My PhD Was About Alien Worlds

This episode starts with the story behind the science: how a football injury, a lost sense of identity, and a Cosmos documentary helped send me toward astronomy and exoplanet research.

From there, we get into what my dissertation was actually about: atmospheric mass loss for close-in exoplanets. That means planets getting blasted by radiation from their stars, losing gas over time, and sometimes leaving behind clues we can detect from Earth. We talk Mars, Venus, hot Jupiters, helium escape, WASP-69b, the radius gap, young planets, and why understanding atmospheres matters for the search for life.

Lead with curiosity.

Transcript

SPEAKER_00 0:00

Welcome to Dr. Star Kid. I'm Dr. Dakota Tyler, and let's just go ahead and get right into it. Today, I wanted to talk about something that I have been wanting to talk about at length in long format for a very long time. I got my dissertation right here: Observational Investigations of Atmospheric Mass Loss for Close In Exoplanets. And we'll get into exactly what that means. Um, you can feel free to pull it up. You can actually just Google that, uh, put in my name. I don't even think you have to put in my name. If you just Google it, it should pop up something from a link to eScholarship. So it literally will bring you right to my dissertation if you want to follow along. I'm not gonna be reading out of it. Before that, I wanted to talk a little bit about how I got into studying this specifically because it all ties together. Um, y'all say I got the football with me. A lot of people comment all the time, like, what do you why do you have a football with you? Why do you have a football with you? Because my I like to mind my business and do what feels right to me. And it feels right to have a football in my hand. Like sometimes some people have uh likened it to an emotional support football, which I think is kind of funny, um, but kind of true. You know, you just see the football helmet. Again, if you're locked in uh on YouTube or whatever app that I uploaded this video, I used to play football, I played college ball at the University of Kentucky, go Big Blue Nation, Wildcats, SEC. It was all I ever wanted since a young age. I was never into science, which I think a lot of people sometimes are surprised to hear. And I think it is surprising because a lot of people who find themselves, for example, a lot of my colleagues, did want to do something in science from a young age. And I will hear them talk about, oh, I went to space camp, or I met an astronaut, or you know, I watched this movie, and it just made me want to study the universe, which are you know, those are very cool examples of ways to get people excited uh about science, about space. But that wasn't that wasn't mine. All I wanted to do was play sports. I played baseball, basketball, football growing up. In high school, I just started focusing on football, which was the one that I think I was best at, and just matched my temperament. I was like very physically aggressive on the field. You know, I was like a young man that grew up in the 90s, you know, early 2000s era. There's not a lot of focus on like emotional regulation or emotional development, and just you know, going in a gym, working hard, going out on the field, and trying to punish people made me feel better. Like it made me made me feel better. I think not probably a healthy developmental track for a well-adjusted human being in society. That's that's my take on it. And there is, you know, importantly, some of the stereotype of the the like meat head and or you know, locker room vibe, like the locker room talk type of thing. Like this, that stuff is real. That does shape, you know, your attitude, your perspective, your outlook on things. And I think that when I got done playing, completely against my will, by the way. I think I was a junior and at University of Kentucky, and in a game I tore my ACL in meniscus. That kind of got the ball rolling to me eventually realizing that football was not something that I was gonna be able to do. Extremely depressing time. Again, it took me it took me like a couple years to fully accept that and deal with what that meant, which was like, who are you? What's your identity? It always has been athlete. It was like hard worker athlete, a physical player that other players respected. My teammates respected, other people respected. I played at Kentucky. Kentucky doesn't have other professional sports teams, they don't have a pro basketball or a pro-football team. So in Kentucky, the univer athletes from the University of Kentucky, in I guess also Louisville, are they are like the pro athletes. That is who the people in Kentucky see in that way. It's almost like pro-athlete light. And when I played was different, it wasn't NIL. Like the guys now, they're getting bags. That wasn't, it wasn't like that when I was playing. Um, the only people getting bags off us were the administration, the coaches. We were making them millionaires, but you know, boys was really paycheck to paycheck, like stipend to stipend. They could like feed us certain things outside of meals. I think they could feed us like one, this is a bit of a sidetrack, but they could feed us one meal a day, except when we were away for games. I think they could feed us like three meals a day, something like that. So, but they could feed us things called snacks, which were like protein shakes, bags of nuts, like almonds, uh peanuts, and then peanut butter and jelly on bagels. And so, like, that's what we got. It was crazy, but like it was crazy. Athlete for athletes used to be down bad, down very bad, but got hurt, couldn't play anymore. You know, you lose this like respect that you had almost for yourself, but also from other people. When you're an athlete, uh you know, like a lot of people want to be your friends, people think you're cool, kids want to your autograph, and we you lose all of that. And it's like, who are you? What are you even interested in? And it had never that is not something I had ever really considered, which sounds funny to say now, because all I kind of do is sit around and think, hmm, is that an interesting idea? Maybe we should spend some time here. Oh, well, I know this other interesting thing that I learned last year. Is there a possible connection here? Or or is that too far-fetched? Or maybe the connection is like down this way and you