Searching for Alien Worlds with Anjali Tripathi

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So, Matt, are you Generation Xoplanet?

I don't know.

Am I?

Tune in and find out.

All the latest updates on exoplanets in the cosmos coming up on Star Talk.

Welcome to Star Talk,

Your your place in the universe where science and pop culture collide.

Star Talk begins right now.

This is Star Talk.

Neil deGrasse Tyson, your personal astrophysicist.

I got with me Matt Kirchen.

Matt, welcome back to Star Talk.

Thank you so much.

It's nice to be back.

You're in New York.

I am in New York City.

You're an LA guy.

Right now.

I've made the trip.

I walked across the country.

It took many days.

We lost a lot of people there were uh

we were attacked along the way but we made it so we'll find you on uh mattkirshan.com yes please yeah yeah i love i i always love it when star talk listeners and viewers come out to see the show that's great excellent excellent so today we're doing a cosmic queries on exoplanets it's been a while since we've dipped into that ocean.

I love hearing about this because my understanding, and I'm sure both you and our expert will talk significantly more about this, but this is a very new branch of science.

This is a we knew almost nothing about this fairly recently in the science center.

That's a true fact.

Yep.

A true fact.

And my depths of knowledge of exoplanets stops at just what's the latest number of them.

It's like one of those sort of charity how much we've raised ticker just on thermometer bulb that goes.

I'm good for that.

Yep.

So, of course, we found an expert who works at the Jet Propulsion Labs in Pasadena, California.

Coming in over video, Unjali Tropothy.

Unjali, welcome to Star Talk.

Thanks, Neil.

Great to see you again.

And nice to meet you, Matt.

Nice to meet you, too.

So let me get your titles correct here.

You're science ambassador.

So there's like a United Nations and things, and you resolve conflicts.

Science ambassador for NASA's exoplanet exploration program.

If someone gets arrested on another planet, then you step in and help smooth the way.

Exactly.

You need the ambassadors all

we don't speak about that outside of official facilities.

I'm sure that's not the case.

It's so diplomatic.

I will say the last time I was in the city was to be at the UN last year, Neil.

So

love it.

Also, a science communicator.

And if someone is labeled that in NASA, since so many people at NASA are really good at science communicating, if someone actually has that designation, that's we're talking real.

So we have high expectations of you for this conversation.

No pressure.

No pressure.

And I love this the most.

A former White House fellow.

And this would have been a science fellow.

Is that correct?

It was everything.

So I was the only scientist in my cohort.

There were 16 of us.

The others, one of them's a one-star general.

One's one of the first Congress people who's Native American.

So all strikes.

Right.

If I remember correctly, these fellows represent all different ways you could advise the president.

that the president might not otherwise know natively.

Is that a correct way to think about it?

It's usually one advisor per cabinet agency.

So I took on the Agriculture Department and the Science and Technology Policy Office of the White House.

And that was back about eight years ago.

I love it.

So can you update us on exoplanets?

There's been so many other things in the news.

Meanwhile, you and your research cohort domestically and around the world have been busy at this activity, finding exoplanets.

studying them further.

So could you just catch us up?

What should we be thinking about today?

Yeah, the last time I was on the show, Neil, it was a couple years ago, and we were still, you know, fresh off of being at about 5,000 exoplanets.

And as of today, you know, Matt, you were asking, we're at 5,921.

So within about a month, probably by the time this airs even, we'll be at 6,000 in flashing lights, which is pretty cool.

And, you know, when you think about the fact that when I was born, I think when everybody on screen was born, we didn't know about any of those.

That's a pretty big deal.

But it's just going and going because within a couple of years, once we've got the Nancy Grace-Roman Space Telescope up, taking observations from space, we're going to get tens of thousands of exoplanets counting.

So then 6,000 will just be a drop in the bucket.

So remind us who Nancy Grace Roman is.

Was she the first NASA chief scientist?

Is that right?

She was the first chief of astronomy in the Office of Space Science at NASA.

And she, you know, some people call her the mother of Hubble, right?

She helped architect some of these big missions.

And so we're really delighted to have this next flagship named after her.

And just to be clear, she's not going to be up there operating the telescope.

I couldn't tell you that, but that's not currently the plan.

We've got some redundancy if she's not up there doing something.

I mean, they think of everything at JPL.

Her spirit energy.

There you go.

So the general habit is to name telescopes after dead people.

Just sort of.

Oh, so.

Yeah.

So she's not.

There was one exception to that, but all the rest, that's been the case.

Oh, so she, so she'd be no use up there right now.

That's correct.

Totally no use.

So, uh, and also give us a reminder what it means for a telescope in orbit to be a flagship mission.

So at NASA, we have lots of telescopes of different sizes and lots of satellites.

We've got things down to CubeSats that, you know, universities can build up to these things that cost billions of dollars.

And so this flagship observatory is going to do lots of great science for dark energy and dark matter.

It's going to map all of the structure that we can see in detail so we can understand all kinds of cosmological questions.

All sorts of queries are going to be answered there.

But I'm really excited that it's not only going to, as it's staring at all of the mass out there, look for tiny changes in light that can tell us about thousands of planets using micro lensing, right?

How gravity is distorting light.

But then it's also got this whole tech demonstration, a chronographic instrument that can actually block out light so that you can see things that are about 10 million times fainter than the stars that you're looking at.

So this flagship means that it can do all kinds of science.

It's not just focused on one specific question.

And it probably sounds like flagship is also defined by price.

Like the expense of telescopes would be flagship.

I mean, they're the things that we're most proud of.

Not that you play favorites, but.

This is your most special child.

