Searching for Alien Worlds with Anjali Tripathi

Summary

StarTalk Radio - Episode Summary: "Searching for Alien Worlds with Anjali Tripathi"

Podcast Information:

• Title: StarTalk Radio
• Host: Neil deGrasse Tyson
• Guest: Anjali Tripathi, Science Ambassador for NASA's Exoplanet Exploration Program
• Release Date: July 22, 2025
• Description: Science, pop culture, and comedy collide as astrophysicist Neil deGrasse Tyson explores astronomy, physics, and the quest to understand life in the universe alongside his co-hosts and expert guests.

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Introduction

The episode kicks off with Neil deGrasse Tyson and co-host Matt Kirschen delving into the exciting and rapidly evolving field of exoplanet research. Anjali Tripathi, a prominent Science Ambassador at NASA's Exoplanet Exploration Program, joins the conversation to provide expert insights into the latest discoveries and future missions aimed at uncovering alien worlds.

Current State of Exoplanet Research

Anjali Tripathi shares exciting updates on the number of confirmed exoplanets, highlighting that the count has surged from approximately 5,000 two years ago to over 6,000, with the number expected to reach tens of thousands soon thanks to missions like the Nancy Grace Roman Space Telescope.

Anjali Tripathi (03:10): "Within about a month, probably by the time this airs even, we'll be at 6,000 in flashing lights, which is pretty cool."

She emphasizes the unprecedented growth in exoplanet discovery, underscoring how the field has transformed from knowing almost nothing to now cataloging thousands of worlds.

New Space Telescopes and Missions

A significant portion of the discussion centers around the upcoming Nancy Grace Roman Space Telescope and its flagship capabilities. Anjali explains how this telescope will revolutionize our understanding of exoplanets by utilizing techniques like microlensing and direct imaging.

Anjali Tripathi (07:07): "This flagship mission is going to do lots of great science for dark energy and dark matter... but I'm really excited that it's also going to look for thousands of planets using microlensing."

The conversation also touches on the Habitable Worlds Observatory, designed to directly image exoplanets and analyze their atmospheres for biosignatures such as oxygen, ozone, and methane.

Anjali Tripathi (09:39): "We really want to get a sense of what's in its atmosphere... to look for biosignatures."

Direct Imaging and Biosignatures

Anjali delves deeper into the challenges and advancements in directly imaging exoplanets. She explains the importance of coronagraphs in blocking starlight to reveal planets and discusses the potential to detect atmospheric components that could indicate the presence of life.

Anjali Tripathi (08:30): "We want to be sure that we're looking for life in as many options as we can."

The hosts humorously explore the idea of detecting "alien pollution," expanding the concept of biosignatures beyond traditional gases.

Matt Kirschen (12:14): "We're looking for aliens that have flyaway hair that needs controlling... or toilets that need."

Anjali underscores the importance of designing telescopes that can accommodate various biosignatures, acknowledging that life beyond Earth may produce unexpected chemical signatures.

Unique Planetary Shapes and Formation

The discussion shifts to the formation and shapes of exoplanets. Anjali highlights the discovery of Wasp-12b, an exoplanet with an egg-like shape due to tidal locking and extreme stretching by its star.

Anjali Tripathi (22:34): "There's a really cool planet called Wasp-12b that sort of has an egg shape... it's getting stretched and giving off mass."

Neil adds historical context by referencing early galaxy simulations and the challenges of modeling celestial phenomena without modern computing power.

Habitable Zones and Future of Habitability

Addressing listener questions, Anjali clarifies the definition of the "habitable zone," emphasizing that it primarily refers to regions around stars where liquid water could exist on a planet's surface. She discusses factors like atmospheric composition and stellar activity that influence habitability.

Anjali Tripathi (24:42): "Liquid water may be possible and seen on the surface... but there's so many other factors."

The conversation explores how the habitable zone evolves as a star ages, with Neil humorously contemplating the future habitability of Pluto after the Sun becomes a red giant.

