Planetary Radio • May 01, 2019

The Skies of Super-Earths and Mini-Neptunes

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Hannah Wakeford

Giacconi Fellow for Space Telescope Science Institute

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

There appear to be more mini-Neptunes (also known as Super Earths) across our galaxy than any other type of planet. Hannah Wakeford wants to learn if some of them support life, and she’s doing this by exploring their skies. Curiosity, the Mars Science Laboratory rover, has reached an exciting and critical part of its mission of discovery. Senior editor Emily Lakdawalla provides an update. The beautiful Pasadena Public Library hosted Bruce Betts and Mat Kaplan for a special afternoon that included recording this week’s What’s Up.

GJ 1214b (artist's concept)
GJ 1214b (artist's concept) GJ 1214b is a "super-Earth" orbiting a small star located 40 light-years from our solar system. Observations suggest that its density is lower than that of Earth, so that it probably has a Ganymede-like composition (a metal and rock core overlain by a thick mantle of water in liquid or ice form). Unlike Ganymede, GJ 1214b is probably covered with a thick atmosphere of hydrogen and helium.Image: ESO / L. Calcada
Clear Skies on HAT-P-11b
Clear Skies on HAT-P-11b Scientists were excited to discover water vapor in the atmosphere of a relatively small planet, about the size of Neptune, using the combined power of NASA’s Hubble, Spitzer, and Kepler space telescopes. The planet, called HAT-P-11b, is probably gaseous with a rocky core, much like our own Neptune. Observing HAT-P-11b was the first time that astronomers were able to detect anything measurable in the atmosphere of a planet in this size range.Image: NASA/JPL-Caltech

This week's question:

What comet’s debris is responsible for the Eta Aquarid meteor shower?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, May 8th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

1036 Ganymed is the largest Near Earth Asteroid. What is the second largest NEA?


The answer will be revealed next week.

Answer to the April 17 space trivia contest question:

There was no space trivia contest question in our April 17 episode, so no answer this week!


NOTE: This automated transcript is currently being edited by a human. Check back soon for updates.

[00:00:00] The Skies of super-earths this week on Planetary Radio.

welcome. I'm Mat Kaplan of the Planetary Society with more of the Human Adventure across our solar system and beyond by super-earths were not talking about Superman's home planet of Krypton. You may prefer to call them many Neptune's as scientist hand awake for does and a great Planetary Report article.

I'll talk with her about these Skies including their clouds. This week's what's up segment with Bruce was recorded live at the beautiful Pasadena Public Library join us there near the end of the episode. We'll Begin by heading to Mars which has its own wispy clouds. Here's Planetary Society senior editor Emily Lakdawalla.

Welcome back Emily. It has been a while since we have talked about curiosity our Martian friend. How is she doing up there? The Rover's doing pretty well showing [00:01:00] some signs of age for sure, but still getting a lot of science done in a place on Mars that they've been trying to get to since they landed.

So the sides are pretty happy. Actually. Yeah happy team you make that report in your April 25 update new drill holes despite memory problems. How is the health of the spacecraft? There were some frustrating issues with the Rover's memory a few weeks back. You may recall that close to the beginning of the mission actually install 200.

The Rover had to switch from its main computer. It's a side computer to its vacuum computer its B-side computer because of a memory problem and things were fine on the B-side computer for a long time until there's a couple of memory issues on the B-side computer that they were having trouble figuring out so they swapped over to the a side computer again and turns out the ace I can.

Had some new memory problems. So they're back on be right now B's been working well for a while because they've partitioned off a part of the memory that was causing problems. [00:02:00] Probably. This is all just age-related. The Rover's getting science done. There is going to be more Souls Lost to various little problems like this, but they're still doing well.

So at least I have one thing in common with curiosity age-related memory problems. Let's talk about the science and and sightseeing the Rover is doing. You have as always some delightful images including collections of pebbles in in what you called are described as lag deposits. I've seen these many times here on Earth.

I should have known there was a name for them. Yeah. So these are it's an interesting landscape Curiosities in this topographic low named glentoran. It's on the opposite side of the hematite Ridge curiosity was aiming for this Ridge for a long time now named Vera Rubin Ray. They explored the ridge looked at all the Rocks there had a tough time drilling because who knew that a resistant Ridge would also be hard to drill into and now they're in the valley Beyond it which seems like the rocks for [00:03:00] reasons.

They don't yet know are weathering a little bit more easily and like sediment is blowing away. And what happens is that as the the fine sediment gets blown away. Then the Pebbles that whether it out of the Rocks get kind of concentrated on the top of the surface and so you have this kind of Sandy looking surface.

That's just. Bird with pebbles everywhere the eye can see but the Pebbles have different shapes from place to place in some places. They're remarkably round which is just cool. So it's been a really interesting place for curiosity to drive through. It's a great shot. There is one particular Pebble which appears to have been.

Well met like someone started to drill a hole through it and initially looks just like a green olive, but I've measured the scale and it's only about a millimeter across it's a little bit more. It's basically the situs of a seed bead if you've ever done any bead work in your life, and that's that's the size that it is is kind of crazy.