Neil is everyone's personal astrophysicist here at NASA's Exoplanet Exploration Program Office.

We are the nation's exoplanet purveyors.

We'll take it.

I'm good with that.

So you mentioned this coronagraphic capability.

So right now, we don't actually look at planets, exoplanets.

We're looking at their effect on the host star.

So you're going to be able to directly image exoplanets.

with this telescope.

Is that correct?

That's going to be how we're going to see some of them.

Right now, you can get a handful of these with the James Webb Space Telescope.

We've also directly imaged some planets from the ground with really big telescopes like the Keck telescopes in Hawaii.

But this is going to be the first time that we actually fly a demonstration that can get us down to these fainter things because, you know, something big like Jupiter is a lot easier to see than Earth.

And so we're going to push on that a little bit, getting ready for some of our future flagship missions.

So our catalog is overrepresented by Jupiters, would you say?

Those have been easier to find with some of these early techniques.

But, you know, we actually find a lot of different types of exoplanets that are also smaller.

So it's quite the range.

Okay, very good.

So tell me also about the Habitable Worlds Observatory.

Yeah, so this is one of these missions that we're really excited to be working on.

So the idea is that we now know that there are so many exoplanets out there that we think there should be enough nearby around stars that you could just go out and look and take a picture of them.

And what you really want to do is not not just take a picture of an exoplanet, but you really want to get a sense of what's in its atmosphere.

So hopefully you can actually take a picture using ultraviolet, infrared, visible light, and this whole wavelength range to get spectra and look for biosignatures.

So biosignatures, like on Earth, that would be oxygen, I guess, right?

Right now, that would be oxygen, but it's funny because if you look at Earth's past, the biosignatures actually change over time.

So way in the past, you know, when we were 4 billion years ago, up until about 2.5 billion years ago, if you had looked at Earth's atmosphere, you would have mainly seen methane.

And that was the metabolism of the earliest organisms.

But then over time, oxygen built up.

And then when you went into the Proterozoic, you would actually get from then two and a half to about 500 million years ago, you would actually see lots of ozone as the thing to look for in the atmosphere.

And it's only when you get to the modern era then you get the oxygen, all of this coming from photosynthesis and signs of life.

Okay.

Three planets.

And you don't know when, in the planet's evolution, you're peeking in upon it.

Exactly.

So you want to design a telescope that can cover all of those possibilities because we want to be sure that we're looking for life in as many options as we can.

Even presumably, you don't know that it would evolve in similar ways and produce similar

gases.

It could go a whole other direction.

Might there be chemical signatures that could be signatures of life as we don't know it, and therefore you're not looking for it?

You know, there's all kinds of things that if they produce life, we might miss it because we don't know how to look for things that aren't familiar to us.

But there are lots of interesting signatures of life that we can look for that go beyond oxygen and ozone and methane, right?

You can look for nitrogen dioxide, which is an industrial pollutant.

You can look for some of these other things, you know, like looking for what's in your hairspray, all kinds of things out there to look for

like we know it the chlorofluorocarbons in the hairspray exactly is that still in the hairspray do they still do that i thought they took i don't know but yeah but what you're saying is you could look for yeah alien pollution that's what you're telling me we're looking for aliens that have uh flyaway hair that needs controlling like if they have unmanageable hair and or toilets that need i don't think i've a little on the smelly side i've never seen an alien in a movie that had hair yeah they're always bald let alone just having bad hair day they never seem to have bad hair days.

They must.

Or bad tentacle days.

I don't know what.

Bad tentacles.

But they sometimes need controlling and sometimes that the things they use to control them have damaging effects on their atmosphere.

That would be great for us to see, right?

Because we want to see those signs of pollution, of hairspray.

I mean, even looking for the satellites that they've got going around their planets or, you know, looking for their city lights at night.

All of those are things that we could hope to look for with this telescope and to look for signs of life.

So it's not just the oxygen.

Are you also looking in binary star systems where the planet orbit might be a little unstable?

So we'll look at some binary star systems.

But so one of the tricks though about the Habitable Worlds Observatory is to find something actually like Earth, it's actually got to look at something that's 10 billion times fainter than the star, right?

So this is like a bird flying near the sun.

So if you're trying to look at Icarus, right, before bad things happen.

It's kind of hard.

You'll need some sunglasses.

And so this telescope will also have a coronagraph instrument or a high contrast instrument that'll be able to dim that down.

And so once you can actually do that, then it becomes possible to look for planets like Earth and to see all of the sort of variations in what might be there.

So tell me about the formation of exoplanets.

So in my day, in my professional days, I remembered the very first images of a protoplanetary disk, where it's a disk of gas around a star that hasn't made a planet yet.

And is that big time industry now within your community?

So I'm very biased, Neil.

You know, my PhD thesis was on protoplanetary disks, except back, you know, 10 years ago or so when I did this, You were basically looking at blobs.

It was the science of blobology.

And we've come a long way since then because now you can actually use radio telescopes like the ALMA telescope in Chile to look at these radio wavelengths of the dust and these beautiful spiral structures.

You can see gaps and rings.

There's a lot of beautiful science that's coming out of it.

So I don't know if it's as big time as looking for alien life, but it's something that's definitely advancing quickly.

And I just love talking about disks because everyone gets really excited about planets.

But I think that in the same way that you think like, oh yeah, I'm going to be an astronaut.

I'm going to go to space and I can see this beautiful picture of Earth.

We'll see these beautiful pictures of Earth.

But you might want the 23andMe of the astronomy world of, you know, where did we come from?

What else is out there?

And you can get all that information from disks, because if you look at a protoplanetary disk, all of that material goes into forming planets.