Neil deGrasse Tyson (27:11): "I heard this and I double checked it and it checks out... making Pluto a place where we might all have to escape to survive."

Anjali mentions the potential habitability of moons like Titan, which could resemble early Earth with their methane-rich atmospheres.

Exomoons and Life Search Complications

Anjali addresses the complexity introduced by exomoons in the search for extraterrestrial life. She explains that detecting moons requires distinguishing their signatures from their host planets, adding a layer of difficulty to observational techniques.

Anjali Tripathi (36:22): "There's a different level of complexity... because you have to get rid of all the information about the planet."

Neil muses about the shifting focus towards moons, especially with the myriad of moons orbiting Jupiter and Saturn, citing their intriguing features like Saturn's hexagonal pole.

Detection Methods and Limitations

Listener Matt Guerrentz from Pittsburgh poses a technical question about the limitations of current exoplanet detection methods, specifically the transit and Doppler wobble techniques, and whether planet detection is hindered when a star's ecliptic is angled away from our line of sight.

Anjali explains that while these methods rely on specific geometric alignments, statistical models help compensate for undetected planets due to unfavorable orientations. She also highlights the Roman Space Telescope's microlensing capabilities, which are not dependent on such alignments.

Anjali Tripathi (44:15): "The Roman Space Telescope is going to do planets through microlensing. It doesn't care about the geometry."

Validity of Remote Measurements

Addressing skepticism about the accuracy of remote measurements for determining exoplanet atmospheres, Anjali emphasizes the rigorous testing and predictive power of scientific methods. She likens it to anticipating solar eclipses, where predictions based on models are validated through observation.

Anjali Tripathi (45:12): "You can make predictions and then you can test and then you can get more data... that's magic."

Neil adds historical perspective by referencing how spectral analysis revolutionized our understanding of celestial compositions, dismissing the notion that distant measurements are inherently untrustworthy.

Simulation Insights

The episode delves into the role of simulations in astrophysics. Anjali shares her enthusiasm for how simulations based on physical laws can predict and replicate complex cosmic phenomena, such as galaxy formations.

Anjali Tripathi (52:34): "When you 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."

Neil recounts the ingenious methods early astronomers used to simulate gravitational interactions without modern computers, showcasing the ingenuity behind foundational astrophysical discoveries.

Conclusion and Final Thoughts

As the episode wraps up, Neil and Anjali reflect on the monumental strides made in exoplanet research and the boundless possibilities that lie ahead. They encourage listeners to stay curious and continue looking up, embracing the ever-expanding frontier of cosmic discovery.

Neil deGrasse Tyson (57:35): "Until next time, I bid you to keep looking up."

Anjali expresses her excitement for future discoveries and the ongoing collaboration within the scientific community to uncover the mysteries of the universe.

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Notable Quotes with Timestamps:

• Anjali Tripathi (03:10): "Within about a month, probably by the time this airs even, we'll be at 6,000 in flashing lights, which is pretty cool."
• Anjali Tripathi (07:07): "This flagship mission is going to do lots of great science for dark energy and dark matter... but I'm really excited that it's also going to look for thousands of planets using microlensing."
• Anjali Tripathi (09:39): "We really want to get a sense of what's in its atmosphere... to look for biosignatures."
• Matt Kirschen (12:14): "We're looking for aliens that have flyaway hair that needs controlling... or toilets that need."
• Anjali Tripathi (24:42): "Liquid water may be possible and seen on the surface... but there's so many other factors."
• Neil deGrasse Tyson (27:11): "I heard this and I double checked it and it checks out... making Pluto a place where we might all have to escape to survive."
• Anjali Tripathi (36:22): "There's a different level of complexity... because you have to get rid of all the information about the planet."
• Anjali Tripathi (44:15): "The Roman Space Telescope is going to do planets through microlensing. It doesn't care about the geometry."
• Anjali Tripathi (45:12): "You can make predictions and then you can test and then you can get more data... that's magic."
• Neil deGrasse Tyson (57:35): "Until next time, I bid you to keep looking up."