Then you've got a shot of some really beautiful outcroppings that curiosity is traveling among. Have we seen something like this [00:04:00] before? Well broadly, they look pretty similar to a lot of the Marie mudstones that Curiosity has been measuring ever since it arrived at Pahrump Hills, you know at the very base of Mount sharp, but they're weathering a little bit differently.

They have slightly different looking veins. They may have mud cracks in them. That indicated that this was a low stand of the lake or those could be features that just appeared while when The Rock was getting made. So it's all kind of new science right now. There isn't a lot of scientific interpretation available.

I think the thing that's that's really tough on curiosity is that these rocks are so old and so many different things have happened to them. It can be a little hard to figure out did they all start out the same and then they just experienced different groundwater and different, you know geology ever since they formed or do they actually reflect different environments when they first formed and that's a story that the scientists are still trying to figure out say something about this little to.

Sure animated gift that shows curiosity trying [00:05:00] to drill in into some of this surface and it doesn't exactly go as planned but it still looks fascinating. Yeah, that's really interesting. So curiosity drilled into this rock at a site called a burr lady. It looks like perfectly flat Bedrock. The drilling went really.

Well. It was so easy. In fact that Curiosity didn't need to use any percussion on its percussive drill. It only needed to use drill rotation in order to just peel right into it. But that may have been as it turns out because the rock wasn't very thick. It looks like when curiosity pulled the drill back up it lifted the whole Rock so it's not totally clear what it actually drilled into they did deliver a little bit of the sample to one of the analytical instruments, but they didn't want to put it into the the major like the Organics laboratory instruments am and so they decided to dump that sample out actually and try again nearby.

Nice to be in such good shape that you can actually be a little bit picky about what you what you want to analyze before we go. We got to look up [00:06:00] because it's also apparently Eclipse time. That's right Mars has two moons, of course Phobos and Deimos and the orbit exactly in the plane of the Equator, which means that twice a year when pretty close to when Mars goes through its equinoxes both of those moons Transit the Sun.

Quite frequently and so twice a Mars year curiosity looks up to see transits of Phobos and Deimos across the Sun and these are just super cool animations. They're useful for science because scientists use them use the exact time that the moon's cross the disk of the sun to help track very minutely the Motions of Phobos and Deimos in their orbits, but it's also they take them just because they're cool.

Yeah, I mean they they really look like the transits of Venus that we see from here. If you if you protect your eyes they really do what's next for the Rover more traveling around glentoran. The team is pretty much finished kind of a first Walkabout. They've driven down to the very lowest elevation in the valley and they've kind of scoped out the different kinds of rocks.

They have identified three main rock types and now they've drilled and one of them [00:07:00] so the next steps are. Start driving back toward the mountain and pick out two more drill sites in the other two rock types before they start climbing again. Wow. All right. That's the report 75 souls are Martian days all in this April 25 blog post from Emily our Planetary evangelist, and you'll find it at Planetary dot-org and we will add that more than what you've written here.

You've included more of those official mission updates from members of the Curiosity team, and they also make for great reading. So thanks Emily. Look forward to talking again soon. Thank you Matt. She is our senior editor and the editor. In Chief of the Planetary Report that you can read at Planetary dot-org another issue coming out before too long.

There appear to [00:08:00] be more many Neptune's across our galaxy than any other class of planets. That's in spite of the fact that our own solar system lacks even one might these worlds be hospitable places for life. That's just one of the questions though a very big one that Han awake furred wants to answer Hannah is the Gia Coney fellow at the Space Telescope Science Institute in Baltimore, Maryland, that's where she also develops models of even more exotic Skies those that are above hot Planetary Giants.

Think of Jupiter but much closer to the Sun but we started with those smaller planets that are much closer in size to our own Hannah week four heard. Welcome to Planetary Radio. Hello. Thank you for having me great pleasure to have you on the show and also to have enjoyed your article in the 2019 spring equinox issue of the Planetary Report.

You called it. The Skies of many Neptune's sniffing the air of other worlds to learn [00:09:00] how planets. Formed and evolved this seems to be an ongoing informal series of topics we're doing on the show are a topic and that is studying the atmospheres of other worlds. Obviously something that gives you enormous Fascination.

Yeah. It's a nice fascinating thing that we can do since the mid-90s many thousands of planets outside of our solar system have been discovered. And we want to learn more about them. We don't want to just know that they're there we want to know what their environments are. Like, what is the nature of these alien worlds?

Let's start at the most basic level, which do you prefer super-earths or mini Neptune's as you put in the the title of this piece. I'm a mini Neptune fan my work really in exoplanets. We planets that orbit Stars other than the sun is. Kind of rooted in the giant planets planets that are like Jupiter and Saturn in our solar system mostly made up [00:10:00] of hydrogen and helium and as you get smaller you head towards the Neptunes and the urine us' and those are kind of the start of the transition into this mini Neptune to super-earth regime so I'm really coming at it from the giant planet end and pushing down towards the small world.

So they really are kind of a hybrid or a transition between Rocky worlds like our own and the gas giants like like Saturn and Jupiter. That's exactly right these planets occupy that region of space we don't have in our solar system where you have rocky if size. Nas penis like whilst which are dominated by their Rocky cores and and outer regions and then a very small atmosphere and then you've got the giant planets like Uranus and Neptune which are dominated by this big envelope of hydrogen helium.