It's, you know, left over from forming a star when the gas and dust collapse.

And, you know, most of it goes into the star, but about 1% or so goes into forming planets.

And then long after that gas has dissipated and you formed your planets, you have some leftover material, right?

In the solar system, we have the zodiacal dust where the planets are.

And then further out, we've got the Kuiper belt, which we know is your favorite for giving Pluto a hard time there, Neil.

And one other thing about the disks,

only 1% goes into planets.

Where does the rest of the gas go?

So most of the mass, right, from that gas cloud is going into forming the star, right?

And then you've got a lot going into forming the planets.

So a lot of this is going to dissipate in time, right?

The star has UV radiation that's going to interact with the material there.

Some of it's going to blow away.

Oh, wait, wait.

So, so maybe I misunderstood.

So, the 1% number you gave, is that 1% of the disk mass or 1% of the cloud, the total cloud mass, the proto-cloud?

Right.

Okay.

Sorry.

So, I complained to two things there.

So, of the protostellar nebula, you have about 95% of that mass goes into the star and the rest goes into the disk.

And of what's in the disk, about 1% is solid material, right?

So it's the little dust and grains, and the other 99% is gas.

Got it.

Got it.

And so you've got these couple stages of disks.

You've got that protoplanetary disk early on.

And later on, after that gas goes away and you're left with the planets, you have things fighting each other and colliding.

And that's what gives you debris disks like the Kuiper Belt and the zodiacalite here in the solar system.

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This is Ken the Nerdneck Zabara from Michigan, and I support Star Talk on Patreon.

This is Star Talk Radio with Neil deGrasse Tyson.

So now update me on the latest from JWST because that's been going like gangbusters.

It's so cool what we can finally see from space.

So they were actually able to use the near-infrared superpowers of JWST to actually see water ice in crystalline form in this debris disk around a star called HD 181327.

And this is really exciting that you can actually see water ice in a debris disk because in the Kuiper belt, we've got all of these dirty snowballs, right?

We've got the comets, all kinds of icy material.

And there's been hints of this from the ground before, but we've never actually been able to see it.

So when they took a look at the light scattering off of this disk and compared it to what we see in the Kuiper belt it looked pretty similar you've got these dirty snowballs and so what this tells us is that Kuiper belts are not just something that we only see in the solar system they might be kind of common so you found a Kuiper belt in an exoplanetary system exactly very cool all right that's with JWST that's right and so it means that there's all kinds of icy material out there just waiting to form planets so water might be more common in the early solar system so that somewhere out there there's another Neil deGrasse Tyson dismissing another Pluto.

Because there's a Kuiper Belt waiting for that to happen in there.

No, I'm not.

I was an accessory to the demotion.

I didn't pull the trigger on that.

So this is fundamentally a Cosmic Aquarius edition.

It is.

And we solicited questions from our Patreon fan base.

They've sent in a fantastic assortment of questions.

On this subject.

Well, let's bring it on.

Go.

Well, I always like to start with, I think it's always fun when there is a young fan.

So Hugo Dart from rio de janiro says with my seven-year-old daughter olivia who is also a big fan of star talk here is our question what do you find most surprising or humbling about the current state of knowledge of exoplanets compared to when you first entered the field

good one so obviously there's so many more exoplanets now than when i started you know 20 years ago but i think what's really humbling is the fact that we keep finding new worlds in places where we've looked we thought oh we've already found what's there but then you find another one for example James Webb recently found some planets in a system where they're puffy planets.

This is Kepler-51.

And suddenly they said, oh, there's one more that we missed.

You know, the Kepler spacecraft was up a while ago.

And we're still analyzing that data and finding new information.

And the fact that we can find worlds that are so different from our own, right?

There were these ocean worlds, there were these lava worlds.

It's all just so spectacular that it's really exciting, but also kind of humbling to find that diversity of planets.

It's like a zoo.

Did you not expect that diversity?

I think for so long, we assumed everything looked like the solar system and Earth, right?

Because it was all we knew.

And in the solar system, we don't have worlds covered in lava.

So the fact that that can be out there, that's great.

Well, while we're talking about different types of worlds and things that look different, Adrian Martinez from Houston says, My question is, is it possible for a planet to naturally form in a doughnut shape, like a torus?

And if not, what are the weirdest or most unusual planet shapes we've discovered in the universe so far?

Do we even know the shapes of a lot of these planets?

Because a lot of the time you're just going on mass, aren't you?

Or can you see a shape even?

I don't know.

So that's a good question, Adrian.

I don't think it's possible to form a donut planet.

You know, Neil, correct me if I'm wrong, but that seems hard with gravity concentrating everything.

And, you know, the easiest shape to be is round because it pulls everything in nicely.

I wrote an essay back when we opened the Rose Center for Earth and Space because in the middle of this facility is a round thing.

There's a sphere.

So I wrote an essay called On Being Round.

And it was all about how nature just wants to make things round.

And when it's not round, there's a really interesting reason why it's not round.

But I don't think we ever get anything a donut because the gravity wants to put it all in one place.

And it wants to put it in the middle.

In the middle, exactly.

I was just going to say, though, there is, though, a really cool planet called WASP-12B, though, that's sort of egg-shaped, right?

So I think that's pretty cool because it's really hot.

It goes around its star almost, you know, once a day.

And because it's so hot, it's actually tidally locked and it's getting stretched.

So not only do you have this planet that's like an egg, it's not perfectly spherical anymore, but it's actually giving off mass.

And so we often find that planets can actually disintegrate a little bit and leave a torus of material from where they were.