---

Key Takeaways:

• The field of exoplanet research is experiencing explosive growth, with discoveries rapidly increasing in number.
• New missions like the Nancy Grace Roman Space Telescope and the Habitable Worlds Observatory are poised to revolutionize our understanding of alien worlds through advanced detection and imaging techniques.
• Direct imaging and the search for biosignatures are critical for identifying potentially habitable exoplanets, though they come with significant technical challenges.
• The diversity of exoplanets, including unique shapes and compositions, highlights the vast range of possibilities beyond our solar system.
• The concept of the habitable zone is evolving, with increasing recognition of the role exomoons and other factors play in fostering life.
• Scientific simulations, grounded in established physical laws, continue to be essential tools for predicting and validating cosmic phenomena, driving forward our knowledge of the universe.

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Engagement: This episode of StarTalk Radio offers a comprehensive exploration of exoplanet science, blending expert insights with engaging discussions and listener interaction. Whether you're a seasoned astronomy enthusiast or a curious newcomer, Neil deGrasse Tyson and Anjali Tripathi provide a captivating guide to the search for alien worlds and the ongoing quest to understand our place in the cosmos.

Transcript

[Neil DeGrasse Tyson]

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[Neil DeGrasse Tyson]

So, Matt, are you Generation Exoplanet?

[Matt Kirschen]

I don't know. Am I?

[Neil DeGrasse Tyson]

Tune in and find out all the latest updates on exoplanets in the cosmos, coming up on StarTalk. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil DeGrasse Tyson, your personal astrophysicist. I got with me, Matt Kirschen. Matt, welcome back to StarTalk.

[Matt Kirschen]

Thank you so much. It's nice to be back.

[Neil DeGrasse Tyson]

You're in New York.

[Matt Kirschen]

I am in New York City.

[Neil DeGrasse Tyson]

You're an LA guy right now?

[Matt Kirschen]

I've made the trip. So I walked across the country. It took many that we lost. We lost a lot of people. We were attacked along the way, but we made it.

[Neil DeGrasse Tyson]

So we'll find you on mattcircian.com.

[Matt Kirschen]

Yes, please.

[Neil DeGrasse Tyson]

Yes.

[Matt Kirschen]

I always love it when StarTalk listeners and viewers come out to see the show. That's great.

[Neil DeGrasse Tyson]

Excellent, excellent. So today we're doing a cosmic queries on exoplanets. It's been a while since we dipped into that ocean.

[Matt Kirschen]

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 science terms.

[Anjali Tripathi]

Right?

[Neil DeGrasse Tyson]

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.

[Matt Kirschen]

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

[Neil DeGrasse Tyson]

I'm good for that.

[Matt Kirschen]

Yeah.

[Neil DeGrasse Tyson]

So of course we found an expert who works at the Jet Propulsion Labs and in Pasadena, California, coming in over video, Anjali Tripathi. Anjali, welcome to StarTalk.

[Anjali Tripathi]

Thanks, Neil. Great to see you again. And nice to meet you, Matt.

[Matt Kirschen]

Nice to meet you too.

[Neil DeGrasse Tyson]

So let me get your titles correct here. You're Science Ambassador. So there is like a United nations and things, and you resolve conflicts. Science ambassador for NASA's Exoplanet Exploration Program.

[Matt Kirschen]

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

[Neil DeGrasse Tyson]

Exactly. You need the ambassad.

[Anjali Tripathi]

We don't speak about that outside of official facilities, unfortunately.

[Matt Kirschen]

This is so diplomatic.

[Anjali Tripathi]

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

[Matt Kirschen]

So wow, love it.

[Neil DeGrasse Tyson]

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.

[Anjali Tripathi]

No pressure.

[Neil DeGrasse Tyson]

And I love this the most. A former White House Fellow. And this would have been a science fellow, is that correct?

[Anjali Tripathi]

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.

