#20: Finding exoplanets at the racetrack
TRANSCRIPT
Moiya McTier
Hello, and welcome to pale blue pod the astronomy podcast for people who are overwhelmed by the universe but want to be its friend.
Corinne Caputo
Uh huh. And that's definitely me. And I am Corinne Caputo, writer, comedian, and friend to the universe for sure. This is a big week in gossip world, although I'm dating myself now, because Moiya, do you watch any of Bravo's reality shows.
Moiya McTier
I do not
Corinne Caputo
No. But there's a lot of gossip going on.
Moiya McTier
Not because of my age.
Corinne Caputo
No, no, no, no, but I'm saying this episode is going to come out in a few weeks. So like, I'm thrilled to be existing in the universe right now because there's some good juicy gossip going on. And hopefully by the time this airs, there will be even more.
Moiya McTier
Oh, interesting. Yes, the universe does like to provide good gossip for its best. I am another one of those best buds. Hi, I'm Dr. Moiya McTier. I'm an astrophysicist and a folklorist. And, yeah, the universe has thrown some juicy gossip my way mostly not not from Bravo. Just from love Island. Oh, I feel like the universe makes it dramatic. Just for me. Yeah, sure.
Corinne Caputo
Yeah, sure. I saw a I feel like I'm literally always talking about tick tock. But this is how I spend my evenings. I saw a Tick tock of a woman who was like announcing to her boss that she just got cast on love Island and it needs to take like six weeks off.
Moiya McTier
I always wonder how that conversation goes. Because there's someone on this season who's a teacher, he's like, a middle school teacher. What like first of all, how do you just just take off? I know it's it's not like it's summertime.
Corinne Caputo
Yeah,
Moiya McTier
they're just taking off to go be on love Island. Second of all, no way in hell would I ever respect a teacher again? If I saw them doing the shit they did on love Island?
Corinne Caputo
You're completely correct. It's just too weird.
Moiya McTier
Yeah like seeing your teacher make out with people. Seeing your teacher like flirt with people seeing your teacher get shot down by people. And it's just too much.
Corinne Caputo
Seeing Your teacher at the grocery store is strange enough like they exist in school and only in school. And in fact, they sleep there. So yeah, there's no
Moiya McTier
and they should always be wearing long pants. I don't want to see teachers knees, but I can see way more than just his knees.
Corinne Caputo
Yeah, you're seeing a whole lot.
Moiya McTier
A whole torso. That's too much.
Corinne Caputo
I feel like when you're a teacher and you got a reality show like you use that as like a way to be charming. You're like, Well, I'm a teacher, so I must be a good person.
Moiya McTier
Right you know I work with with the kids. They love Exactly. Anyway. Anyway, I love love island so much. But we are we're not talking about love island in today's episode.
Corinne Caputo
That's our other podcast.
Moiya McTier
Oh God, I wish. I do want to do an exolore episode about love Island actually.
Corinne Caputo
That's so fun.
Moiya McTier
That's the thing I have to do, but in the future. But today we are talking about exoplanets and how astronomers find them. But we are doing that at an f1 race track.
Corinne Caputo
Yes, we are
Moiya McTier
because Because planets go around stars. and cars go around this track I lead I thought it'd be an appropriate place to record this episode. So we're in the stands, it's between races right now. The last one was very exciting or at least as exciting as it can be to watch cars just go around, track them anytime. But people are drinking, people are screaming and people are having a really good time. And there's gonna be another race like the big the big race of the Day is coming up in about an hour.
Corinne Caputo
Perfect timing.
Moiya McTier
I know. Right. So let's let's talk about how we find exoplanets. I know that we have, I think probably in like five or so many episodes that we've done. I've said we're going to cover an exoplanet detection methods in a future episode this this is that episodes today. Today's the day we finally made it here. We survived. It is our 20th episode. This is a huge deal. And for our 20th episode, I figured we should talk about something that is very near and dear to my heart. I studied exoplanets in undergrad and grad school. It was a big chunk of my PhD dissertation. This is the stuff that I like when I close my eyes at night instead of counting sheep. I just I just like picture exoplanets. I just trust discovering more exoplanets. I love these things. So I want to tell you how we find them.
Corinne Caputo
I'm so excited to hear. I mean, you get so excited about so many topics, but I love the ones that are near to your heart.
Moiya McTier
You will have to keep me on track Corinne because I might just get too giddy.
Corinne Caputo
Okay,
Moiya McTier
about exoplanets. Please, please keep me on track. I want to start of course, as I do with many episodes with a bit of a history lesson. The first exoplanet ever was discovered in 1992. Though by that point, we had been thinking about exoplanets for actually hundreds of years, ancient humans were thinking about the potential for other planets out there. Scientists in like the Renaissance era and the whatever came after the Renaissance era. They were thinking about planets around other systems, they were starting to think about whether or not life was on the other planets in our solar system. So it was just a natural next step to start thinking about exoplanets. But we found one for the first time in 1992. It was two astronomers working together one Alexander Wolszczan. Yeah, it's it's WOLSZCZAN That's it. Wolszczan
Corinne Caputo
Wolszczan. Yeah, you know what? You said it right.
Moiya McTier
Thanks.
Corinne Caputo
I'm not even gonna try.
