June 4, 2020 • 41 mins
Can a Thorne-Zytkow object, a neutron star inside another star, actually exist? Did we find one?
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Speaker 1 (00:08):
Hey, Daniel, do physicists ever run out of crazy ideas? Well?
We all have our slow days. I mean I get
science blocks sometimes. Yeah. So what do you do then
to get fresh ideas? Well? Probably very similar to what
creative people do. You know, you just let ideas bounce
around in your head a little bit and see what happens.
I should try that. I usually just take an end.
(00:30):
All right, So what happens, Well, let's see, let's say,
let me try, let me see. Um, I'll just let
an idea bounce in my head. I'm thinking chocolate chip particles.
That a good physics idea. I don't know. We have
to go see if we can find those out there
in the universe. They could exist, They could exist chocolate chippos. Yeah,
I mean, if I just let ideas bounce around in
my head, I think of alien black holes. Is that
(00:53):
a black hole that's an alien or a black hole
made by alien? It's a bifurcated ideas that allows for
both possibilities. Well, does this ever work? This process? Does
it ever actually give you a good ideas? Yeah? You know,
the universe is pretty crazy, and so sometimes the crazy
idea that comes out of the head of a physicist
is something that's really out there. Okay, I got a
(01:13):
good one for you. Chocolate chip black Holes, where each
chocolate chip is actually an alien. Hi. I'm or Hammad,
(01:37):
cartoonists and the creator of PhD Comics. Hi. I'm Daniel.
I'm a particle of physicist and I'm the co author
of the book We Have No Idea together with Jorge,
a book all about the things we do know and
mostly the things we don't know about the universe. And
it's also a huge coincidence because we don't really have
an idea of what we're doing here. But welcome to
(01:58):
our podcast, Daniel and Horr Explain the Universe, a production
of I Heart Radio. Danie and Jorge make it up
as they go along. When it comes to podcastings, right
it does it called science improv No, But we try
to be honest about what we know and about what
science doesn't know, because it's on that edge of knowledge
that all the interesting questions lie. That's where the wonder is,
(02:18):
that's where the curiosity is, that's where the mental exploration is.
That's where people go when they want to get new
answers to questions about the universe. Things everybody wants to
know the answer to how our stars formed, how do
they die? Can they eat each other and start taste?
But yeah, it turns out there's a lot we don't
know about the universe. There's more that we don't know
(02:39):
than what we do know, kind of in a way,
And so it's interesting to sort of talk about that
because you know, I feel like people have the sense
that the scientists know everything that's going on in the
universe until they meet a scientist and then they realize, boy,
that guy is clueless. This one doesn't know anything that's right.
How can she call aselvel scientist if she doesn't understand
what most of the univer versus about. But actually, that's
(03:01):
a key step to being a scientist is understanding what
you don't know and then confronting that ignorance, because confronting
your ignorance is the first step in discovery. Is being
open to new ideas and asking questions about the things
you don't know. That's the best part of science, and
so that's why on our podcast we try to take
you to that forefront of knowledge, bring you up to
(03:22):
speed on the questions that scientists themselves are asking. Yeah,
because who knows what could be out there, what kinds
of crazy phenomenon that we've never seen before or even
thought about. It could be out there right now, happening
in the universe. And so to be on the podcast,
we'll be talking about one such kind of crazy idea
that has been proposed by a couple of famous scientists.