Most of the worlds that have been discovered outside of our solar system actually occupy this space in between. Some kind [00:11:00] of transition where you go from an earth-sized rocking world to a natural size gassy world, and we're trying to discover exactly where that transition happens. So it seems like a bit of a downer for our own planet to learn on Earth Day as we speak that it's a little bit below average in size.

But but that's alright. How do we now know that this category of In Between Worlds is so prominent across the. Well, we had the fortune of launching an amazing Mission into space called the Kepler space telescope. This was launched in 2009 by NASA what its job was. Let's look at a small patch of the sky study 1,500 different stars.

Look at them for 3 years solid and try and determine what planet were orbiting them. And we do that by using something called the transit method where you look for a [00:12:00] planet passing in front of its star. Which causes the light of the star to dim a little bit as that planet causes a shadow and we see this in our own solar system with the transit of Venus and even with the eclipse of the moon, which is just a very very large Transit.

So we're looking for these changes in the amount of Light which will indicate the size of the planet that is passing in front of it. And from the amount of light that's being blocked. We work out the size of the planet and Kepler found thousands of these worlds. It was actually more likely 50% more likely that a planet will be in this radius range between the Earth and Neptune then it would be larger than that June and in our solar system, that's really interesting because we've got four giant planets bigger than Neptune of four planets smaller than them to you know, what we're finding is that 50% of the worlds that are out there that we've discovered so far near to our star near region of our [00:13:00] galaxy.

In this region between those two and that's something we never thought we would find as you might imagine and as I'm sure it is on your own podcast the exoplanet podcast the Kepler spacecraft comes up a lot on this program because it is made such terrific discoveries there. Is that other way of discovering exoplanets that the Doppler method, but are we still discovering exoplanets using that other?

Yes, the Doppler method is fundamental in our discovery of exoplanets. It looks for slightly different types of exoplanets, but actually where it's incredibly important for these worlds that we're talking about is we have to use this Doppler method. To measure the mass of the planets with the transit method we get the radius we get the relative size of that planet relative to the size of its star.

So the amount of light blocked out is relative is the relative size of the planet to the star. The Doppler method [00:14:00] is needed to actually put a mask. To that planet to understand the actual density of the world is a combination of the radius and the mats. So if we don't use the Doppler method, we can't actually work out just the basic nature of these planets.

One of the great illustrations in your Planetary Report article is this graph that shows the distribution of all these different worlds including the ones in our own solar neighborhood where you plot diameter against Planetary Mass. There are some surprises here in what we've discovered yet.

There's always some surprises the right. It's it's the beauty of studying our universe Nature's. Shin is vast and we're learning just how to match it what we're seeing. If you look at this figure is you're seeing this trend as you increase your radius you increase your mass and then at some point your radius doesn't increase anymore, but your mass [00:15:00] can keep increasing and that's in that Jupiter Saturn range.

So as you get to the size of Jupiter the radius of Jupiter, which is 11 times the size of our Earth. You can increase the mass hundreds and hundreds of times in the size of that planet will stay relatively the same. So we're seeing these different types of planets and different densities of planets as well.

We're finding planets roughly the size of Neptune but weigh as much as Jupiter. Now Neptune is 17 times. The mass of the Earth and Jupiter is 300 times the mass of the Earth. So there's a huge difference in the densities you would have there. And in fact, if you look across the EXO Kai population with finding planets with densities of Styrofoam up to solid lead.

There's a huge diversity of Worlds out there that we're just trying to understand and explore a little bit more. Which is pretty exciting in itself. We'll talk some more about the the composition [00:16:00] of these worlds and in a moment or two, but I've have to bring up that I had no idea that the transit technique for detection of exoplanets was first suggested so long ago we talked about the first person to come up with this concept.

One of my favorite things to do is talk about the history of exoplanets discoveries. It's not a new thought. And through or planets outside of our solar system has been around since 450 BC with the Epicurean philosophy the ancient Greece, but it wasn't until the 1600s where After the Dark Ages in medieval Europe when Christian Huygens, who is a Dutch astronomer.

Postulated that we would be able to observe planets as they pass in front of the star and block out that light. Now the reason he came up with this is because he was studying the moons of Jupiter and he observed that the moons of Jupiter as they pass in front of you to block out a [00:17:00] small amount of Jupiter's light.

Now if you translate that out to the Stars, you should be able to find planets as we do now. However back in the 1650s when he came up with this idea. They had absolutely no idea how far away the stars were they had no way of being able to measure the distance to other stars and therefore how difficult this method is.

What we're doing when we're looking at these planets pass in front of their star is looking for a change by 1% 1% of the light is blocked out. That's roughly the equivalent of a small fly or mosquito passing in front of a Street Lamp. That is a mile away. It's a really small change in amount of light that we're measuring and if you don't know the distance to the star, you don't know the size of the staff and if you don't know the size of the star.

All that streetlamp. You don't know the size of the thing blocking out the light. So while it was postulated in The Sixteen hundreds, it wasn't until the mid 90s [00:18:00] 300 years later. That something happened now, of course with Kepler and with some ground-based observations as well. We have learned as we love to say on this program and across the Planetary society that we mean our fairly certain right that there are more planets in our galaxy than there are stars.