know, requires this other thing that I learned. But at the time, you know, that wasn't really a thing. And this is one of the reasons that I have complicated feelings about young people specializing in sports. And I say young people, I think I I really feel strongly about this for young men. I think it also applies to young women. There's guys in Major League Baseball that sign contracts for damn near a billion dollars. You know what I mean? Guys in the NBA is making like half a billion dollars over their career, and so that's it seems much more uh like illustrious. And it's can be dangerous because very few, very few people will ever reach that level. Um, anyways, the only reason I differentiate that is I I think that it applies for all athletes, but I think that there's something appealing in a grander way for um for a lot of young male athletes. And oftentimes you do gotta be super locked in, right? Unless you're like this one in a billion gifted individual, which some people are, you really just need all your focus to be on that thing. And that's how it was for me. But that means that I didn't know what else I was interested in, I didn't know what else I liked, I didn't know what I was curious about. Again, it's it is very interesting to reflect back on. During the time that I was injured and I kept re-injuring my knee, the reason it took so long to accept it was because after a long extended period of time, I just was not the same. My knee was not the same. You know, of course, I got the reconstruction, I did rehab, but I kept re-injuring it. At this point, I've torn my meniscus so many times that I don't even have one. So my it's like shin on femur, straight bone on bone grinding. There is no meniscus, which if you don't know is um kind of like a it's this cartilac cartilaginous material that's sort of a a shock absorber. So eventually came to the conclusion, wasn't really able to play, very depressed, very lost. Um, I think probably something that uh a lot of us go through at various times, but it was a little bit more explicit and the fall-off was a little steeper for me. And I started watching these astronomy documentaries, the Cosmos documentary that rebooted somewhere around 2010, 2011, 2012, I forget. Um, and it was the second season. Remember, the first season of Cosmos was Carl Sagan, legendary season, one of the highest watched shows in the world, I believe, at the time, which is crazy. And Cosmos 2, again, it was like spectacular. It was the first one that I had seen. I had not seen the Carl Sagan one, and obviously, more modern times, it was about 15 years ago now or so, but they're able to just do these beautiful visualizations of other planets of like microscopic life, and it was it was so immersive. I think they had um there was this orchestra that did the score for it, it was great, you know, phenomenal. Got me interested in astronomy, specifically into planets, into these other planets. There are these other planets that are out there, like you know, we live on Earth, and this has always resonated deeply with me. Um maybe it will with you. So we live on this planet, and you could spend your entire life traveling around the earth. You go to a different city every weekend, somewhere in the world, uh, and you would never see all of the earth. And like three-quarters of the earth is covered in water. So let's so forgetting forgetting the ocean, you couldn't hit all of the places on land throughout the course of your life. You would just run out of time. That's how big and vast the planet is. And again, this is forgetting the oceans. If you add the oceans, for you know, forget it. Forget it. And that's just our planet. There are other planets. There's Mars, there's Venus, there's Jupiter, there's Mercury, all of these other planets, many of them much larger than the Earth. Many of them like unimaginably larger than the Earth. And we have this perspective that is a perspective that makes sense for us, where it's just life through our eyes, existence through our eyes, standing on, you know, the thin crust of this one planet. And for me, something like an injury that pulled away my sense of identity and sense of future and and what success was gonna be was gonna look like, what my life was gonna be like. And it feels like the life is ending, it feels like the universe is collapsing, is like imploding into a black hole. And that was how how it felt at times. But this isn't true, it's just the perspective that I had, you know, as a little conscious being with a brain sitting behind my eyes. In reality, there's like this vast universe, and there's not only countless other conscious beings on this planet having their own experience that feels like they're at the center of the universe, but other aliens on other planets that are having something similar, maybe they maybe they have like the same type of consciousness we we do, maybe not. You know, that's not a question that we have the answer to. But I remember thinking, damn, so you know, life got started on Earth. Apparently, it didn't take that long, maybe happened within the first couple hundred million years of the Earth cooling down. So when a when a planet forms, there's all this chaos and collisions, and planetesimals are slamming into each other, and everything's getting liquefied because it's so hot. But eventually that cools down, the crust kind of cools off and gets hard, so it's not just lava. And then you you start to get water that is vapor in the atmosphere, it can condense, right? That's you're that's what happens in the water cycle. Like water in the ocean is liquid, heats up, evaporates, goes into the air, and eventually like goes up high enough and cools down, and it can condense back into water, and then it falls down because the gas is light and can exist in the atmosphere, but the water is dense, so falls down. And this happened on Earth, and enough of this cat condensation happened that we get oceans, and seemingly life shows up damn near as soon as that happens. We get these liquid water oceans. Now, you know, a lot of the estimates that I've seen are somewhere around 3.5 to 3.7 or maybe 3.8 billion years ago. We find these things called stromatolites that are you can look them up now, stromatolites. They are you they're found in like shallow areas of water where some you have like tides coming in and out. So sometimes it dries out and sometimes it gets submerged