So you don't get a torus-shaped planet, but you have the leftovers in a torus, which is pretty cool.

And what about the, was it a comet or an asteroid that looked like it was two spherical pieces stuck together?

It looked like a dumbbell, like there were two.

So you can get that, but it didn't form that way.

So it formed as two round things and then it sort of kind of made it.

I think that's the understanding of well.

So you can get all kinds of weird shapes in asteroids and these smaller bodies because it's one that you get up to being a planet when you have so much mass, then you're becoming round and forced to sort of circularize.

oh because the smaller things have less mass yeah they have less mass and gravity right and so the rocks win whatever the rock is doing it stays that way

well i've got a couple of there's a couple of questions here about habitability that i i like to combine questions sometimes uh if they're on similar topics so william warren from abingdon maryland says what exactly defines a planet as potentially habitable is it just being in the habitable zone where liquid water good exists or should we consider atmospheric composition magnetic fields plate tectonics and more Love it.

And then also, Sean Browning from Hood River, Oregon, when our star inevitably expands and consumes the inner solar system, what effects would that have on the remaining planets and what planets would fall into the new habitable zone?

Or would the expansion of the sun change the remaining planets' orbits, or would the mass not change, therefore leaving the planets in their current orbit?

So what makes a planet habitable and how will that change as the sun starts to

swallow our worlds?

No, that's such a good question.

I mean, right now we use the term habitable zone, but really that should, you know, the long, you know, the asterisk, read the fine print should really be region around a star where liquid water may be possible and seen on the surface.

So just because a planet is in the habitable zone, that just means it's the right distance from the star where liquid water could.

hopefully persist on the surface.

So sometimes people talk about the distance from Venus to Mars because, you know, in the past, these looked different.

But people use different definitions.

And part of how we think about habitability on a planet is involving liquid water right because that's what we know life on earth uses today

um but there's so many other factors right so you need water you need energy so starlight all that uv radiation is good stuff right makes the crops grow but too much and that's a problem so if you've got you know the stellar wind and all kinds of stellar flares from your star coming and beating down on you that's bad news so you want just the right amount of um energy and then you of course need nutrients um to make everything happen.

So I think there were some questions in there about, you know, what happens as our star changes, right?

And our relationship with our world is not the same.

And I think.

you know, where the habitable zone is in the solar system today is not where it was in the past and it's not where it'll be in the future because it used to be a little closer into the sun.

That's why Venus used to be wetter than it is today.

You had more Earth-like conditions.

And then, of course, you had this runaway greenhouse effect.

And now it looks kind of hellish.

And so in the future, we expect as the sun gets brighter and expands out, Mercury and Venus are actually going to be sucked into it and eaten up.

But we should be okay.

But out by Saturn is going to look pretty good for habitability.

So maybe Titan, you know, the moon around Saturn could have a good day because it's got a lot of methane in its atmosphere, kind of like early Earth.

I heard this and I didn't believe it until I did the calculation, that when the sun becomes a red giant and Earth is long gone, so is Mercury and Venus, and Mars becomes uninhabitable as a hot zone, Pluto becomes a habitable place.

Right.

I heard this and I double-checked it and it checks out.

The numbers crunched correctly.

They crunched correctly to make Pluto a place where we might all have to escape to survive.

There'll probably be a picture of me at the immigration.

No interest.

You get taken into the second room.

Aren't you going to be considering your life choices at that point?

We've found some things you've said, and we'd like to

ask you some more questions.

Speaking of more questions, Ben Grund from Detroit, Michigan says, I hear it's sometimes said that our solar system is pretty atypical in its constituency.

Is every solar system a snowflake, or are there some common themes to their layouts?

Oh, I like that.

Well, I mean, we were just talking about the debris disk with water ice.

So we do have some snowflakes out there in other systems, quite quite literally.

But I think the thing that we originally thought was that everything was like the solar system.

And then we found always these big planets like Jupiter, close into their star, hot Jupiters, because they were easy to find.

We discovered that actually they're nothing like the solar system.

But over time, we're finding more elements that are pretty similar.

So I think that we can say that we are not, you know, totally unique, but totally dissimilar.

So I like the snowflake analogy because I actually think that there's enough similarities and differences for it to work for us.

Also, people just tell me I'm a special snowflake.

I love the fact that you have exoplanets discovered all over the world, right?

It's not just telescopes in one place.

And say you have WASP, right, this wide-angle search for planets that found exoplanets in its early days, and then they've souped up versions.

There's super wasp now.

So I think there's even a super wasp telescope in South Africa.

They're all over the place.

And this is just one of many.

Many of them have awesome names, by the way, right?

There's the Trappist ones that come out of Belgium that are making these great discoveries.

And then we can keep studying them both from the ground and in space.

God, scientists love a contrived acronym.

Nothing makes scientists happier than finding some acronym.

When I was in college, there was some computer scientist.

This is early days.

Before that was even a title.

There was some program we were all using and its acronym was Magic.

Okay, what does that stand for?

He says, mnemonics are generally idiotic constructions.

So ever since then, I've not overdone my mnemonics.

So what else you got?

All right.

So Ryan Goerents from Pittsburgh, Pennsylvania says there are many different types of telescopes with a variety of sizes, but none of them have the resolution to actually see exoplanets.

So my question is, how big would a telescope have to be to have the resolution to actually see a nearby exoplanet?

Could we align multiple telescopes on Earth to make a telescope effectively as large as one of our planet's hemispheres?

And would that even be big enough?

Doesn't he,

I'm betting, because we do have images of planets.

I think this questioner wants to see continents and oceans and cities.

What do you think?