(03:43):
That's right and maybe even discovered, Because there are several
ways to find weird new things in the universe. One
is to sort of stumble across them when you weren't looking, like, oh,
what's this thing, We've never seen it before. And the
other is to think of it first and say, I
wonder if you could make a black hole all out
of chocolate chips or whatever, you know, could you have
(04:06):
a planet the shape of a squirrel or something like that,
and then send experimentalists and astronomers out there to look
forward to see could this actually work? The planet in
the shape of a squirrel. That's just nuts, Daniel. But
today we'll be tackling one such crazy idea, And so
today on the episode we'll be asking the question, can
(04:30):
you have a star inside of another star? Sorry, I'm
still having your squirrel nuts joke. Let that play out. Yeah,
but This is a kind of a crazy question. I
don't even think I even understand it. How can you
have a star inside of another star? Well, you know,
some stars are really big and some stars are really small,
(04:51):
and you're used to thinking of stars is really far apart. Right,
our star is really far from other stars. But they
can get closer together, and you can imagine what might
happen if they get really close together, with one go
inside the other one. It would be a star on
star battle, they merged into one megastar. Yeah. So who
came up with this crazy idea star inside of another star?
(05:13):
Well it was from two scientists, Kip Thorne and Anna Zikkov,
and they had this idea that maybe you could have
one tiny, really dense little star called the neutron star
inside of a really big, puffy star called a red
super giant. And they were just wondering, hey, is it possible?
And they did some calculations and they thought, it doesn't
(05:35):
seem impossible. I wonder if it's also really I think
there were signs blocked when they came up with that
and just sat around drinking whiskey or eating chocolate chips,
and they're like, oh, what if you could have a
star inside of another star. Yeah. I bet they just
wrote a bunch of random things on the wall and
then threw darts at them, and they were like, all right,
neutron star, okay, red super giant. Hey, what if you
(05:59):
got one inside the there? You know, maybe they had
a hundred terrible ideas that day and this is the
best one. They're like, what if they're best friends? No,
not that. What if they're mortal enemies? Now? Not that?
What what if one is the evil twin of the other.
We need to that's been done. We need a better
plot twist. You see. There is something, though, there's a
deep connection between being creative in physics or in science
(06:22):
in general, and being creative when you're doing writing or whatever.
You just sort of let the ideas flow and and
think about what's been done before and then try to
find something new, Like has anybody thought about whether you
know these could actually be black holes reflected into this
dimension by some alien supercomputer whatever? Dot dot dot. You know,
you need to let your mind wander a little bit
(06:42):
when you're being scientifically creative. Sounds like there's a fine
line between science fiction and science for real. And I
tried to straddle that line. All right, Well, these things,
these stars inside of other stars, they have a name,
and they're called the thorn Jitkov objects. And so we
were wondering, as usual, how many people had heard of
(07:03):
these weird and crazy objects out there in the universe.
And so, as usual, Daniel went out there and pulled
the Internet for people to ask him this question. Yes,
so thanks to everybody who volunteered. If you'd like to
volunteer to answer random physics questions for a future episode,
please write to us at questions at Daniel and Jorge
(07:24):
dot com. All right, well here's what people had to say.
I think it is some type of a hybrid star
or something. I have no idea, Man, I have no idea.
I've never heard of that. Well, absolutely no idea. I
have no idea. Um, I have not heard of a
thorn site cow psit Co object. So I have no
(07:48):
idea what that is. No idea, I never heard of it.
The name looks like it might be something to do
with Kip Thorne, who is an astrophysicist, So I'm going
to guess it's something astrophysical. Al Right, not a lot
of name recognition. I feel like a lot of these
people maybe read our book We have no idea. We
stole our idea that we have no idea. That was
(08:10):
our idea being clueless. It was our idea not to
have an idea. I think that's that's an old human
kind idea. Yes, I think that's true, but also not
really much of an idea for how to pronounce this name?
And you know, I gave it to them in writing,
and it's sort of a strangely written name because it's
got a Z with a dot on top of it.
