on the sail so I keep looking at the area to mass ratio in meters squared per kilogram versus exit velocity in AU per year and and if we could get to a thousand for example we could get up to velocities of 20 over 25 au per year which would be pretty fast for missions like this having said that that used to tell you that all the solar sails that have been built or are flying right now are down in this range under 10 so it's a challenge as well and then finally there's the laser like the laser idea of just propelling it with a laser as the interstellar propulsion people want to do but they're to get even a this is a hundred kilometers per second which is 20 au per year out - with a moderate-sized spacecraft like even one to ten kilograms which is a nano spacecraft that small spacecraft requires many megawatts and even I'm sorry many gigawatts and even almost a terawatt of power so it it - is a it's a challenge that isn't suitable for this kind of a mission but it is the only way to do an interstellar mission and that's a different subject that I won't get into but and I put the names of the people who are responsible for those del velocity calculations now here's a solar sail mission example that suggests we might be able to get to these kinds of velocities and get out there in a 25 to 30 year mission and the but this is just an example mission it still requires a 200 by 200 meter sail a 30 kilogram spacecraft which is for an interplanetary spacecraft would be very great achievement maybe 50 half of that would have to be for an hour power source a radio RTG or that would also give you some small electric thrusters for maneuvering because you want to maneuver out there and obviously the sail far away from the Sun won't be useful for maneuvering oh it gets that you want to also apply your pick up all the velocity change as low as you can so the sail goes into a low perihelion this is a tenth of an au we're actually going to investigate even lower perihelion and this has an area map to mass ratio of 800 which is optimistic for considering where we're at so it's a it's this is a push on all the technologies I personally believe this is still the nearest term technology but it is a push beyond what we can do and but the idea of being able to do this in a small spacecraft may make this an affordable mission which I think it opens up a whole lot of possibilities for the mission design oh this is the trajectory that goes along with that example mission or similar one this one actually is a little slower but but basically you you apply the solar sail you deploy the solar sail the perihelion and very quickly you're on a straight line trajectory this inset shows it straight line going out to where about Voyager is at this point if you wanted to extend it out to the solar gravity lens Hogan it would just continue as a straight line and I and another end set down here and this is a key one to keep in mind is is what you will see when you get there you'll look back you'll see a Sun and there will be this Einstein ring where it hopefully will contain the image of the planet that we're looking for and that's what Slava will talk about other mission examples I mentioned that there's been a chemical mission study for was limited to about 14 au per year JPL and Marshall Space Flight Center are studying a solar thermal design that they hope can achieve 28 per year solar thermal has yet to be used in any spacecraft mission but it is something that is receiving some research study nuclear electric this is an old study that John Brophy told me about that could perhaps get out to a 40-year trip time with a somewhat hybrid system east sail also a paper study none has ever been Bill theoretically calculates they gave 23 a you per year but it requires 20 kilometer tether 1020 kilometer tethers picking up this electric charge and and then the laser idea Phil Lubin that I mentioned already and the laser electric of John Breaux fees that I mentioned already so you can see that any technology we do not have the propulsion technology to do this mission today but there are developments and studies underway and that's what we're going to trade off in order to do it and and the viewpoint that I think we can have it we can make design that's simple enough we could perhaps accomplish a mission to go out and use the solar gravity lens the image and exoplanet now the angle you have to know which exoplanet you want to image before you go out to its unique focal line but that's like any orbiter of any planet you have to know which planet you want to see before you go orbit it and and the Fogler the fact that you fly and the focal line allows you to study it for months even years even tens of years and so you're in essence this is very analogous to a planetary orbiter that would be studying and trying to get kilometer scale resolution or tens of kilometers scale resolution and that may be the only way we could do it short of building a huge telescope which sloths will talk about I'm not going to spend any time on this these are two examples spacecraft one for the solar sail one for solar thermal that are being studied and I know I'll end with this which is what you see when you get out there you kind of want an image you want to block your there's the Sun and there's the Einstein ring that's formed around it this law will explain all the pixels you want to collect are in this ring and you have to collect them sort of almost pixel by pixel and assemble them into a view of the planet and with that Slava will tell us how to do it thank you all right Lou thank you very much for giving us a very interesting introduction of the technology possibility because without Voyager I think we have not we didn't have a confirmation that we can actually get to those distances and so having the two events coincide in a sense that we reached the distance of roughly 140 astronomical units away from the Sun and also the fact that we find in that many exoplanets actually now put in the two things together that we can actually dream not only dream but really this started to think about the design in the mission that actually will look for those eggs of planets