Low-Mass Mania with Emily Rice

Coming up on StarTalk Cosmic Queries, my friend and colleague Emily Rice is going to tell us all about the latest in brown dwarfs and exoplanets.

Oh yeah, that all comes to you from right here in my office at the Hayden Planetarium of the American Museum of Natural History.

Welcome to StarTalk, your place in the universe where science and pop culture collide.

StarTalk begins right now.

This is StarTalk, Cosmic Queries edition.

Got Chuck Nice with me, Chuck, how you doing, man?

Hey, what’s happening, Neil?

All right.

You know, there’s a part of the universe that is a little foreign to me because most of my research back when I was like active with it was galaxies, large scale structure, Big Bang.

And you come down, you get closer and closer and closer.

There’s a whole world there.

Literal and figurative world.

People think about planets and stars being born around which you would find planets.

Right.

And we got one of the world’s experts right here in the house.

And here she goes.

Emily Rice.

Emily.

How you doing?

I’m very excited to be here again.

Welcome back.

Thank you.

Yeah.

To StarTalk.

And just let the record show that whatever I’m wearing that’s cosmic, and people say, oh, that’s cool.

That’s cosmic.

I just want you to know that when I…

Emily will come in with something cooler.

When I’m with my people, it’s just camouflage.

Because everybody else has got something.

Now it is.

Yeah.

And you were like leader of the pack there.

Aren’t you involved in some haberdashery or something?

The haberdashery.

What?

The clothing.

A little bit of this, a little bit of that.

Or do you still have a jewelry line?

It’s a super long story, but yeah.

So, it started as a phenomenological, like we noticed people, you know, you were one of the originals, but other people were doing it too.

I think you might be one of the first.

To be loud in my attire.

But a bunch of people were doing it.

And so we started a blog originally, Summer, Ash and I.

Summer was at Columbia at the time.

And we were doing our outreach stuff and wearing our stuff, like our galaxy leggings and our NASA swag and stuff like that.

We were like, this is so cool, because some of the stuff we noticed was real Hubble images and stuff like that.

And so we started a blog that was meant to share it with the public.

Like, oh, you bought this thing.

What is it?

Where did it come from?

Astronomically, how was it taken?

Yeah, they added some science to it.

What I didn’t expect is for the rest of the astronomers to be so into it that we presented it at a research conference, but there’s always room at the research conferences for outreach and education and things like that.

And the number one question we got at our poster at the research conference was, where do I buy this stuff?

Like from the other astronomers.

The Genesis.

You can make stuff with my science.

And at the time, we were just finding things that were out there.

People’s Etsy shops and small designers.

It was kind of everywhere.

A curator.

Cosmological Joan Rivers.

Oh, who are you wearing?

What galaxy is that?

And it’s now become a shop, so long story short, we became an online shop, so we create our own stuff as well.

It’s called StarTorialist.

StarTorialist.

You see what she did there?

Okay, well, cool.

That’s online.

We can find it online.

StarTorialist.

So, I really thought it would be a fad that would just kind of happen and fade away, not be popular anymore, which is kind of fine.

But it hasn’t.

It’s continued to grow.

We’ve added our own stuff.

So, I say that we’re the dark energy of the fashion universe.

Look at that.

For astronomy.

All right.

Dark energy is a power of expansion.

Exactly.

It accelerates the expansion of the universe.

Which you don’t know.

In other words, you’re unaware of why you are successful.

Absolutely.

Fully.

It’s not fully understood.

It will be.

We just need a little more grant money.

We don’t know.

So, your expertise is newborn stars, exoplanets, brown dwarfs.

Yeah.

And I have an issue, first of all.

So when I think of a star, it’s self-luminous and it’s burning bright, even though burning to us means something different than to a chemist.

Fusing bright.

Fusing bright, but that doesn’t have the alliteration and it’s not as cool.

So stars will burn bright.

Even if they’re burning dimly, they’re still sort of luminous in the infrared or somewhere.

At no time am I thinking I’m looking at a brown object.

So why did these objects, which are in the Netherland between planets and stars, because I don’t call planets brown, because they’re going to reflect light and they’re going to have whatever colors they have.

And I don’t call stars…

Where do you get the color brown from?

The color brown apparently came from Jill Tarter, who you’ve had on your show before.

Yes, Jill is a friend of StarTalk.

Active with SETI, Jill Tarter.

I watched her interview on StarTalk once and she told the story of her early career.

It was actually in her PhD thesis where she did some research on these objects that were previously called black dwarfs.

And so it started in the 60s.

Oh, so we had to take it away from the black.

Well, that makes perfect sense.

Couldn’t just let it be a black dwarf.

No, no, we can’t have that.

Sure, a hole can be black.

No problem.

Yes, exactly.

You know, we have white holes too, apparently.

Well, I got paper, but not in a real thing.

Okay.

Anyway, sorry.

Yeah, they were black dwarfs originally because the idea was that was purely theoretical was what happens when the stars don’t have enough mass pushing down from the outside to get a high enough temperature at the inside to fuse hydrogen and helium as a steady source of power.

And so they were called…

Yeah.

So this is why the sun creates energy.