and is wet, and they're just like little mounds of bacterial colonies. And you can you can radiometrically date, you can you can like assess the the different isotopes in the rock, which will let you know how old the rock is, because isotopes um are decaying at these very, very reliable rates. And it's like, oh, the rock that has this bacterial colony is like 3.6, 3.7 billion years old. Therefore, that thing was alive 3.6, 3.7 billion years ago, which is very close to when the planet formed, right? On a geological time scale. And if it happens fast like that, sh like surely it can happen in other places. It wasn't that hard for life to get started. In another episode, maybe we'll talk about, we definitely will talk about how life got complex, because that's different. Getting life started appeared to be very easy and happened very fast, but getting life complex, like multicellular animals, plants, fungi, that in my opinion, seems to be something that's much more rare, much harder, and relies much more on these like random chance events. So, regardless, I think think about all these exoplanets out there, extrasolar planets, uh, planets outside of our solar system. And I'm thinking there's probably an alien on one of these planets that lives in an alien society where they have high reverence for some sort of sports. I don't know what type of sports aliens will play. Maybe something with a ball that could kind of make sense. Maybe glort. Something called Glort Balls, like an alien that has wings and antennas and tentacles. And that on one of these planets, you know, it was the it was the Super Bowl in the Glorp League, and he like ripped a tentacle. And the thing about these aliens and the way that their tentacles evolved is that they're very dextrous, like they're very sturdy and flexible, and they last a long time. But if you tear one, you're just cooked. It can't re sort of like a horse, you know. If a horse breaks its leg, it's just cooked. Because the way that horses stand and walk, it has to put so much pressure on its leg that it just has no hope for um having that heel. So that's why they put down horses, it's kind of messed up, anyways. And I'm thinking, like, yo, you know, what would that alien, this galorp league all-star champion, be thinking? The same thing. Damn, like, what am I gonna do? This is the whole universe, this is everything. And weirdly, uh some sort of empathy, I think, uh, emerged and helped me to expand my perspective beyond the crushing blow that I felt. Okay, so there are these other planets out there, and then I started getting these crazy ideas about huh, could there, could there be a planet that was, for example, all gold? Like, imagine a planet that's similar to the Earth, but instead of like all these rocks and all this, all the all the silicate and carbon that we see on the surface, it was just all gold. And then, you know, there was like gold mountains, right, and gold valleys and gold plains. Is that possible? Or a planet that's all diamonds or or all silver? Is that possible? In my mind at the time, which I you know I didn't have any training uh or any knowledge base, I was like, yeah, you know, it it could happen somewhere, right? The universe if the universe is infinite, or if it's practically infinite, then uh there's no reason that physics would disallow something like that. Of course, as I go on and start school, um, start taking community college classes while I'm working at nights, very tests your resilience. It tests how bad you want it. And uh a side note, anybody who's listening to this that has an inclination or have been thinking about going back to school or something like that, highly recommend starting at community college. You can take the exact same classes, right? Like math is not different if at a community college than it is at Harvard. It's math, calculus is the same, it's all it's all you know, it's all the same. And you can take the classes for like, depending on the school you're thinking of, a tenth, a twentieth of the the price, maybe even more than that. And I think that that's uh it's a great thing to do. And it when you take the prereqs, it'll be much easier for you to transfer into a different program, and you'll have a lot of those classes already done, and you will have demonstrated the competence and like the efficacy as a student that will increase the likelihood that they would accept you into the program to finish. So that's a little pro tip. I'm a huge advocate for community college. So eventually I transferred to the University of Cincinnati, and this is when I really start to learn more about um astronomy and astrophysics, as opposed to just physics, which is what I was taking in in community college. And it becomes very clear to me over time that this kind of fantastical universe that has golden planets and diamond mountains is mostly a fantasy. And it's not that it's not that the laws of physics preclude something like that, right? You you could imagine a giant reservoir of gold that was that had the mass of the earth, right? And you could imagine that thing being somewhere and and being a planet. Like there's not gold exists, it exists in high amounts. You throw it all together, gravity's gonna take hold, you know, it's gonna, it's gonna form a um, you know, a spherical object. Inside would be incredibly hot, you know, it'd probably have like a molten uh gold core, maybe a solid core. I don't know enough about the specific physics of gold at high temperatures and pressures, which um these like the phases of different materials are very weird when the pressure and temperature gets super high. Regardless, that's actually not something that could happen. And it's evident when you understand how something like gold is produced. Why could you not have a gold planet? Well, the way that you produce something like gold is in one of these extremely high-energy explosions, like a supernova or a kilonova, like two neutron stars colliding and exploding. And in the aftermath of either of those type of explosive events, the collapse and explosion of a star, supernova, or the merger and explosion of a couple neutron stars, kilonova, you have so much energy and so many neutrons that are flying all over the place that they can get bound, they can get captured. There's something called the R process, like a rapid process of neutron capture, where you can just jam a whole bunch of neutrons