Why t k o W. But it's pronounced jitkov to
(08:33):
my best understanding, right right, And I guess if you're
googlly and you would have to type in z y
t k o W. Yeah. But Kip thorne Is is
sort of well known and he has kind of a
brand name in physics, he certainly does. He's also got
a Nobel Prize and he's worked on Interstellar the movie,
so he's sort of a celebrity and lots of different
arenas these days. And you know him, don't you. Yeah,
(08:54):
I do. I've met him a few times before. Super
nice guy and very cool. So so he came up
with this idea with Anna Zitkov. So let's dive into it, Daniel,
How can you have a star inside I don't even
know what that is or what that looks like. How
can you have a star inside of another star? Yeah? Well,
I think it's only possible for a couple of different
categories of stars, because what you need is one star
(09:15):
to be really really big and the other star to
be really really small, so it can sort of like
slip inside the other star. And so we've got to
like extreme categories of stars involved here. One is the
red super giant star, and the other is the neutron star,
and that's the really small one. And each of these
are like already fascinating just on their own, so you know,
(09:37):
you could write a whole science fiction movie about just
one of these. So combining the two of them together
it is like, hey, man, that's a bit too much,
but you know, hey, they're not limited in their scientific creativity. Okay,
so when you see a star instead of another star,
then you're talking kind of about specifically two kinds of
star that kind of come together, and then one of
them kind of eats the other one. Yeah, I mean,
I'm not sure which one you would describe as being active,
(10:00):
Like is the bigger one eating the other one? Or
is the smaller one sort of like boring into the
larger one? Or is it a poetic dance of two stars?
I'm not sure, but I guess that can happen, right,
because why not? Why can't a star fall into into
another star? Or why can't two stars kind of merge together?
(10:20):
That thing happens, right, Yeah, that kind of thing does happen.
And if the very different kinds of stars, like a
red super giant is very low density compared to a
neutron star, then the neutron star can enter the red
super giant without being disrupted, without blowing up, without you know,
being dispersed, and just merging into part of the red
super giant. But aren't sons like stars. Aren't they sort
(10:42):
of like giant explosions? You know, isn't there a lot
going on? How can something hold together inside of a star?
These are some of the largest stars in the universe. Like,
the largest red supergiant we've ever found has a radius
that's fourteen hundred times the radius of the Sun. Fourteen hunt,
you mean, if you take fourteen hundred of our sons,
you would get a super giant exactly. These things are ginormous,
(11:05):
like they make our Sun, which is already huge compared
to Jupiter, which is huge compared to the Earth, which
is huge compared to you write, this thing dwarfs our Sun.
If you put it in our solar system, it will
go all the way out to the orbit of Jupiter.
It's incredible. It's it's almost as big as our entire
solar system. Yeah, but it's not that much more massive, right,
(11:27):
So it's thousand times bigger and radius, which makes it,
you know, like a billion times bigger in volume, but
it's only about ten to forty times the mass of
the Sun. Oh. I see, it's like a thousand times
less dense than our Sun. More like ten over a
billion times less dense than the Sun. So it's millions
of times less dense than our Sun. Now it's still hot, right,
(11:50):
it's like thousands of degrees kelvin. It's not a place
you'd want to be. But compared to our Sun, it's
more like a cloud, right, It's more like a burning,
diffuse cloud. And so while it's a huge, burning ball
of gas and not a pleasant place to hang out
or have a picnic, it's not a hot, dense environment
like the center of our Sun. I see, it's just
kind of a hot cloud of stuff, but it's still
(12:11):
kind of igniting and burning, definitely burning, right. You have
a lot of pressure and temperature and a huge amount
of fusion is going on, and you've got light being admitted.
These things are big and they're glowing their ten thousand
or a hundred thousand times the luminosity of our Sun.
And they're pretty hot. You know, there's like four thousand
degrees kelvin on the surface. And there's one that you
(12:32):
can even see in the night sky. Wow, where yeh
Betel Juice. Betel Juice is a red supergiant in the
Orion constellation. You mean one of the one of the
points in the Orion Baiel Juice. And these stars have
fascinating histories because they started as a blue supergiant, like
the same size, but much hotter and more intense when
(12:54):
they were burning hydrogen. And then remember they burn that
hydrogen and they sort of start run out of hydrogen,
and as the temperature increases in the center, they start
to burn helium instead, and then near the end of
their life they turn into these red supergiants. They're cooled
off a little bit. It flipped red the sun. Yeah,
you know, yeah, it got more conservative in its older age.