Yes. That's absolutely right. There is almost certainly more planets than there are stars and just think about that for a second how many. Billions and trillions of stars and galaxies that are in our universe and then think about how many planets there would then have to be it's a truly staggering and very difficult number concept to kind of really put something to staggering and yet I find it kind of comforting to know that we have all that company.

And of course you are. In the work that you do part of this Grand goal of [00:19:00] finding life elsewhere across that vast universe and even just our vast Galaxy and and to do that. It seems to make very good sense to be learning about. The are the atmospheres of these different worlds, which is really where your focus is, right exactly.

If we want to try and understand more about these planets. We have to look at their atmospheres. We have to look and understand what their atmospheres are made of how they're circulating around. What is their weather like weather is simply defined as the presence of atmosphere how it changes in time and space?

We need to try and understand just the fundamentals of what is making up that atmosphere so that we can move on and try and understand how it changes in time and space around the planet make them 3D objects rather than you know, 1D objects that are on the sky. So it's a really fundamental concept that we have to really understand the planets deeper [00:20:00] than just their size and their math.

To understand their potential for this life with the transiting technique if the planets passing in front of their star typically only reduce that stars the light the number of photons reaching Us by 1% the reduction of that light or the filtering of that light by that planet's atmosphere must be yet again a tiny percentage of.

Who started with for a large gas SeaWorld like Jupiter? We would be measuring roughly 1% on top of that one percent. Wow. I like to joke that we're measuring a point source on a point source on a point of that. That's great because it makes it sound just as ridiculous as it is and it really highlights how.

This measurement that we're making is for all of these worlds and we've got roughly I would [00:21:00] say right now about 300 planets give or take out of the roughly 4,000 in total that have been discovered that we can actually measure their atmospheres. So it's quite a small number of these worlds in Total that we were able to make this really difficult measurement for.

But we're getting better and we're learning as we go along and that's really the process that's been happening over the last decade. So that's really been the thing that the community is the characterization community that I work in is building up just an understanding of the techniques were using getting better and better and pushing the number of planets that we can study.

To larger numbers and a promise of much greater Improvement, but we'll get to that later in the conversation as well with what we have been able to do so far. Here's much to broader question. What are we finding in the air of these worlds? What we're finding is that there's a huge diversity out there.

If you look at all of the planets in our solar system every single one of them is unique. It's got its [00:22:00] own little differences little nuances. We're finding that in these worlds that we're discovering as well. But one of the fundamental things that we're currently looking for in these atmospheres is signatures of water vapor in their atmospheres now water vapor is not.

In any way related to biosignatures or evidence for life. It is a fundamental molecule in the universe. In fact, it's the third most abundant molecule in the entire universe. You can find it absolutely everywhere and we're really looking in these atmospheres to try and see this water vapor because that will tell us a little bit about the temperature of the atmosphere the Dynamics of the atmospheres and the just bulk.

Extent of those atmosphere how much atmosphere there is and that's really important as just a first principle. For looking at these worlds. What we're also looking for is evidence of different Atomic species and carbon-based species, but that's a little bit harder for us because we need the wavelength of coverage.

We need to be [00:23:00] looking in lots of different colors build up a spectrum of that atmosphere because each different molecule has its own unique fingerprint and we're looking for those individual fingerprints. So at the moment we're really focusing in on these. Signatures of water vapor what about Organics like methane, which is causing so much curiosity and and no pun intended about Mars the perhaps most likely representative in our own solar system for finding life other than what we know is Diggs is on our own world.

Are you talking about Organics like methane as this search goes on. We certainly are talking about Organics like methane. In fact, the search for methane has been there since the first transiting exoplanet was discovered in 2000, but. Thus far it's remained incredibly elusive where we thought we should be seeing signatures of methane.

We [00:24:00] haven't seen them. This is likely due to the way that heat is distributed around these planets the way that the heat is distributed will change the chemical makeup of the part of the atmosphere that we're looking at. So we're starting to try and understand that and to look for methane. You need to be looking at that cold world's now, I will Define.

My temperature structure here some of the worlds that we're looking at are in excess of 1000 Kelvin. Hmm. These planets are often anywhere between 1,000 and 2,500 or maybe 3,000 Kelvin. This is the equivalent of sitting under a rocket when it's taking off. It's just hot enough to melt lead. Like it's really hard to imagine.

It's really difficult to think of a planet existing in those temperature regime. Or of Life existing in those are like yeah, that's right that we've looked at so far what there's a handful that we're not so sure they have the potential to Harbor life. But the ones that we've really been [00:25:00] able to study in detail, they're not any nice place that you would want to go on on your travels.

Mmm. They're pretty hellish hot giant gassy worlds, and that's really where we're at in terms of the ability to characterize things right now. And we're really pushing it towards these more terrestrial World such as the Trappist one planets that you can see in the article in that diagram. These smaller world's just a much much more difficult and they sit around stars that are very different from our own star and that's because of the relative size of the planet to the star is really the fundamental measurement that were making so the smaller the star the smaller the planets that we can see and measure.

So we're talking about very different environments from our own and trying to understand the fundamentals of these worlds the Organics that we're talking about really exist at colder temperatures. They exist at temperatures below this 1000 Kelvin limit or in [00:26:00] equilibrium. If we think about how all of the chemicals balance out if they're all balanced in equilibrium, it should exist below this 1000 Kelvin temperature bar.