into a nucleus. And it turns out that this is really the only efficient and effective way to create heavy metals. They're not created in stars beyond like iron and nickel. So gold, silver, platinum, uranium, thorium, these things can only be created in these explosive events. And you cram a whole bunch of neutrons into or some little nucleus, and what happens is some of the neutrons will become protons over time. It's a strange quantum mechanical effect that we can do some other episode on quantum mechanics. But basically, by capturing a a Boatload a ton of neutrons in a nucleus, eventually that will be gold. You know, we define elements by the number of protons that they have in their nucleus. So this is how you get gold. Well, okay, so that's how you create gold, and you need really energetic events like these Killanova mergers to create that much gold. But the problem is when you're creating a lot of gold, you are creating a lot of everything else. In fact, you're creating much more of everything else. Ah, and so there you have the limitation. It's more so statistical. It's not that enough gold couldn't exist to create a planet that was solid gold. It's that by the time you accumulate enough gold into one place, you have accumulated far more of a whole bunch of other stuff. And so when you start making that planet, you end up with a ratio of gold that's similar to what we have on Earth. And so through very basic uh physical processes, you can roll out a planet like an all-gold planet. There is no circumstance in that in that in nature, right? There's no no no natural circumstance in which you will have a population of gold high enough to create a gold-only planet or a silver only planet. Just can't it can't happen. But in terms of just any type of planet existing, that's not that's not true. But there are some very interesting planets that exist. And we covered those in the last episode. You go back and listen to that, uh, some of the cool different types of planets that exist. Well, okay, I want to know more about the planets that are possible. What do they look like? What are they are they habitable? Are they are they planets that like are interesting from a biological perspective, like astrobiology? Are they are they just weird? Um, are they planets that we think are horrible places for life to exist? And it turns out that in the field of exoplanets, um, we you know we've confirmed 6,6300 maybe as of today. We don't know a lot about them. We know the size of a lot of them, we know the mass of a lot of them, you can get an average density, but that that doesn't tell you exactly what it's made of, you're right. An average density gives you an idea of potential combinations, but it's kind of hard to say exactly what it's made of. Yeah, I think the earth has an average density of somewhere around 5.5 grams per cubic centimeter, somewhere around there. Now we know the composition of Earth because we live here. Um, I think it's a third iron and then two-thirds silicate rock. So these would be like the rocks on the surface, and then in the core, mostly heavy metals like iron, bunch of other stuff sprinkled in. But big picture, that could account for the entire mass of the earth. Mind you, that doesn't that doesn't let an alien astronomer that knows the mass uh and density of our planet in on the fact that we have an atmosphere, which is kind of negligible in terms of mass because gas is so much lighter than rock, or water, which again, we don't have enough for it to be meaningfully um contributing to the overall mass of the planet, like 0.02% of our planet's mass. All right. So it's hard to determine these things about planets, and that's that's like the boundary of knowledge in exoplanets. It's what are these things exactly made of? How do they change over time? Right? We know that planets evolve. We can see in our own solar system that planets evolve. Look at a planet like Mars. Mars is is small and it's cold and it barely has an atmosphere, it has like 1% the Earth's atmosphere. It has so little atmosphere that water cannot remain liquid on the surface. Like it's freezing cold there. But forget that, because there are some places on Mars where the temperature would be okay. Mars also has seasons, which is a fun thing to think about. Mars has a summer and it has a winter, same as same as we do here on Earth. Mars is has a similar tilt, about somewhere around 23 degrees, which is remarkably similar to the Earth. It also has a day that's very close to an Earth day. So that's in a lot of ways, Mars was our little sibling, which I think is really cool to think about. And it's not just the tilt uh and the rotational speed, it's also because we know that there used to be water on Mars, and the evidence is really overwhelming. You see an image of Mars, you can actually see these runoffs like the tributaries and deltas that look like what it looks like on Earth when you have water flowing. Uh, lakes, rivers, perhaps oceans. I don't know if we've concluded the overall amount of water that it had. That's kind of hard to determine. But it clearly used to have water. And many of the rovers that we've landed on Mars, there's several active right now. Curiosity and perseverance are both currently active, and they were both landed intentionally in these dried riverbed, lake bed areas. Which makes sense, you know. If you are an aerospace engineer, if you are a NASA scientist and you suspect that Mars used to have running water, and you know, on Earth, we know where we find running water, we find life. You wanted to probe for some sort of suggestive evidence of past life on Mars. Where are you gonna land your rover? You're gonna land it in a place that looks like it used to have water. That's exactly what they did. And last year in 2025, there was a paper coming uh that came out, this discovery, this announcement, that they found these signatures, what they called um poppy seeds and leopard spots, these small iron phosphates, these small chemical signatures that on earth we associate with metabolic processes for microbial life. Uh, which is to say, when we see things that look exactly like that on Earth, we can link that to past life on Earth, past microbial life on Earth. And they found the same thing, it looks like the same thing, on Mars. The only reason that they couldn't conclusively say we found evidence of life outside of the Earth. This is positive