Here’s a familiar question: how’s the weather? We’re familiar with the weather on Earth and telescopes and missions are watching the weather on other planets in the Solar System. But for the first time in history, astronomers can now answer that question for exoplanets, located light-years away from us.
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Transcript
Fraser Cain:
Astronomy Cast Episode 722, Weather on Exoplanets. Welcome to Astronomy Cast, our weekly fact-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Sciences, and the director of CosmoQuest. Hey, Pam, how are you doing?
Dr. Pamela L. Gay:
I am doing well. And it is time for our regular reminder that if you want an ad-free version of this show, go to Patreon. Patreon.com/astronomycast, and we give everything usually a day early act usually, and ad-free to all of our patrons.
Fraser Cain:
But that’s not all.
Dr. Pamela L. Gay:
That is not all.
Fraser Cain:
You also get Office Hours with Pamela.
Dr. Pamela L. Gay:
You get Office Hours, you get first notification of stuff that’s going on, unless I’m on The Walk with Twitter. Sorry, then you might get it first on Twitter.
Fraser Cain:
We gratefully mispronounce your name in our podcast.
Dr. Pamela L. Gay:
I’m so sorry. So, $10.00 and up if you would like me to attempt to actually pronounce it, and usually fail to pronounce your name. Yeah, there’s all sorts of benefits. They’re all listed out. It’s Patreon.com/astronomycast no-ads version –
Fraser Cain:
Right.
Dr. Pamela L. Gay:
– of the show.
Fraser Cain:
And then, if you want to support either of us directly, for Pamela, it’s Cosmo Quest, Patreon.com/cosmoquest. And –
Dr. Pamela L. Gay:
X – add an X.
Fraser Cain:
– cosmoquestX, yeah. And for me, it’s Universe Today. So, Patreon.com/universetoday. And that way, you’ll be supporting Astronomy Cast, if that’ what you like. If you like the podcast that I do, if you like all of the cool work that’s being done over at Cosmo Quest, there are ways to support all of the work that we do. Because, as we talked about, we don’t take salary. All the funds that come into Astronomy Cast just go to pay for Astronomy Cast. So, all right. So, here is a familiar question. How’s the weather? Now, we are familiar with the weather on earth, and telescopes and missions are watching the weather on other planets in the solar system.
But for the first time in history, astronomers can now answer that question for exoplanets located light years away from us. So, how’s the weather for you, Pamela?
Dr. Pamela L. Gay:
Oh, it is summer, which means it is currently absolutely glorious.
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
Blue skies, and of course there will be thunderstorms with a chance of tornadoes at any moment.
Fraser Cain:
And for us, we’re having what we call “Juneuary”, which is when we have a very cold, very wet –
Dr. Pamela L. Gay:
Oh.
Fraser Cain:
– late spring. And it just rains and rains when it should be sunny. So, these are the kinds of weather variations that we’re familiar with. But it blows my mind that we are now starting to learn about weather on exoplanets. And they are not anything like what we are familiar with here on Earth. So, give me a sense, pick one of the planets that has weather, and give me a weather forecast for one of these.
Dr. Pamela L. Gay:
So, I think the most recently discovered fascinating new world is WASP-43 b. It wasn’t discovered recently, but what was realized recently, thanks to JWST data is that if you look at a line between the star and the planet, and then you look to see where the hottest point on the planet is located, it’s actually east of that line, which tells us that there are massive winds on this world that are moving that heat so that the hottest point is offset.
Fraser Cain:
Wow.
Dr. Pamela L. Gay:
They’ve been able to find water vapor in the atmosphere of the planet. They assume that there are clouds on the night side and not the day side. And they’re figuring that there is wind that is moving at thousands of kilometers per hour because there is no nothing in the atmosphere.
Fraser Cain:
Correct.
Dr. Pamela L. Gay:
Which means that the atmosphere is moving too fast for methane to have time to form on the cool side of the planet, the night side of the planet.
