Thank you thank you very much Jane it's a good great pleasure to be here it looks like the weather here is much more habitable deeper in The Hobbit was on around the sun than than Boston is. And I would speak mostly about life in the universe today. Which is a subject that they became fond of in recent years before that most of my career was that he hated to. Looking at objects that carry no life in them that are sort of the physical objects in the universe including galaxies black holes and so forth and that's what most of the astronomy community is doing right now but there is no reason to expect life to be unique to earth as I would try to argue and it's one of the most exciting questions in science are we at all and so. Let me start by describing the current status of the search for planets which. Is the. First week attack this problem because we find life on the planet called the earth that is orbiting a star like the sun and obviously if you want to find life Similar out to what we find here you would look at planets around stars similar to the sun and the one method for finding planets is by the rather velocity that they impart on their host star so the reason reflects motion of the stars the planet orbits around it and one can pick this up by monitoring the spectral lines of the star and seeing the shift back and forth the Doppler effect that's called the rod velocity method. And then another method to find planets is as they transit in front of their star the. BLOCK If a portion of the starlight than one can without even imaging the starry one can tell that the reason the fraction of the light that is missing and so that's another very effective way to find relatively small planets. And the Kepler started I discovered thousands of candidate. Planets since two thousand and nine this way and you can see here a compilation of as of June two thousand and seventeen of the thousands of planets. That were found and were Earth Neptune and Jupiter stand in terms of their size as a function of orbital period the orbital period here is in they. For the earth as you can see we move around the sun every three hundred sixty five days. And you see that there are plenty of Kepler planets roughly the size of the earth mostly at orbital periods shorter than the Earth because. Of the ration of the mission and it was difficult to find many that are. The same or with their peers as the earth or longer. But there were some that were found and you can see from six months ago here of planets that have the same. Type of star as the sun with a similar surface temperature to the sun. And also receiving roughly the same amount of energy given their distance from the star so they may have the surface temperature of of the earth and then potentially liquid water on the surface allowing the chemistry of liquid water and life as we know it and. These are candidates in the blue ones are confirmed planets and so you can see that we are not very unique. There are quite a large number of such planets out there and in terms of the Abundance about a quarter of all the dwarf stars in the Milky Way galaxy have planets that are of the order of the size of the earth in their habitable zone that's the region around the star where the amount of flux impinging on the surface of the planet allows room temperature such that liquid water may exist. And about that eleven percent of all the sun like stars have a planet of the order of the size of the earth. That is warmed up to a similar temperature. Now planets appear to be coming in two sizes either mini Neptunes that have gas a blanket of gas an envelope surrounding the rocky core or there are also super Earths planets that are slightly larger than the Earth and you can see here and by model distribution that was revealed last year. The statistics is not great but it indicates the there is some physics behind the split between the two populations. And of course we are looking forward to many more missions especially space me based missions that will bring more data the first one will be tests that will come to fruition very soon later this year. And then beyond that of course the James Webb Space Telescope and W. First the whose fate is unclear at the moment. So this there is a great potential for more data in this field now all together if you use the mystics on the number of stars in the universe there are three hundred billion stars in the Milky Way galaxy and for. Three billion similar galaxies to the Milky Way within the observable volume of the universe and so all together there are about if you take this that this examination before there should be of the order of ten to the power of twenty. Earths within the observable volume of the universe and of course. The universe may extend well beyond the region that we can observe since the Big Bang so. The question is are we really unique is it reasonable to assume that life exists only on Earth and I should say that. Even though Copernicus made this Lucian a while ago about us not being at the center of the physical universe a lot of my colleagues still believe that we are special biologically speaking that perhaps we are alone we are unique and that's a natural tendency because when my daughters were younger and they're now ages twelve and seventeen when they were much younger they tended to think that everything in the world centers on them. And as they mature they became to realize that they're not at the center of the stage in our civilization follows the same path it just takes us a while you know centuries to do the same in. And many scientists that you would speak with mainstream scientists would argue that life is probably rarer and that. It's not out there but to me this number is quite Man mind boggling and I don't you know out of modesty I don't think we're special. So I wrote this very short essay that was published in and. The principle of course make more this. Just given the fact that we find both primitive and intelligent life together here on earth it should exist out there. And we will eventually find it if we will not have