and in my research I think they're two questions I have in my throughout my research the in the main question I think is what was there before big bang so essentially the gravid gravitation and cosmology and now the second question is looking for life in the cell in the universe and so here the two questions are now combined in one mission that we will be that way discussion today essentially the social or gravitational lens allows us to think about those interests and possibilities but why are we talking about those exciting possibilities that will take us that far from the Sun at those amazing distances here I'd like to basically the basically the simple point is that we still all kids at heart because like why maybe someone out there was wondering what it's like here I guess do you think what underneath them I hope so don't you don't you so that's why we are looking for those planets that may bear some life but what we know about the solar system about ourselves these are the planets that are in the solar system and so we know all of them pretty well we looked for life and now around those planets and this is our cradle cradle for civilization but we are destined to leave this cradle at some point so when it will happen maybe 200 years from now maybe 300 years from now we don't know but a reality is that we have the technology now that will allow us to look at the distant worlds that are far away from us how do we do that first of all we looking for life in the solar system in this chart you see the history of solar system exploration for the last 40 years we visited every planet we traveled around many satellites and this is how many different spacecraft we have flown for that purpose if we studied every every possible object that may bury some life and of course we know that there are some objects in the solar system that may have some microbial life but it's not enough you want to look for intelligent life elsewhere and so where do we look for this intelligent life of course in the galaxy so here we are so this is our Milky Way galaxy and we are somewhere here and so there's so many planets there are so many stars billions of stars and in the galaxy and so of course we we understand that there will be at least of fifty-two maybe five trillion planets in our galaxy alone there are some planets had been born as we speak and there at least five new planetary system being born developed every year in our galaxy alone so we're talking about the roughly fifty billion to five trillion planets in our Milky Way galaxy alone so this is amazing our number of planets where some planets may bear some life and what we have today for by may 2018 we have roughly thirty seven hundred planets confirmed we have many more candidates and roughly thousand planets of terrestrial so the may that the may resemble are the conditions that you have on earth so the point is that finding earth 2.0 it's pretty much as a matter of time at some point in the near future now not a distant future we will be witnessing the fact that some planets will show signs of habitability and we have the technology to look for those signs and so what do we do next but before we go or - that's the to answer this question let's look at what we have today we have multiple technologies that we use to look for exoplanets of course we use planetary transits we use micro linson we use radial velocity we use pulsar and imaging direct imaging so this is our sensitivity look at this as our galaxy and so we are sensitive for micro lens and planets are I discovered through looking at the at the center of our galaxy this is Kepler field of view this is what transiting planets were discovered a lot of those planets using using our planetary transits and so as of today we have that many planets and essentially the transmitter transits are most most effective planets planets search a method and looking at what Kepler did so this is an interesting interesting chart showing how many planets discovered they different they are very only in unusual places they're different sizes they're amazing in terms of the orbital evolution the orbital parameters they Giants are sittin in the Mercury's position we are discovering the zoo of different and interesting species out there we don't know what we found where the life can be a king can exist but the point is there are so many exciting targets for us to look for those EXO exerts none of those objects they still are in the habitable zone detection they can be reliably you know we can reliably say that this is indeed something that the life can exist and so we are continue to look for those planets and this is sort of the size of the solar system different orbits and so we know that many planets exist in very unusual unusual places looking forward in the future what we see today is that those planets that we've discovered they of different conditions that have different temperature are on the surface and none of them a majority of them do not bear life because the temperature is too high or maybe too cold or they may be tidally locked so we are looking for those planets that actually may present the science of habitability and we're looking not only in the own own the own the nearby planets but looking very far away for example are the planets that we have discovered we'll take Voyager me a lot of a lot of million years to reach those plant those planets are the most closest planet in the system of a Centauri it's it's a it will take also significant number of years to reach that the planet even for Voyager but can we do something better let's look at the technologies that we have today and of course talking about telescopes how big the telescopes where we can build this is the picture showing the current technology what we know and how what what type of telescopes we can build starting from almost a hundred years ago going all the way to TMG which is thirty meter telescope this is 39 meter telescope European extremely large telescope which is shown here just for the scale this is here the car and human standing in front of that telescope which is 39 meters again for the scale a receive a radio telescope is right