Fraser Cain:
So, imagine that, right? You are standing on the surface of this planet, which you can’t because it is a –
Dr. Pamela L. Gay:
Right.
Fraser Cain:
– Jupiter-type world. But let’s imagine that you could somehow hover in the atmosphere of this planet. You would have essentially clear skies above you. And then, winds that are thousands of kilometers per hour. You would be baked in eternal sunlight –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– incredibly hot. But also, kind of steamy because it’s the high quantity of water vapor in the air. And then, you’ve got these just intense winds that are blasting away from the day side over to the night side. Crazy.
Dr. Pamela L. Gay:
And this is directly observed because –
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
– this is a transiting exoplanet that goes into eclipse behind its planet and – behind it’s star, rather. And as it goes around, we are able to see differences in the temperature of the world that allow us to, as it’s about to eclipse, we know we’re seeing mostly daytime. We can see what that appears like when it is transiting in front of its star. We are seeing the night side of it. And by looking at the variations as the world goes round and round, we are able to piece together the differences in the world in different locations.
Fraser Cain:
And you mentioned this lack of methane.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
I mean, these are very precise, I mean, we already know that JWST is making these really precise measurements of these atmospheres of these exoplanets with very strong lines that scream, in the spectroscopic data –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– there is carbon dioxide here. There is carbon monoxide. There is water vapor. There is sulfur dioxide, all of these amazing chemicals –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– that are being found in the atmospheres of all of these different worlds. But that’s not enough that they can actually make these observations so that they can see these indications of what the weather is doing, the speeds of the wind, places where things are clear, places where things are cloudy. It’s pretty amazing. And would you say this is almost entirely thanks to JWST?
Dr. Pamela L. Gay:
Well, so, we’ve been trying to do this for a long time. And JWST isn’t the only thing that has been able to measure characteristics of exo atmospheres. It is simply the most precise. Preparing for this particular Astronomy Cast was a lesson in how many papers have been retracted over the years. There was one poor world where Gliese 1132 b. And they kept making claims of, they saw this. And then, it was retracted. They saw this, and then it was retracted. Because people are trying so hard, but they were dealing with just barely visible lines that kept not being reproducible.
And so, we don’t know for certain were the early observations just completely seeing noise? Was it seeing something else? Or was it that there’s transitory phenomenon? And we can’t know with that data. We need more JWST data. And JWST can only do so much, so fast.
Fraser Cain:
Right. So, this example that you gave, you picked one at random, the most recent one –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– with tidally locked, Jupiter-type world, hot Jupiter, clear skies on the sunward side, probably cloudy skies on the far side. This is just one example. So, can you give me another example of an exoplanet –
Dr. Pamela L. Gay:
Oh.
Fraser Cain:
– where we are looking at the weather on it?
Dr. Pamela L. Gay:
So, in some cases, it’s not that we’re even directly able to see the weather. It’s the computer models are able to tell us what the weather is. Lava worlds are my favorite. Of course, they’re my favorite. And so, we have found a number of worlds that are tidally locked, and on their day side are so hot that you have rock turned molten. And what they’re imagining is happening is crustal material is vaporizing. And as it gets pushed by the tremendous winds of these tidally locked worlds, around the night side of the world, it is condensing out of the atmosphere and essentially raining down. So, you only get an atmosphere really on the day side of the planet. And then, it races around and falls out.
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
Races around and falls up. And I just love this concept. And the idea of having really weird stuff that doesn’t belong, according to our human imaginations and atmospheres, like the surface of your planet, is proven out observationally in other places. My favorite planet is KELT-9b because it is hotter than any planet has any right to be, and is located where no planet was expected to be. It is snuggled up next to an extremely hot star. It has iron and titanium in its atmosphere.
Fraser Cain:
Clouds of iron and titanium.
Dr. Pamela L. Gay:
Yes, it’s not even clouds. Everything is thoroughly mixed. So, it’s like the nitrogen, and carbon monoxide, and dioxide, and oxygen in our atmosphere is just everywhere. This world’s atmosphere contains titanium and iron.