a prejudice in the church not to look for a telescope and maybe to help them for a little while but not much longer and so eventually the truth will come out irrespective of the prejudice it's just that the prejudice delays progress that's the only problem and if we hide our head in the sense say there is nothing out there obviously there will be nothing out there as far as we're concerned so we should be open minded to finding intelligent as well as if you ask astronomers in the mainstream right now they will tell you that makes a lot of sense to search for primitive forms of life. And I find that very puzzling because. There is no reason not to expect intelligent life out there in the search volume could be much greater in that case so we are talking about life as we know it and what does it mean it means that operationally we need to liquid water to have the chemistry of life and to have liquid water you need an atmosphere of pressure if you look at the face diagram of water you cannot go from us to liquid without an external pressure so the only way to have an external pressure is to have a strong enough gravity of an object such as retains its atmosphere Mars most its atmosphere because it's a tenth of the mass of the earth and presumably doesn't have strong enough gravity or magnetic fields were not strong enough to keep to the atmosphere so it was basically stripped off. And so planets of the order of the size of the earth could retain an atmosphere and allow any quid water in the chemistry of life as we know it so it's not a coincidence that we find ourselves on the surface of this planet. And. We know of planets in the habitable zone around nearby stars an example for a system of such planets is the Trappist one system. That was discovered to have. Seven planets and you can see them at the top here compared to those of the solar system and e F. and G. are in the habitable zone this is the dwarf star that is only eight percent of the mass of the Sun saw in order to keep yourself warm you need to be closer to the furnace and so these planets are twenty thirty times closer to habitable ones. To this dwarf star than the Earth is from the sun and. This star is by the way most of the stars in the Milky Way galaxy are dwarfs are less massive than. Sun. So they're much more abundant and they are longer lived they live for trillions of years so a star like this one would live for up to ten trillion years so a thousand times longer than the sun can leave so if you think about going somewhere or buying a house on a planet in the habitable zone of another star you would definitely prefer at war like this one it has been jetty. And the question then arises as to why aren't we next to a star like that and I'll talk about that later so here are the sizes of these planets in the Trappist one system versus their mass you can see the earth here one one relative to the earth. And those other planets and F. and G. they are in these colors here the bluish colors. You can see that are correct there is sticks are not very different than Earth. Or Venus Now here is a plot of the lifetime of a star as a function of mass so the sun has a life time of the order of the age of the universe. The fact that we live next to the sun is not surprising given that the universe has roughly the same lifetime if we were to live in a universe that is ten times all the stars like the sun would be very rare they would die by now. The Trappist one star is a dwarf star it has eight percent of the mass of the sun and it will live for up to ten to the thirteen years so it's much or it could outlast the current age of the universe by a factor for a thousand. And. The interesting thing is the first stars formed when the universe was about one hundred million years old which is roughly the lifetime of stars of the order of ten times the mass of the sun. The more massive A Star is the. Shorter is its lifetime. And so it's interesting to ask you know if the first stars formed so early when the universe was so young. And the last stars will survive up to a thousand times the present age of the universe an interesting question to ask is When did life start in the universe and when will it end and are we in the most likely place right now next to a star like the sun at the present time or is life more likely to be in the future or was it in the past in the history of the universe so when Could life have started in the universe where there is a hard limit if if you go back far enough into the union into the past of the universe the universe was too hot for liquid water to exist so room temperature was achieved at the redshift of a around a hundred hundred ten that's when the tire universe was a room temperature the universe was only about ten million years old. But you didn't need to be next to a star like the sun at that time you could be anywhere in the universe and you would feel comfortable. And so in principle if planets existed back then they didn't need to be warmed up by a star. Life would have been possible the problem is that the first stars according to the start of course more logical model started forming only later. When the universe age by another factor of five or ten. So it's an interesting point to keep in mind that fifty million years after the Big Bang everything was quite comfortable but then soon after that the universe school. And became inhospitable for life anywhere except close to stars. So then the question is the first stars could they have had planets around them and could life have started this as soon as maybe the second generation of stars once you produce the heavy elements because you need the oxygen for the water in the carbon for their life. So apparently there are some stars called carbon enhanced metal poor stars camp stars these are the lowest mentalists the lowest. Stars with the lowest abundance of heavy elements that are found in the Milky Way galaxy in the head of the Milky Way and they have very low they are mimic they have like one part in a hundred thousand the abundance of Iran that is found in the sun so