[Neil DeGrasse Tyson]

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, is that a correct way to think about this?

[Anjali Tripathi]

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. Yes, about eight years ago.

[Neil DeGrasse Tyson]

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.

[Anjali Tripathi]

Yeah. 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 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.

[Neil DeGrasse Tyson]

So remind us who Nancy Grace Roman is. Was she the first NASA chief scientist? Is that right?

[Anjali Tripathi]

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.

[Matt Kirschen]

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

[Anjali Tripathi]

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 things.

[Matt Kirschen]

I mean, they think of everything. At jpl, her spirit energy will be controlling.

[Neil DeGrasse Tyson]

So the general habit is to name telescopes after dead people, just so you know. Yeah. So she's not. There's one exception to that, but all the rest, that's been the case.

[Matt Kirschen]

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

[Neil DeGrasse Tyson]

That's correct. Totally no use. So. And also give us a reminder what it means for a telescope in orbit to be a flagship mission.

[Anjali Tripathi]

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 OBS 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 microlensing. 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.

[Neil DeGrasse Tyson]

And it probably sounds like flagship is also defined by price, like the expensive telescopes would be. Flagship.

[Anjali Tripathi]

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

[Neil DeGrasse Tyson]

All right.

[Matt Kirschen]

Not that you play favorites, but this is your most special child.

[Anjali Tripathi]

Neil is everyone's personal astrophysicist here at NASA's Exoplanet Exploration Program Office. We are the nation's exoplanet purveyors.

[Neil DeGrasse Tyson]

Yeah, 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?

[Anjali Tripathi]

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.

[Neil DeGrasse Tyson]

So our catalog is over represented by Jupiter's.

[Anjali Tripathi]

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.

[Neil DeGrasse Tyson]

Okay, very good. So tell me also about the Habitable Worlds Observatory.

[Anjali Tripathi]

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 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.

[Neil DeGrasse Tyson]

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

[Anjali Tripathi]

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 at four billion years ago, up until about two and a half 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.

[Neil DeGrasse Tyson]

Okay. Three planets, and you don't know when in the planet's evolution you're peeking in upon it.

[Anjali Tripathi]

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.

[Matt Kirschen]

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

[Neil DeGrasse Tyson]

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?

[Anjali Tripathi]

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, you know, like looking for what's in your hairspray. All kinds of things out there to look for. For life's like we know it.

[Neil DeGrasse Tyson]

The chlorofluorocarbons in the hairspray, is that still in the hairspray? Do they still do that? I thought they took it out.

[Anjali Tripathi]

I don't know.

[Neil DeGrasse Tyson]

But yeah, but what you're saying is you could look for alien pollution. That's what you're telling me.

[Matt Kirschen]

We're looking for aliens that have flyaway hair that needs controlling. Like if they have unmanageable hair and. Or toilets that need.

[Neil DeGrasse Tyson]

I don't think I've.

[Matt Kirschen]

They're a little on the smelly side.

[Neil DeGrasse Tyson]

I've never seen an alien in a movie that had hair.

[Matt Kirschen]

Yeah, they're always bald, let alone just having bad hair. They never seem to have bad hair days they must. Or bad tentacle days.

[Neil DeGrasse Tyson]

I don't know what bad tentacles.

[Matt Kirschen]

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

[Anjali Tripathi]

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 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.

[Neil DeGrasse Tyson]

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

[Anjali Tripathi]

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 gotta 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.

[Neil DeGrasse Tyson]

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?

[Anjali Tripathi]

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, you know, 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, and, and I, 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 gonna go to space, and I can see this beautiful picture of Earth. We'll see these beautiful pictures of Earth. But, you know, 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, leftover from forming a star when the gas and dust collapse and 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.

[Neil DeGrasse Tyson]

And one other thing about the disks. Only 1% goes into planets. Where does the rest of the gas go?

[Anjali Tripathi]

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.

[Neil DeGrasse Tyson]

Oh, wait, 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 protocloud.