I mean, because I'm right there with you, Neil, that we've seen exoplanets already, right?

Again, they don't look like Earth so far, and we just get a couple of pixels.

Although, you know, as Carl Sagan's famous moniker of the pale blue dot from Voyager 1 spacecraft, and it's, you know, out at the edge of the solar system looking back at Earth, you just see a pale blue dot.

So we're not yet at the level of continents and oceans.

But actually, one really cool thing about the Habitable Worlds Observatory, you might actually be able to get a sense of oceans because of how the light, you would have the glint coming off of the water.

So to get to the stage of continents is pretty far off.

I haven't done the math on what you would need to do that.

It seems hard, but certainly we can take pictures of exoplanets now from the ground that are big like Jupiter.

And again, with HWO, in the future, we'll be able to see the planet itself without that level of detail.

So, not to displuto even more,

but when you describe this pale blue dot image taken by the Voyager 1, prompted by the efforts of Carl Sagan when Voyager 1 exited the solar system, that picture was taken when Voyager 1 passed Neptune.

That's the edge of the solar system.

Wow.

It was well inside of the orbit of Pluto.

So the idea was aliens would come upon our solar system and they'd see the first planet, and that would be Neptune.

And that's when they take a picture of all

inside.

So I didn't want people to think the edge of the solar system, that they were way out there.

No, it was relatively nearby, right?

Yeah, relatively nearby, exactly.

Because we draw a picture of the family portrait, right?

It was taken on Valentine's Day in 1990, right?

It's showing the love, right?

The love of a couple of pixels here and there.

Yeah, yeah.

I have time for a few more, I think.

Yeah, absolutely.

So Jay Starks from Waco, Texas says, here and reporting for Cosmic Query Duty.

I've been thinking a lot about how planets in our solar system are impacted differently by the distance from the sun, such as temperatures and the number of days it takes each planet to orbit our helios.

Do all exoplanets follow this pattern with their stars too regarding distance?

I'm curious if this is a universal truth for all exoplanets in outer space.

Interesting.

I think he's asking, are the laws of physics that describe orbits, does it change from one planetary system to another?

I mean, the beautiful thing about physics is you don't have to have a great memory.

The same rules apply over and over again.

So you just have to learn at once.

But I think it's kind of interesting to think about the solar system because you know Bode's law, right, Neil, right?

How back in the day when people were looking for, you know, Uranus and Neptune and things, they would look at the distance from the star, from the sun, and say, like, oh, there's a planet at these geometric distances.

And so then they found the planet and they went, yep, that checks off.

And then they said, oh yeah, we found Ceres because back then Ceres, dwarf planet, was viewed as a planet.

And then they said, oh yeah, there's these other things.

And then it didn't quite work.

And so we stopped.

But the notion of distances from the star having planets is one that people have thought a lot about over history.

And I think it's actually pretty cool that when we look out at these exoplanet systems, what we see looks nothing like the Earth and the solar system.

And that's partly because they're different systems.

But also, even within our own solar system, everything moved around.

You know, Jupiter and Earth didn't just form exactly where they are today.

They did a little dance to get there.

So, planet migration.

Yeah.

What's going on there?

Yeah.

So I'm reminded that when Isaac Newton first wrote down his gravity equation, and it worked for Earth and the moon, it worked for the sun and earth.

It also worked for Jupiter and its moons.

So it wasn't just like a sun thing.

It was, oh my gosh.

And so that we correctly, though audaciously, said it's a universal law of gravitation.

That's kind of bold, but I mean, why not?

We're egocentric as humans, right?

While we're talking about moons, there's a moon question from Fred Dogg.

That's a patron Fred Dog.

I don't know if you're from the Westchester Fred Dogs, any relation?

But Fred Dogg's

Fred Dogs.

It was once thought that habitable worlds had to exist within the habitable zone and would require a magnetic field to protect itself from harmful solar wind particles however this has since been determined to not necessarily be the case as our understanding of habitability continues to grow now moons like enceladus and europa have become candidates for housing possible life but fortunately they also happen to be protected by the magnetospheres of their respective planets My question, how has the inclusion of moons further complicated the search for life beyond our solar system?

I love that.

And I'm going to add to it,

will there come a day where we just abandon this concept of habitable zone?

Because if the conditions are ripe somewhere else and it's not in the zone, it could have life.

So maybe the habitable zone concept is constricting our creative thoughts of how, when, and where we might find life.

Yeah.

So, I mean, it's great that Fred Doug mentions these moons, right?

Europa and Celadus, where you might have this thick layer of ice and you've got all this heating that makes a nice cozy ocean underneath.

So one of the things about the habitable zone, like I said, that fine print, long liquid water may be found on the surface here, right?

If there is life under the ice, you won't be able to see it from the atmosphere as we know of now, right?

So when we talk about the habitable zone, it's about where could we actually look at our telescope and say maybe there's a biosignature for life here.

So it's not saying that moons are out of the question.

People are definitely looking at moons.

I think David Kipping, who you frequently have on the show, here

down the street there in New York, he's always thinking about exo-moons.

And so up the street, he's up the street.

Excuse me, my

kids are very specific about direction.

Yeah, yeah.

Get my New York straight here.

No, yeah, he's up at Columbia, and we're delighted when he's on the program.

So, you know, I don't know if we can detect the signatures of life from a moon yet, but it's one of the things that we want to look for.

And actually, the question of does it complicate things?

Yes.

Because if you want to get the signature of a moon, now you have to get rid of all the information about the planet.

You can't just say, oh, I'm only seeing the moon there.

In the same way that when we study exoplanets, we have to get rid of the star to study the planet.