I call them anemic but they. Have carbon that is about one hundred times more abundant than. Compared to the Sun So in principle such stars could have planets that are made purely of carbon around them carbon planets. And we calculated how far away such planets could exist they should exist within the Earth's sun distance roughly around the stars and planets that are made purity of carbon have a particular relation between the rad use their size and their Mass so one can in principle look for those planets by searching for transits around those stars nobody did that for now but in principle in the future that could teach us. Whether planets existed around the first or the second generation of stars when the heavy element abundance was small. Now you can ask OK starting from the first stars in the universe going all the way to the future a thousand times the present age of the universe when was life most likely. One can plot the likelihood of life. Or the likelihood of having a. Planet around the Assuming that for example a quarter of all the stars have habitable planet next to them and then you take into account the age of the star so just from the star formation history of the universe and the ages of stars you can figure out how likely it is to find the planet like the earth in the habitable zone of a star at any given cost me time and that's what this likelihood is that's the probity Pirlo very quick time interval as a function of the age of the universe going all the way to ten three or New Years from now. And if you allow the low mass stars just like Trappist one eight percent of the mass of the sun to have habitable planets around them then the likelihood function peaks in the future. Ten trillion years from now that's where life is most likely to exist because that's where most of the time is being spent. However if you allow only stars like the sun to host the habitable planets there now is the peak in the history of the universe in terms of the likelihood of life so that's an interesting conclusion that in principle we are not typical If stars dwarf stars like Trappist one have life around them. The problem is that maybe they are not. Very hospitable because these stars when they're born the they are known to have very strong flares in the were to Violet and in order to be. In the habitable zone next to such a star need to be very close to it because the star is much fainter and at that point you are exposed to very powerful wind the powerful wind from the star that can strip the atmosphere of the planet so that maybe these are maybe risks for life that may explain why we exist next to the sun and not next to a dwarf. STARR And in fact if you take the wind into account you find that stripping is very likely the strength of the of the wind from the star is about one hundred to a thousand times larger than the solar wind on earth and saw it's quite possible that the atmospheres of these planets are being stripped. But the good news is that we don't need to speculate about this we can actually observe the stars in our vicinity and figure out whether they have life on the planets surrounding them in the habitable zone so we can address this question empirically and figure out whether we are special. Being next to the sun or whether we are typical and life is really most likely around the star like the sun at the present time. And this is work for the future so taking into account the stripping of the of the atmosphere we found the following results that what what we showing this plot this is a work that we did with Manasseh building a post-doc of mine we calculated the time that it takes to be four species to reach to generate new species on Earth which is related which is thought to be related to that were a valid flux that is impinging on the planet's surface so if you have very little U.V. light emitted by the star then. The time between cycles of biology that increase the number of species gets longer and longer and what we show here is that time scale as a function of the mass of the star. And compared to the present age of the universe and so if you are below one value of one here then there is not enough time for biology to start. To produce multiple a large number of species. And the sun is somewhere here and saw clearly there was enough time. Given the illumination of the earth by the U.V. light from the sun. And then you can calculate the number of species that will grow exponentially on this time scale and that number is enormous when you consider the the earth. And also stars that are somewhere between a half or point six times the mass of the earth and the mass of the mass of the sun and the mass of the Sun This is the range were biology could develop to the levels that we find on Earth but much lower mass stars are unlikely to have biology and very massive stars as were due to their short lifetime so there is a range of masses for stars that could horsed life with a large number of species as we find here on Earth. Another thing to keep in mind is that the environment could be hazardous for life and for example the center of a galaxy could be dangerous many people here are interested in black holes for their I mean these are fascinating structures of space time I called them the prisons these are regions of space time where you get you can check in but you can never check out from black holes are really fascinating but you can ask whether they are good for life or not and you know that we are located about twenty four thousand light years away from the nearest super massive black hole at the center of our galaxy every galaxy has a black hole at its center and the question is how dangerous it is for life and so we do the simple calculation with. John Forbes. Considering the. Activity from the black hole in the form of. Red The Asian and their fact that it has on a planet like the earth. And in terms of a bill a thing as much as Marsa most fear or evaporating the atmosphere of the earth or. Evaporating the ocean of the earth these are the different colors here so and what we plot here as a