[Anjali Tripathi]

Right. Okay, sorry. So I conflated 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.

[Neil DeGrasse Tyson]

Got it, Got it.

[Anjali Tripathi]

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 a planet. You have things fighting each other and colliding, and that's what gives you debris disks like the Kuiper Belt and the zodiacal light here in the solar system.

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[Anjali Tripathi]

This is Ken the Nerdneck Zabera from Michigan and I support StarTalk on Patreon. This is StarTalk Radio with Neil Degrasse Tyson.

[Neil DeGrasse Tyson]

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

[Anjali Tripathi]

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 and 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.

[Neil DeGrasse Tyson]

So you found a Kuiper belt in an exoplanetary system.

[Anjali Tripathi]

Exactly.

[Neil DeGrasse Tyson]

Very cool. All right, that's with jwst.

[Anjali Tripathi]

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.

[Matt Kirschen]

So that somewhere out there there's another Neil Degrasse Tyson dismissing another Pluto because.

[Neil DeGrasse Tyson]

It'S a Kuiper belt, waiting for that to happen in there. No, I'm not. I was an accessory to the demotion.

[Anjali Tripathi]

I was not.

[Neil DeGrasse Tyson]

I didn't pull the trigger on that. So this is fundamentally a Cosmic Queries edition.

[Matt Kirschen]

It is.

[Neil DeGrasse Tyson]

And we solicited questions from our Patreon fan base.

[Matt Kirschen]

They've sent in a fantastic assortment of.

[Neil DeGrasse Tyson]

Questions on this subject. Well, let's bring it on. Go.

[Matt Kirschen]

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 Janeiro Sundays, with my 7 year old daughter Olivia, who is also a big fan of StarTalk, 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?

[Neil DeGrasse Tyson]

Mmm, good one.

[Anjali Tripathi]

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 and 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, 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 are these ocean worlds, there are 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.

[Neil DeGrasse Tyson]

Did you not expect that diversity?

[Anjali Tripathi]

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.

[Matt Kirschen]

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 donut 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. Do we even know. Do we even know the shapes of a lot of these planets? Because a lot of time you're just going on mass, aren't you? Or can you see a shape even? I don't know.

[Anjali Tripathi]

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. Nice.

[Neil DeGrasse Tyson]

Yeah. 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. Okay, 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.

[Matt Kirschen]

It wants to put it in the middle.

[Neil DeGrasse Tyson]

In the middle, exactly.

[Anjali Tripathi]

I was just gonna say, though, there is, though, a really cool planet called Wasp12b though, that sort of egg shape. 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 Taurus shaped planet, but you have the leftovers in a torus, which is pretty cool.

[Neil DeGrasse Tyson]

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.

[Matt Kirschen]

It formed just two round things. And then it sort of.

[Neil DeGrasse Tyson]

I think that's the understanding of it.

[Anjali Tripathi]

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 froz force to sort of circularize.

[Matt Kirschen]

Oh, because the smaller things have less mass.

[Neil DeGrasse Tyson]

Yeah, they have less mass and gravity.

[Matt Kirschen]

Right.

[Neil DeGrasse Tyson]

And so the rocks win. Whatever the rock is doing, it stays that way.

[Matt Kirschen]

Well, I've got a couple of, there's a couple of questions here about habitability that I like to combine. Questions sometimes 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 could exist? Or should we consider atmospheric composition, magnetic fields, plate tectonics and more?

[Neil DeGrasse Tyson]

Love it.

[Matt Kirschen]

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?

[Neil DeGrasse Tyson]

Ooh.

[Matt Kirschen]

Or would the expansion of the sun change the remaining planets orbits or where the mass not change, therefore leaving the planets in the current orbit? So what makes a planet habitable? And how will that change as the sun starts to, I love it. Swallow our worlds?

[Anjali Tripathi]

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. 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 energy and then you of course need nutrients 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.

[Neil DeGrasse Tyson]

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.

[Matt Kirschen]

Right?