It’s a stable source of energy, of pressure, pushing outwards against gravity.

And the idea is that these things that started to form like stars but wouldn’t have enough mass would kind of still continue to exist, but what would they look like?

What would their structure be?

How would they radiate?

Things like that.

That was first kind of described by a theoretical physicist in the 1960s, SS Kumar was his name.

And then Jill Tarter, I think it was in 1975 in her thesis, kind of proposed the term brown dwarfs and that kind of stuck.

So she originally studied these objects.

It’s still at that point theoretical.

And of course, to Chuck’s point, black holes were gaining very serious attention around that time.

Yeah.

And so I think that’s what’s like, the way that we call stuff dark now is…

It was a cover story of the New York Times magazine, black holes, new research.

So it took the word.

I think you’re right.

Yeah.

But then they realized like, okay, they’re not fully, you know, they’re not fully unexplained.

Like they are reasonably well explained by like kind of normal physics.

And so they moved away from black and just called them brown.

Jill Tarter on your show said, oh, you know, so I started out doing this and then I wanted to do research that mattered.

Talking about her shift into SETI, which I’m like, I can’t argue with that too much, but it’s stung a little bit.

But it’s an amazing, so she coined the phrase in 1975.

And they still weren’t known to exist.

Like they weren’t actually discovered until the 1990s, even then it kind of took a while.

Just for context here, right?

And I hate thinking this way, but it just jumps into my head.

You realize, you just described something that happened 50 years ago.

Yeah, more that we had a conference actually 50 years after to celebrate the original paper as 1963, 64.

Had it been 1975 and we had this conversation, you’d be talking about 1925 as 50 years earlier.

That’s what I’m saying.

This just to put that where…

Yes, put it in the proper context.

In the proper context.

You know, you guys are old.

It is amazing how far we’ve come and how quickly…

I do feel like it’s not typical.

This is the first time in our civilization possibly that these cutting edge research results are disseminated to the public so quickly.

That’s actually something that I love doing at StarTorialist.

There was the press release of the new polarized image of the black hole in the center of the Milky Way galaxy.

And it came out and I showed it to my students that day in class and described it to them.

That’s amazing.

I can put it on a t-shirt for you and sell it at StarTorialist.

The three of us sound a little bit like we’re on the porch.

I remember we had to teletype each other and let them know about the discoveries that we made.

We had to send a telegram.

Dots and dashes is how we had to tell people about our great significant discoveries.

Who started it?

Feels a little bit like that.

So before we go on to our Q&A here, let me give you a full, dutiful introduction.

You’re a research associate here in our Department of Astrophysics of the American Museum of Natural History.

And you even have a desk.

So we get to count you as a resident research associate.

So continued welcome to those ranks.

You’re also associate professor of astrophysics at the McCauley Honors College in CUNY, the City University of New York.

And you’re in the faculty PhD program at the CUNY Grad Center.

So you’re all in there.

It’s kind of all over the place, yeah.

And we see some students of yours.

They come through here.

It’s very communal.

So thanks for helping.

I bring my tests here as much as I can.

Yes.

Didn’t I talk to your class one time?

Yes.

Twice, yeah.

Thanks for bringing them by.

I’m delighted.

Just call me.

And you’re a founding member of BDNYC.

And all those letters are like in Subway.

And what line is that?

We are very proud.

There’s a whole story behind it.

There’s no why.

There was no why.

So we made up the why.

We made it red and white in the center.

There’s no why train, but it’s kind of the inversion of the WNOIC logo a little bit.

But we had a joke going for a little while.

So these brown dwarfs, we have the stars that have the letters that go with them.

And there’s a whole story about that.

OBAFGKM, that was kind of set into order about 100 years ago by the Harvard College computers or the Harvard Observatory women who were working as computers there.

Annie Jump Cannon took that letters.

They were originally done by the strength of the hydrogen absorption line, but then they were realizing that actually it’s a little bit different.

It needs to be if we order it by temperature, we change up the letters.

And so that’s why it’s not alphabetical anymore.

But when we started to discover these new…

So rather than re-letter them, they kept letters, they kept them, and just rearranged them.

And confusing people for the century to follow.

I call it confusion, I call it job security.

And there was a bunch of different systems that they were dividing, and a lot of controversy routed at the time.

But since the brown dwarfs were discovered, so the M dwarfs are the coolest and the faintest stars.

But for the brown dwarfs, we had to introduce new letters for the spectral type.

And there are full papers going through the alphabet to say, which letters should we use, basically.

And so the next ones were L and T.

They were kind of proposed about the same time.

That is, like, forever messed up my understanding of the alphabet, because it goes M-L in stars.

But then the next one, when we realized, okay, there might be things fainter than these T dwarfs, cooler than the T dwarfs, they’re going to have different spectral characteristics and things like that.

They proposed that there would be Y dwarfs.

And so this was even in my, like, scientific career in the last 20 years or so.

And so for a little while, we had a joke with the BDNYC logo, where there was no Y dwarfs yet discovered, and there was also no Y train, that we would have to explain to people from outside New York City.

Then the Y dwarfs were actually discovered with the Wide Field Survey Infrared Explorer, this NASA mission in the infrared.