function of the mass of the galaxy or the mass of the head of the galaxy so the Milky Way is around ten to the twelve solar masses right here what which fraction of stars within the galaxy are being affected so if you require operation of a Martian atmosphere you find that we're talking about tens of percent of all the of all the. Stars in the universe basically being affected. Or actually more than that if so if you go to two galaxies more massive than the Milky Way you end up with in total about half of the planets could lose them are Saddam's here in the universe and then if you consider earth atmosphere about ten percent of them. And then if you want to evaporate the oceans that requires being much closer to the black hole and about a fifth of a percent of all the stars suffer from that we also calculated as a function of friendship. How this developed this state of affairs and of course at high redshifts. That these are the the dish lines the situation is. Quite more. Hazardous for life because the galaxies are smaller and the stars are closer in closer to the black holes now there is also a benefit for being illuminated by the black hole and for example in the Milky Way galaxy there is the black hole terrace a star that is four million times the mass of the Sun So indeed there is the risk that flares from Senator say Star would would evaporate the atmosphere of the earth but but if you had a mini Neptune with. A blanket of gas around the rocky core then that gas that envelope could be eroded evaporated. By the flares from the black hole and you can turn many Neptune's into super earths that potentially could be habitable so it turns out that this is a function of the distance from the center of the galaxy in. In parsecs and the timing of when the flare of this black hole takes place the general trend is that the. Closer You Are to the center of the galaxy the more Rocky the planets get and saw if you have a population of mini Neptunes they would be evaporated and you would be left with more rocky course on which in principle life could exist next to the center of the galaxy. Now if you're if you happen to be close to a supernova explosion that's tough luck because the explosion would release in a large amount of energy and that could affect life on the planet turns out that the chance for that to happen is very small this is the location of the sun from the center of the galaxy it's about eight point five parsecs or. About twenty five thousand light years away and the probability of us being affected by a supernova is very small it's about one party in a million over the age of the universe so it's not. Really. Something to worry about to sleep over more important is the possibility that an asteroid would hit the Earth and we know that that killed the dinosaurs it didn't eliminate it in the exterminate their life if you ask how likely it is that there would be a big enough asteroid hitting the earth such that life would be completely. Erased from the surface of the earth that kind of an event takes longer than the age of the universe so it's really within the current age of the universe it's not a risk this is the range of masses about somewhere between ten to the power eighteen to ten to the twenty one kilograms is the mass range were an asteroid that impacts the earth would. Either. Eliminate the sterile eliminate the atmosphere or in the higher mass and boy of the oceans but such events take place over a timescale much much longer than the age of the universe so again we shouldn't worry about it. And as I said before the question of whether life exists around other stars can be tested observation in talk about how to find such a life so the nearest star to the star system to the sun is the Alpha Centauri system it's actually a triple the result for Centauri A and B. these are sun like stars in a tight binary and then there is a third star Proxima Centauri and this is them is about four light years away. And. Turns out that Proxima Centauri the third star which is twelve percent of the mass of the sun. It has a lifetime again of trillions of years just like Trappist one. And the seem to be a habitable planet that was discovered just. A year and a half ago around Proxima Centauri It's called Proxima B. and that planet moves around in the habitable zone. Twenty times closer than the Earth is from the sun it moves around the star every eleven point two days so if you were to leave on that planet you would have a birthday every eleven point two days which is great fun to have a celebration. The other fact about this planet it's most likely tidally locked so it's showing the star the same face at all times so there is a permanent dayside and a permanent night side of this planet moves around. And probably real estate value peak. Just in the sun's Sunset Strip between those sides. And you would probably benefit from having infrared eyes because this star is quite faint in the optical. But in order to have life around such a such a planet do you need liquid water and to have liquid water you need an atmosphere. This is by the way the inspiration I got for the Sunset Strip. Around Proxima B. When I visited why Last summer I thought how nice it would be to see this sunset forever on a planet. Can we tell if there is an atmosphere around the planet. And one way to tell it is simply as the planet goes around because it's facing the star with one side. You tend to see all of its phases you don't need to image that but you would see more of the limited side along some phase and. Less on the opposite side of the orbit and so if you're just more knit or the light curve of the planet you can tell the temperature on the surface the temperature contrast between the Nightside and the day. And it turns out the temperature contrast should be sensitive to whether it has an atmosphere because if you have bare rock you get very large contrast between the hot day side and the cold nights. However if you have an atmosphere that would moderate the temperature contrast and if you have an ocean it would be even more redistribute