So there's a different level of complexity.

And to your point, Neil, of maybe it's time for a new definition.

I think it's just, you know, you need something without the asterisk and the fine print of, you know, liquid water and the surface here.

And let me tell you how old I am.

So when I was in graduate school, the Voyager mission was doing its grand tour, and everyone was in high anticipation of what it would discover about the planets.

And when it started imaging the planet moons, oh my gosh, the moons became more interesting than the planets themselves.

And now people don't care about the planets.

Jupiter's moons are way more interesting than Jupiter by far.

I don't know.

I'm speaking out of turn here.

Tell me, would you...

You got to agree with at least some of that sentiment here.

I think that moons are spectacular, right?

I mean, I think the fact that, you know, you can look around Saturn and see hundreds of moons and they all, you know, you've got ones that look like the Death Star, right?

Yes.

It's got this big crater in it.

It looks like the Death Star bit that would send out the ray.

Yeah.

Don't you guys call it the Death Star moon?

I think we normally call it Mimus, but, you know.

We can have different names, sure.

When no one's listening.

Behind closed doors, when you're just for a few points.

Exactly.

So there's all kinds of beautiful things there.

But I wouldn't count, you know, how awesome Jupiter and Saturn and the solar system planets are because there are things we don't understand.

Like, why does Saturn have a hexagon at its pole?

And, you know, why do all of these outer planets have rings?

Right?

Saturn gets all the credit for, you know, the hula hoops that shine.

But, you know, all of these giant planets do, Neptune, Uranus.

So I think there's a lot going on there.

And I can't wait to see this for other systems.

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There's a nice question here from Andy L, who lives just up the road from Angeli and me in Thousand Oaks, California.

My understanding of the two main exoplanet search methods, periodic stellar dimming and stellar Doppler wobble, is that they both rely on their star's ecliptic being in line with our line of sight.

Does this mean that if a distant star's ecliptic plane is angled off our sight line, neither of these methods would work?

Could that explain why some stars don't seem to have planets?

Don't our people ask good questions?

Your people...

Ask great questions, Neil.

I mean, and that's one of the best parts of getting to hang out with all of you is it's just the most fun.

You know, people say like, oh, it's a secret.

I don't want to tell anyone.

I want everyone to know how cool exoplanets are.

Oh, yeah.

Answers to the questions.

Like, once we find life, you know, you were joking earlier, Matt, like, I can't tell anybody in my ambassador role, but now I want everybody to know.

You know, call your senators, call everybody, tell them.

It's amazing.

We have two methods for finding exoplanets that Andielle mentions, and it's exactly right that the transit method, right, where the planet is lined up just right to block out the starlight every time it goes around, you do need that geometry to be pretty close to at an angle.

We call this sort of edge on.

If it was so-called face-on, 90 degrees off, you wouldn't actually be able to see that starlight getting blocked.

And in the same way, the radial velocity or Doppler wobble method is where the mass of the planet tugs on the star.

and we go back and forth.

And this only works, of course, if that star is moving back and forth from the telescope.

So both of these don't work if it's at exactly 90 degrees or face on as we call it.

But if it's even a little bit off, we can actually see components there.

And this actually tells us some interesting facts about the mass of the planet because there's a famous system that was early on detected as a possible planet in the early days of exoplanets.

And it turned out that they had that angle totally wrong.

Later, when they had astrometry, right, they were actually able to look at the positions of the planets, then and look at the position, sorry, of the stars, they could see it was actually the other way around.

And this was actually a brown dwarf, actually even a little bit bigger than that.

So the angle matters, but we can get there as long as it's not exactly 90 degrees.

And there's another piece of this where we know the statistics.

If these systems are randomly oriented to our field of view, then we will know precisely how many systems we're missing.

So I think just because you don't see a planet because that it's tipped out of the field of view, we have a way of arithmetically compensating for that.

So in fact, we have this number of planets in our catalog, but again, like Andy L said, if it's not lined up, we don't see a planet, even if there is a planet there.

So statistically, presumably we know this and we can scale up the number of planets we detect as if we would have seen all planets around all stars.

So do you have a latest planet count for that?

I don't have the exact numbers, Neil, but I'm totally on the same page as you and Andy L.

That just because we don't see it today doesn't mean that there couldn't be planets in the system.

And that's actually one of the really cool things that the Roman Space Telescope is going to do.

Because it's going to be finding planets through microlensing, it doesn't care about the geometry, right?

So, it can actually look for planets that are farther away than what we do with the transit where it's nearby and we have to see it regularly.

And so, we expect we're going to see planets in systems where where we thought, oh, didn't see that there, but okay, I guess I could have seen that cutting.

Just to be clear, what was what you were saying a second ago, Neil, you can sort of just assume that planets' orbital plane is evenly distributed in all angles.

So you can go like, well, we can see these angles and these angles.

So you can then calculate, well, these ones must also exist.

Exactly.

You extrapolate.

You extrapolate into.

the galaxies that don't, where you didn't see any

planets at all.

Once you know what fraction of stars have planets that you've detected, and there's all all these other planets that don't, then you just look at the statistics of the orientations and you can fill in those missing numbers if it's randomly distributed out there.

While we're talking about that kind of detection and validation of things that are a distance away, Alan G says, hello, greater mystic diviners of the cosmos.

How accurate do we believe these remote measurements and determination of atmospheres and life conditions are?

when we have no way of validating something 50,000 light years away.

Ooh, those are fighting words.

No way of validating.

Show your work.

What does he want to say?

Go there and get a beaker of sample.

Like, no, no question, though.

Indicted your whole community right there.