And so now the joke has become far too long to be actually interesting anymore.

But we’re very proud of our BDNYC logo with the subway things on there.

So it’s a local community of people of like interest, professional interest.

Yeah, the three of us started out myself, Kelly Cruz, who’s faculty at Hunter College in CUNY, and Jackie Farrity, who’s Senior Scientist and Educator here at AMNH.

And it was, man, over 10 years ago now, something like 12, maybe 14 years ago, we founded BDNYC.

It was one of the first groups that was led by a bunch of women.

It was still rare back then for kind of the three of us to be working together, leading papers together.

We were counting how many papers could we find with only female authors.

For example, we published one with just the three of us.

We couldn’t find another one that had any more…

There were no souls.

That were more than three authors, but only women.

It sounds like that black toll test on movies.

Yeah, the BDNYC test or something like that.

Sounds like black people in Utah.

If you see three in one street, there’s something…

You’re no longer in Utah.

It’s getting better now, I feel like.

Parallel dimension or something.

So, again, one last thing before we cross over.

How does your interest in brown dwarfs take you to an interest in exoplanets?

Oh, they’re very, very similar.

So, the interesting thing is that the difference in between brown dwarfs and stars is actually relatively straightforward, relatively.

It’s the nuclear physics on the inside.

Like, it’s whether they have enough mass to create the high enough temperature at the core to fuse hydrogen in the helium.

Like, that’s a big difference.

Kind of evolutionarily and structurally.

It’s a clean line, too.

Yeah, it’s a very, like, they either turn on or they don’t.

So, they ignite it or they didn’t.

Yeah.

But for the lower mass things, it’s not as clear.

And originally, we had a kind of, we wanted to have a similar definition, and so there was this lower mass demarcation that was 13 Jupiter masses instead of, between the stars and the brown dwarfs, it’s about 75 Jupiter masses.

And that was, again, derived in like the 1960s.

For the 13 Jupiter masses, we wanted to make this nice clean break between the brown dwarfs and the planets.

And so 13 Jupiter masses is the mass.

Just to be clear what you’re doing, you’ve turned Jupiter into its own measurement.

Into its own measurement.

Oh yeah, we always.

Oh yeah.

Oh, with the masses, yeah, yeah, yeah.

I don’t know how common an exercise that is in the rest of society, okay?

So, but yes.

In New York City, I don’t know, yeah, it’s one block, but it’s one avenue block versus one street block or something like that.

It’s whatever miles.

But yeah, then we do this in astronomy all the time.

This is the great, like, astronomers, you know, we say astrophysicists, if we want people to be impressed or something like that, we’ll take anything and call it one, or like set it relative to one another to make the math easier.

Like we’ll do anything to make the math easier.

Oh my goodness.

Earth-Sun distance is one astronomical unit.

This is one.

And how far away is it from the sun?

It’s 10 of us.

Or five of us.

Right, right.

Yeah.

So the 13 Jupiter masses, above that, there would be some nuclear fusion going on.

So more massive than that, you might fuse a little bit of hydrogen, a little bit of lithium, because that’s easier to fuse.

Deuterium, which is heavy hydrogen, is also easier to fuse.

And so that easier means it will fuse at lower temperatures.

And so above 13 Jupiter masses, there might be a little bit of fusion going on.

And then below 13 Jupiter masses, they figured out there’s no fusion going to happen ever.

But the thing is that this demarcation doesn’t actually make a huge difference in the long term for these things.

Like not in terms of the structure, not in terms of the evolution.

So how does it get you interested in an exoplanet?

Yeah, so what ends up happening is that the brown dwarfs are actually really similar to the massive exoplanets.

And some of these massive exoplanets are things that we found more easily than we found the Earth-like exoplanets.

So the size of your party grew.

Five, 10 times the mass of Jupiter.

We found those exoplanets around other stars even more easily.

So you find yourself at the same conferences as these other…

Yeah, we used to have kind of, we called them Cool Stars Conferences, and first the brown dwarf people went to the Cool Stars Conferences, but then when the exoplanets got big enough, now there’s a ton of different exoplanet conferences that the brown dwarf people go to.

We kind of go to both, too.

And we bring our karaoke along.

But it’s kind of like…

And it’s also where collaborations are born.

I mean, you can’t undervalue…

And then the planetary science people who have studied the planets in the solar system for so long are like, what are you guys doing?

Because so much of it needs…

Like Jupiter we know in a lot more detail, but there’s still a lot of open questions.

Saturn we know in a lot more detail.

Even Earth atmosphere stuff, brown dwarf people can learn in order to study these things.

Hi, I’m Ernie Carducci from Columbus, Ohio.

I’m here with my son Ernie because we listen to StarTalk every night and support StarTalk on Patreon.

This is StarTalk with Neil deGrasse Tyson.

Let’s go jump right in.

Okay, we got questions.

And they are all from our Patreon people, and they are all for you specifically.

All right, so this is from Lara Fortier.

It says, greetings from Arizona.

Hello, doctors Rice and Tyson, Lord Nice.

I have heard that brown dwarfs and hot Jupiters are similar.

In what ways do they differ?