Moiya McTier
The other scientist involved was Dale frail.
Easiest name we've ever said on this podcast.
Corinne Caputo
So opposite.
Moiya McTier
I know. Dale frail and Alexander Wolszczan Were studying pulsars. Pulsars are neutron stars, which we talked about in the stellar types episode. Neutron stars are the extremely dense remnants of massive stars that aren't quite massive enough to make a black hole. But these are specifically neutron stars that emit radio waves at regular intervals. And so scientists started referring to them as pulses. And so because they pulse they're called pulsars.
Corinne Caputo
Nice.
Moiya McTier
We're so good at naming things. They were looking at the pulsar, I'm gonna say its name and be warned it is just a string of numbers and letters. PSR B 1257+12.
Corinne Caputo
Yeah,
Moiya McTier
which actually probably tells us the the coordinates the location of this pulsar. That's typically how these long stringy names get reduced. So they were looking at that pulsar, which is about 2300 light years away from our solar system. And the cool thing about pulsars is that their pulses, these radio wave emissions are so regular, that we can time things based on them. There are a rays of pulsars in space that we call pulsar timing arrays, and we use it to get even more precise timing measurements than we can with like atomic clocks here on Earth.
Corinne Caputo
Wow,
Moiya McTier
they are extremely regular. And so these two scientists were looking at this pulsar, and they noticed that the pulse became a regular every once in a while, which is weird because pulsars are so regular, but another level to that weirdness was that the irregularity in the pulse came back regularly. It was a regular irregularity.
Corinne Caputo
Oh, interesting.
Moiya McTier
So they were like something is happening to this pulsar or something is around this pulsar. That happens periodically that happens on a set frequency. And so because people had been thinking about planets, that was one of the things they tested. And what they found was that this pulsar indeed had two planets. The two planets were both a few times more massive than the earth. And after that, it was just like, that just opened the floodgates for for finding planets. So it was 1992. People were excited, but not super excited because it wasn't a normal star. It wasn't a main sequence star, it wasn't a star that was fusing hydrogen in its core. So the first time we found a planet around one of these normal main sequence type stars was in 1995, was the year I was born. So I like to say that I have never lived in a world that didn't know about exoplanets around main sequence stars. Well, I've never lived in a world that didn't know about exoplanets at all. But I just I love that I was born the same year, my field of research was born.
Corinne Caputo
That's very cute. Yeah, that's really I guess I was around for one year before the exoplanets were born. Wow. So old?
Moiya McTier
Well only on tik tok Corinne,
Corinne Caputo
only on tik tok,
Moiya McTier
Only on tik tok, and when you're texting your little sister,
Corinne Caputo
exactly.
Moiya McTier
So it was in 1995, that we found this first planet around a main sequence star, that main sequence star was called 51 pegasi, and it's a kind of Sun type star. It's just a little bit more massive than the Sun. And this planet was discovered by Didier Queloz and Michael Mayer, both of whom jointly won the Nobel Prize in Physics in 2019, for discovering the first main sequence type, exoplanet, the planet itself was a hot Jupiter. So it was about 70% the size of Jupiter though it was more massive, and it orbits the star every four days. It's extremely close to this star. It's almost grazing the surface of the star.
Corinne Caputo
Wow.
Moiya McTier
And they discovered this planet with the radial velocity method, which I covered a bit in the redshift episode, what we're going to talk about it again later in this episode. So after 1995, what commenced were a couple of decades of an intense era of exoplanet discovery, people just wanted to find as many exoplanets as we possibly could. And it was really hard for us at that point to characterize these exoplanets. Meaning it was hard for us to, like determine the physical properties of these exoplanets. But then we moved into the era of exoplanet characterization. And I basically started doing exoplanet research right around this time, when we were developing more methods and the telescopes were getting good enough to really start characterizing these exoplanets. So we could learn more about their atmospheres and their surfaces, and maybe even something about their internal processes. So now we are in the era of exoplanet characterization, and I think soon like we're these areas are overlapping. But we're like getting into a time when we have discovered enough exoplanets that we can now do cool population statistics studies on them. So as of today, when we're recording, it's March 6 2023. As of today, astronomers on Earth have confirmed the existence of 5272 exoplanets.
Corinne Caputo
Whoa, now, is that changing? Do you think that's going to change by the time this comes out? Or like, is it changing that frequently?
Moiya McTier
Yeah, well, yeah, I think that we will be a few off by the time this episode comes out on the 20th 27th. On the 27th. Or even more,
we'll be really off by then
no, it was a big deal when we crossed the 5000. Mark, because when I was in grad school, and I was giving talks about exoplanets, I would always say we found about 4000 exoplanets. And around the time that I graduated, we crossed the 5000 mark. And now it's like 300 planets later, we are finding new planets all the time. And there are also 1000s of exoplanet candidates that are waiting to be confirmed. Because you can't just look through a telescope, see something you think is a planet and be like, Yep, I haven't found a planet? No, there's a whole process.
Corinne Caputo
Yeah.