Fraser Cain:
Right, right. That is so metal.
Dr. Pamela L. Gay:
Oh, richly, richly.
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
I love it. So, so, this world has an atmosphere at 37,000 degrees Celsius. And – and that is a lot. It’s just a lot.
Fraser Cain:
Yeah, that’s hot.
Dr. Pamela L. Gay:
It’s a lot.
Fraser Cain:
Yeah, that’s hot. And so, I mean, is this the trend right now? I mean, this capability has just come online with JWST –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– able to image, get enough data about these exoplanets that it’s able to start making these kinds of discoveries. But when I think about the first planets that were found, right? We found those hot Jupiters. Apart from the pulsar planets – I always have to give that disclaimer.
Dr. Pamela L. Gay:
Yeah, I know, I know.
Fraser Cain:
The hot Jupiters. So, the hot Jupiters were found, and they are extreme. We don’t have any hot Jupiters here in the solar system. And in fact, these things aren’t very common. But they’re easy to find.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
So, is it the same thing that the kinds of atmospheres that we are observing today are the ones that are easy to observe, as opposed to the ones that are more likely?
Dr. Pamela L. Gay:
Yeah. So, the two types of things that we’re seeing are these hot Jupiters snuggled up right next to their star, that are eclipsing their stars. They are transiting. That’s what we’re looking at right now, is transiting systems. And then, the other systems that we’re looking at are with the extremely cool stars, just because planets stand out so much better next to these extremely cool stars. But the cool ones just seem to be tied to the hotter star, not the cool temperature-wise.
Fraser Cain:
But the awesome ones that –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
The metal ones.
Fraser Cain:
The metal ones, yeah.
Dr. Pamela L. Gay:
Seem – yeah.
Fraser Cain:
Literally and figuratively, right?
Dr. Pamela L. Gay:
Right. So, I don’t know, we’re currently at an early point and a lot of this being done where it’s what is most able to be looked at. That’s the stuff that JWST is going to give them a form. Let’s get in. Let’s get out. Let’s prove it can be done. And then, we’ll go back later for more tedious things when time isn’t quite as competitive. And in terms of that looking at these kinds of things, we’re able to see super weird objects. So, there was WASP-193b that came out a couple weeks ago. And because it’s JWST, a lot of what we’re talking about is recent weeks, recent months. KELT-9b is an older HST discovery.
And WASP-193B is a hydrogen and helium world that is bloated up by the heat from its star to be the density of cotton candy.
Fraser Cain:
Right.
Dr. Pamela L. Gay:
And so, we’re just finding weird stuff. And we’re not yet at the point of knowing what is the normal stuff.
Fraser Cain:
Right. And one of the things that people are waiting for to hear is, for example, how we detected an atmosphere on any of the TRAPPIST worlds. And so far, the answer is, no. One and two have – B and C, which are the first, the two inner planets. They have no atmosphere. They’re like super Mercuries. But now, we move into the ones that are in the habitable zone, and we haven’t heard any results yet.
And look, I’ve been doing a ton of interviews with people about this. And there is a group of exoplanetary scientists that think we’re not gonna find anything, that these red dwarf stars are so awful, so flarey, that they blast away their atmospheres. But then, other people who have done calculations say, no, you still can get an atmosphere –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– even if you’re getting direct flares. It might not be very thick, but it will still – should stick around as long as you’re far enough away from the star. So, do we have any indication of what these more earthlike worlds are like weatherwise around these red dwarf stars?
Dr. Pamela L. Gay:
So, the closest we found right now to something that we think could have an atmosphere but it’s not yet confirmed is Gliese-12b. It orbits its host star every 12.8 days and it’s about the same size as Venus, a little bit smaller than Earth. It has an observed temperature of just over 40 Celsius, just over 100 degrees Fahrenheit. And this makes it one of the lower temperature worlds that’s been found that’s rocky so far. And we just don’t have enough data to say if it has an atmosphere.