And how are they made when they are clearly separated from a solar system?

I heard somewhere that we don’t really know how low density stars are even created.

Have we learned more from people doing their homework before they come in on you?

Yeah, they really are.

So the hot Jupiters are one of these things that we found around other stars that we haven’t found in our solar system.

And the hot Jupiter is a nice one because it is what it sounds like.

It’s a Jupiter-sized planet, Jupiter-mass planet.

That all the other planets think are super sexy.

Oh, hot Jupiter in the house.

Close to its star, so that it’s irradiated by the star.

So it’s not hot on its own doing.

That’s the thing, it’s not hot on its own.

So that’s a little circumstantial.

Yeah, and so that’s the interesting thing is that these hot Jupiters end up being similar to mass and maybe a similar temperature to a brown dwarf, but for a different reason.

For a different reason.

Yeah.

Like whether the radiation is coming from the outside or the inside.

And so there’s similarities, but there’s also differences.

Yeah.

So those are one kind of overlap.

Okay, thanks for clarifying that.

And what’s the other part of that question?

She said, I heard somewhere we don’t really know how low density stars are created.

Yeah.

So, did they mean low mass stars, low density?

Yeah, they can be kind of the same.

The interesting thing is that because of the physics going on at the very, very cores, these things kind of plateau in size, and so they do get lower and lower density.

Because the mass decreases while the physical size stays the same.

And so they do get lower and lower density, but we talk about them more in terms of their mass.

Yeah, we don’t fully know how many of the low mass ones are out there.

That’s just like counting them.

We don’t fully know that.

We don’t really know how they formed or how low the mass can go when it forms like a star does.

Why did we invite you to this?

We don’t know.

Job security, yeah.

So let’s get to brass tacks.

I have a gas cloud out there.

There’s so many beautiful images of gas clouds.

From Hubble, especially from the WST.

WST, beautiful ones, yeah.

So, and we see stars being born.

Why weren’t those stars born a billion years ago?

Why are they being born now?

What happened in that gas cloud ever at any time to make a star?

Oh, it depends on what the, yeah.

And how does it know to make a high mass star or a low mass star?

Yeah, I mean, the universe does that.

Like, we don’t necessarily, you know, we.

Now, why did she get away with that answer?

Yeah, well, I was about to say, she actually gave you your answer, but much more succinctly, which is the universe is under no obligation to make sense to you.

That’s true, yeah.

We, that’s kind of figuring out, seeing if there’s a law.

So, there does seem to be a law that, like.

We should allow that in the PhD defense, the thesis defense.

Right.

So, excuse me, why do you get this, the universe just does that?

I feel like that is, like, as soon as you can say, like, confidently, I have no idea, or I don’t know, or I don’t think we can know, like, that’s when you’re an actual scientist.

Like, there’s a lot of pressure to know the answer.

Very important, right?

The confidence and the uncertainty, like, makes.

That is.

Makes a scientist.

Because everybody else is trying to give an answer.

I was gonna say, and that is the difference between, like, I hate to bring it up.

But science and religion, and you said somebody BSing you.

I said science and religion, but yeah.

Oh, I didn’t mean to complain those two, but.

But no, it’s the truth.

Like, you know, religion has an answer for everything.

Basically, yeah.

They have an answer.

Even when one answer contradicts the other answer.

It does make a difference.

I gave you an answer.

You know, that’s, yeah.

That’s very cool.

Or I should say maybe it’s like my parents, which were, because I said so.

Yeah, exactly.

That’s the ultimate answer.

That’s the ultimate answer, because I said so.

That’s very cool.

All right, well, this is great.

That was great.

That was really informative.

Thank you very much, Laura.

And say her last name one more time.

Fortier.

Which is not my forte, to pronounce Fortier.

Okay, this is Jason Dorickson.

And Jason says, what is the largest dwarf star ever discovered?

Oh, look at that.

He’s going for the jumbo shrimp angle.

He’s going for the jumbo shrimp angle.

What is the largest dwarf star that we have actually seen?

That’s a good question.

I don’t think I can answer that very concretely.

And the reason why is because there’s more weirdness here that I haven’t even really touched upon, which is the fact that when the stars are formed, they then kind of form and they start to fuse the hydrogen and helium and they kind of, once they turn on, they stay that way for a while.

They get stable, right?

And so they have the same temperature, the same luminosity, the same mass for a long time.

That’s the other thing.

Wait, wait, the same mass, except for the little bit they’re losing when they convert it into energy.

Oh yeah, but it’s a tiny, even for the small stars, it’s a tiny bit of mass.

Yeah, a tiny fraction of mass.

Even for the big stars, the mass doesn’t change a huge amount with the nuclear fusion.

But the big stars have shorter lifetimes, and the small stars have longer lifetimes.

So the low mass ones?

The low mass ones, we think they can last, and I can’t believe we can throw around this number, but for like a trillion years.

Yeah.

Well, you can throw it around because nobody understands what it is.

Yeah, and probably nobody can be around to prove me wrong here.

It’s way longer than the universe has been alive to this day.

Look at that.

But the tricky thing is, so that star becomes stable and kind of doesn’t stay, but the brown dwarfs will kind of gradually cool and fade over time.