there showing just the age of the telescope this is what we can build our today on the ground and essentially we have some space telescope guys here James Webb which will be launched soon hopefully so the Kepler and Hubble Space Telescope are here so essentially what else can we do this is ground-based looking at space again I'm showing what systems we can build today and we have flown the technology that exists today Kepler is 1.5 meters and Webb it's 6.5 meters and so this is this is something that we can deploy today but is this enough to look for exoplanets it's enough for Laura to to look for them and not enough for search to find them exoplanets but if we are interested about imaging of those exoplanets are those systems enough the system will be assessed efficient for our purposes and so let's look at what is planned in the future in the near future of course we have Kabul we have Spitzer Kepler telescope test was launched recently so this is very successful we expect a lot of interesting discoveries made by this satellite of course kuroh Gaia cubes those are the missions that are flown by our European colleagues so we hope to see a lot of missions in the in the future and those instruments will tell us not only about the demographics of those systems that you'll find in in nearby around nearby stars but also we'll start characterizing them looking for atmosphere looking for signs of possibly atmospheric disturbance that will tell us what can we expect from from those eggs or exit systems but let's rescale the sensors so this is what we actually trying to look for this is the image it is the these are the spheres this is our Sun and this is a little sphere called Earth so this is what we are looking in comparison to this large object so if you're looking for exoplanets that will resemble our earth and which has orbiting this a sun-like star we need to look for the directly image of that little object can we do something like that this is our made a major challenge if Cassini took this the full picture of our home on terraces right here it's from Cassini but this has only few Western emotive units away so if you're talking about light-years or can we see something out there do we have technology that will help us to move to that level of precision and accuracy and so we have those systems is of course looking at the star map you see that there are many planets we know already at 100 light-years away so a 30 per second we have multiple systems that actually bear some planets and that we will see more of those planets in the future tests and multiple other missions but if I'm put in our earth at 100 light-years away how big should the telescope be if I'm defective if I have a diffraction limited telescope meaning the best telescope I can built today how big should be the diameter of this telescope 90 kilometers so for us we're sitting here JPL Caltech this is Dana Point so that's the size of the telescope you must have to be able to hear that our XRF at hundred light-years away with one pixel so and just for comparison this is the distance to the Karman line it's at the edge of space right so this is a visitor field the field circle distance the 90 kilometers and this is external thin line is the lines of space so so hundred kilometers so just for you to give that that sense how big that should be that the telescope should be and this is remember one pixel and if I do the same analysis if I want to build a thousand pixels image of interest how big should be my tad diameter of my telescope of course if you multiplied by a by a factor of thousand and that's what you get so I mean this is what I'd like to hear this is our earth it pretty much this is a kilometer scale resolution what would it take for us to build an image like that of X which is situated way out there hundred light-years away this is what we are all dreaming to have and essentially you see wonderful picture you see the the night side of the earth you see the city lights and you have a beautiful picture of our planet what does it take to get an image like that for a planet that is orbiting around around star very far away from us so the answer is 90 thousand kilometers this is the diameter of your telescope field aperture telescope that you must have just for comparison this is our earth this is the moon so the distance between Earth and the moon in the earth diameters is 30 earth diameters is the distance between Earth and the moon the telescope you must have is roughly 7 earth diameters for you to be able to make an image of an exit earth with thousand pixels so this is something we are dealing with this is that this is called diffraction limit tyranny so you have to overcome the difficulty and so that's that that's the challenge and this is why we are thinking about using solar gravitational lens as a means to actually get that image because no technology that we know today can help us to get to those scales of you know 90 thousand kilometres building a field aperture telescope in space of course right and so first first of all suppose I'm able to build a 90 90 kilometer telescope I'd fly it in space and will be made out of few atoms thick mirror and that it will wade through the intones and I'll deployed miraculously in space within one year this object will be removed from the solar system by the solar radiation pressure it's me it's a big sail Louis talking about solar sail the ninetieth 90 kilometer telescope would be big sail that will be removed from the solar system so something like that is difficult to imagine and so to move on I guess the first practical application of a solar gravitational lens came in the paper written by professor for national in Stanford in 1979 he was pio on radio science team on Voyager experiment and he had written the paper in science in 1979 saying that at the a wavelength of 1 millimeter solar gravitational lens will provide a magnification of hundred million so magnification is very significant it's not obtainable by other means if you talk about optical wavelength we're talking about ten to the eleventh and so if you have one meter aperture it's this gain is average - so this is where