[Neil DeGrasse Tyson]

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

[Matt Kirschen]

The numbers crunched correctly, they crunch correctly.

[Neil DeGrasse Tyson]

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 entry.

[Matt Kirschen]

You get taken into the second room.

[Anjali Tripathi]

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

[Matt Kirschen]

We 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 sometimes said that our solar system is pretty at typical in its constituency. Is every solar system a snowflake or are there some common themes to their layouts?

[Neil DeGrasse Tyson]

Well, I like that.

[Anjali Tripathi]

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 literally. But I think the thing that we originally thought was that everything was like the solar system. And then we found all of 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 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. 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.

[Matt Kirschen]

God, scientists love a contrite acronym. Nothing makes scientists happier than finding some acronym.

[Neil DeGrasse Tyson]

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.

[Matt Kirschen]

Mm.

[Neil DeGrasse Tyson]

Okay, what does that stand for? He says mnemonics are generally idiotic constructions. So ever since then, I've not over overdone my mnemonics. So what else you got?

[Matt Kirschen]

All right, so Ryan Guerrentz 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?

[Neil DeGrasse Tyson]

Doesn't he. I. I'm betting, because we do have images of planets. I think this questioner wants to see continents and oceans and. And cities. What do you think?

[Anjali Tripathi]

I mean, because I'm right there with you, Neil, that we. We've seen exoplanets already. Right again. They don't look like Earth so far. And we just got 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 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.

[Neil DeGrasse Tyson]

So, not to dis Pluto even more, but when you described 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.

[Anjali Tripathi]

Mm.

[Neil DeGrasse Tyson]

That's the edge of the solar system.

[Matt Kirschen]

Wow.

[Neil DeGrasse Tyson]

It was well inside of the orbit of Pluto. Yeah. 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. They were way out there.

[Anjali Tripathi]

Nah, it was relatively nearby, right?

[Neil DeGrasse Tyson]

Yeah, relatively nearby, exactly.

[Anjali Tripathi]

Because we saw 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.

[Neil DeGrasse Tyson]

Yeah, yeah. Time for a few more, I think.

[Matt Kirschen]

Yeah, absolutely. So, J. 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.

[Neil DeGrasse Tyson]

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

[Anjali Tripathi]

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 it 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.

[Neil DeGrasse Tyson]

So planet migration.

[Anjali Tripathi]

Yeah.

[Neil DeGrasse Tyson]

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, and 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 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?

[Matt Kirschen]

Well, while we're talking about moons, there's a moon question from Fred Dog. That's a patron Fred Dog. I don't know if you're from the Westchester Fred Dogs any relation, but 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 search for life beyond our solar system?

[Neil DeGrasse Tyson]

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 is 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.

[Anjali Tripathi]

Yeah. So, I mean, it's great that Fred Doug mentions these moons, right? Europa, Enceladus, 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 bio signature for life here. So it's not saying that moons are out of the question. People are definitely looking at moonshine. I think David Kuping, who you frequently have on this show, your neighbor down the street there in New York, he's always thinking about exomoons. And so he's up the street.

[Neil DeGrasse Tyson]

He's up the street.

[Anjali Tripathi]

Excuse me, my very specific about direction.

[Neil DeGrasse Tyson]

Yeah, yeah, get my New York straight here. Yeah, he's up at Columbia and we're delighted when he's on the program.

[Anjali Tripathi]

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. 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 on the surface here.

[Neil DeGrasse Tyson]

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, you gotta agree with at least some of that sentiment here.

[Anjali Tripathi]

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?

[Neil DeGrasse Tyson]

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?

[Anjali Tripathi]

I think we normally call it Mimas, but, you know, we can have different names. Sure.

[Matt Kirschen]

When no one's listening. Behind closed doors. When you're just over a few pints.