Moiya McTier
You have to discover that exoplanet. You have to do your due diligence as a scientist to make sure that it's not some other thing, then you have to confirm that planet by looking for it with another method, or at least with a different telescope, just to make sure it's not some like weird, funky thing that your telescope is doing. And then you have to write a paper about it and put it out into the community to be peer reviewed and potentially ridiculed if you're wrong, and other people discover that you're wrong. So there's this whole process to it. There are 1000s of candidates just waiting to be confirmed. Which is why I'm confident that by the time this comes out, there will be more exoplanet confirmation. That's so fun. So now we're gonna get into the different methods. There are a handful of them, most of them haven't actually found that many planets, but we're going to talk about most of the methods here today. Any questions before we get started with that?
Corinne Caputo
No, I'm just thrilled.
Moiya McTier
You're just you're just ready. Okay. So often when I am giving a talk about exoplanets, I don't want to just tell people how we find them. I like to do some crowd work, and ask people how they think we found exoplanets. And I'd say about 80% of the time, when I ask an audience, how do you think we find planets? Someone will say, take a picture of it.
Corinne Caputo
Yeah,
Moiya McTier
that is extremely difficult to do, but we have done it. This method is called direct imaging. And it is exactly what it sounds like. You take a telescope, you point it at a star, you do have to block the light of the star because it's too bright, and it will overpower any signal from a planet. But you can block the light of a star with an instrument called a coronagraph. I think we've talked about them before.
Corinne Caputo
Yeah.
Moiya McTier
Well, in the Eclipse episode,
Corinne Caputo
yes.
Moiya McTier
So you use a coronagraph. Like put it over the body of the star and block its light. And then you can see other more faint light sources like a planet. And this works best for planets like hot Jupiters really big planets that are kind of close to their stars, especially ones that are hot in and of themselves, because they will emit in the infrared. So they're actually emitting their own type of light. But we really have only found like 100 planets using this direct imaging method, because it's so difficult, you know, a star is going to be 1000s of times brighter than even the hottest, exoplanet.
Corinne Caputo
Yeah,
Moiya McTier
so it's really hard to do. But I'd say the first directly imaged exoplanet was discovered in 2004. And then confirmed a year later, because remember, there's this whole long confirmation process, and that that exoplanet was called 2M1207b. Of course, it was the first exoplanet that was directly imaged and the first exoplanet discovered orbiting a brown dwarf star. I don't think we've talked about brown dwarfs before.
Corinne Caputo
Yeah, show I don't think so.
Moiya McTier
But a brown dwarf, some people will call it a failed planet. But I don't I don't, or a failed star. But I don't like either of those. But it is something that is a ball of gas like a star. But it's not massive enough to do the typical hydrogen fusion in its core. It does a slightly different type of like helium fusion in its core. There's a whole research group in New York City that's based largely out of the Museum of Natural History in New York called bd NYC, brown dwarfs of New York City, they do really good work, they would not like it, if I call it a brown dwarf of failed stars. But brown dwarfs are like between the mass of Jupiter and a low mass star.
Corinne Caputo
Yeah, that makes sense. That is the way that I would have guessed, we do it. But obviously, there's more to it,
Moiya McTier
it's the most obvious it's the most straightforward. And the only reason we haven't found more planets using this method is because planets aren't bright. And when you're taking a picture of something, what you're doing is capturing light from that object. So if these planets aren't very bright, we're not going to be able to take a picture of them,
Corinne Caputo
right.
Moiya McTier
But luckily, there are a lot of other methods that we can use. The next one, the next one is my favorite method for finding exoplanets. And it's called transit photometry.
Corinne Caputo
I love this so much.
Moiya McTier
So transit photometry works. But let me let me break it down transit is when a planet passes in front of a star from our point of view. And the like geometry is really important with all of these observation methods, because there's no guarantee that a planet would be orbiting in the right plane around its star for it to pass between us and the star. Like it could just be off plane, right. So we have to get very lucky with the orientation of these planets, which means there are many planets that will never transit from our point of view, there are many planets that we could not discover using the transit photometry method.
Corinne Caputo
Interesting.
Moiya McTier
So a transiting planet really is its own category of planet, but it just has to do with how things happen to be oriented in space. So that's the transit part when a planet passes in front of a star. The photometry part tells you what type of information we're collecting photo metric, which means we are measuring the amount of light transit photometry method works by having it tell us gonna stare at a patch of sky and measure how much light you're getting from that patch of sky. And if you have pixels in your camera, then you can get really specific about light from individual stars in your field of view. If a planet transits or if it passes in front of the star, it will block some of that stars light. And when you graph this out, you see a beautiful curve that we call a transit light curve. And we can study that transit light curve to learn all kinds of things about the planet we can, depending on how often the curve happens, you know, like, if you observe the system long enough, you'll see multiple transits. And the time between transits is the length of that planet's year.
Corinne Caputo
Cool,
Moiya McTier
so you get the period of the planet. And because Kepler Johannes Kepler was kind enough to give us Kepler's Third Law, if you have the period of the planet, and you know how massive its host star is, you can calculate how far away the planet is from its host star.
Corinne Caputo
I love that I love when we use information to inform other information.
Moiya McTier
yes that's all of astronomy. So you can then calculate the distance from the star. If you know the distance from the star. And you know how bright and hot the star is, you can also calculate, like an average temperature, we call it the equilibrium temperature for a planet so you can get an idea of how hot or cold the planet might be. There are so many cool things you can learn you can learn the size of the planet from the transit because the depth of that curve is basically just like the fraction of the stars body of the stars surface that the planet is covering. It's just this is just like algebra and geometry. My I love that math that I learned as a seventh grader helped me get a PhD in astrophysics.