But we're looking at planets now in this temperature range in this colder temperature range where we should see it and the atmosphere should be big enough that we can measure that but we haven't found it yet. And this is really baffling us. Right now with what we're doing but in the future with new technologies that are coming online very very soon.

We should be able to solve this mystery. So more big surprises you'd already mentioned that our solar system. Perhaps sadly has none of these mini Neptune's for us to study is our own solar system proving in other ways to be a good model for what we find elsewhere are the answer in your article was kind of surprised.

Also systems a little tricky. It doesn't currently match much of what we're seeing out there [00:27:00] now. I want to make it very clear that what we're seeing out. There is biased towards the technologies that we're able to use to measure it. And right now we aren't able to measure a solar system like our own.

It's incredibly difficult for us with the technology. We currently had if we were sitting on another alien planet and looking at our solar system. We would perhaps see Jupiter and that's it. So it's very difficult to say fundamentally whether we are alone unique, but from the evidence that we have thus far.

There's nothing like our solar system that we're looking at and investigating right now and one of the things that. Been learning throughout my career is just how nuanced all of our understanding of Planet formation is and it's all been focused on trying to recreate our solar system. Hmm. And what we're finding is planets that are nothing like those in our solar system.

We're finding these jupiter-sized [00:28:00] world's sitting right next to their star these things called hot Jupiters, which are 20 times closer to their Stars than we are to the Sun but they're the size of Jupiter. None of these formation models that can create the service and can create those worlds. None of the solar system models are creating these super are for mini neptune-sized worlds because they're so.

They've got these little tuning Forks which allow them to create our solar system and we need to really broaden that again. We need to go back to basics and really pick them apart and go. Okay. What if we break it down in just to fundamentals take all of these little things that we've learned about our solar system about the fact that Jupiter formed and moved in and moved out again, which helped create Mars and the size that Mars is now.

How can we use all of those little things turn them off and see if we can create the diversity of Worlds that we're seeing out there and that to me is truly fascinating trying to link the things that we're measuring to our [00:29:00] understanding of the formation of Worlds. And that unfortunately is is even more difficult than measuring the atmosphere.

I can sense how anxious the audience is for us to get on to those new technologies there around the corner. But before we do that, you've already mentioned Trappist one that system of Worlds get such good press but you have some other favorite world's. I think it could you help us explore some of these.

Yeah take you up in the size range. They Trappist ones worlds are roughly the size of the Earth roughly the same density as the Earth. So they're Rocky. What we would call terrestrial like worlds as we move up in the mass range. We're heading towards the neptune-sized worlds. And there's this one world, which is really really fascinating.

It's called GJ free for 7 0 B. So we call it 3470 be and I like this one because it is a. Mini Neptune so it's got a [00:30:00] gassy envelope of hydrogen helium around it. But what we've done is we've used the Hubble Space Telescope to measure it in the UV and in the UV what we're what we have measured is that the atmosphere is being stripped from this planet.

It is being ripped away from this planet's atmosphere and it's lost a huge amount of its hydrogen helium envelope since it was born. So it possibly started out bigger than Neptune, but it's so close to its star that the star has ripped that atmosphere away and this leads me to another type of world right on that super F mini Neptune boundary.

It's called gj1214b and I talked a lot about this in the article. Do you do 1214b has been studied the most out of all of these super Earths with the Hubble Space Telescope and from the ground and from many [00:31:00] many famous ground-based telescopes like the VLT in Chile. This world appears to be completely shrouded in a thick dense cloud.

Now because of its temperature roughly 900 Kelvin or say this cloud has to be made of salt based materials. So potassium chloride or zinc sulfide or sodium sulfides. So it's made the clouds in this atmosphere are made of very alien material that we have is rocks here on Earth. So think of rock salt and then turn that into a liquid Cloud droplets in the atmosphere.

But it's completely shrouding this planet's atmosphere and we're really baffled by that and it was the first evidence that we had of this just completely shrouded planet. And that's been really a focus of a lot of people's attention on this super F mini Neptune rating for this GJ [00:32:00] 1214 and it's all in this Mass boundary where we have evidence that the star that they're orbiting has a huge impact on that planets environment.

As you mention gj1214b in the article, you say that well, it could be a rocky core with a hydrogen helium atmosphere hundreds of kilometers deep. I'm reading directly or much more intriguing. It could be a world covered in a deep ocean and atmosphere of steam you talking about an ocean of water there.

It sounds. We are talking about notion of water there and what we're really talking about for these what we would call Water World's is in fact a very very deep oceans that at Deep pressures would be forming these massive massive shells of high pressure ice. Now high pressure ice is actually ice that would have to form globally around that that planet like a almost like a nice mantel.

Hmm, but it would be hot [00:33:00] ice because it would be under pressure. So it's really weird regime in terms of chemistry in terms of physics. And if you look at the phase diagram of water, there's many different and very interesting portions of waters phase diagram where ice water liquid gas can exist in different combinations at different pressures and temperatures.

So these ocean world's can be anything from a nice. Rocky world with a crust on top of it and then covered in a global ocean. So imagine you took away all of our continents and just had ocean around the earth. It could be anything from that to something like more Enceladus which is a global ice ball.