[Anjali Tripathi]

Exactly. So there's all kinds of beautiful things there, but I wouldn't count 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 why do all of these outer planets have rings? Saturn gets all the credit for 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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[Anjali Tripathi]

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[Matt Kirschen]

There's a nice question here from Andy L. Who lives just up the road from Anjali and me in Thousand Oaks, California. My understanding of the two main exoplanets, planet 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?

[Neil DeGrasse Tyson]

Don't our people ask good questions?

[Anjali Tripathi]

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, ah, it's a secret. I don't want to tell anyone. I want everyone to know how cool exoplanets are.

[Neil DeGrasse Tyson]

Oh, yeah.

[Anjali Tripathi]

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 no, 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 Andy L. 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 where 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.

[Neil DeGrasse Tyson]

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 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 El 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?

[Anjali Tripathi]

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 you have to see it regularly. And so we expect we're going to see planets and systems where we thought, oh, didn't see that there. But okay, I guess I could have seen that. Cut time.

[Matt Kirschen]

Just to be clear, what you were saying a second ago, Neil, you can sort of just assume that planet's orbital plane is evenly distributed in all angles. So you can go like, we can see these angles and these angles, so you can then calculate, well, these ones must also exist.

[Neil DeGrasse Tyson]

Exactly. 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 these other planets that don't, then just look at the statistics of the orientations and you can fill in those missing numbers. If it's randomly distributed out there.

[Matt Kirschen]

While we're talking about that kind of detection and validation of things that are a distance away, Alan G. Says, hello, great and 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?

[Neil DeGrasse Tyson]

Ooh, those are fighting words. No way of validating.

[Matt Kirschen]

Show your work.

[Neil DeGrasse Tyson]

What does he want to go there and. And get a beaker? A sample?

[Anjali Tripathi]

Like, no question, though, you just died.

[Neil DeGrasse Tyson]

Your whole community right there.

[Anjali Tripathi]

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.

[Neil DeGrasse Tyson]

So I think it was in 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.

[Anjali Tripathi]

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. 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 discs, like I said, when they fall to Earth. 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.

[Neil DeGrasse Tyson]

Where was that?

[Anjali Tripathi]

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

[Neil DeGrasse Tyson]

No, I have not seen it.

[Anjali Tripathi]

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.

[Neil DeGrasse Tyson]

Not all of us just hang out in all the rooms of the White House. Just let the record show I was just staff.

[Anjali Tripathi]

Right, You're a fancy, distinguished guest.

[Neil DeGrasse Tyson]

I did spend a little bit of time at the White House, yes. I know. Bits and pieces, the White House.

[Anjali Tripathi]

I don't know.

[Neil DeGrasse Tyson]

All the White House.

[Anjali Tripathi]

No, no. It's just cool, though, because people look at this and they go, that's just an ugly rock, right? Cause it's like a little black rock with white dots. And I used to go and explain to people like, no, this is amaz. 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 little fossilized flower 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 start 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.

[Neil DeGrasse Tyson]

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.

[Matt Kirschen]

Program that we know of.

[Anjali Tripathi]

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

[Matt Kirschen]

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.

[Neil DeGrasse Tyson]

Man, we got time for one more question. It better be a kick ass question.

[Matt Kirschen]

All right, well, I like. I like this question. Hello, doctors, tnt. Oh, this is Nancy from Hell's Kitchen nyc.

[Neil DeGrasse Tyson]

All right.

[Matt Kirschen]

Are we up or down or across the road from that? Which direction are we?

[Neil DeGrasse Tyson]

They're down from us.

[Matt Kirschen]

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?

[Anjali Tripathi]

So I will first of all say lots of bugs. No chatgpt in my coding, so have seen plenty of those. But I actually don't think I've ever had a 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 gases 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 sub grid 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 tomb 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.

[Neil DeGrasse Tyson]

Well, except 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?

[Anjali Tripathi]

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 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.

[Neil DeGrasse Tyson]

Yeah, she mentioned this experiment by Tomre. 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 arm 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 different times. And Anjali, do you remember how he figured that out, how he did the experiment?