Corinne Caputo
Yes see it does come in handy.
Moiya McTier
It really does as long as I'm it does, even if you don't become an astrophysicist, the math that you learn in your algebra and geometry and trig classes, it's still all very useful.
Corinne Caputo
It really is
Moiya McTier
the first transiting exoplanet was seen in 1999. And it was another hot Jupiter, you'll you might notice this trend, but many of the planets we found first were hot Jupiters, because they're the easiest planets to see.
Corinne Caputo
Yeah,
Moiya McTier
they're the biggest ones. So they will block more starlight, they're the most massive ones. So they will tug on their stars more, and they're hot. So they're emitting their own infrared light, so we have a chance of taking an actual picture of them, which is why they dominated the exoplanet detection era for a few years. But it was 1999. This hot Jupiter is orbiting a star called HD 209458, which is a sunlight star about 150 light years away from us. The planet was originally detected with radial velocity, which is the next method we're going to talk about. But then it had to be confirmed and it was seen in transit by two separate teams. One of those teams was led by Greg Henry I know nothing about him. The other team was led by Dave Charbonneau who I was advised by in undergrad and there is somewhere I'm going to try to find it. He he was the professor in charge of my undergrad senior thesis class. So I had to turn my thesis into him. And I, I'm I was gonna say I suck but no, I'm fun. So I I printed out my thesis I had to hand in a physical copy. I printed out my thesis and wrapped it in a blanket like I was swaddling a baby. And then I made Dave Charbonneau who was like six foot five he like the towers over me. I used to get extremely intimidated talking to him because he has this habit of like he'll say something and then he'll stop talking.
Corinne Caputo
Yep.
Moiya McTier
And I felt like I should say something but I never knew what to say but like he's just one of those people. He has a very commanding presence
Corinne Caputo
Yeah.
Moiya McTier
So I made Dave Charbonneau one of the first people to ever detect a transiting exoplanet the six foot five intimidating man, I made him pose with me and my thesis baby, as if he was like a very proud grandpa
Corinne Caputo
as he should have been,
Moiya McTier
as he should be when. he was such a good sport about it. So yeah, Dave Charbonneau great guy, and he was one of the first to see a transiting exoplanet back in 1999. And now, the transit photometry method is by far the most successful method for detecting exoplanets. So I said that we've confirmed about 5300 exoplanets 5272 to be exact. 3945 of those confirmed planets were discovered using transit photometry cool, like most Yeah, definitely. Probably most of the planets have been found with transit photometry. And that is due in large part thanks to missions like Kepler and tests. So Kepler named after Johannes Kepler was launched in 2009. It's a space based telescope. For four years It stared at a single patch of sky and measured how much light we were getting from it. That's like called the Kepler field of view, you can look it up where it is. And then this really tragic thing happened to the Kepler space telescope, it had these four reaction wheels that would stabilize its position in space, so it can stare at that one patch of sky continuously. But in 2013, two of its reaction wheels broke. So it wasn't able to stabilize itself anymore. But the fucking geniuses who are in charge of the Kepler mission can you tell I love this, they figured out a way to use the two remaining reaction wheels, along with the solar wind pressure from the solar wind to kind of stabilize the Kepler spacecraft. So instead of looking at a single patch of sky, it would look at, I want to say 13 different patches of sky all along the ecliptic. The ecliptic is like the the plane of the Sun's apparent orbit around the Earth because it was using wind from the sun, like at its back to stabilize it. Like if that makes any sense. It's like the wind is at its back. And its two wheels are in the front, just like making sure that it's always facing away from from the sun.
Corinne Caputo
That's really fun.
Moiya McTier
It's so fun. It's so cute. And so Kepler had this second life as the k two mission, which was less stable. So you're like you're getting less data from all of these stars, but then gave us information about exoplanet populations in different parts of the sky, which was really cool. So I have used so much data from the Kepler spacecraft, and I love it so much. And I am I was really sad when it was officially decommissioned in 2018. But you know, it outlived its original planned lifespan, like you can make a movie out of this and make an epic movie out of the hard working determined Kepler spacecraft, breaking its reaction wheels, and then getting back up and continuing to look at space. Oh, I really love it. I get so really, I get so emotional thinking about Kepler, because I would not be the scientist that I am today, if I hadn't used Kepler data.
Corinne Caputo
Hi, it's Corinne. And I want to give a shout out as always, to our patrons who are supporting this podcast. It means so much to me and Moiya and everyone who helps make this show. We really appreciate your support. So thank you, as always to our sun like stars, Sharon Whelan, Finn, Ann Williams, and Megan moon. And you can support us here your name on this podcast and make it to our patrons star chart. All by supporting us on Patreon for just about $1 per episode, find the star chart, Patreon info and more at our website pale blue pod.com. Or by going right to patreon.com/pale blue pod.
