 Climate change, population increase, pandemics, wars, maybe you know which planet I'm talking about. The last message from aliens received by Arecibo was please don't settle on the planet while you still can't handle your own. Knuth Henke is a hobby astronomer, friend of stars, and he's a volunteer at the planetarium in Bübeck. And he will be talking about the possibility to find exit planets or talk about what they're dreaming of a better world is possible. So welcome to our stage Knuth. Thank you very much for the intro. My name is Knuth and I chose astronomy or astrophotography as my hobby. Astronomy is a very broad field and I have compiled a number of topics that I would like to share with you tonight. I chose the topics of exoplanets, planets that are outside of our sun system. If you imagine what would happen if we actually managed to destroy our world and we had to look for a new one on the left, you can see. Well, former Syria, it used to be a very lively state and now it's a good place for watching stars. So I hope that during the next half hour I'll be able to give you some insight into exoplanets and the state of research. First, we will talk about what are exoplanets and how to detect them. We will be talking about two methods. There are more, but this would exceed the scope of this talk. And then we will talk about the next steps in science and what scientists are doing in order to get insights into the secrets of exoplanets and how to discover them. So let's start what are exoplanets. A definition from 2006, some of the older listeners might remember. That was the moment Pluto was no longer considered a planet. The International Astronomic Union defined criteria on what is a planet. A planet is a body that turns around a sun that has a symmetric form. So it's not square, for example, like some other objects in space. And it also has to have a clear path so that there are no bigger objects around it. And that is why Pluto was no longer considered a planet. The same would go for our moon or Jupiter or Saturn that have many more moons than the Earth. So it can't be a moon either. So what are exoplanets? That's very simple, basically. It's changed the sun with another star and then an exoplanet is short for extra solar planets. So it's out of the range of our sun. It rotates around another sun on a defined path that we can try to find. We have some examples in the next slide. So let's talk about the terms. The exoplanets are in court, that one, Pluto or Mars, but they're named after the star. They rotate around and then they get a combination of letters that are in the order of their discovery. Our sun is called Sun. So we would have Sun B, Sun C, Sun D, Sun E, which would be the planets we have in order. So this is how the exoplanets are named. And you will see that you start with one planet and then another is found and so on and so on. That has its reason and we will be talking about those reasons. So how do you find exoplanets? There are different possibilities, the nicest of which is just looking at it and seeing the exoplanets directly rotating around a star. Here we have a satellite image of the sun and you can see a device that allows the camera to see the sun in dark to make it visible. What you see here is a satellite recording from 2013. And you can see an asteroid there that is approaching the sun and then distancing itself from the sun again. And in this way a lot of satellites and asteroids that rotate around the sun have been found and it's also possible to visualize Venus. You can do that for other stars as well. I've got two examples here. On the left you can see from how to be. It rotates around the star from how. And from how to be was a very celebrated discovery. But unfortunately last year it turned out there was an error. It's not a planet. I still took it in here because the discovery was that huge. Actually it's two gas clouds that collided and now one that now have taken a path around this star. And on the left you have HR 8,799. It's 130 light years away from us and it's more than 60 million years old. And there are four exoplanets known right now that were discovered from the outside in. And on the left you can see HR 9,799 B. And you can also say C,D and E. And the recording was made by the Kepler observatory. Similar to the image of our sun. So in comparison to the planet the sun is very bright. So our sun is about one million times brighter than our earth. So that's a contrast that is very hard to visualize. It's comparable to like trying to take a photo of a mosquito next to a floodlight from a football stadium. So this only works for suns that are very weak, that are not very bright. So suns that are just starting to exist at this very moment. So this is about the direct method. The method we are mostly using is the so called transit method which is very easy. You can do it yourself using a lens reflex camera in your garden or a webcam even would work. And Harald will show you in detail how to do that and how to spot exoplanets yourself and measure them. This is a NASA illustration. NASA always makes very colorful and beautiful images. So what is happening here? There is a temporary darkening and you have to be on the same level as the rotational path. So the planets have to rotate in a way that they are positioned between their sun and our camera. And that is how you are able to see them. You are more likely to discover a large planet than a small planet. And it would be very improbable for our earth to be spotted using this method. This probability depends on the size of the sun. This method can be carried out terrestrial in an observatory for example. And you also need several rotations around the sun. In the first rotation you can see there is something. In the second rotation you can see there is a certain path. And then you have a third measurement in order to confirm that it is really just one exoplanet that rotates around the sun in its year. So that takes quite some time to do that measurement. So here we have an example, I hope you see my mouse. On the top we have a planet, the small ball. And on the left we have the light curve over time. So