Like they have this kind of residual heat leftover from forming, but then they just kind of cool and fade.

And so as astronomers just looking at them, we can’t really tell whether we have a young, low-mass brown dwarf that’s just formed or an old high-mass brown dwarf that’s been cooling off for a while.

Because they last for so long, you can’t really tell.

They look the same.

The regular, the stars last for a long, long time, but the brown dwarfs cool off.

Yeah, and so we have this, we call it the age-mass degeneracy.

So we don’t know if we have a young, low-mass thing that’s just hot because it’s still young, or an old, high-mass thing that’s hot because it’s a little bit higher mass, but it’s been around for a long time because they’re cooling off over time.

We have to get her to explain degeneracy.

Degeneracy, yeah.

It’s like where you can’t, degeneracy is you can’t tell the difference.

I know, degeneracy.

It has a gambling problem.

The browns worse of today.

Oh, God.

They’re just not what they used to be.

I’m never gonna be able to explain my research again.

It’s so funny, we get so used to using these terms.

So degeneracy is a mathematical, physical mathematical, so give it a gamble here.

There’s a couple different kinds even.

So our degeneracy, the age-mass degeneracy, is that you don’t know one without constraining the other.

So it’s ambiguity is the colloquial, like that’s the…

Two things look alike, but they can be very different from each other and just happen to look alike in that moment.

And you can’t distinguish one from the other without another dimension of data.

Yeah, we have to be able to measure the mass somehow, or we have to be able to measure the age somehow.

You need another data point to break the degeneracy.

And there’s another degeneracy.

Yeah, and then the other degeneracy is like the cores of the objects are partially degenerate, we say.

And that’s like a quantum mechanical thing, where the actual electrons in the atoms get so close together that they fill up the quantum states, and that provides pressure against the mass pushing down.

Can’t keep squeezing down.

That’s called degeneracy pressure.

So I’ve forgotten we have degeneracy used in two completely different ways.

Yeah, they aren’t two different, I never thought about that before either.

Yeah, that’s such a weird, we speak our own language sometimes.

Yeah, and so this high mass, so it’s really hard to tell actually exactly how high mass something is.

Like normally we have the 75 Jupiter mass cutoff, but we also don’t know is it younger, or is it old, or something like that.

Which will factor into whether or not it is or it isn’t, which factors into whether it’s the largest brown dwarf we’ve ever seen.

I gotcha.

Wow, you put all the, damn, that’s rough.

Science is hard.

Here’s the answer to that question.

Yeah.

You find new problems as soon as you dig a little bit deeper.

So Jason, the answer to your question is we don’t know.

We don’t know, man.

Sorry.

How many is that?

I think that’s, I don’t know for the first few questions.

Oh, that’s pretty cool though, I love it.

But who is it that says the only thing I know is that I know nothing?

What’s that quote from?

All I know is that I don’t know nothing.

That’s Operation Ivy, but.

I think before that, I’m thinking Ancient Greece, Socrates.

Socrates and Operation Ivy.

So it’d be Socrates, actually.

So it’s Socrates Johnson.

Socrates, it was, if I know anything at all, it’s that I know nothing.

I’m paraphrasing.

All right, this is Nobble Gobble.

And Nobble Gobble says, Salutations, doctors and Lord.

My name is Caleb Noetgen.

Mm-hmm, okay, No-eh-getten, mm-mm, Noetgen, there you go.

My name is Caleb Noetgen.

Oh, thanks, Caleb.

He says, good luck with that one, Chuck.

He even knows.

Son of a gun.

He knows.

I can’t believe you, man.

Then he says, this is Caleb from Wichita, Kansas.

People are cold.

People are getting no respect.

So he doesn’t let the cat mash on the keyboard.

Chuck is gonna have fun with this one.

Yeah, tell me about it.

Yeah, he says, Since brown dwarfs are sort of an intermediate object between a planet and a star, I was wondering if there was a common trend between mass composition and magnetic field strength.

Oh, gosh, magnetic fields.

Look at that.

This is one of those things where if you want to trip up an astronomer, you ask them about dust or you ask them about magnetic fields.

And it’s nice because it applies really across any kind of research.

We try to ignore it, because those things complicate things hugely.

So yeah, these things do have magnetic fields, but we actually don’t know how the magnetic fields are generated on these stars.

We think we know how magnetic fields are generated on the sun, because there’s this cool thing called the tachocline, and it’s like these moving charges are going to generate the magnetic field, and we think that’s where it comes from on the sun.

And that tachocline is the border between a radiative zone and a convective zone.

So there’s energy transport is happening in different ways.

But for brown dwarfs, what we think we understand of the structure, and this is all from modeling things and understanding how energy transport is supposed to happen, we think at some point they become fully convective.

So this is kind of cool.

It’s like the convection is this big bulk motion of material that happens when you like boil water and stuff like that.

So it’s relatively familiar to us.

It’s like an internal churning.

Yeah, it’s this churning.

But instead of the churning only going down part of the way inside the stars, which it does for the higher mass stars, it goes all the way down.

So the two of those together, you have a radiative effect, which is the outward pushing of the star.