But I love this question because this gets at the very heart of what it means to do science, right?

Because of course, we test the heck out of our equipment so that we know what to expect.

And so we can say that maybe we trust what's coming out of it.

But the beautiful thing about science is you can make predictions, right?

Like that you know when that solar eclipse is coming.

So you can be the kid in King Arthur's court.

And so even though we can't go there and see it up close, you can make predictions about other things you expect to see.

Like maybe when that planet goes to another part of its orbit, what might you see?

And so I think the fact that you can make predictions and then you can test and then you can get more data, that's like, that's magic.

I mean, imagine that you could predict the stock market.

So I think that's great.

I'm not worried about not being able to go there and visit, although I would love to do that.

I mean, I just have to wait for pieces of the solar system to fall to Earth and then we can see them.

So I think it was in the 1840s, somewhere around there, before spectra became a tool to understand the chemistry of something from afar, there was a philosopher who in his thesis, first he

asserted, there will never be more than the seven known planets.

He just asserted that.

Okay.

And then quickly thereafter, we discovered more planets.

But he also said that the stars in their beauty in the sky, we will know their colors and their locations, but we will never know what they're made of because they're just too far away.

That's what your man here sounds like.

Right.

And within a few years, we turned spectroscopes to the stars, and we know exactly what they're made of.

Right.

So I'm not ever going to say we will never know because I don't know that we'll never know.

If you look at these drawings of the solar system from long ago, right?

And you know, they're still drawing, you know, Saturn is the furthest we know about because, you know, up until the time that America was a country, that was the furthest planet we had known about.

But there are some people who draw all these different orbits and saying there might be other worlds.

And you might think it's kind of fantastical, but some people had that imagination.

And of course, the data bore us out.

So I don't know.

I get excited about seeing planets, about seeing disks.

Like I said, when they fall to Earth, you know, as long as I'm not a dinosaur, I'm cool with that.

But meteorites are great.

I mean, did you ever hang out with the meteorite at the White House, Neil, the little one that's there?

Where was that?

So in one of the rooms in the White House, there is on loan from the Smithsonian a piece of the Allende meteorite.

No, I've not seen it.

Okay, I called up a friend yesterday to check.

They said, oh, yeah, the Smithsonian just came and cleaned it, but it's still here at the White House.

Not all of us just hang out in all the rooms of the White House.

Just let the record show.

I was just staff, right?

You're

a fancy distinguished guest.

I did spend a little bit of time at the White House.

Yes, I know bits and pieces of the way.

I don't know all the White House.

No, no, it's just cool, though, because people look at this and they go, that's just an ugly rock, right?

Because it's like a little black rock with white dots.

And I used to go and explain to people, like, no, this is amazing.

This is older than the Earth, right?

You've got more than four and a half billion years here.

And this is like if you were baking a cake, right?

And you were messy and you got flour everywhere.

You bake the cake, you eat the cake.

Okay.

In this case, the cake are the planets.

But, you know, you've got like a little soft line

in this meteorite, you know, and it's here that we can study on Earth and sort of observe at the White House.

Because it's something that that meteorite landed here around the time when we were getting ready to analyze lunar rock samples.

And in the end, the meteorite ended up being cooler than moon rocks.

So I'm just saying I'm here for planets in all their forms,

as long as I'm not a dinosaur

by the way we might still be dinosaurs because we don't have a way to deflect an asteroid and we'll be if we go extinct from an asteroid we'd be the laughing stock of intelligent life in the galaxy for going extinct even though we had a space program see the dinosaurs didn't have a space program that we know of

We just don't know if the dinosaurs called their congresspeople to say, hey, make sure you put more funding into that.

Yeah, they

had, they had the beginnings of it, and it was going well, but then it got into trouble.

They got into committees and then they got bogged down with red tape.

And you know how things go.

Fake news, you know.

And then money got redistributed and somehow.

Man, we got time for one more question.

It better be a kick-ass question.

All right.

Well,

I like this question.

Hello, Doctors TNT.

Oh,

this is Nancy from Hell's Kitchen NYC.

All right.

Are we up or down or across the road from that?

Which direction are we?

They're down from us.

They're down from us.

Okay.

So Nancy is down from us right now.

And Nancy is wondering, have you ever had a simulation give you a result so strange you thought either this is a bug or the universe is trying to tell me something?

So I will first of all say.

Lots of bugs, no chat GPT in my coding, so have seen plenty of those.

But I actually don't think I've ever had the moment of thinking, oh, that's so weird, but instead, oh, that's so beautiful.

Because I always think it's amazing that we can just code the laws of gravity into our simulations.

And then you can watch stars and gas form into galaxies.

And you can look at these pictures, these simulations that are, you know, cosmological in scale, and then compare them to real observations.

And they look the same.

So I think the universe is telling us, you're doing great.

You can do a little better on that subgrid physics, but you know, the big scales, you got it going on.

And

it's just amazing that we can see it on the computer.

Because if you go back, have you ever seen those two-ray simulations from the 70s where they actually use different characters like the letter Q and the number seven as their particles in these really early computer graphics of galaxies coming together?

It's so primitive compared to what we have now, but even then it was right.

So I feel like at that point, you would have been like, my computer is telling me something.

Well, except.

When generally when you have a simulation, when you are simulating something, I like Anjali's point about the fact that you get to put laws of physics into your code.

But if you've done that,

the code is not going to show you something that is based on some new undiscovered law of physics because you put the laws of physics in it.

All right.

And so

for me, the most

interesting part of a simulation is if I simulate something with my best understanding of all the laws of physics and it still doesn't match,

that means something else is happening in the universe that I have not reckoned in my models.