Moiya McTier
The fact that you're listening to this show tells me a couple things about you. And I can recognize those patterns because I am a scientist and an analytical thinking genius. But here are the things I know. One, you're listening to an astronomy podcast. So you clearly like to learn but to you're listening to specifically this astronomy podcast, which means you'd like to learn in fun and friendly and interesting ways. So please, let me tell you about brilliant.org which is the best way to learn math and science interactively. Online. Brilliant has 1000s of lessons in math, science and data analysis, and they're adding new ones every single month. Brilliant doesn't just teach you facts and formulas, they actually help you develop your intuition for these subjects through interactive gameplay. So there's science courses can help you get a deeper understanding of things we talk about a lot on here, like planetary orbits with their classical mechanics lessons, or particle physics with their quantum objects course. Whatever you learn on brilliant, you'll have a fun time doing it. And it will strengthen your general analytical thinking skills, even outside of the specific topics that you're learning about in your lessons. So you as a pale blue pod listener can get a 30 day free trial by going to brilliant.org/pale blue pod and the first 200 People who sign up using our code will get 20% off their annual subscription. Again, that's brilliant.org/pale blue pod for a 30 day free trial. And then if you are early enough, if you're an early adopter, you will get At 20% off your annual subscription.
Corinne Caputo
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Moiya McTier
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Um, so that was that was one telescope that really made transit photometry. so successful. Another one that is more recent is called TESS. It's the Transiting Exoplanet satellite survey or Survey Satellite. And it is also using the transit photometry method to discover a lot of planets. But that's that's a cool, it's not looking at one patch of sky tests looks at the entire sky regularly, like it's over and over again, looking at taking pictures of the whole sky. So we can see how things change in the sky over time, which is really nice. This method, the transit photometry method is best for planets that are closer to their stars, because then it's easier for them to block.
Corinne Caputo
Sure,
Moiya McTier
right from our point of view. And the bigger the planet is, the easier it's going to be defined. Which is why when you look at a catalog of exoplanets, especially ones found with transit photometry, which most are you have to be really careful about making claims about exoplanet populations in general, because it's really easy to look at these catalogs of discovered planets and think that small planets aren't common.
Corinne Caputo
Sure, yeah.
Moiya McTier
But really, the small planets are just harder to find. And since one of the big missions one of the big goals for Kepler was to determine how common earth like planets around sun like stars are, you know, it's hard to find an Earth like planet, especially around the sun like star because we are so small compared to the sun.
Corinne Caputo
Yeah.
Moiya McTier
So you just have to be really careful about systematic biases in your telescopes and in your spacecraft. That was the the big theme of my third third year research project in grad school. Oh, beautiful stuff. Beautiful stuff. Do you have any questionS?
Corinne Caputo
I wish that I looked back on school with this kind of love. Oh, to
Moiya McTier
Oh to be fair, I also look back on grad school is the thing that made me go through multiple rounds of therapy, get several stress tattoos and create a crying nest under my desk. But I do love data.
Corinne Caputo
Yeah.
Moiya McTier
Academia makes the process fucking miserable. But I do love data.
Corinne Caputo
I love that.
Moiya McTier
Okay, goodbye transit photometry. It really truly is my favorite. On to radio velocity. So we have talked about radial velocity in the past. radial velocity is specifically the velocity of an object towards and away from us. So when we were talking in the redshift episode, about stars appearing to be red shifted or blue shifted. The redshift is when the star moves away from us along our line of sight. And the blue shift is when the star moves towards us along our line of sight. And we expect stars to be moving towards and away from us because they aren't static. Be beings, I mean, they are moving around the galaxy, like they're doing their own orbits. But also if you remove that motion from your data, you can see that stars still dance a tiny little bit around the center of mass of the star itself and any other bodies that might exist in its system. And most of those bodies are going to be planets. So essentially, the gravity of a planet will tug a little bit on the star and make it do a little dance. It'll make it wobble and in wobbling, it will move towards and away from us, which means that the light emitted by it if we capture that light and put it through a spectrograph, so that we can see the beautiful, usually absorption lines to see the molecules that are being absorbed by the star, you can measure how much those very precise absorption lines shift as the star is moving. And the distance that it shifts tells you the speed with which the star is moving radially and you can translate that speed that velocity into the mass of the planet that is tugging on it, because the more mass of the planet or I actually shouldn't say it's just about mass, it's also how close they are to each other. But the the stronger the gravitational pool, the faster the star will wobble.
Corinne Caputo
Oh, cool. Okay.
Moiya McTier
So that's that's essentially how the method works from that. So with with transit photometry you can learn the size of the planet like its its diameter. With radial velocity, you get a sense for the mass of the planet,
Corinne Caputo
okay
Moiya McTier
Because it's, it's due to its gravitational influence. So these, this method is best for massive planets that are very close to their stars, like a hot Jupiter, which is why the first planets discovered were done using radial velocity. And they were hot Jupiters
Corinne Caputo
Cool. Yeah, I was gonna I was wondering because it seems like transit photometry and rebuild velocity are great for these like, larger planets, but its radials more about mass and transit is about size?
Moiya McTier
mhm mhm
Corinne Caputo
Got it Got it
Moiya McTier
it is also much easier to see a small planet with the transit method than it is with a radial velocity method.
Corinne Caputo
Sure, yeah.
Moiya McTier
So of the roughly 5300 confirmed exoplanets about 1000 of them. Right now the the number is 1027 have been confirmed or detected with the radial velocity method. Cool.