if I start it we can see how the planet goes around the star once. And now check the light curve. The planet is in front of the star, the light curve goes down, the planet passes by and the light goes back up. And so I got my signal. And this is what happens when we use a camera to use the transit method. Depending on the size of the star and the planet I have a difference in how much the light drops. On the right side there is a smaller planet, on the left side there is a bigger planet. And so of course the bigger planet lets the light drop further. So I can say how big is the planet compared to the sun. And it doesn't really matter how far away I am. And I can even find a very small planet with this method. What does it look like with several planets? Let's look at the light curve. I have three planets here. A big one, a middle one and a small one. First the big one and the first dip. Then the middle one, again a dip. And then the small one behind it. The curve goes further down and then back up. And you can also check that there is a small mistake here. Because of course the factor, how far it goes down and back up. This dip is ridiculous of course. But the principle stands. Okay, how does it look in reality? So we are looking at hat P7B. It's a huge planet, which 1.8 times the mass of Jupiter. And one year for it takes 2,205 days. No, 2.205 days, sorry. So it's very big and very heavy. Its star is about double the size of our Sun. And here you can see this huge dip and then the curve goes back up. So 2.2 days are one year. But on the lower here we have the average value in blue. And that's the standard brightness. And it drops a little. Then there is the eclipse. And then the dip. Then it goes up. And then there is the second dip. And so on. So ideally it's really constant. And the second dip is the reflection of the planet before the planet disappears behind the Sun. And we can see that here. And we can measure that here. And that's how we get this curve. Okay, so much for the transit method. We have a few satellites launched for that. So there's the Kepler mission in 2009. There's a sensor. You can see that on the upper right side with 42 CCDs. And in about an hour it will go down. And we were taking constant measurements. And it was discovering a lot of exoplanets. It started with four pieces. Two were surviving. And then it could also still look for 80 days. So only for very short transition periods because we need long observations to really observe also long transits. Then the next method. At the beginning it was the most successful one. It was the radial speed method. A star has a mass. A planet has a mass. And when they circle each other, then it's not the case that the star remains in place and the planet moves around it. They both rotate around the common virtual point of mass. And what we can do now is we can check the light, the star sends out. And if we then use prisms, we get the rainbow. The typical rainbow. And if we really look at the spectroscopic, the absorption lines, those are the black lines in here. And whoever paid attention in physics, these lines are specific to certain elements in the star. And they are specific to certain wavelengths. So I can say what kind of atoms are within the sun. And you all know the Doppler effect, of course. The best example is an ambulance that approaches you, passes by you and moves away. So first the sound is very high, the pitch. And then it goes down on the way away. And the same happens to the light here. So the characteristic lines in the light, they change depending on whether the star moves towards us or away from us. And using that, we can determine a speed with which a star pulls on the star. So in which the planet pulls on the star. We have a small animation again. The planet moves around the sun. And the sun moves away from us. And the light goes, has a longer wavelength. And then it moves towards us. It's a shorter wavelength. So it becomes more red or more blue. And when we have a spectrum of a star, we can tell by how the light changes in which direction it moves. So we can detect that there is something pulling on the star. And if it's one planet, then it's a perfect sine curve. If it's several planets, then we have multiple superpositioned sine curves. So we can also calculate the transition periods of all the planets. So let's check the efficiency of all the methods. The whole topic started some 20 years ago. I think 95 was the first time an exoplanet was found. And back then, many people couldn't believe that there are other planets at all. Well, no, the Earth is not unique. And the more we look, the more planets we find. And there is several methods, actually. And the most successful one at the beginning was the radial velocity method. Then there was the transit method. And it was used in many satellite missions. Of course, the microlensing method that works by how the planets can bend a light just by having gravity. I didn't talk about it. But yeah, we can see how black holes bend light, for example. And we can find patterns in that. And we can use that to measure our whole star systems in a very short time. Microlensing is very interesting. So now we are at around 5,000 exoplanets that we found. And now the important thing is to check is it really an exoplanet or not. It comes more exact. And we can now use methods to find planets around weak stars. And we were able to find big planets more easily. To find something like the Earth, you have to be very precise. But by now we can do it. And the better our instruments become, the more planets we find, of course. So now we found a planet. Now the question is, is that an Earth-like planet? Could we live there? So we are talking about the habitable zone. Primarily it's defined by the temperature and that's defined by the distance from the star. And we are carbon-based life forms, so we need water. So the question is, is this planet in a temperature range, in a distance range, so that water is a present, but also be in liquid form. So it isn't frozen over, but it's also not blown away. So we don't want an ice planet, of course. But there is water, but we can't get to it. And