confirmation of alien life on another planet in all won Nobel Prizes, is because we're stuck testing it with a relatively limited um instrument tool belt because it's on Mars. We we really need to bring those rocks here and test them in uh labs that we have on Earth that have much more sensitivity, many more instruments. You can do a much more conclusive and thorough job, uh like a robust job of ruling out potentially abiotic sources for these. Abiotic meaning didn't have anything to do with life. Because you you could recreate what was found without without life, even though we know that it can also be associated with life. So this is interesting. If we could prove one day, and and it may be reliant on us getting those samples back here on Earth, but if that happens one day, if all the losers stop slashing all the science funding, and one day we get these rocks back on Earth and test and prove that also billions of years ago, there was life on Mars, simple life again, then I think that that seals it that simple microbial life is easy. If it happens twice in the same solar system in planets that are literally right next to each other, you know, Mars is the next planet out from Earth, then I think it's it's a foregone conclusion that simple life is something that, given the right conditions, will happen. Again, that's not to say anything about complex life or animals or thoughtful, reflective consciousness that looks off and says, Well, you know, what am I? Who what is this about? Very interesting. So, how did Mars used to have water? But today it can't. Today the atmosphere is so thin that you know, if you if you opened up a bottle of water on Mars, it would kind of like flash, boil, and freeze. The outer layer would evaporate immediately because the pressure is so low. And when something evaporates, it kind of draws from, you know, you think about a liquid, the top layer evaporates, and it draws from the energy of the bottom layer of water, which freezes the bottom layer. Does that make sense? So it's like at the same time, uh exposed water on the surface of Mars will evaporate and then freeze below because what evaporates stole some energy, uh, basically, from the liquid layers beneath. But that was not the case, obviously. If there were lakes and rivers and life, simple life, it was clearly not the case. So that means that Mars used to at least have enough atmosphere to host liquid water, but what happened to the atmosphere? That's actually pretty clear. When I say that Mars was like, you know, a little sibling, I mean in a lot of ways, it it belonged in the Earth's family, but it was too small, and that's a problem. A small planet probably cooled off first and maybe could form life first, but it doesn't have as strong gravity. The gravity is not as strong, and that's very important for holding on to an atmosphere. If your gravity is weaker, then the sun, which is constantly emitting this stream of particles called the solar wind. This is what causes the uh the northern lights, the aurora borealis. Fun fact, there's also southern lights that happens at the top and the bottom of the planet, it happens at the poles. Why? Because we have a convective core, there's like iron that's circulating in the core, and the earth is spinning, and we have a spinning core, and there's convection going on, and all of this craziness basically generates called a geodynamo. It generates a magnetic field. If you've ever seen magnetic field lines on a magnet, they kind of loop from north to south, right? So when these charged particles come from the sun and slam into our magnetic field, they just follow the magnetic field lines. This is a cool thing that you learn in EM, electromagnetism. Charged particles will behave the way that magnetic fields tell them to. That's just like the way that they work. This is the electromagnetic force. And what happens is those charged particles they get funneled along the field lines to the top and the bottom of the earth. And when they slam into the top or the bottom of the earth, they run into the atmosphere, they have a bright flash that can be green, purple, pink, depending on how far down they go and what gases in our atmosphere they hit. And that's where you get the northern lights. Okay, so there's always been this stream of solar wind on Earth, interacts with our magnetic field, gives us northern lights. On Mars, Mars is not strong enough to resist the excitation of its atmosphere. It doesn't have a strong magnetic field, and it doesn't have enough gravity to keep any gas there that's getting stripped away from the solar wind. So there's an important thing there, which is that planets evolve. The atmospheres of planets evolve. Let's go back to my dissertation. Observation observational investigations. So I'm using, you see my little mini telescope there, I'm using telescopes to make observations and investigate atmospheric mass loss, this process of planets, other planets, losing their atmospheres for a close-in exoplanet. So I'm looking specifically at other planets that are close to their star. So Mars lost its atmosphere because of the sun, but Mars is pretty far away. Imagine what that process would be like for a planet that was much closer, that was on like a 20 or 30 or 40-day orbit. Um, for reference, Mercury has an 88-day orbit and it doesn't have an atmosphere because it's way too close to the sun. It just doesn't have the ability to resist the star's radiation, the the solar wind from eroding the atmosphere altogether. Okay. So one of the areas that we need to but beef up our knowledge in, which is what what what a PhD is about. It's about it's not just about learning the classes and learning the physics. That's that's undergrad, and then masters as well. That's taking it to the next level. That's like learning a lot of the same stuff, but at the graduate level, like the much more technically refined, um, much more nuanced, a much deeper understanding of everything that we know. But a PhD goes the next step and says it's not just that you know the things in the field, it's that you yourself have conducted unique, independent research that has added something new, something that future bachelor's or or master's students will learn about, right? Something that other researchers in the field will learn from. So PhD is about creating new knowledge. And an area that we do not have a lot of knowledge about for exoplanets