Where the surface is completely iced, but underneath we think that there's a liquid Global ocean with liquid water at pressures of roughly 80 times that standing here on the earth. [00:34:00] So the ocean World definition is so vast and we're just starting to explore it with starting to explore in detail in our own solar system.

Trying to understand the difference between an earthlike world where we've got liquid water pooling on the surface to a ice world where we expect there to be a liquid ocean underneath the ice surface and for exoplanets, we can expand that even further by putting these types of world. Much close to their star in a more energetic environment in terms of the radiation they receive and we might then expect not only ice and water but also an atmosphere just completely composed of water vapor steam.

So water its existence is. It's one of the most important things in our universe. And as I said before it is the third most abundant molecule in our universe exploring the places exists and how it exists in these different. [00:35:00] Environments is really important. So amazing as you talked about this diversity that we discover everywhere.

We look that even water itself seems to display incredible diversity. I'm sorry. The Kurt Vonnegut is not around to hear about this and that there actually may be real world. Corollaries for the ice 9 as as he put it in one of his books not something you'd want to come in contact with her. Bring home.

Let's get on to new tech new technologies the stuff that you and so many other astronomers are so looking forward to you work a lot with the Hubble. We all know that it's follow on sad to say delayed. Once again, not long ago. The James Webb Space Telescope is still going to be making its way out there.

And with any luck knock on my desk unfolding properly and and revealing far more of what we can learn about exoplanets. It's an infrared [00:36:00] telescope we know and and how much of that is key to what you hope to get from the jwst the James Webb Space Telescope set to launch in Spring of twenty twenty one is going to open up our eyes.

It's going to take the blinders off. We will be looking at wavelengths in the infrared like you said and that's going to allow us to see the Fingerprints of carbon-based species. It's going to allow us to detect methane if it's there in multiple different bands in multiple different parts of the planet spectrum, and that's really important for the confirmation of these molecules.

We going to be able to measure carbon dioxide carbon monoxide in these atmospheres for the smaller terrestrial worlds. If we look at Venus as an example carbon, dioxide has a really nice Spike. It's got a signature that we can measure for a Venus like world and we should be able to see that for a.

Maybe [00:37:00] less than a handful of some of the best planets we can point that telescope at so the carbon dioxide is hugely important for these giant planets as well. Take this back to Planet formation Planet formation. We want to understand how planets form how they evolve over time and end up the way they are and the way that we see ourselves today.

The ratio between the water and the amount of carbon monoxide and carbon dioxide tells us a huge amount about potentially where that planet formed in its disk and how it evolved over time. And that's something that we're really interested to find out and we can't do that without the James Webb Space Telescope.

So I understand your enthusiasm for the web, but we have all these this whole new class of ground-based telescopes also about just start coming online in the next few years. What role will they play? And are they because they're ground-based are they're going to be less useful than a space-based telescope the difference between [00:38:00] a ground-based telescope and a space-based telescope is.

The Earth's atmosphere from the ground we have the Earth's atmosphere in the way and it's made up of many different molecules, which absorb light in the same way that when measuring the absorption of light in Alien worlds. So the Earth's atmosphere has a lot of water vapor in it. That's what all of our clouds are made of as well and that blocks light that absorbs light in these infrared waves amps.

So in fact, it's much harder for us to make these measurements from the ground, especially of water because we would be measuring the water in our Earth's atmosphere. I always like to make the analogy that it's looking for a small fluffy kitten the philosophy of cat and you can't unless it squeaks.

We don't have that. So it's much harder from the ground at these particular wavelengths, but what you can do from the ground, which is beautiful is build 30 meter telescopes and by the end of the 2020s, we should have [00:39:00] multiple 13 meter telescopes on the ground. Now the biggest one that will be in space when James Webb is open and ready to take it science later with 6.5 meters.

So that is a vast difference in the amount. Of collecting area for our Photon buckets. And all we want to do is count those photons. So from the ground if you have access to all of these beautiful Optical wavelengths the wavelength that we can see with our eyes and a number of gaps in the near-infrared.

Those are really really important for understanding and detecting planets. One of the things I'm really excited about with these very very large ground-based telescopes is the direct Imaging method now the direct Imaging method is looking at a planet directly. So it's taking a star you block out the light from that star and you have to be able to then see the light coming directly from the planet orbiting that star and this method is [00:40:00] really very difficult to do it involves very.

Instruments and we're trying to put those in Space the James Webb Space. Telescope will have a coronagraph on board. But from the ground we can use these incredibly complex. Instruments and we can customize them for different situations and I'm really hoping and I'm really looking forward to getting way more information about these directly imaged worlds where we can get a spectrum directly from the planet rather than what we're currently doing which is inferring indirectly different things about that country answer.

So there's a big combination and they all really work together to give us this full picture. Which really puts our solar system in context which is something that we're just trying to understand is the fundamental question that human beings have had is how did we get here? Why are we here? And we're just really trying to use everything that's out there this beautiful array of hundreds of thousands of planets that are out there to look back at [00:41:00] ourselves and understand it a little bit more.

We live in the most amazing time. So I've mentioned before on this program and I'm considerably older than you are I suspect reading books as a kid. At least one book that said we will probably never have a telescope powerful enough to reveal any star other than our own as more than a point of light.