even in our own solar system, where we are wondering where is the water of Mars. So you can imagine finding the answer on an exoplanet is even more challenging. But still there are methods for this. So everything we are talking about now is based on quite many assumptions. But there are methods and there are reasonings. So let's look at one system. It's called Trappist 1. It's a very small dwarf star. It's 1,250,000 of the brightness of our Sun. And there are multiple planets around it, and all of them are rocky planets. We can detect that. I will get back to that later. So the habitable zone of our solar system is marked in blue, here in the upper area. So the Earth is right in there, including the Moon. Also the Mars is in there. Venus not really. It's a bit too hot. Mercury, of course, is way too hot. Water could not exist there for long. The yellow cross are exactly Earth's data. So on the y-axis we have the density, and on the x-axis we have the illumination. So how much energy enters the planet from the star? So we see the Trappist planets, B, C, D, E, F, G and H. Many of them are in the habitable zone. And yeah, we can find water on there, mostly. And for example, Trappist 1F, we assume is an ocean planet. The whole system is 40 light-years away from us. So pretty close. And considering astronomical distances, 40 light-years is a distance that we might reach one day. But of course, if I want to speed up a lot of mass, it's a bit difficult. But small masses are easier, of course, to move it there. And just assume that we managed to travel with 1 fourth of light speed, which theoretically is quite possible. We would need 160 years, which is quite possible if there are no alternatives, of course. But what does this show us? Well, before we take this path, we need to see, and we need to check, is it worth it to go there? And we need more information. So I want to mention a few frame parameters for that question. One is that we need more concrete metrics. So we need to know whether it's a gas planet, for example, the mass and density of the planet is... One of the best diagrams in astronomy is the Hatch-Pung-Russell diagram. You can see it on the right here. This red object is a real measurement of all stars within 5 million light-years of the Earth. Each dot represents one star, and the red areas are just heaps of stars on top of each other. So you can see the light of the star here. It starts very weak here on the y-axis. The x-axis has categories like temperature and type of star, and you also have the light color. The sun is somewhere in the middle. The light temperature is measured in Seoul, which is a sun strength. And all the other stars are here in the diagram. So a newborn star starts somewhere in the lower edge here, and then it becomes hotter and hotter. You have a star that either dies or it becomes dwarf planets and ends up as a white dwarf. There are other things to consider, for example, the weight of planets which we can measure using the radial speed method and also the diameter density. And when looking at the atmosphere, we can also do that. We have the star, we have the planet passing it, and the atmosphere of the planet gives a different wavelength of the star. And if we subtract that, we can look at the wavelength of the planet. We have WASP 39B. Here as an example, it has four days at four-day orbits. And here you can see how molecules of an exoplanet can be measured, taking an exoplanet with 700 million light-years distance as an example. So now I'm being told that our time is up. Thank you very much for listening. There's a lot of material. If you're interested in Kepler, it's also starting new missions again and again, and we're working on enhancing the measurement values. Thank you Knut. This was really fascinating. Just imagine a large room of people who are in awe and who are giving you a huge round of applause. I'm so sorry that we cannot give you this experience because we're here virtually. But the number of questions alone is very telling of how fascinating people find your talk. So we have a lot of questions, so this is why we wanted... We had to cut you short, although we would have liked to listen to more of your explanations. So the first question, the pad is still filling. Can you assume that the orbit level or the path level of all planets is always the same? No, you can't. So when a star system is spawned, it happens in an aggregation disk. So in a cloud like a typical star birthing area, and we will get back to that on our group stargazing session. So then the gas molecules come together and a disk forms. So typically, yes, the planets are usually on a plane, but it can be disturbed. For example, for us Pluto, well, the dwarf planet Pluto, it's disturbed. It's not going in the same plane as the other planets. But then, two years ago, made quite an interesting discovery. They found an exoplanet that runs backwards compared to the rotation direction of their star. So basically we know that we don't know anything. Yeah, that raises another question. If you've found an exoplanet using the difference in brightness, isn't it extremely unlikely that the planets between us and the other star? Because you said it's really, really improbable. So how many exoplanets that we miss? Yeah, quite a lot. We now assume that any star will have planets. You can just assume that. With a planet on the size of Earth, we are below 1%. On Jupiter, we have 10% chance of detecting it if it passes by the Sun. Yeah, just following up. Did I understand correctly that we can assume that any star has a planet system? Yeah, pretty much everyone. We've found them pretty much anywhere. Most stars out there are... And so 50% of all the stars we see are double star system. So it's two stars rotating around each other. And even with those, we found exoplanets. So either they rotate, they traverse each one of the stars or both of them. So basically we found everything already. And there is triple star systems, quadruple star systems and single star. Are the exception. Yeah, that explains or answers the question whether a Earth-side planet would be measurable and how we would find such smaller