And then you have the internal churning and the two of them together, like the Earth’s core rolling around inside of us makes a magnetic field, is that?

Well, we don’t know for the bond.

That’s the thing, is that because…

All I know is that it went to seven Idle Knows.

Yeah.

So, and we also think the magnetic fields are going to be different across the different types of bond scores.

A tachocline.

A tachocline, and not just a dynamo?

Or is a dynamo the broader term?

Dynamo is the broader term that generates the magnetic fields, yeah.

Am I messing up my solar physics?

Hopefully not, I could be.

Somebody can get their five cents back.

Their five dollars back.

So what is the difference between that and a star, because we know that’s what had happened in our own sun?

Yeah, in our own sun, we’ve kind of got these bigger motions.

In the brown dwarfs, we don’t know fully where, there isn’t this separation between the inner layers, and so we don’t know where the magnetic field comes from.

But there is a magnetic field.

We see spots on the low mass stars and on the brown dwarfs.

We see aurora on the brown dwarfs.

On the sun, spots always come in pairs.

And one is plus and one is minus.

Oh, I didn’t know that.

Yes, it’s a cool fact.

There’s a bright spot that goes along with the dark spot.

I think the bright spot is harder to see.

Look at that.

That is the first I’ve ever heard of that.

And the solar wind that we’re going to see.

Here’s something else I heard, which is consistent with what you just said.

Back in my day, you would accuse someone of, if they’re presenting their research, and they say, the bigger is the effect of a magnetic field in what they describe, the less they know about the subject.

The less they can explain, they put in more magnetic fields.

Which is what accounts for everything that they don’t otherwise know.

Magnetic fields are challenging.

They’re very hard to understand.

Astrophysically.

We’re talking magnets, it’s no big deal.

Wow, well, Caleb, that was a great question, man.

Three, I don’t know, it’s rough to say.

It doesn’t make it, but here’s what I’m saying.

I was counting seven, but if it’s only three, good, all right.

But this is what I’m loving about the I don’t knows.

Every time we don’t know something, I learn something.

Like something else comes out of it that I’ve never heard before.

That’s the third time that we’ve had an I don’t know, but every single time there’s something really cool that we find out in place of I don’t know.

And by the way, it’s also a measure that the field is very much embedded in its own frontier.

When you’re on a frontier, every step you take is into the unknown.

Thanks Okay, this is Atticus Thompson.

Atticus says, hello, Dr.

Tyson, Dr.

Rice.

Is this a letter from the Civil War?

We need that voice.

My dearest Dr.

Tyson and Dr.

Rice, today was an especially difficult day.

Signed Atticus.

Is anybody named Atticus today?

Yeah, they’re all in Brooklyn.

Oh, is that right?

100% they’re all at the playgrounds in Brooklyn right now, I guarantee you.

And you are so right.

But that’s Atticus from Atticus Finch.

Yeah, I would think.

But anyway, he says, my name is Atticus, and I’m nine years old.

He’s nine?

Yeah.

He says, I live in Sotty Daisy, Tennessee.

I want to know if two brown dwarfs collided, do they become a larger brown dwarf, or would they just become a low mass star?

That is a very good question.

Okay, so Atticus, first of all, you ain’t fooling nobody.

I don’t care if you’re nine or not.

I know your father helped you with this question.

You’re not fooling anybody, Atticus.

I’m Atticus, and I’m nine years old.

I would like to know.

Wait, dude, when I was nine, I could have asked that question.

That’s what I’m like.

My interest in the universe was birth when I turned nine years old.

Okay, all right.

Well, Atticus, I take it back.

No, I don’t.

No, no, you want to get at him?

Ask him if he paid the $5.

Yeah.

Yeah, but if he’s asking questions like that, he might have a job.

I’m just saying.

Okay, so what happens when stars collide?

Yeah, it’s going to depend on their mass.

Really?

Yeah, it’s not outside the realm of possibility if you have, like, that’s just a multiplication or an addition problem, really.

If the two brown dwarves come together and have more than that, 75 masses, in theory, yeah, it could ignite hydrogen fusion.

Wait, so the whole star will reorganize.

Quite possible.

It’s something that we don’t expect it to happen a lot.

I don’t think.

It wouldn’t be an object with two separate cores, we don’t think, because gravity and friction would bring it together.

As they get closer together, they would get torn apart a little bit, and so it would probably, like, if they did coalesce.

And then coalesce again.

Yeah.

We know this happens for, like, the higher mass stars, because we see that, you know, black hole mergers are what trigger the gravitational waves.

We have, you know, stellar mergers, like it creates more energy, and so we have more evidence of it for the high mass stars.

So we don’t really think about it too much for the low mass stars, because I think we don’t have a lot of super close binaries, like there’s not going to be a huge amount of energy loss, like you’re going to need some kind of energy loss to get them to get closer and closer to one another.

Something has to eat the energy of their orbit, the orbital energy.

If they’re going to come together.

That’s why we don’t just collide into the sun right now.

It’s a very slow process for any kind of orbital change like that.

But if it did happen…

And blue stragglers are similar objects.

Yeah, that’s how these weird stars kind of…

What’s a blue straggler?