the heat better than than in the case of pure rock and so if you consider a case where there is no redistribution of heat so that it's bare rock you get one curve the blue curve for the day and night contrast in parts per million from all the light that is arriving to us from from Proxima Centauri and if you allow for a third of the heat to be redistributed then you get the red curve and the good news is with the James Webb Space Telescope we should be. Able to separate these curves so we should with the James Webb Space Telescope we should in principle be able to answer the question of whether Proxima being has an atmosphere. Now having next door this this habitable planet is very tempting you would like to visit it or maybe even settle there at some point in the distant future and so about a year. Almost two years ago we announced the project called breakthrough star short and I just wanted to briefly mention the rationale behind it the idea is to take photos of the habitable planet Proxima be through a fly by flying next to do that within our lifetime so within our lifetime in this planet is four light years away it takes light four years to travel the distance if you want to do it within the next twenty years. You need to move it a fifth of the speed of light. And so that's. A very challenging task to launch a spacecraft at a fifth of the speed of light or a camera but in principle it's doable and that's the concept and the method is to use light to push on a sail such that you don't need to carry the fuel with you you have a lightweight sail that is being pushed just like a sail boat is being pushed by light instead of the wind of a sail boat so let me show you. The video that we produced at the launch of of this project. Here. This is one. Of our. Crew. We awaken others in the world in the light of the stars without words we wouldn't. Be on. Here and never lose the rest of the cosmos. It was only four centuries ago when the hands loose ends for a few meters. And rip off. Only silence. It's at the insurance cover. It's continuity the bonds. It's standing on the shoulders shines before us. Looking out across a valley over up to the stars and asking. Wonder what's their. Mode of course these are. The US. And our place in. Our galaxy alone the booms of stars. And of the visible universe contains at least a building since. The last decade we have discovered over to the planets beyond our source. It's not just to the earth since the habitable planets are again it's almost. Over and eat some of these stars all these worlds are. We're taking you to the sky. Walk on. Black violence. OK so this didn't give much of the data so let me explain. The physics behind so it's just the same as with a sailboat where you have the wind pushing on the sail here you're using the pressure of photons and idea is to have a sail that weighs roughly a gram which electronics is the tach also with a weight of roughly a gram that part of the concept is relatively straight for the except the sail has to be made of material that is strong enough such that it will and also a perfect reflector such that the very little of the light will be absorbed because if one part in one hundred thousand of the laser gets absorbed. It will burn the. But there are Tronics part I mean you find in the guts of an i Phone these days and it's not much of an issue to put a camera on of a Geisha device communication device on him the real challenge the biggest challenge is actually the laser making a coherent laser beam with a hundred G. go out of power that would shine for a few minutes that could launch a gram scale sale to about the fifth of the speed of light across a distance which is five times the distance to the moon and the sail will be released from above the atmosphere and then the laser will have to go through the atmosphere there are many challenges involved and of course we are just attempting to do the very first step here so it would take a while before we get the technology but the idea is to construct the Nano craft this this small miniature spacecraft and there would be many of them that could be launched one after the other and then the laser and then the reason the launch of the cruising over a couple of decades in time so most of the journey is relatively boring going through space. And then eventually encountering the. Arnot taking photos and sending them back to earth and collecting the data. It's a very challenging technology I mean this is I can show you a brief video that shows the various components. I mean this is of course an artistic restriction The idea is to release the sail above the atmosphere at the right location and then shoot the laser beam in the direction of the say and the say should go in where Proxima B. will be in twenty years of course it's not where Proxima B. is right now. And then there is another one released so there could be hundreds of them most of the cost is in the infrastructure not in the. In the same each spacecraft like this could cost hundreds of dollars it's not very expensive because it's very lightweight and by the way these probes could in principle principle be targeting also targets within the solar system it would take only a few days to get to Pluto compared to new horizons that took nine and a half years the NASA administrator changed during that period this is this will be in the same week you will launch and see the image of Pluto the same week. And so there is there are many big challenges including the communication because. Of course the optics is on a rather small scale at the spacecraft and then you send the bin back to Earth the spot size will be bigger than the Earth scientists on separation in that's in principle a benefit because you just aim at the the beam of communication at the sun which you can see from a distance but the texting is the single photons that arrived to to Earth would be quite challenging. In principle if we are thinking of. Such as the chronology of the might be another civilization that the ready must that it and so you might ask OK well how would we see