is how these atmospheres are evolving over time. And we can do a lot of theoretical work. Uh, I have a lot of colleagues that are theorists and they model well, here's what we know about the star, and here's what we know about planets. How would the two things interact over time? And that's an important piece of the work, but theory is never really enough. Theory informs observation. A theorist may say, Hey, I bet what's happening is these planets are getting baked in high-energy rays from their star, and it's causing the atmospheres to disappear to like to dissipate, to get peeled away. That's a very cool prediction. And if we understand the theory right, if the theory is good, then we should be able to predict the fact that there will be other planets in which that's happening. We should be able to observe that. And there you see where theory and observation combine. The theorist says, Hey, I think this is what should happen. If the math is right and the physics is right, you should see X observation. An observer has to take that information, figure out what types of instruments exist, which telescope would be big enough? Uh, what's the right spectrometer? What's the what's the wavelength that we could look in? Hmm, what what what do we know about quantum mechanics? What sort of quantum behavior would be exhibited in a hydrogen atom or a helium atom or a CO2 molecule? How can we try to find that thing? And then observers will go, you know, put all this together, try to find it. And maybe you find it, and then you get like a thumbs up, right, on the on the theory. Uh, and maybe you don't find it. And maybe it's because your setup wasn't good enough or your sensitivity wasn't high enough to find it. Or maybe it's because the theory was wrong. Maybe you find something that you didn't expect. You find something that the theory couldn't predict. And then that's how the observation forms the theory, right? The theorists have to create models that account for all observations. This is why when people say, oh, it's just a theory, oh, evolution is just a theory. Well, what is a theory? Theory must describe the facts, it must describe the evidence. Because the facts are never wrong. An observation that somebody makes isn't wrong. It's just a fact. It's like that's this is how something is. And a theorist has to be able to account for all of those things. The theory has to account for all the observations. And this is why over time, theories by far are the best understanding that we have because they account for all of the evidence that exists. And there can be competing theories, and some theories can fall out of favor, right? It's not, I'm not saying that, you know, like every scientific idea that anybody ever had has had is correct. Of course not. But over time, the theories that fail to explain the vast array of observations or evidence, you kind of use those uh interchangeably, the theories that can't explain all that stuff, nobody talks about. They just they fall they fall away. And what's left are the things that have just been confirmed and verified and validated and iterated on with so many other observations. All right. We think what's happening in these planets, you know, based on the theory, is that their atmospheres are specifically getting excited and energized by something called XUV photons. So this will be like X-ray and extreme ultraviolet. So these are very high energy photons that are coming from stars. They have so much energy that when they slam into a molecule in a planet's atmosphere, they give it a bunch of energy, right? Kind of absorbs the photon. Now the molecule has a bunch of energy. Well, if it has enough energy, if it can move fast enough, it can actually escape the gravity of the planet. Ah, okay. So now you start to develop this overall understanding of each individual planet has some specific individual relationship with the star that it orbits, where because of the mass of the planet and the radiation coming from the star, you should be able to determine, predict how much of the atmosphere is leaving at a time. And maybe it's so much that that planet shouldn't have an atmosphere anymore if it's old enough, right? You think about um a mass loss rate. This is very important in my research. Like, how much mass is being lost every second? Well, if the planet's been around for three billion years and it was losing X amount of mass per second, it shouldn't have any more atmosphere at this time. Or maybe, maybe, if the planet was extremely massive, then it could hold on to enough and just slowly leak the atmosphere away. And this was my first research project. It was looking at a hot Jupiter, a giant, enormous, Jupiter-sized planet, a gas giant, that orbited its star in just three days, Wasp 69B. And what what we were doing was trying to probe the helium in the atmosphere of this gas giant. So a gas giant is going to be mostly hydrogen and helium, similar to a star. This is why sometimes you'll hear people call Jupiter a failed star. I don't really like that terminology because if you're saying that if Jupiter got a hundred times more massive, then it would be able to fuse hydrogen and become a star, okay. I mean, if you got massive enough, you'd be a star. Are you a failed star? I don't like it. And that's in a, you know, that's sort of an extreme uh example as a critique, but you know, if anything gets massive enough, it'll it'll become a star, it'll start fusing atoms, right? So this planet is is losing its atmosphere, and we have to try and figure out how we can see it. There's this specific helium feature called helium-10830, not super important, but it's in the infrared. So, what we can do is we can take these huge telescopes, I use a Keck telescope, and there's this instrument called Near Spect that we used, and we looked at this planet as it transited in front of its star, it kind of crossed in front of the star, and we wanted to see when it crosses in front of the star, do we see a bunch of helium that's blocking the sunlight? Right? You should see a dip. You should see a dip in the intensity in this very narrow range where this very specific band of helium exists in the spectrum. If we see that dip, that'll be evidence that this planet. Is leaking helium. It's no longer just bound to the planet, but it's spreading out around the planet. So this is called transmission spectroscopy. The stellar light is getting transmitted