You know about the blue straggler?

No, tell me.

Yeah, so you look at a cluster of stars, all born together, so they all should be evolving together, as we understand stellar evolution, and there’s some stars that are hotter and bluer than anybody else is.

And it was a big…

In my day, it was a big mystery until someone said, maybe these are two stars that have merged.

And when you merge, you get to re-energize your core with fresh material, so that you will have a prolonged life expectancy and you’ll come out a little hotter than you’re otherwise supposed to be.

They’re the late bloomers of the stellar nursery.

Well, they got an injection of new…

Had a growth spurt over the summer.

Look at me.

Yeah, so they stand out from all the rest of the stars.

Wow.

Blue stragglers, because everyone else has evolved together.

Yeah, because they all were born together.

They were born together, and this one got an extra infusion.

High-mass ones especially are bluer to begin with and shouldn’t live as long.

Right, and so these are standouts.

So I never thought about the brown dwarf.

Do you can ignite a brown dwarf that otherwise would have had to live its life?

Yeah, in theory, I think.

In practice, I don’t think we see it a lot.

It’s hard to tell whether or not things are binaries.

Yeah, maybe they just turned into these stars.

Could be.

Maybe they’re just a star you’re ignoring over the side, and it used to be two brown dwarfs.

Yeah, would we see evidence of it?

Could very well be.

Hidden in plain sight.

Look at that.

Like a YouTuber that actually crossed over to regular entertainment.

What?

Okay, anyway, sorry.

That’s all, though.

So this is Atticus?

That was Atticus.

Atticus, thank you, Atticus.

Thompson, that was a great question.

And you know he’s building something in his basement.

Something I don’t want anything to know about, but I’m sure the US government does.

And the power grid dims every once a week as he turns on his experiment.

All right.

Okay, here we go.

This is Jimmy Golightly.

This is Holly’s brother.

It says, hi, this is James and Charlotte.

How does the life…

But for those who were not alive in 1964…

Oh, it’s still on the air.

It’s still on the movie channel.

Is it?

Okay, Turner movie classics.

It’s a great movie.

Yeah, so that was…

What’s her face?

Breakfast at Tiffany’s.

Audrey Hepburn.

She was Holly Golightly.

Holly Golightly.

Based on the novel by Truman Capote.

Oh!

You didn’t know that?

I did not know.

You’re learning something every day here.

Let me tell you, that’s why I come here.

Because I’m stupid.

Alright, this is…

He says, Hey, James and Charlotte here.

How does the lifespan of a low mass star compare to the lifespan of other stars such as our sun?

The brown dwarfs are going to be around forever.

That’s what makes them super useful.

The sun is going to stably fuse hydrogen for about 10 billion years, and we’re about halfway through that.

So if you want something to worry about, like the sun is about halfway through its lifetime.

But the brown dwarfs, like we said, are going to last basically forever, for like our practical definition of forever, which we use it in kind of a neat way, which is we call it galactic archaeology.

Because some of the low mass stars that we can see now might have been around already since very early on.

The high mass stars are going to have come and gone, but the low mass stars are going to be around.

And one of the interesting things is that…

Wait, but you can make a low mass star today, and it’s going to be a low mass star, but some of the pool of low mass stars could have been born first.

Right at the very beginning.

And they’re still alive.

You might ask, how can we tell the difference?

How are you going to know the difference?

This way we can tell the difference, and the answer lies in those high mass stars.

Because the high mass stars that have been fusing and then exploding have been creating heavier elements.

And so the older a low mass star is, the longer ago it was formed, the fewer heavy elements it’s going to have.

And so the more recently formed low mass stars are going to have more of the heavy elements that were created in the subsequent generations of high mass stars.

Which is kind of cool if you think about it.

To get spectra and look at those elements.

Yes, you get the spectra, you look at the elements, and we have a special name for the low, we call it low metallicity because we call this composition how many heavy elements are in it, we call that metallicity.

The low metallicity stars are called sub dwarfs.

Oh.

Because they’re under the main sequence of stars on this HR diagram.

Yeah, it’s a little bit weird.

And they also tend to be blue in color.

They are fun to study.

Because they reveal themselves as their own population.

Yeah, subsolar metallicity.

Got it, got it.

All right, this is Matt Curtis.

Matt says, hello, Doc Doc Lord.

Matt here, and Chuck is pronounced Matt.

He’s talking.

Well, these people are brutal today, man.

They are brutal.

He says, coming from South Carolina here, given that our space telescope technology is improving and we keep discovering more and more exoplanets, what will it take to directly capture an image of one of them, deducing their existence through transit or gravity wobble is great, but what improvements would be required to show an image to the public directly?

You want to see like oceans and continents.

So I like to call it, because we do have images of exoplanets.

This is an amazing thing.

Direct images of exoplanets.

How many pixels?

Yeah, a handful.

And how many planets?

It’s like also 10 planets maybe or something like that.

But one of them has stood the test of time.

So this is also kind of back in my day of exoplanets.

Back in 2008, two directly imaged exoplanets were announced.

One was in around the star Fomalhaut, which famously had a disk.

And it was a little like bright thing in the disk.