[Anjali Tripathi]

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 simulations.

[Neil DeGrasse Tyson]

I'm trying. Was 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.

[Anjali Tripathi]

To figure out the mergers even before.

[Neil DeGrasse Tyson]

Tomb Ray's first computer simulations of this, as Anjali describes Eric Holmberg, another galaxy guy, he figured out how to do it with light. Cause 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 gonna simulate that on a table? How are you gonna 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.

[Matt Kirschen]

That makes sense.

[Neil DeGrasse Tyson]

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 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 back and forth.

[Anjali Tripathi]

Oh, Neil, galaxies are beautiful, right? I'm cute too. So maybe you think anything that comes out of a puppy is cute.

[Matt Kirschen]

But yeah, Puppy vomit can be beautifully artistic.

[Neil DeGrasse Tyson]

Okay, that's pretty clever, right? You think?

[Anjali Tripathi]

I mean, it's amazing what people do in all sort of senses, 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.

[Neil DeGrasse Tyson]

So presumably some of these planets might have hydrogen sulfide.

[Anjali Tripathi]

You did not poison anybody, Neil.

[Matt Kirschen]

That's what I was about to say.

[Anjali Tripathi]

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 puppy vomit smells, but we had some other smells there that were very.

[Neil DeGrasse Tyson]

Your perfumer brought you manure?

[Anjali Tripathi]

No, no smells of manure. Aren't you glad you don't work at NASA with me just smelling?

[Neil DeGrasse Tyson]

Yeah, thank you for clarifying.

[Matt Kirschen]

Not the actual. Just the little manure scent that you can just dab on your wrist and behind your ears.

[Neil DeGrasse Tyson]

Remind me not to buy that person's perfume.

[Anjali Tripathi]

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 G and T 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 in the 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.

[Neil DeGrasse Tyson]

Well, thank you, Anjali, for participating in our cosmic queries.

[Anjali Tripathi]

It's so good to be here.

[Neil DeGrasse Tyson]

And when you pass 6000, give us a call. 6000 exoplanets?

[Anjali Tripathi]

I honestly suspect it'll pass 6000 by the time this airs.

[Neil DeGrasse Tyson]

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, which is a lot of people. A lot of people. Yeah, a lot of people. 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 X. So planet. And then they sit down.

[Anjali Tripathi]

I love that, Neil.

[Matt Kirschen]

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

[Neil DeGrasse Tyson]

That's how you began the whole conversation.

[Matt Kirschen]

Yeah.

[Neil DeGrasse Tyson]

Yes, Laura. I tell all my friends at jpl, I said hi.

[Anjali Tripathi]

Will do. Will do.

[Neil DeGrasse Tyson]

Matt, we'll see you on your website.

[Matt Kirschen]

Yeah, I'm on tour and on Probably Science. We will get you back very soon.

[Neil DeGrasse Tyson]

Probably Science. That's your podcast?

[Matt Kirschen]

That is my podcast, Probably Science.

[Neil DeGrasse Tyson]

Okay.

[Matt Kirschen]

We're very happy to steal you.

[Neil DeGrasse Tyson]

I've been on it only once, apparently.

[Matt Kirschen]

We're making it happen again. We're making it happen again.

[Neil DeGrasse Tyson]

Near my phone the whole time.

[Matt Kirschen]

You're a busy man. We need to pick up moments.

[Neil DeGrasse Tyson]

All right. This has been another installment of Cosmic Queries. This would be the Exoplanet edition. I thank my guests Anjuli Chapathi and Matt Kirschen. Until next time, I bid you to keep looking up.

[Shankar Vedantam]

Are you on the right track? What do you want to be remembered for? Is this really all there is? Asking big questions about your life can feel overwhelming. But the Hidden Brain podcast, hosted by me, Shankar Vedantam, is here to help you get started. All through the month of July, Hidden Brain will bring you our you 2.0 series with a special focus on purpose, passion and meaning. If you're feeling adrift, alone or burned out, this series is for you.

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