Would you agree that you're more likely to not match the real world because the real world has something more interesting going on in it than your simulation?

And now you got to go back to the drawing board of your simulation and figure out what's going on.

I think there's always so much complexity in nature, and we always start from the ground up.

And so you always think, oh, there's that more detail I could add.

Just like when I draw, I'm not a great artist.

I start with a stick figure and you go, okay, I can add some eyelashes and some more things, but it needs some color.

It needs a little bit more.

It's just the same way with our simulations.

So oftentimes you can think about what's missing here and how do we add that little chef's kiss of color.

Yeah, she mentioned this experiment by Tumre.

He's a very famous astronomer of the day.

And we saw these galaxies out there that were very disturbed looking and we didn't know why.

There was even a catalog of disturbed galaxies, okay?

The Atlas of peculiar galaxies.

And why do they look peculiar?

But we look perfect.

We have two arms, spirals.

And

are they a different kind of galaxy?

And so we had to figure out that these are the products of colliding galaxies.

And all the gravity, they distort because they all feel different parts of the gravity at all times.

And Anjali, do you remember how he figured that out?

How he did the

experiment?

I mean, I just, I have the visual in my mind, right, of the Tomb Ray and Tomb Ray because it was Alar and his brother, right, who were doing

simulation.

I'm trying to, was it he the one or was it someone before him?

Because how do you simulate, you don't really have a computer yet to do it full-blown.

Oh, no, no.

It was someone before him.

Before him.

I forgot who it was.

First figure out the mergers.

Even before before tombray's first computer simulations of this as anjali describes eric holmberg another galaxy guy he figured out how to do it with light because gravity drops off as one over the distance squared okay

one over the distance squared now if you don't have a computer how are you going to simulate that on the table how are you going to do that you can like move everything every moment and then calculate everything but that's too much effort so what he did he had light bulbs and light meters

because light drops off as one over distance squared, the intensity of light.

That makes sense.

And so, the light bulbs were the parts of galaxies.

And he took light readings at what the intensity of the light was, and that was a proxy for the intensity of the gravity.

And you got to see the distortions in the spiral arms of the galaxy, and you could recreate all the messy galaxies that look like puppy vomit on the sky.

Backwards.

Galaxies are beautiful, right?

I mean, cute too.

So maybe you think anything that comes out of a puppy is cute, but puppy vomit can be, can be beautifully autistic.

Okay.

That's pretty clever, right?

You think?

I mean, it's amazing what people do in all sorts,

right?

It's not just looking at it on a screen.

We did that actually this past year where we actually had a museum exhibit and we tried to make it multi-sensory for exoplanets.

So I worked with a perfumer and a sound engineer.

So we had the sounds and smells to get you in that world.

We didn't do any experiments with it, but it helped bring people in with different ways, which was pretty cool.

So presumably some of these planets might have hydrogen sulfide.

We did not poison anybody, Neil.

That's what I forgot to say.

No, actually, the most interesting part of working with a perfume artist is when you said, oh, we wanted to get towards habitability and life.

She brought me lots of smells of manure because she said there is nothing more lifelike than manure.

So we didn't have the the puppy vomit smells, but we had some other smells there that were very

perfumer brought you manure.

No, no, smells of manure.

Aren't you glad you don't work at NASA with me smelling?

Thank you for clarifying.

No, the actual, just the little munio scent that you can just dab on your wrist and behind your ears.

Remind me not to buy that person's perfume.

No, the rest of it, though, was incredible because what we ended up doing is we had smells like rose garden and horse stables and things like GNT on a Saturday night.

It wasn't the TNT drink that we apparently need to come out with, but you know, things that people would recognize.

And then the other wall had these smells of, you know, what does lightning on Saturn smell like or interstellar space or a rock garden on Mars or a clean spaceship, getting you imagining that one day in the future, those smells could be just as realistic and familiar to us as the rose garden where you don't have to read the plaque.

And so going from there to then being immersed in the sound bath where the distances of these exoplanets were represented by pauses and then music, it just sort of brought it together.

And even though some of the smells maybe were not what you would choose for, you know, going out on a Friday night,

it was still pretty cool.

Well, thank you, Anjali, for participating in our Cosmic Queries.

It's so good to be here.

And when you pass 6,000, give us a call.

6,000 exoplanets.

I honestly suspect it'll pass 6,000 by the time this airs.

Oh, okay.

And you know what I do at every one of my public talks?

I ask everyone to stand who was born since 1995

because that was the first exoplanet discovered.

And that's a lot of people.

A lot of people, yeah, a lot of people.

And because they only known life with exoplanets in the catalog, right?

Okay.

So they're all standing up, and I say, raise your right hand.

And they raise their right hand.

And I say,

I declare all of you to be Generation

So planet.

And then they sit down.

I love that new.

But again, that just hammers home how absurdly new this entire branch of science is.

That's how you began the whole conversation.

Yeah.

Yes.

Well, I tell all my friends at JPL I said hi.

We'll do.

We'll do.

Matt, we'll see you on your website.

Yeah, I'm on tour and on Probably Science.

We will get you back very soon.

Probably that's your podcast.

That is my podcast.

Probably science.

Okay.

We're very happy to steal you five.

I've been on it only once, apparently.

We're making it happen again.

We're making it happen again.

Near my phone the whole time.

You're a busy man.

We need to pick up moments.

All right.

This has been another installment of Cosmicquaries.

This would be the Exoplanet Edition.

I'm going to thank my guests, Anjali Chapothy and Matt Kershan.

Until next time, I bid you to keep looking up.

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