And then there was another.

And the star is in the southern hemisphere.

Yeah, it’s a pretty bright star though.

It’s got a name.

The star with a relatively normal name is the star that you can see in the night sky.

And then the other one was HR 8799, which with a number like that, you can’t see it in the night sky.

But it had three planets detected around it.

And both of these, one was done with a Hubble Space Telescope, one was done with a ground-based telescope.

But they were amazing discoveries.

Yeah, it’s a handful of pixels, and it’s really fuzzy images.

But the Fomalhaut one actually seems to have been a spurious discovery.

It’s just a clump in the disk that didn’t move the way it was expected to move and has since gone away.

The HR8799 system, they found another planet even closer in.

So there’s four planets in the system.

And you can, over the time, put the images together and watch the planet’s orbit.

It’s beautiful.

And so somebody, Jason Wang, I believe his name is, has made GIFs that every once in a while go around social media of like a little animation of the images where we can watch planets orbit around a star other than the sun, which I think is just amazingly…

It’s crazy.

The planet takes years to go around its host star.

You need data over that entire time.

Decades, yeah, basically.

To really get the good…

The HR8799 system is like a souped up solar system.

It’s a bigger star than the sun.

The planets are bigger.

They’re like five to ten times the mass of Jupiter.

And they’re all further out than our…

So it’s bigger and brighter.

But similar to…

That’s cool, man.

Time for one more question.

Okay, so since we’re on exoplanets, let’s do Paula Patsova who says, hello, Dr.

Rice, Dr.

Tyson, Lord Nice.

Paula here from Slovakia.

What is the potential of habitability of orbiting planets around a brown dwarf or low mass star?

Yeah, especially the low mass star.

Like the brown dwarfs, maybe, but they’re kind of the extension of the low mass stars.

But the low mass stars, they might actually be better targets for finding Earth, I don’t want to say Earth-like, but I’ll say Earth-size planets at the very least.

Because for these indirect methods that were mentioned earlier, the indirect methods, it’s easier to see small planets relative to small stars.

It’s easier to see planets close in to the stars.

And so both of those mean that if you look around a small star, it’s easier to find Earth-size planets and kind of Earth-temperature planets.

Because those are going to be closer in to the star because it’s a cooler star.

So it’s like a smaller fire.

If you’re going to have an Earth temperature, and it’s way dimmer or way less luminous than our sun, you’ve got to be way closer to get that same temperature.

Yeah, to get that same equilibrium temperature.

But then it’s easier to find that planet with these indirect methods that we use most of the time.

And so now these small stars have been really intriguing targets for searching for exoplanets.

So the TRAPPIST-1 system is a very famous system that was discovered a handful of years ago with seven Earth-sized planets in orbit around that star.

And something like three or four of them are solidly…

Yeah, this one.

Well, weirdly enough, the star was known before.

TRAPPIST is actually the acronym for…

An acronym?

A survey.

The catalog.

Transiting, blah, blah, blah, blah.

But it’s a Belgium…

The group includes Belgium Observatory.

And so it’s…

We call it a BACRONYM sometimes, where they think of the clever term that they want, and then they make up the acronym to go with it.

Yeah, a BACRONYM.

Yeah, that’s a fun portmanteau.

So the TRAPPIST-1 system is super great because a solid three or four of those planets could be in the habitable zone.

So the habitable zone is where it’s the right temperature for liquid water.

Goldilocks zone.

Yeah, Goldilocks zone.

But it doesn’t tell you anything about the atmosphere, which you would also need to have liquid water on the surface.

And so there’s still a lot of unknowns, a lot of what-ifs for those, but the low-mass stars are really exciting targets for Earth-size exoplanets, at least.

Wow.

Cool, exciting.

All right, that’s great.

Emily, thank you.

Thanks for having me.

We just reach out.

I’m right upstairs.

Yeah.

Walking by.

Well, thank you for bringing back your expertise on this zone of ignorance that existed for so long that finally people are jumping in, getting their hands dirty.

We’ve always kind of wondered, right?

But now we know for sure, which is amazing, a lot of the things.

All right.

Good stuff.

Well, let me take us out with some reflections on this moment.

In my field, astrophysics, many of us confront people who ask the very sensible question, why are we spending money on anything you’re doing when we have all these problems here on Earth?

And okay, before we did all this, did you not have those problems on Earth?

I think you had them long before any of us spent a dime of tax money or any other money trying to understand the universe.

What we do know is what we discover expands our view, not only of the world, but of our place within it.

And when I was growing up, there were planets and there were stars.

And no one really thought much about, well, how do you get between one and the other in the universe?

What does the universe say about that?

And then we learned there’s an entire field that we didn’t even know would exist or could exist and now does exist that specializes in the transition between what you are as a planet and what you would become as a star.

This is more about our world, our universe, our home.

And it could be that this will help us discover life on a planet around a star sometime in our future.

And so whether or not that specifically puts food on your table, I’ll ask you a little differently.

I’ll say, how much is the universe worth to you?

And that’s Cosmic Perspective.

Neil deGrasse Tyson here for StarTalk Cosmic Queries.

As always, I’m Neil deGrasse Tyson.