exoplanets. Well, it's detectable and measurable. And by now we can use the transmission method. But the chance is so low and keeps us from finding it. But our cameras are good enough to find planets that are similar to Earth. And soon, in 2026, the next satellite mission for this will start. And it specializes and concentrates on Earth-like planets orbiting other stars. We hope that this will be enough for astro-sysmology to detect volcanics on those planets. Because if we can detect eruptions, we can tell... And if we have information about the resonance frequency of a star or planet, we can tell what's happening inside it and what does it look like inside it. So we can tell a lot about what it consists of. And we can detect a lot more closely what does it look like with the planets. And AI plays a huge role as well. And I already said that planets are usually being born together with their star, pretty much always. I mean, there are planets that wander through the universe alone and are then caught by a star. But usually by knowing what the star is made of and what the star emits, we know what the planets consist of. We also can tell what pressure and what temperature do I need for certain molecules. So we can check what does a star consist of, and we're working hard on that. And we try to create AI models to check what planets might be there. Yeah, before we come to the last question, just let me use the opportunity to give you an impression of what is happening here in the questions catalog, but also on Twitter. Twitter really likes your voice and thinks it's really pleasant. And you're so full of knowledge, so when will you have a podcast? People are asking that. This is actually my first talk like this. Yeah, the idea is born, isn't it? Thank you. Hopefully soon. The co-orates cloud that is limiting our solar system, can you measure it? I don't know about that. So I have another question. Would you be able to detect alien civilizations? Yeah, the question is obvious, but the question is, what is an alien civilization? We are quite human-centric as carbon-based life forms, so we are looking for methane for oxygen, both gases that don't accumulate in an atmosphere on their own and decrease over time. So if you can find those molecules, then today we assume that there must be some form of carbon-based life. Yeah, so that's what we're looking for. There could be other forms of life that are not like us. And with this topic of exoplanets, we can see that first we were always trying to extrapolate from our star system, and we were looking for rocky planets in the center and gas giants at the outside, and we made measurements and then saw that that's basically not always the case. We saw a gas planet that's giant, and it has a 2.2-day gear. There shouldn't be a gas giant there. It shouldn't be able to exist there. It shouldn't develop there. Yeah, we then checked our models and found, well, it is possible, because a gas giant will slow down on their orbit around the star, and it will turn slower and slower, and the slower it becomes, the closer it gets. Would James Webb, as an instrumentarian, be able to help you? The one that was launched recently has very fine precise instruments that also will help us with measurements, especially with spectography. So thank you again. There's a lot of positive feedback. Twitter is thanking you, not just for your voice, but also for your presentation. Maybe let me ask one question that is motivated from computer science. Claude Scheller is very well-known in computer science. I'll read the question because it's hard for me to understand. When looking for information, shouldn't you also be looking at the density of information in the sense of Claude Scheller? Can you answer that question? Unfortunately not. Well, sorry to those who raised the question. Okay, maybe about the AI models. So of course we put in everything we have concerning information. The interesting thing about the models is that they try to deduce the probable ways of planet construction or how they develop. And one of them is a conduction of heat. And Mars is rather boring because it's quite dead. There is some Vulcan activity, but basically nothing. But Venus and Earth are quite interesting. It's rocky planets that develop quite differently. And we use the same models for the... We use our models on these planets and try to check what parameters determine what. And that's what we are doing. And we are planning quite a few Venus missions to check what happened with Venus. So until 2030 there is quite a few planned. And we have greenhouse effects and we know what happened, but not exactly how. Yeah, looking at the time I want to place with one question. What are the hopes that people connect with exoplanets and how likely is that hope to fulfill? We don't have much time left unfortunately. So please remember there will be a breakout room. The link will be posted in the IRC. So if you have time we can continue the discussion. And I cordially invite you. Yeah, so we can be certain that the exoplanets Earth like exist. If you assume that each star has two exoplanets and in the Milky Way alone we have 400 million stars. A few billion galaxies. So we have a few trillion and more exoplanets. So statistically speaking that there are no other exoplanets with life. The chances are really low. So getting there is difficult. Do we have a chance to get there? So we might be able to get there in the next years. The hope is that if we build huge sunsales, solar sails and shoot on them with lasers, then we could speed up quite quickly. We could reach 25 to 30% of light speed. That would be cool. Okay. So you just demonstrated that it's more plausible that we have extraterrestrial intelligence than not. So if that isn't a good prospect for the next talk. So please remember the idea with the podcast and thank you very, very much for your presentation. I imagine that lots of being out there and thankful for your talk. And please get to the breakout room. Knut will be available for more questions. Also you can visit the observatory in Lübeck and after coronavirus is over. We will hopefully be able to offer more.