through the atmosphere of the planet, which we think is escaping. And made these observations and found not only that this planet was losing helium, but that its helium because the stellar wind of that star was so strong, it like pins the atmosphere back into a tail like a comet. So this is a planet the size of Jupiter that has a tail like a comet, and the tail is like 350,000 miles long, which is crazy to think about. And it's also interesting because something like the solar wind, we know and we can measure in our solar system because we could send a probe to the sun. There's something called the solar Parker probe. The solar Parker probe is this probe that we made that we have sent in and it has skimmed something that could be defined as the outer atmosphere of the sun. It's crazy. So we can make measurements of our solar wind and our solar system, but we can't do that for other stars. There's no way to measure that. You need something there. You need to stick something there, some sort of uh instrument to make to make that measurement. Here we we use probes, but you can't do it there. But the atmosphere that's getting pinned back in that tail is allowing us to infer a very strong stellar wind coming from that star because it's pushing that escaped atmosphere back into that long tail. A way that you could think of this is we're using the planet itself as a wind sock. You know those those big those tubes that are at airports and they they like tell the air traffic controllers and the pilots which way the wind is coming from. It's almost like using the planet as this enormous cosmic wind sock that is measuring kind of, or um I don't know if measuring is exactly the right word, but it's interacting with the solar wind coming from that star. So that's very cool. That was one of my projects. I think that's chapter three in my dissertation. Alright, so here we were able to determine a mass loss rate of about one Earth mass per billion years. Okay, this planet is about 90 Earth masses, it's a hot Jupiter, and it's losing if we take our rate of loss to be constant, which it may or may not be, but we we're we're assuming that it is, and as long as that's an assumption that we're explicit about, that's fine. But it's orbiting a K, what's called a K star. This star will live longer than the Sun, but not much longer. So the star is only gonna live to be maybe 14, 15 billion years. The planet is 90 Earth masses and it's losing one Earth mass per billion years. By the time the star dies, the planet's still gonna have its atmosphere. So it will not lose all of its mass. Uh, if we were to have found a rate that was much higher, where in just a few billion years it would lose everything, we would call that catastrophic mass loss, which is kind of funny. I think that's uh I bet that I think that's kind of a dramatic, like catastrophic mass loss, is gonna lose all of its atmosphere. So that's one of my projects. And that's looking at a planet that we intentionally picked because we knew we knew that it would have some sort of mass loss going on because it's a jet, it's a giant gas planet parked right next to the star. It was kind of a um, you know, we we predicted that that would be a signal that we could get. What we really want to do is we want to be able to describe other populations of planets instead of just hot Jupiters. So one of the major takeaways the last maybe 10, 15 years in exoplanets, is that and listen to this, it's most sun-like stars have a planet in between the sizes of Earth and Neptune on an orbit that's closer than Mercury's. The most common configuration is that you've got inside the orbit of Mercury, usually less than even 50 days, less than 40 days. You've got all of these close-in planets that are larger than Earth but smaller than Neptune. And you know, we're missing that in our solar system. We don't have a planet inside the orbit of Mercury that's a super Earth or a sub-Neptune. So that's very interesting. Why exactly, why exactly is that? A bit of an open question. Okay, we find all these planets in there, but it appears that those planets come in these two different categories. Either the planet is a super-Earth, just larger than Earth, maybe by up to 50%, or it's a sub-Neptune, two times the size of Earth, up to four times the size of Earth, which Neptune is four times Earth radius. But there's this window in there of planets that are between 1.5 and 2 Earth radii, and there's almost no planets that we find in there. We call it the radius gap. So that's weird. Why you I mean, you would expect, I would expect, right? I don't know what you would expect, but you would expect that if nature is just making a bunch of planets, they there would just be a distribution of sizes, right? You wouldn't expect that there's this really narrow range of planet sizes that nature kind of just refuses to make. Why? Why why would that happen? And the theory emerges that what's going on is you have this population of planets, and some of them are massive enough that they can hold on to their puffy atmospheres, and so they look bigger. We call those the sub-Neptunes. But then some of them just didn't have enough mass for that radiation coming from their star. They lose all their atmosphere and they get stripped down. And we call those super-Earths. So the idea is that that gap where you don't find planets is because any planet that is in that size range is basically on the way to losing all of its atmosphere. The process, um, it's within like the first 300 million years that this process is sort of works out to completion. Then at the end of the day, you know, with a astronomers on a planet, which look out and um see the majority of systems, which the majority are going to be old and not young, and you see this huge pocket of super Earths and this huge pocket of sub Neptunes. But what we haven't been able to do yet, or what we are still rather, I should say, what we are still trying to build observational evidence for, is the process early on of those planets losing their atmospheres. We've seen it for older planets, we've seen it for hot Jupiters. Can we try to see it for these smaller planets, particularly ones that are younger? So I had a couple more projects. One of them was trying to pinpoint the masses for uh an older system, which requires getting a whole bunch of observations, which we did basically refine the masses for a couple planets. But