the billionth time a hundred billion times come comes from essentially a tenth of the ninth with one meter telescope if you fly one meter telescope at those significant distances 55 r550 economical units away from the Sun you your telescope will have a significant gain 10 to the ninth so what can we use this for of what this telescope can be used for essentially let's again take some numbers if I take our earth and I put it at 100 light-years away this will be an object of roughly 14 big radium in size what it is it is of a thickness of human hair on the moon so if we are sitting here and if you think about if it's a tenth of a human tense about boots of a human hair on the moon so that's the if you are able to see that this is what the 19,000 90 kilo meter telescope will provide you with so this is the the the this is the angle you need to be able to resolve to see something like this so and as I mentioned another and another difficulty comes here and suppose we actually built an interferometer and interferometer would consist of several approaches let's say 50 meter aperture maybe even 10 meter aperture integration time that we need to get to signal-to-noise ratio of roughly 10 it will be prohibitively long be talking about million years millions of years so that's another sure hard stop essentially because you have a significant so dial into the deco background and the light travels from exoplanet towards the telescope that we are we use will go through interstellar dust interstellar background and so when you start integrating the signal the noise is to each other stood too high to get to that signal-to-noise ratio for a reliable detection takes hundreds of millions of years so a using solar gravitational and so there is another advantage of using this object because it has a very narrow field of view so that you can actually look at the planet without being affected by the parent star because the parent star will be completely outside the field of you you don't need to put a very significant masks you don't need to put a star shades you don't need to put additional technology that actually will complicate things you don't have this issue the solar gravitational lens this is why it is interesting now a little bit about the history of solar gravitational engine Einstein himself when before publishing the his paper on general theory of relativity he computed the deflection angles due to gravitation and this is the paper that he was looking at the 1911 essentially this is where the first sort of discussion of light bending by the gravity came from and then as you know in 1919 Eddington conducted a wonderful experiment confirming that general relativity is correct in describing the light deflection by the gravitational field of the Sun and essentially there's a telegram confirmed that indeed the light deflection that was predicted by Einstein's general relativity is indeed a correct value that Eddington in his expedition there confirmed today we know that in fact light bending or gravitational microlensing is everywhere so those pictures are everywhere that you look at you know Hubble archive you will be using Micronesian to discover exoplanets and so that's now turning the question can we use gravity a gravitation is applied discipline can you talk about general relativity not a theoretical science but now can we build something using your well the question is how well do we know gravitation right and the JPL of course now a laboratory is the solar system we flew many spacecraft everywhere in the solar system we use multiple technologies we use the radar engine we use that multiple spacecraft flying to different locations and in this chart allow me to walk you through the progress for the last 10 to 40 years parameters beta and gamma are basically one in general relativity and beta is not only non linearity of gravitation to proposition parameter gamma is the unit curvature of space produced by unit mass in general relativity both of those parameters are one if I move on so essentially a Viking Lander on Mars constrained parameter gamma to ten to the minus three move alone you have mercury engine constraint even further now of astrometric with very very long baseline interferometry further constrained than lunar laser ranging then of course Cassini and the latest result came from essentially a spacecraft tracking so we trust general relativity as the theory and of course the culmination of the of the multiple year effort of the discovery of looking for gravitational waves it's essentially resulted in Nobel Prize in Physics on discovery of gravitational waves and so now it's the time to think about using general relativity as apply discipline can we use it for some for something and that something came along during our workshop in 2015 when we discussed essentially traveling traveling outside the solar system and this is where gravitational lensing came about essentially it is for light days so this is full for in 4.3 light years this is for light days to get to that point so for comparison and so we have Voyager spacecraft and which is now 840 streamwork units away and we have this this magical area where essentially light is being bent that's better solar gravity this is a picture that Lou showed in his his his talk let me move to the next one essentially here so this is the geometry that a light light propagation from infinity from the distant source as it reaches the solar gravitational influence essentially the trajectory of light is being bent and the bending angle depends on the something called impact parameter the proximity of the light ray to the center of the Sun the fruit of this light ray travels the less it being bent so the closest race to the light may be as those that are grazed in the surface of the Sun collected they'd emitted the focus which is roughly before 547 astronaut the units away from us and so these are geometric optics here we need to have a wave optical treatment because this is the area of interference this is where the significant gain in the light amplification comes into into the picture this is the wave France so essentially somewhere in the bottom here you