So, it is the one that is being looked at the most because the temperature that we’re seeing, given the temperature of the star, indicates that either there is a Venus-like atmosphere with greenhouse gases, or there’s something weird going on. So, while greenhouse gas worlds brought up to water is it’s triple point kinds of temperatures, is super exciting, we don’t have confirmation in the data yet.
Fraser Cain:
Yeah, yeah. So, I mean, this is one of those examples of a podcast where we’re recording at a certain time in history, in the history of humanity.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
And what we can talk about today are hot Jupiters with winds blowing at thousands of kilometers per hour around extreme planets, where some constituent of the clouds in the atmosphere is sand or metal.
Dr. Pamela L. Gay:
The sand ones are amazing.
Fraser Cain:
Yeah, yeah. So, that was another one where you’ve got –
Dr. Pamela L. Gay:
107 B, it’s thought to have, it’s the fluffy one –
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
– that has silicate clouds.
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
So, density of cotton candy, super fluffy silicate clouds, water vapor, sulfur dioxide –
Fraser Cain:
Yeah, clouds made of sand. That’s bonkers.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
Imagine trying to fly through a place like that.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
That just seems like a science fiction world. You can imagine some Star Wars show where they’re flying down through the atmosphere where the clouds are made of sand.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
And it’s funny because right now, we don’t have a definitive answer on this. And yet, because everything that’s been seen is in the extreme. And yet, the observations are being attempted right now. Somewhere out there, somebody knows the answer to the question, did GWST find an atmosphere at TRAPPIST 1E, right? We don’t know the answer, or D – we don’t know the answer. But that answer is in the data somewhere because the data have been taken. But it is a very funny time and because we are really just at the very limits.
And yet, the only kind of planets that we can actually see are these earth-size worlds orbiting within the habitable zone of a red dwarf star, which is not sun-like. And we talked about the level of the flares. But then, even just these worlds are tidally locked to their star. And –
Dr. Pamela L. Gay:
But what’s amazing is to think of what’s been discovered over the course of us starting this podcast. We started in 2006, which was about 10 years after the ’95 discovery of 51 Peg. And when we were first discussing the discovery of planets, it was primarily in the form of looking for the gravitational tugs to and fro in Spectra, just hoping to see the wiggle wobble of little worlds. And that’s still happening. But now, the primary way that we’re finding worlds is through all of these transit methods. We were there for the entire Keppler journey.
We’re now here as first Hubble was measuring atmospheres, and now GRWST is measuring atmospheres. This is a topic we’re gonna just have to keep redoing every few years –
Fraser Cain:
Yes.
Dr. Pamela L. Gay:
– as our show grows with the growth of this entire field of study and it’s just an amazing journey. And we get to share as we become old people still podcasting.
Fraser Cain:
Right. Now, one question that people always ask me is, well, could you have a planet that is tidally locked actually be habitable. And I think the traditional idea is okay, yeah, the sun side is gonna be scorching hot. The far side is gonna be in shadow and be incredibly cold. You’re gonna get these winds that are going from the hot side to the cold side. And really, both sides are gonna be not habitable. Maybe you’re gonna have this terminator area. But in fact, if you have enough water vapor, then you actually can have a reasonable temperature on the sun-facing side.
Dr. Pamela L. Gay:
It’s gonna be geology-driven.
Fraser Cain:
Yeah, yeah.
Dr. Pamela L. Gay:
You’re gonna need to have the right-shaped landscape. And if the landscape gives you that protection –
Fraser Cain:
Yes.
Dr. Pamela L. Gay:
– all things are possible.
Fraser Cain:
And all we have as examples are Venus, where we see one version of this, where –
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
– geology interacts with the atmosphere, and what do you get? And then, we have Mars. But Mars isn’t a great example because Mars is too small. And so, we have two earth-size worlds in the solar system that we can compare their weather.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
And so, we just don’t know. And this is kind of exciting. What are some tools that are coming in the future that might give us a sense of – to finally let us –
Dr. Pamela L. Gay:
You’re asking me about the future, Fraser. You know better.