the really cool project is in my last chapter. It's around this young system. It's a very young system, several million years old, um, in the tens of millions of years old. Very young for a star. It's not even a main sequence star yet. Like the star itself basically is still forming, it's still contracting, it's still like becoming mature. Mote, you know, our sun is four and a half billion years old for reference. This star, V1298 Tau, is 10 million years old, 12 million years old. It's hard to know exactly. But it has a bunch of planets that are the wrong size, if you will. They're like larger than sub-Neptunes, um, larger even than Neptune. They're kind of like sub-Saturn, they're like just below the size of Saturn, but they're close to the star. And it's very rare to find planets of that size. And the thinking is the same. When nature makes planets, it probably just makes them of all sizes, but the only ones that survive long enough to go into our population data sets are the ones that last over time. And ultimately, what's happening is we think that these planets are losing their atmospheres. My last project, the most fun one, was trying to see this similar type of uh helium escape, this atmospheric escape, in one of these really young sub-Saturn planets. And ultimately, it's in con it was inconclusive. Our results are inconclusive, and the problem is that the signal that we're looking for is has to do with the planet's atmosphere, but the stars themselves are super noisy. A young star is doing all sorts of crazy things. And when you look at the system, it's hard to tell is the star behaving weirdly? Is it a high activity star, or is this a planet atmosphere? And ultimately, it was just inconclusive. The evidence wasn't strong enough for us to rule out um activity from the star. But I think the idea holds. And it's like you just you just have to be, you know, you have to be a little bit more clever in determining how you can account for the behavior of the star. But so although we didn't get the result that we wanted, we still learned something, these additional observations that can kind of help you determine what the activity bounds for the star are. It's one thing to say, well, the star is really active. It's another thing to say, ah, is the star more or less active now and how wide is that range? And then over enough time, it's possible to try and account for that and then make these same observations. But it may be the case that looking for helium the way that we did just won't work for these super young planets. Overall, my dissertation was about trying to find evidence in many different ways for the evolution of these planets' atmospheres, these close-in exoplanets. And one way that I did it was by looking at a massive hot Jupiter that's really old and seeing that active mass loss. Another way is getting the masses of these older sub-Neptune planets and then trying to fit them, see where they fit in, in what models would expect the planets of this certain size to be, given the fact that they were orbiting a star for however many billion years. So it's kind of a different an indirect way of trying to measure the same sort of mass loss. Like, are these planets the right size that we expect that they should be if they evolved in the way that we think that they do? And then the last project was trying to get that real-time active mass loss, but in a really young system. And it was by far the hardest one to do technically. Like, just technically, the signal that you're looking for is messier in a system like that because young stars are crazy active. I had a bunch of other projects, those are the ones that are included in my dissertation, but I had a bunch of other like co-authored projects that I worked on. My the one that I thought was coolest was I made observations of this supernova. So I've talked about supernovas already a couple times, and we made observations of the supernova, which just happens randomly. Like you can't, when I want to observe a planet, I schedule it. I like propose for it because I gotta look at the right time. You know, the planet doesn't pass when you want it to, it passes when it passes. So you gotta try to schedule that. But somebody who studies supernovas, you can't schedule a supernova. It just happens. Somewhere a star blows up and it gets so bright that we can tell that it's happening. And it just happened to be that the night that I was on the telescope doing some observations, there was a supernova, and this other group had what's called takeover time. They get to take over the telescope, and you know, the people that are using it are supposed to get their observations for them, which is very cool. So we I got to like collaborate with them and got my name on that paper. And that's the only supernova work that I've done, but that was awesome. So they were doing polarimetry, they're basically like trying to understand magnetic activity of the region around this supernova that happened in a distant, distant galaxy. Very cool. So I think that's about it. Hopefully that made sense, and I wasn't um throwing too many jargony terms out there, but the idea is that planets evolve, and what we can say, what we can predict about where to look, what we can conclude about life in the universe, about astrobiology, right? The places to look for it, the places to not waste our time looking. It it depends on our understanding of activity on planets. And one of those phenomena is the evolution of the planet's atmosphere. Does the atmosphere start off with something Earth-like and then evolve into this greenhouse hellscape effect, like on Venus, where you know the surface temperature is hot enough to melt lead? Does it evolve in sort of the opposite way instead of on Venus, where the atmosphere is 90 times as thick as the Earth? On Mars, it's only 1% the Earth's atmosphere. It's important. It's important to know how these atmospheres are evolving. And that is one of the knowledge boundaries that we're currently at. How do these planets evolve over time? Very cool. That's my dissertation. Check it out. If something didn't make sense, you leave a comment or whatever, and maybe I'll try to uh clear it up. Very, very cool stuff. This is my favorite book. I think I'm gonna order like 30 more of these and fill out my uh one of my rows on my bookshelf with it. That's it for Dr. Star Kid this time. As always, lead with curiosity.