see Plouffe lit by a flat wavefront coming from the infinity and then suddenly when you go past solar of a Sun you see that is the Q wave fronts that the enveloping the Sun from two different sides now start to start to intersect forming something called caustic and this is where you have a cow's degree which is different from the typical lens because in the typical and you have focal point here you have focal focal line and so this is what we would like altom Utley to see in in in our our instrument but before that let me show you so essentially the game is proportional to this ratio which is worldsheet radius of the Sun which is three kilometers and the ratio over to the to the wavelength of observing wavelength so if you take three kilometers divided by pretty much one micron you get a magnification on the axis of 10 to the eleventh and so it's a very sharp point spread function very sharp so sort of a very selective point in here which actually helps to to to mix images but actually also makes a little bit more complicated I will talk about this a little bit later so this is what we would like to see this of course not the Sun it's Einstein beam around another another object but that's what we would like to see in the future so that replacing this the the forbid the Sun and this is the N Stein reading that we would like to do to observe with the solar gravitational lens telescope let me summarize the basic parameters of the fourth for this object so for for the sake of argument we had we are taking here wavelength of one micron so on the axis on the optical axis what is optical axis is the center of mass of exoplanet center of the Sun and the reaches the line creates the four grades the focal line when they reach into the focal when I reach the focal distance beyond this 500 fish astronomical units I'm in the focal region on the focal line the game is 10 to the 11 so this is significant game this is what we would like to have and so it also has a very native it has a native angular resolution which has point five nanoseconds and that's what the sort of the benefit of this object that nature just gave us so we have the Sun into the lens and so it's very a narrow pencil beam which is formed in the focal region for example hundred the planet that we have hundred light-years away is now focused to a cylinder with a diameter one point three kilometers so we need to fly a spacecraft to visit this cylinder and suppose everything is static we have the cylinder we need to navigate the spacecraft within the cylinder and then collect information pixel by pixel and so that's what we would like to do let me show you a little movie that summarizes the concept of solar gravitational lens and will give you a sort of a better picture of what actually is happening so with this so enjoy the movie oh so I guess I switched it too fast and the movies here exoplanets they're just like regular planets but found in other planetary systems besides our own so far over 3600 discoveries have been confirmed since 1992 these fuzzy dots are a few examples of the best direct images that we've got and these are all gas giants like Jupiter what we don't have is a really good image of an earthlike exoplanet it may actually be possible to get an image like this but how we could do it may surprise you we could use the Sun as a lens the Sun is massive to say the least therefore so is its gravitational effect which warps the very fabric of space itself when incoming light from a hypothetical exoplanet approaches the Sun its path is also warped these curved light rays are brought into focus starting from about 550 astronomical units away from the Sun the effect of gravity on the deflection of light is inversely proportional to its distance from the Sun the Sun approaching light rays further from the Sun are not curved as much as light rays closer to it so they come into focus past 550 au which results in a focus line rather than a single focus point this is the solar gravitational lens if we take a one meter telescope place it at 650 au away on the focus line targeting an exoplanet one hundred light years away how much magnification and resolving power do you think it will have from a fuzzy dock to a slightly larger fuzzy dot not even close it could resolve details off the scale of ten kilometer squared that's like resolving the width of a single human hair on the moon from Earth or an equivalent resolution like this image of Earth if instead you targeted the closest exoplanet to us Proxima be at about four and a quarter light-years away the resolution would be even greater in the hundreds of meter scale but there are not as many planetary systems to choose from right next door to us relatively speaking the Sun obviously does not function exactly like a conventional lens the Sun's gravitational force warps the incoming light in addition to focusing it resulting in a ring shape around the Sun called an Einstein correcting this is a lot more work than a D warping filter in Photoshop adding to the difficulty we can't resolve the whole Einstein ring at once with just a one meter telescope either if this same example exoplanet has an earth-like diameter of around twelve thousand seven hundred kilometres then that will result in an Einstein ring approximately 1.3 kilometers thick this animation is at the scale as a ring would look more like this compared to the Sun but with those variables in mind the area of the focus line that our telescope needs to cover would be a cylinder with a diameter of about 1.3 kilometers you would need a telescope that's at least that size to resolve the entirety of the Einstein rate in one pitcher that's 206 times larger than the primary mirror in the Hubble telescope fortunately you don't need to resolve the whole ring in just one picture our one meter telescope can image an area on this example exoplanet 10 kilometers squared so you can think of each picture it takes as a single pixel you can still result the whole ring you just need to assemble it by pixel the proposed goal is for a final image with 1000 by 1000 pixels but that'll take some time as that adds up to a total of 1 million pictures before the