evidence for a beam of light this would be the linkage of the light from around the sail that we could see from a distance. And it would appear as a flash of light because the beam would move across the sky because we are moving the source is moving. And saw one could potentially search for beams of light as a method of search for extraterrestrial civilizations So that's one thing that we proposed back with James will EDITION. And potentially fast thread your birth could have been. These these flashes of light of I admit that the cosmological distances there requires much power as the power intercepted by the earth from the sun so they require the civilization to actually use harvest all the power that comes from the horse star and use it in a beam of radio waves. A few additional comments about searching for life around on other planets first in the trap East one system that they mentioned before. There is a higher chance of life moving from one planet to another resort ready the. Speculation that perhaps life on Earth arrived from Mars and life can be transferred via rocks but in a system as densely packed as the Trappist one system the chance for that is much greater because the travel time between those habitable planets the F. and G. is one hundred times shorter than between Earth and Mars and moreover because they are closer together these planets it's twenty times more likely for a piece of rock to heat one planet coming from another as compared to the earth Marcius them so the transfer of life within such a system could be much more likely and it resembles the integration of life forms between neighboring islands on earth and many people looked into that. Another interesting anecdote is that a few months ago astronomers discovered the very first object that entered the solar system from outside the solar system so it's an interstellar object that was given the name ONE MORE MORE. Which is why in for a visitor from a great distance. And it was given the Hawaiian name because the telescope the discovered it is. In. Mountain in Hawaii in Maui and so it's so happened the object appears to be unusual in its shape from the light curve we infer that it's ten times longer than it is wide and the most there on gated Astro. It's or rocks in the solar system were three to one axis Russia so the already the very first object that has positive energy that is to the sun that we fly out of the solar system as it moves out is very unusual compared to objects that we find within the solar system and an interesting point is that the Sun and Jupiter are the two most massive objects within the solar system if a third body comes in in principle the object can be captured if it passes close enough to to Jupiter because it will give Jupiter a little bit of energy and by that get captured so you can think of the solar system as a fishing net that is moving through interstellar space and objects get cold in this fishing net just like fish get caught in a fishing net and that is an interesting opportunity for us to examine these objects that are being called from in the US the space instead of visiting other sites other system of planetary systems how do you tell if an object came from outside the solar system well it has if it has a cometary tail then in principle. The would be. You could do spectroscopy of the water vapor in the cometary tail and you can infer the eyes of top ratio of oxygen there and you can tell whether oxygen sixteen relative talks in eighteen has a different abundance rashly or compared to the objects in the solar system so that's one way of telling and it would be fascinating for you found a trapped object that came from interstellar space in the solar system we can in principle launch a mission that will land on that object and examined examine it and I mention that the Earth Jupiter system is a good fishing net but an even better one is Alpha Centauri A and B. because you have two stars to follow my stars that much more effectively to capture objects. In principle life is also possible under the surface of Forbes jek So what I was talking before is about the life on the surface of a planet but if you allow life to form in liquid water under any circumstances then you can have an ice shelves that surrounds liquid water down deep and people talked about that in the context of Europa in principle you can look for their life by drilling a hole in the ice and just seeing if there is fish underneath. But. The thickness of the ice could be somewhere in the range of kilometers so it's not an easy drill to make the pending on the right use of the object. In general it's something to keep in mind that you could have life under the surface of objects and one more important point about transferring life on rocks is that if life can be transferred between planets you would expect when once we start to accumulate data and find a population of planets that has life on the surface those planets would be clustered if there is transfer of life. But there would be completely independent of each other if there is not transfer of life so one way to search for transfer of life is by the Clustering of. Life hosting planets. And in principle planets could travel not just between stars or objects not just travel between stars but they could also travel between galaxies it turns out when two galaxies come together if each of them has a black hole at its center then you form a binary black hole system and many people here in the audience study these systems. Because they produce gravitational waves they also appear in the mergers of galaxy. And the stars around the binary black hole system can get scattered it's sort of like a slingshot you can throw stars out of the system if they pass close enough to one of the black holes and when the black hole binary gets very tight the speed of the of the planets of the stars that gets thrown out could be close to the speed of light and so we wrote a paper in which we calculated. The sea of stars filling up the universe that move almost up to the speed of light there are stars moving