Corinne Caputo
Cool Wow. A fifth?
Moiya McTier
Yeah, like a fifth. I know several people who work on radial velocity missions, you can do this with space and ground based telescopes. What you need is a telescope to collect light and a spectrograph or a spectrometer to pass the light through. So you can see those beautiful absorption and emission lines, but I have never used radial velocity data in my research.
Corinne Caputo
Okay, interesting.
Moiya McTier
I'm a kepler girl. A transit girly.
Corinne Caputo
Yeah, you stick with what you like.
Moiya McTier
Yes. So that's radial velocity, that has a kind of interesting, like, complementary companion. There's radial velocity, which is towards and away from you on the line of sight. But there's also astrometry, which is a motion. It sounds
Corinne Caputo
like astronomy, but like I've had a few drinks.
Moiya McTier
Yeah. If photometry is measuring how much light you get astrometry or like Astro metri is measuring the astronomy of stuff it is measuring the positions of celestial objects. We have actually only found two planets using this method
Corinne Caputo
two
Moiya McTier
but but we expect to find a lot more in the coming years. That is thanks to the Gaia spacecraft. So Gaia launched in 2013, the same year that Kepler's two wheels broke, rip, rest and so much power. So Gaia launched in 2013, and it studied the positions and motions like proper motions like motion around the galaxy of more than a billion stars. It gave us the most abundant and accurate map of the Milky Way galaxy that we had ever had before. I also used a lot of Gaia data in my research when I was trying to so Kepler told me about the relationship between planets and their host stars. Gaia told me about the relationship between stars and how they move in different parts of the galaxy. So Gaia launched in 2013. It has had three different data releases so far. And this is the way that telescopes often work, they don't just like observe, and then spit out a bunch of data and like never get used again, especially these space based survey mission telescopes because they're you can design a telescope to be used for for different purposes. But these mission based telescopes, they have a plan for what they're going to observe you can't request time on on Gaia, they have a plan, and they execute that plan. And at set intervals, they release different types of data. So the first data release had just like the positions and kind of honestly kind of shitty information about how those stars were moving with the second data release, it had been observing these stars longer so it had longer baselines and more precise measurements of their motion. And in dr three, which came out in June of 2022. So after I defended my PhD, which means I used Gaia DR2 for my research, but DR3 gave us more information about the chemistry of these stars actually. And information like their their temperature and their chemical composition. Gaia DR4 which won't come out until on their website, it says no sooner than 2025 or like the end of the end of 2025. So no sooner than 2026 Can we expect to see Gaia DR4 but it will have time series astrometry data, I made the distinction earlier I said that it measured the proper motions of stars like the motion of stars around the galaxy. If you can remove that motion from your data, then you can see that the very small scale motion that these stars have because of planets tugging on them. And so very similar to the radial velocity method, these planets will make these stars wobble but there'll be moving like up and down and left to right. And we can measure that motion to figure out the mass of the planet orbiting the star. But we won't be able to do this until like 2026 with Gaia data. But once that happens, they expect to find 10s of 1000s of exoplanets
Corinne Caputo
Oh,
Moiya McTier
using the astrometry method
Corinne Caputo
like opening the floodgates,
Moiya McTier
really, it really is. I tried to do a project in grad school to determine like how feasible it would be to find planets using astrometry. And it's just it's just really difficult. Yeah, until Gaia releases that. That's it.
Corinne Caputo
That sounds like me googling like when is succession coming back or something? And it's like no sooner than this date. Or like, Have you watched severance?
Moiya McTier
No, I haven't. Well, you gotta scary. No, it's not scary. No, it's dramatic.
Corinne Caputo
It's not scary, but it is kind of mysterious.
Moiya McTier
Oh I like mystery.
Corinne Caputo
Yeah it's not like Sherlock Holmes Z. But it is like what's going on in there? You know,
Moiya McTier
Noted. But yeah, it is it is very similar. And I think another similarity here, people I imagine have like watch parties when succession or sovereigns come back. Astronomers go fucking wild for the data.
Corinne Caputo
I'm like, is there some kind of like culminating event that to celebrate or is it like on the calendar and it's like, I can't hang out the day. Gaia. Four is dropping?
Moiya McTier
Yeah. yes yes yes to both. When Gaia DR2 was released, like 100 Different astronomers descended upon New York City. Because the Center for computational astrophysics, which is in the flat iron District of New York, had a Gaia DR2 hackathon where the the goal, the objective for the day was to have as many astronomers come as they want to download the date, like start as soon as as soon as it came out. And Gaia is a it's not NASA. It's the European Space Agency. So like we're working on European time. So as soon as the data gets released, dozens of astronomers in a room, download the data and just start doing science.
Corinne Caputo
Woah
Moiya McTier
they just start like, like, they have an idea for what they're interested in. They just they just start doing science. And then they do that for a whole day. And it's just like a, it's a party. To them. I went, this would have been my second or third year of grad school, I went to the CCA hackathon. And I hated it. I hated it so much, because I was surrounded by it. Let me back up a second. First of all, it's not as straightforward as it should be to just download data.
Corinne Caputo
Yeah,
Moiya McTier
you have to know a specific querying language like a specific type of coding syntax to request the data. So first of all, I like I couldn't do that. So right off the bat, I felt like an idiot failure.