(13:15):
I think that tends to happen. It's very brief period
of moderation in the middle, and then boom all the
way to the Fox News side, a Republican. Yeah. So
that's the red supergiant. That's like what is going into
And so you can imagine it's much easier to fall
inside a red super giant than it is like our
kind of sun, because it's so big, right, Yeah. And
(13:37):
so then the second kind of star for this to
sort of happen and stay happening, is that you need
a neutron star, which is almost like the opposite of
a red super giant. Yeah, exactly. It's super duper dense.
It's like the mass of our sun or the mass
of the Sun, but it's collapsed to like the size
of the city of den what like an object like
(13:59):
just like twenty kilometers. Why so the whole Sun the
size of Denver. Yeah, take the whole Sun, which is
already a hot, dense mess, and collapse it to something
that's you know, much much smaller than Earth. It's incredibly dense.
And this is what happens when a star collapses, like
at the very end of its life. It can go
(14:20):
black hole, or can go neutron star, or various other outcomes.
This is like the core remnant, the hard little nugget
that's left over after the collapse of a star. And
it's kind of almost almost at the point of a
black hole, right, Like it's so dense it could kind
of maybe easily tip into a black hole. Yeah. And
one way that you can get a supernova, at least
(14:41):
to a black holes, you start with something like a
neutron star and then you add a little bit more
gas and then it turns into a black hole. But
these things don't yet have enough gravitation of power to
overcome the neutron pressure. It's like a bunch of neutrons
all packed in together, really really really tightly. It's like
a bunch of people squeezed onto you know, the metro
(15:01):
in Mexico City at rush hour. Have you ever ever
done that? But it's a pretty intimate experience. It's a
big negative, as they would call it. And neutron stars
are fascinating because we only discovered them because we found
a particular type called a pulsar. This is the kind
that shoots a huge beam of light and rotates really quickly,
and so it appears on Earth like a flashing light.
(15:24):
And they discovered this in the night sky, you know,
several decades ago. And that's how we even know that
neutron stars exist. Because neutron stars don't have fusion inside them.
They're not fusing. They are emitting light in the same way.
They're not exploding. They just glow from all of the
compact stuff being squished together. Yeah, they glow because they're hot.
They're like six hundred thousand degrees kelvin. They're much hotter
(15:47):
than a hundred thousand degrees kelvin. It's pretty it's pretty hot.
They're smoking hot. It's much hotter than the inside of
a red super child. All right, So they're small but
super hot and supercompact, and so while the other one
is kind of big and fluffy. And so I'm starting
to get kind of the picture here what's going on,
And so let's get into how these things would happen
(16:09):
and what would happen and are they even real? But
first let's take a quick break, all right, Daniel, we're
talking about neutron stars being eaten up or invading the
(16:31):
space of red super giants, and so I think I'm
getting the picture here. Another, in order for this to
sort of happen, you need one big, fluffy star that's
kind of it's hot and it's a star, but it's
in a big and a kind of diffuse and then
you have one another one that's really compact and you know,
super duper hot, and then that can go inside of
the first one and exist there or an orbit there,
(16:54):
or what does it do once it gets eaten up. Yeah,
it's sort of like a bullet into a pillow. Right,
one can go into the other one. And there's a
few ways that this can happen. Like one way this
can happen is that they just bump into each other,
like you got a bunch of stars flying around and
these two things just sort of happened to hit each other.