through the universe at speeds approaching the speed of light they're just. Rare now to find. Coming back to the original theme of finding evidence for life in the utmost in planets. In the atmosphere of planets one way to do that is as the planet orbits the star you can look for. The fingerprints of various molecules like molecular oxygen which is indicative for life in the atmosphere of the planets and as it moves in front of the of the star it blocks some of the light of the of the star and the light that goes through the atmosphere. We. Have the information about the composition of the atmosphere through absorption lines. And so one can do this in principle and search for molecular Hawks oxygen on the in the atmospheres of planets it's much easier to do this when you deal with a star that is smaller than the sun because the earth is one hundred times smaller than the Sun the mount of light that goes through the atmosphere of the earth is even less than ten to the minus four because it's just the thickness of the atmosphere so it's a very tiny bit of light that you are trying to Him to analyze. But if the star has the size of the planet it's much easier so it turns out that wide wharfs the end result in the evolution of the sun the sun will eventually turn into a wide war and white dwarf has are awfully The size of the earth so if you happen to have planets around why dwarfs which we don't know if there is but we have evidence that there are rocks around the right words then potentially we can very easily in fair the composition of the atmospheres of those planets because a significant fraction of the light is being blocked by the planet. So that's an interesting possibility and in principle you can detect the oxygen with the James Webb Space Telescope in the atmosphere of the planet around in the habitable zone around the white war. If we just stick about five hours of integration with Jay The biggest thing to do that I should say that you can search not only for molecular oxygen but also for signs of intelligence or not intelligence. Industrial pollution you can look for molecules that are a result of the cannot happen naturally in nature a result of industrial activity on the planet saw that could be done as long as the planet is much more polluted than the Earth or the levels of the earth it's very challenging with the current. Telescopes that we have but we calculated that in principle one can look for all these molecules that are indicative of industrial pollution in the atmosphere of a planet. And finally just like people are arguing that you can look for vegetation on the surface of the planet through the so-called red edge so it turns out that the vegetation or the leaves on trees they use violet light from the sun to do the photosynthesis and they don't need the infrared light so they basically reflect it. It's considered trash as far as they're concerned and saw if you look at the reflectivity of plants on earth it rises in a very abrupt way around zero point seven Micron This is called the red edge so if we had infrared eyes we would be blinded by all the planets by all the plants because they reflect infrared. And so. This is one way for searching one method for looking for. Vegetation on the surface of the planet looking for this red edge but at the same time if the planet happens to have four cells on its surface you could look for the reflection spectrum of those which is quite abrupt as well but it's a shorter wavelengths and a good way to find it is again as a planet moves around the star you see different phases of it and if it's tidally locked for example around the law must star you can imagine a civilization coating it's permanent they side with silicone with them. Photovoltaic cells solar cells such that they transfer the heat than light to the dark called permanent night side and so that kind of. Coating could in principle be observed from the reflectance of the planet this moves around obviously will if there is light on the dark side you will also see signatures of that in the light curve so it's good to check the future datasets for these signatures and I will close with a note that I wrote about just a few days ago about the implication of neutron star mergers for life. So the neutron stars are the most compact stars that we know about. They are made of neutrons they have nuclear density the size of a big city of all the twelve kilometers in terms of the size of neutron stars is almost independent of their mass they can have a mass up to twice the mass of the sun but they always have a size roughly twelve kilometers and so when two neutron stars collide a little bit of material about a percent or less of the material gets flung out and that is Newton rich material that is going into free space and as a result there are all kinds of nuclear reactions that involve wrapping in the term ization not from. Absorption and that leads to the production of elements heavier than our own so for example gold if you ask yourself how was that produced. Now it seems thanks to lie Gore that astronomers believe that. One of the main channels for producing Gore that you find in your wedding ring is the collision of two neutron stars and so it's Gore the new random and elements like that that were produced in those events and if you look at the periodic table you see emerging neutron stars account for all these purple color elements. And so you ran your most of course is being used on earth for nuclear weapons you might argue that depending on the distance from a neutron star nozzle star merger. If you were to do to video. Tape this the evolution of civilizations on planets around as a function of this and you would see nuclear wars happening very frequently close to the neutron star merger and as you move out the civilizations become much more peace loving him or they even if they don't like each other they don't have any material to use for their nuclear weapons so the longevity may be correlated with distance from and from start of the merger and the same I mean significant effect could be on