Fraser Cain:
Oh, right, right, right. Don’t even answer. It doesn’t exist to you. So, I can’t even mention the arial telescope launching in 2028.
Dr. Pamela L. Gay:
You know the answers to this.
Fraser Cain:
Yeah, that’s all I think about, yeah. So, ARIEL is gonna be launching in 2028. It’s only job is to characterize the atmosphere of some exoplanets. So, it’s gonna take known exoplanets and really try to pin down what are their atmospheres. We’ve got the extremely large telescope probably coming online in 2027 – 2028. So, we’re just a couple years from that. And in theory, it should be able to distinguish earth-sized worlds orbiting around sunlike stars. And it will potentially be able to detect the atmosphere. And that’s a ground-based telescope.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
Web can do this. But it needs more time, and it’s a busy, busy telescope.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
And then, we’ve got the habitable worlds observatory, which is coming online in the 2040s. And its job is to observe the atmosphere of earth-sized worlds orbiting around sunlike stars. And maybe that’s what it’s gonna take for us to get this answer about whether or not there are other earths out there, and even potentially detect the presence of biosignatures in other atmospheres. But that’s a whole other conversation.
Dr. Pamela L. Gay:
And I just love what the modelers are doing. So, while any world near a star is going to probably end up getting itself tidally locked, moons, unless they are locked into a Lagrange Point, are still going to have the chance to orbit. So, you get a multiple Jupiter sized planet tidally locked snuggled up to its red dwarf star, and a moon going around. What is going to be possible when the moons can easily be the size of Mars?
Fraser Cain:
Right. And so, the moon might be tidally locked to the planet, but from the perspective of the star, it’s not tidally locked.
Dr. Pamela L. Gay:
Exactly.
Fraser Cain:
And so, it does experience [inaudible – crosstalk] [00:22:53]. Yeah, yeah. Again, I know I’m sort of saying the same thing over and over again. But it’s so exciting to be at this moment, at the beginning of what could end up – the end of this journey is the answer to possibly the most profound question that humanity has ever asked, is are we alone in the universe.
Dr. Pamela L. Gay:
Yeah.
Fraser Cain:
If we get good at studying the atmosphere of exoplanets, we may come to that point where we have detected the presence of the chemicals of life in the atmosphere of one of the other worlds, and we will have a definitive answer to that question. And even if we keep observing worlds and we don’t find an answer, that’s as interesting as if we do. It’s the whole Arthur C. Clarke, right? Either we’re alone in the universe, or we’re not. And either possibility is equally terrifying.
Dr. Pamela L. Gay:
I think that’s the correct phrasing.
Fraser Cain:
Yes, yeah. So, I guess, if you were to synthesize our understanding of exoplanet weather today, from sort of the knowledge and the discoveries that have been made so far, what can we say?
Dr. Pamela L. Gay:
That water vapor is something that we are capable of finding. So, planets tend to have water, if they can have water. That real worlds are far weirder than what our imagination had previously expected.
Fraser Cain:
Yeah.
Dr. Pamela L. Gay:
We are finding planets anywhere and everywhere. So, expect the universe to be more creative than we are, and learn to be surprised and not surprised at the same time with each of these amazing new discoveries.
Fraser Cain:
Yeah, a lot of those things we’re hoping to see, clouds, wind, they are all there.
Dr. Pamela L. Gay:
Yeah, yeah.
Fraser Cain:
Various chemicals in the atmospheres that go along with these, carbon dioxide, carbon monoxide, sulfur dioxide, methane, and yet, they are so alien, which is amazing.
Dr. Pamela L. Gay:
And just keep waiting, keep voting for more money for science because honestly, that is going to be the greatest slowdown in our rapid fire discovery of what’s going on out there, is just not enough people funded to take advantage of the amazing technology that we’re now capable of developing. So, if you want to see more of this, fund science.
Fraser Cain:
All right. Thanks, Pamela.