Well, we've certainly made a great deal of progress. Do you feel fortunate to be doing this work at this time in our human evolution? I am insanely fortunate just to not just to be in the time period where we have the discovery of these planets, but the time when I started working on these was the time when it all just started picking up and we started getting a bit better understanding we started pointing the Hubble Space Telescope of these were.

I started right at the point when we were really getting that data from the space space missions and I am incredibly lucky to be working in that time period the way that the science works is the [00:42:00] right people at the right time doing the right things, but it's really just that timing. That timing is so vital in really pushing just the frontiers of instrumentation.

We need these amazing Engineers are just insane. Leaks and technology that have happened to make the James Webb Space Telescope work and functional is amazing when you think about it and I was lucky enough to be working at the place. They were building it. So I got to see it be built and evolve and change every time I went back to look at it.

And now I'm working on trying to understand how we can use those instruments and it's it's incredibly. Lucky and it's all about timing thrilling indeed. Before we go. There's another statement in your article that I never really never thought about although it may on in hindsight seem obvious. You say that every planet we've ever found that has an atmosphere.

Also has clouds and thinking that even includes Mars which has so little air to begin with and I know [00:43:00] that another part of your work has involved the study of clouds understanding them on those bigger world's the gas giants with apologies to Joni Mitchell. Are we getting to know clouds at all? We are and I love clouds.

I'm British as most of you can hear from my accent. I I grew up with clouds shrouding. I love them. I definitely think because they really Define the Dynamics of a Planetary atmosphere. They defined the temperature and the way the air is moving and the weather and in these alien worlds. We're truly finding exotic alien.

Some of the clouds that we're finding in some of the ones that we think are most abundant in these hot Jupiter atmospheres are made of glass liquid glass clouds. This is because magnesium silicates, which is essentially the sand you find on the beach is just broken down block here on the earth in the atmospheres of these planets where it's heated up so much and it's under very low pressures.

It's a vapor that can [00:44:00] then condense into a liquid. Liquid glass droplets forming a cloud in an atmosphere. It's just something that it's a work of Science Fiction, but it's right but it's not it's science fact and it's and it's out there and it's. I'm a massive science-fiction fan. I grew up on science fiction and this is just being the person to work on these and trying to understand these these exotic species is really a privilege and I work on another planet, which is one of my favorite school was 12b.

It's got a temperature over 2000 Kelvin we know from the measurements that it's got clouds in its atmosphere. It's cloudy. There's something in the app to the scattering light. But at that temperature the only material that can exist in a liquid form to scatter the light in that way is something called corundum and corundum is an aluminium oxide and for geologists in the audience know that this is the basis of rubies and sapphires.

Every time I walk around Natural [00:45:00] History Museum, I go into the Hall of gems because it's gorgeous place to go and I go I want to melt that and that and that and that and put it in the atmosphere and see what happens because that's what we're seeing. That's what we're measuring these exoplanets.

It's something we can't do here on Earth. So we're just using them as little Laboratory. To try and test out the fundamentals of geology almost literally Jewels strewn across our skies. I think you've answered this last question just with the enthusiasm that you've expressed, but I don't think anybody ever told you.

Hey Hannah great. But you got to start a podcast and do public appearances. If you want to keep your job, you got to be pretty busy doing just science a why take on these added task because what's the point in learning all this stuff? If we can't tell everybody this isn't this isn't for me. This isn't something that should be limited to myself.

These are fascinating things and they excite me and drive me to do the science that I do and I know as a kid I wanted to know all of this stuff. I wanted [00:46:00] to know everything so why not tell everybody and if you can't explain. The work that you're doing to any audience, then you don't truly understand it.

So it's also really I think for scientists even if you don't have the confidence or you don't want to go talk to audiences practice the language that you might use in front of them because that will help you really understand the problem. And I think that that's something that's missed out a little bit more.

No, appreciate it as much but I think it's it's the stuff that I'm most proud of and with very good reason Hannah. Thank you so much. It has been lovely talking with you. I look forward to the discoveries that will be made with these new instruments. And even with the ones we have now is. You and others continue to use them to reveal the true nature of Worlds across our galaxy.

So do I thank you. It's been a fun conversation couldn't agree more Hannah week four achieves the Geo Coney fellow at the Space Telescope Science Institute in Baltimore, Maryland. Where she focuses on characterizing the [00:47:00] atmospheres of exoplanets and as you've heard she also develops models of exotic Cloud species for hot giant planets like places like Jupiter, although hotter.

You can check out her website its Stellar Planet dot-org. You might also want to check out her podcast XO cast She's a co-host of that and used to do the science our on expression FM. One more thing. I got to mention here Hannah that you primarily work at the stsi with the Space Telescope Advanced research group for the atmospheres of transiting exoplanets.

And that acronym is Stargate. I love I told you I was a science fiction fan. You're in good company. Thanks. Again Hannah. Thank you from the Pasadena Public Library. This is a live version. What's up with the Bruce Betts here on the [00:48:00] stage? Welcome everybody. Thanks for joining us.

We've just been up here talking with Bruce about his great book astronomy for kids and we thought well why not we have this great group of families and others here we got to do. What's up, so welcome Bruce. Thank you, man. It's great to be here and really grateful to have such great audience. Now, you just showed the people.