Corinne Caputo
Yeah,
Moiya McTier
I had to get the data from a flash drive from one of my advisors and then everyone around you is doing their Science and announcing when they found something cool. So like every five minutes, someone who I have looked up to for my career or also just like a random visiting grad student be like, Oh, I found this. Oh, I found that. Oh, I saw that too. But here's something you should consider. And it's just that
Corinne Caputo
that is my nightmare. That is so overwhelming to me.
Moiya McTier
I left in tears. Yeah, like I I stayed until after lunch because the CCA has more money than they you gotta get the free lunch you get they have really good catered lunches, so I stayed until after lunch. And then I was like listening to people do that. I just I started crying. And I just left. Yeah,
Corinne Caputo
I'm really glad he left.
Moiya McTier
But I was I was then able to do my own science. Yeah. On my own time in my own room.
Corinne Caputo
Yeah, exactly.
Moiya McTier
That was good. That was good. But that's I imagine a similar thing happened with Gaia dar three. And it's definitely going to happen with Gaia. DR4 I would expect, you can mark your calendars in 2026. Whenever this fourth data release comes out, they're going to have another hackathon. And those fuckers are going to be finding so many exoplanets like right away. I know it I can just feel it in my bones.
Corinne Caputo
I think you might be right. I'm imagining a pale blue pod live that night and everybody comes and we like place people in the audience at random points jump up and yell a fact.
Moiya McTier
I might cry and leave like that might be too triggering.
Corinne Caputo
Too scary.
Moiya McTier
Too much. I would rather watch the ring then sit through another Gaia data release hackathon.
Corinne Caputo
Okay, I know we're doing data release for is next. Is that it? Okay, we're all watching the ring that we're all gonna self inflict some other trauma.
Moiya McTier
Because that will be less scary to me for sure. So that's astrometry, two planets for now. But give it a couple years, we're gonna we're gonna find a bunch. They're gonna catch up. And then I think the the next method that I want to talk about hasn't hasn't been super successful. We've only found almost 200 planets using this method, but it is called micro lensing. Gravitational lensing is something that people use to study like very distant galaxies. It is a consequence of one of the relativities probably general relativity. And it says that if you have a massive enough object, it will warp space time. And light instead of traveling in a straight line will bend around this very massive object.
Yeah,
so microlensing is that, but on a smaller scale, where imagine you have a system with a star and a planet orbiting it. But that system is way too far away for us to see, if we get extremely lucky, another star will happen to or maybe a small black hole will happen to pass between us and that system, and it will bend the light from that system, and like focus it towards our telescopes.
Oh cool,
which lets us see systems that are further away than we'd be able to detect with other methods. But the downside here is that it's really just a fluke occurrence. You know, we have no control over stars or black holes passing in front of these systems, and conveniently lensing their light towards us. So we we can't study these systems.
Corinne Caputo
Yeah.
Moiya McTier
Which makes the confirmation process a little tricky, but still still very cool. The telescope that will be very good at finding these microlensing. Exoplanets hasn't been built yet. It should be finished in in the next couple of years. It's called the Nancy Grace Roman telescope, named after Nancy Grace Roman, who was the first administrator or like, yeah, one of the first administrators of NASA.
Corinne Caputo
Oh, cool
Moiya McTier
and this telescope, formerly was known as lsst, the Large Synoptic Survey Telescope, but they changed its name because apparently you can change the names of some telescopes and you can change the names of other telescopes you can change you can change the name of a telescope from something that is completely innocuous like Large Synoptic Survey Telescope not offensive at all. To Nancy Grace Roman, great, I'm glad she she got that but when you have a telescope named after an actually offensive person, you cannot you can't change that name. No, no, no, no, no
Corinne Caputo
that one has to say we can't it's better to feel bad. Then.
Moiya McTier
Of course, I'm gonna I won't sub tweet I will tell you that I am talking about JWST, the just wonderful space telescope which is named after a homophobe from the who worked at NASA in the 1950s and was responsible for persecuting a lot of queer folks at NASA during the Lavender Scare. So yeah, fuck that guy. And let's stop calling with something even telescopes after I'm whatever. Yeah,
Corinne Caputo
it is very desert. pointing even if you Google it, it's like NASA refuses to change the name. You're like over and yeah, space is. I think one of the things that's so fun about it is that it's for everybody. And like, it's not. I don't know, we don't need to be mean or unkind or. Yeah, you get it.
Moiya McTier
We, we both get it. But it's nice to say it out loud.
Corinne Caputo
Yeah.
Moiya McTier
So the Nancy Grace Roman telescope expects to find a lot of these microlensing events because it is going to be looking at the whole sky. It's it's in Chile, I didn't go to the foundation of this telescope, back when it was lsst. But I did see it from afar. We were supposed to tour it, but there was a big storm so we could not drive up the mountain. So I saw it from afar. And it's going to be looking at the whole sky. And it's like, specially tuned to see these gravitational lensing events.
Corinne Caputo
That's very cool. That feels so specific. Isn't that amazing?