the economy of any civilization depending on whether they have gold or other of course the economy reacts to the rarity of an element in a peculiar way but it's interesting to think about the implications that we think about those elements as having the balance as we find but in fact these neutron star mergers are very rare and their care once per somewhere between one to one hundred thousand years in a galaxy like the meteor way and of course they generate waves and that's how we can calibrate the vent rate now thanks to ly go from the event that was the tech that back in August seventeenth two thousand and seventeen. And by the way just an interesting footnote them will leave the room is very important for life only a fraction of molybdenum is used to come originating from merging neutron stars but but if you were not to have merely I mean if you take the million new math from food a person may die actually and vice versa if you add more lived in so there is a very delicate balance of our biology that depends on many of them which partly comes from not from Star mergers again we are somehow connected to the cost most. So altogether we live in a very exciting time on the verge of potentially finding evidence for life and it's just fun to to do the search during this generation thank you. Well that's that's an excellent question the thing is with this with this concept I'm not worried because these spacecraft are moving in a fifth of the speed of light so in fact the kinetic energy per proton when in such a spacecraft hits something it's more than nuclear fusion give see who's. There would be no trace left. The Warri would be you know if there isn't and others realization out there they would see it as a whole. Attempt to. Herd them and I should comment that. One more thing that is a kilometer size of that was found you know why that was barely The texted with stars barely in it's a kilometer sized So there could be a lot of things flying around we just don't notice them. Kind of spacecraft would never be noticed by swimmers it moves too fast and it's too small and my guess is once we send something out of the solar system we'll get a message back saying Welcome to the interstellar club because the might be a lot of things flying out there that we can kind of that with our telescopes right now. Well Point two of the sea is not very close to the speed of light but in fact. We we wrote a paper about the relativistic effects and. It turns out this is an interesting point you tend to think about this special relativity as if you're moving you would see things contracting but that's not true if you if you move the camera and there is a paper back from the sixty's and if you move a camera irrespective of how fast you move it the image would always appear symmetric circular if your source is circular it would appear circular. And it has to do well maybe a simpler way of understanding it is that the speed of light is independent of the frame of reference so in all directions you end up. With the photons going at the same speed then you end up with without any distortion in the image except that it will be rotated in terms of taking the images it's not there is nothing special you need to do because it's point to see the correction is small but if you get close to the speed of light then you start to worry about these things. Where very far. Sorry. Right so there are several ingredients here to the technology that are very challenging and you know I don't know if we will ever be able to achieve. The goal I can mention a few I mean when we announced the project we identified twenty big challenges. Interestingly some people think the biggest challenge is is human related getting an international agreement for building such a facility because some people warry about it being used for non peaceful purposes you just put a mirror up there and shine on your favorite enemy and. Then of course once you develop such a technology the user can be both ways you know so. Some people think that the policy aspect is actually the most challenging one dealing with that and getting and Dortmund because this has to be an international project that these you know although the location of the laser beam would be in a particular site that there would be guarantees that it's used only for good purposes scientific but then the first challenge that worried me the most is the say of making it sturdy strong enough and also having it reflect without absorbing much because if you observe more than ten to the minus five of the laser light then it will blow up we're talking about focusing one hundred you've got a lot of laser power on a few meters for a few minutes and that's roughly the amount of power that was used to lift off the space shuttle over the same period of time so it's the same in the jet excess the space shuttle except you give it to a single a few grams of material so that's I am very worried about the issue of the say. Absorbing some of the energy by the way the best design of his save is actually a sphere sort of like. A balloon because of the stability of driving on the on the laser beam it turns out this is the most stable of we found. But the other issue is making the laser it's what you need is to coherently combine a lot of laser beams right now the most you know where the most powerful lasers that are the can operate over a few minutes time scale. Somewhere around ten store hundreds of kilowatt in here you need one hundred G. go out soon and. Make a million of those and. Put them together in an air raid that spends a kilometer so that you can focus that and adding them coherently is non-trivial Moreover compensating for the atmosphere in real time is another issue. I mean obviously any I mean the power per unit area is not huge actually because you're starting from a kilometer it would be large when it gets above the atmosphere. Well that. Yeah but particles do not are not as good as a slight because they can get easily deflected by a magnetic fields you cannot keep the focused we thought about such things like that. Yes.