At the auditorium here at the library. What's up in the night sky from here in Pasadena. You're going to have to do this without any pictures though this time. Okay, close your eyes and imagine. Well, unless you're driving in which. Do not close your eyes we've got in the evening Sky Mars is getting lower and lower in the west looking reddish and fairly dim right now.

There will be a beautiful conjunction two things hanging out next to each other in the sky when Mars hangs out near the crescent moon in the evening West on May 7th in the pre-dawn. It's upon a [00:49:00] party. We've got Venus looking super bright low down in the East and then you go to its upper right kind of in the Southeast and.

You will see Saturn looking yellowish farther to the right actually rising in the East around 11 p.m. Now is super bright Jupiter. It's going to be tough to catch Mercury Mercury has pretty much gone underneath penis. So sorry, but what you can catch is a meteor shower the Ada aquarians meteor shower, which we mentioned last week is better in the southern hemisphere up to 60 meteors per hour there but up to 30 meters per hour in the northern hemisphere.

And that will Peak on the night of May 6th and 7th and there's a thin Crescent Moon that sets early in the evening. So it'll be a nice dark sky and good opportunity to check out some meteors. I love that slide. You showed the people here at the library earlier that showed everything in that wonderful line.

Yeah. No, it's spectacular the whole planet lineup. I hope [00:50:00] people have been getting up to see it. What else have you got for us? All right this week in space history. It was this week in 1961 that Alan. Bird became the first American in space on a suborbital flight up and back up and back but that counts.

Yeah. Yeah, he made it and now we're going to move on to the next segment and here I could use your help. So I'm going to count to three and when I do I want you all to say random space fact ready 1 2 3. Nicely done was very nicely done. So Saturn's rings are. We really thin compared to their width really thin.

In fact, man if they are. In fact Matt if Saturn's rings were the thickness of a pizza that pizza would have to be as big as Belgium the country Belgium I can eat that. Yeah, I believe you [00:51:00] could so really really thin compared to how wide the the Rings are very cool. All right, we're going to move on to the trivia contest and tell me about the trivia contest Well, normally we would have we'd be giving the answer in announcing the winner of a trivia contest right now contest that we do for the listeners to the radio show and podcast but for reasons, I won't go into we didn't have a contest two weeks ago.

So we have no winner today, but we will have. Again, beginning next week and in a moment Bruce will have a new question for people listening to the radio show. So when he asked that question don't shout out the answer because that'll be for the folks at home, but we can go to our contest for the people here.

Let's do that. So I'm going to ask a question. I want you to raise your hand if you know the answer, what is the largest planet in our solar system and somebody's going to come over with a microphone. He's got it right there. Why don't we go to this young woman right here. Angelina and what is that [00:52:00] largest planet Jupiter?

That is correct Jupiter. Here's your rubber asteroid. Fortunately, it's rubber because Bruce has a much better has much better armed than I do. Oh good. I've made it. Okay. She just got a rubber asteroid. Okay, what's another one for our audience? See how much you're paying attention? What star is called the dog star?

What's the name of the star brightest star in the sky? Not a planet? How about this young lady right over here? Wait for the microphone. And what is your name Alexia? And what's that big stars name? Serious? Yeah serious. That is right. Good job. Yes, give her a hand like you want to do it. Thank you.

Everybody you guys, you know your stuff that was really fun now we're ready for the contest for the people at home. Remember don't shout out the answer, but you can enter if you go home listen to Planetary Radio and go to the contest page [00:53:00] that Bruce is going to tell you about. We talked about the Ada aquarians meteor shower.

What comets debris is responsible for the Ada aquariums meteor shower. Go to Planetary dot org slash radio contest to enter and you have until May 8. That will be May 8th. It's a Wednesday at 8 a.m. Pacific time to enter the contest and you will win if you are chosen by random dot or. And you have the right answer you'll win yourself a Planetary Society rubber asteroid and a 200-point i telescope dotnet account.

I telescope is a network of telescopes. They are all over planet Earth. Anybody can use them online. All you need is a computer or a device like this. You can actually work with any of those telescopes and take pictures of some of the things that Bruce was talking about earlier today as he told you about the night sky and as you can learn about [00:54:00] in Bruce's book astronomy for kids, and all you have to do is enter the contest in you might be the one who wins this time.

All right, I think we're done. All right, everybody go out there looking for the night sky and think about your local library. Thank you. And good night. That is Doctor Bruce. That's the chief scientist for the Planetary Society who joins us every week here for what's up?

Join Bill Nye and me at Science Museum, Oklahoma on the afternoon of May 8 for Planetary Radio live and more. Then consider attending this year's great humans to Mars Summit in Washington DC all once again host the h2m webcast and moderate a panel or to an amazing list of Space. Geeks will participate including NASA administrator Jim bridenstine and a guy named Buzz Aldrin.

We've got the links you need on the show page at Planetary dot org slash radio [00:55:00] Planetary Radios produced by the Planetary Society in Pasadena, California. And is made possible by its members who love clouds and clear skies Mary Liz Benders our associate producer Josh Doyle composed our theme which was arranged and performed by Peter Schlosser.

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