Moiya McTier
Oh, yeah. Well, I mean, that's, that's one of the things it's going to you, you do not build a multibillion dollar telescope unless you can do to do one. So yeah. Yeah, that's just one of its focuses. So those are, I'd say that like the biggest methods of detecting exoplanets, that's pretty that's pretty much all of them. There are some others, but they're not really worth mentioning. Because this this accounts for like all of the 5000
Corinne Caputo
Yeah.
Moiya McTier
If you would like to do your own deep dive into different exoplanets, and start doing some like cool statistics with it, maybe you can do that. Thanks to the NASA exoplanet archive,
Corinne Caputo
ooh.
Moiya McTier
This is a an online database operated by Caltech but they're under contract with NASA. Dr. Jesse Christiansen either started the NASA exoplanet archive or managed it for a long time. She's a lovely woman, she does cool exoplanet work. But the NASA exoplanet archive has data on all of the confirmed exoplanets, and many of the candidate exoplanets, and you can they make it pretty easy for someone without any coding experience to play around with the data. So without downloading anything onto your computer, you can go to the NASA exoplanet archive, and you can graph different properties of planets. So you can look at the relationship between planet size and planet mass. You can just like graph those, and they have information about the size, the mass, the distance from the star, the date discovered the discovery method information about the host star like you can do they have so much information.
Corinne Caputo
That's so cool.
Moiya McTier
So I would recommend just going to the NASA exoplanet archive site and playing around with it. If you have zero experience playing around with astronomical data, if you have zero experience like plotting any type of scientific data, it's a good introduction to it. I think because they make it really easy. There's absolutely no pressure and you get to learn about cool exoplanet populations.
Corinne Caputo
That's so fun. I love when it's open source.
Moiya McTier
Yes, this is another thing I love about exoplanets, the study of exoplanets, and one of the reasons I chose it in grad school, is because a lot of this data is publicly available. I was able to get through my PhD program relatively quickly, because I never had to request observations on a telescope and then like wait for them to be done and inevitably get clouded out with bad weather and like delayed and everything. I just went to Kepler's website and downloaded the data publicly available.
Corinne Caputo
That's the best feeling
Moiya McTier
Yeah, it really is. And so if that's something that you are interested in doing, either now or eventually, like a really good place to start is with the NASA exoplanet archive.
Corinne Caputo
I love it.
Moiya McTier
I'm a big fan. Any other any? What are your thoughts on on exoplanets in there and how we find them?
Corinne Caputo
Well I think most of my thoughts are in what they are like, what they're like and when how close they are to earth or not earth or things in our solar system. So I'm thrilled that we're actually finding them and I'm kind of shocked that they shouldn't be shocked by now that it's so recent. But I mean, there's so much clearly so many other things in astronomy that we are looking at and studying. It's not like this is on every the top of mind for everyone. But I love that we're doing it and I think it's amazing. I really like your favorite detection method to transit photometry I think that's so fun.
Moiya McTier
Well, it's because I get very happy about it
Corinne Caputo
But it's the one that I think makes a lot of sense to my brain. I don't know. It just it just fits.
Moiya McTier
It's a good intuitive one.
Corinne Caputo
I think that I'm sorry. I'm really excited that there are more coming all the time. I think that's really thrilling.
Moiya McTier
Yay.
Corinne Caputo
Yeah, I can see why you chose it. It's just seems to be like a field that's kind of ripe for new discovery and lots of information.
Moiya McTier
Yeagh it was the It feels like the Poppins subfield of astronomy when I was developing my persona as a researcher, and it was like one of the fastest growing sub fields, all of the young people in astronomy, that slight exaggeration, but like so many of the young people in astronomy were getting into exoplanets. Because it's a field where we know there's going to be a lot of work to do in the future.
Yeah,
you have like good career longevity.
Corinne Caputo
yes,
Moiya McTier
if you do exoplanets,
Corinne Caputo
that is how it feels to me to have like, this is just the beginning of this.
Moiya McTier
Yeah, it's so exciting. Well, I'm sure we are going to cover a lot of stuff. A lot of other things about exoplanets in the future.
Corinne Caputo
Yeah, I want to hear all about it
Moiya McTier
so much to cover. But yeah, that that will be something to talk about in the future. For now. You now you know, how we find the exoplanets. And I think that's pretty cool.
Corinne Caputo
I mean, that's the first step. And I think, Moiya, look at this, this is perfect timing. The race is about to begin.
Moiya McTier
They're about to go around the track like the planets going around the stars.
Corinne Caputo
Exactly. And they're all going to work together to replace the tires, which is something working together is done and astronomy to
Moiya McTier
so many parallels,
Corinne Caputo
so many parallels. Okay, so for everybody listening out there, just remember, you are space,
Moiya McTier
Yeah you are
pale blue pod was created by Moiya McTier and Corinne Caputo with help from the multitude productions team. Our theme music is by Evan Johnston and our cover art is by Shea McMullen. Our audio editing is handled by the incomparable Misha Stanton,
Corinne Caputo
stay in touch with us and the universe by following at pale blue pod on Twitter and Instagram. Or check out our website pale blue pod.com. We're a member of multitude and independent podcast collective and production studio. If you like pale blue pod you will love the other shows that live on our website at multitude dot productions.
Moiya McTier
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Corinne Caputo
Thanks for listening to pale blue pod. You'll hear us again next week. Bye.