imaging process can even begin something has to be done about the Sun the telescope needs to face the Sun to image the exoplanet but unsurprisingly its light would outshine the exoplanet since the Einstein ring is around and outside the Sun an internal coronagraph tend to use which blocks the Sun and the brightest part of the corona there will still be some light from the corona mixed in but not enough to completely overwhelm the exoplanets life for the coronagraph to be more effective the telescope needs to be positioned further back on the focus line that's why we can't place a telescope right at 550 au but still not too far back as a cadet years to the mission timeline a good compromise would be between 650 to 800 au when the telescope is further from the Sun naturally it will appear smaller the magnification of the actual planet stays the same but the Einstein ring is now at a greater distance from the Sun surface so there's lots Corona light to contend with but how far away are these distances really an astronomical unit for au is the distance from the earth to the Sun at its greatest distance from the Sun Pluto is almost 50 au away Voyager 1 is currently traveling through interstellar space at 138 au away from the Sun farther than any spacecraft has traveled the telescope needs to be almost 5 times further than that that distance while considerable may not be insurmountable here's just one possible hypothetical scenario using the currently in development SLS rocket as the launch vehicle the spacecraft can get to Jupiter within 6 months it can use a gravity assist at Jupiter slingshotting the spacecraft towards the Sun as it falls into the Sun's gravity well within 5 to 7 solar radii its velocity dramatically increases when the spacecraft reaches maximum velocity through this maneuver its rocket engines fire adding to its acceleration and on a trajectory to the focusone traveling between 17 to 22 au per year the spacecraft can get to 650 au in about 30 years in the most optimistic scenario but no spacecraft has approached this close to the Sun before so a fairly robust solar heat shield will have to be designed and employed in order for the spacecraft to survive once there the telescope has to move with the focus line and within it as nothing in the universe is static the exoplanet orbits its parent star while also rotating around its axis if not tidally locked to its own star while the trajectory design can account for much of this a novel design for the spacecraft itself is still needed for it to move steadily within the focus line one idea is to build a spacecraft with the telescope on one end tethered to a counterweight at the other end using ion thrusters for propulsion at this point the telescope can be pulled in or extended out along this tether to move within the focus line while maintaining a stabilized anchor position this enables a telescope to gather a sufficient amount of images with less difficulty than keeping an untethered spacecraft stabilized using this method it should take around three months to finish the task but the challenges don't end there each image that the telescope takes is not a neat slice of the full ring instead the telescope builds a rasterized image where each snapshot contributes more detail and magnification of a specific area on the exoplanet these images end up overlapping each other which can be considered a benefit as we won't need quite as many pictures for the desired resolution next a deconvolution algorithm will be needed to fix the warp ring while that may be a considerable challenge we'll have the variables we need to correct it the position of the spacecraft brightness of each image add those positions and the optical properties of the solar gravitational lens if we are able to overcome all of these technical hurdles we will finally have our first high-resolution image of an exoplanet using spectroscopy we can analyze the light from the exoplanet in more detail than ever before gases absorb and emit their own distinct wavelengths of light so when we analyze light from its atmosphere we'll be able to accurately define its composition is the air breathable are there any telltale signs of life in the atmosphere like methane for example suppose there's actually intelligent life and they to have electricity well it's nighttime and they turn on the lights we'll see them but there's more radio waves are just another wavelength of light if iki is broadcasting those radio transmissions will also be magnified but not to the extent of visible light as the radio spectrum is actually distorted by the interference of the sun's corona while utilizing the solar gravitational lens is a daunting technical challenge it still may be achievable in the near future in fact NASA's innovative advanced concepts program or Nayak recently accepted a proposal led by dr. Sloviter a chef so with this I guess I can finish the movie so you got the point so um this is why we are here today because we have a workshop and the kids they work the objective of this workshop is essentially to improve the design for the instrument and for the mission so that we will be able to reach those distances at a shorter time and to be able to operate at the focal line along the focal line of the gravitational lens and essentially build something like this because this is this is a very important interest very exciting image of the alien world this is our Earth taken and physical colors and physical colors is that adjusting the sensitivity of our Y you know that blue and red colors in our Y in our eyes are sort of we have less sensitivity this is something we could see or from a different on a different planet and so that's the objective of our workshop and this is why we're here today so that's it so there are all the participants of our meeting at here at Caltech and wish us luck so we'll be able for us to design the mission that actually will help us to see images like this of distant planets and not not one but many as many as we want so thank you very much you [Applause] you

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Length: 54min 11sec (3251 seconds)

Published: Fri May 18 2018