That's not very likely because stars are typically very very
(17:16):
far apart. In some certain configurations, these things called globular clusters,
you have higher density of stars, it might happen, but
scientists think it's much more likely that these things already
started out near each other, like a binary star system,
a system where you have two stars like regular stars,
two regular stars, and you know, stars evolve, and so say,
for example, you have two stars and one of them
(17:39):
already is a red super giant, the other one is
a normal star. But then it goes supernova and at
the core it leaves a little neutron star. Well, that
little neutron star might not just stick around at the
center of the supernova. It might get a sideways kick
because these supernova aren't like totally symmetric, and so it
might get sort of shot into the red supergiant. Oh,
(18:01):
I see. Wow, it's like the relationship of alls. Yeah,
or that means that the supernova is like a neutron
star gun. It's like shoots out one huge crazy bullet
from the center of it, which goes right into the
red supergiant. Oh, it goes supernova and the jacksit center
which is a neutron star, which is a neutron star. Yeah,
(18:22):
what a way to go, And it goes into the
red giant super red giant. Remember, the red supergiant is enormous,
so it would be pretty hard to miss. It would
take up, you know, most of the sky from this
neutron star. So it just flies off roughly in that direction.
It's going to get captured by this red super giant.
It's a giant pillow the size of the sky. It's
kind of hard to miss exactly. And the other options,
(18:45):
the other order is that you have a neutron star
and it's got some partner star which becomes a red
supergiant because these stars can grow and you know, like
our sun is going to grow near the end of
its age. It's going to grow and grow and grow
and can do a large your radius. So the other
star can just sort of like grow and gradually engulf
(19:05):
drown star. You can just sort of like creep on
over and take over its space. But the one, the
other one needed to be a neutron star, right, yeah, okay,
And and these things just happen out there in the universe, right, Like,
you know, we're kind of used to this idea that
stars are really far apart because there aren't any stars
around us really close by, But there are places in
the universe where it's like a mess of stars. Yeah,
(19:26):
And it's actually much more common for stars to form
together because remember stars are formed sort of in bunches
when a big gas cloud collapses and so a lot
of stars are formed sort of near each other, and
it's more likely for stars to have a binary partner
than to be solo stars. Our son is unusual. In
the Milky way, binary stars are more common than solo really.
(19:47):
Uh yeah. Out there in the stellar dating field, almost
everybody's already married as somebody. Somebody needs to get our
Sun dating app or something. I'm sorry you want another star, like,
I just feel bad for our our son. I don't know.
Then we'd have like a step star and be a
weird relationship because it wasn't around when we were formed,
and it's trying to like boss us around gravitationally. I
(20:09):
think it'd be a big mess. They won't let us
go to the ball. But yeah, more family, that always
is always better. Yeah, I guess more family, more drama,
But I guess if that's what you're in for. But
I think this is what Kip Thorne and and a
Jikov we're thinking about, Like could you have these two
things end up inside each other. It's not that unlikely
because you have pairs of stars already, So if one
(20:31):
of them turns red super giant, or one of them
turns into a neutron star. Could they then fall into
each other, could they collapse into a single object and
could that work? What would it look like? Right, Yeah,
let's get into what happens. So we have one really
compact neutron star, super hot. It goes into the big
fluffy red supergiant and then what does it just keep
(20:52):
going because it come out the other end kind of
like a bullet, or does it you know, disintegrate that's
just going through or does it just kind of inside
kind of like a like eating a rock. Yeah, it
mostly stays inside. I mean, it depends a little bit
on its initial velocity. But you know, a red super
giant is still a lot of mass. These things are
ten or forty masses of the Sun, and so it's
(21:14):
a big gravitational Well, so most likely the neutron star
is just gonna spiral to the center of this red supergiant.
Oh what do you means spiral? Like? Um, it can't
just keep kind of orbiting around inside of the star
or does it eventually you're saying it eventually kind of
collapses into the middle. Yeah, you could orbit stably at
a fixed radius if you're not losing energy, and like,
(21:35):
you know, if you are a spaceship orbiting the Earth,
you can stay at the same altitude if there's no drag,
But if you're touching even a little bit of atmosphere,
then you're gonna be slowing down and spiraling back intowards
the Earth. If you're inside a red supergiant, then you're
definitely going to be dragging against the hot, burning plasma.
It's gonna be stealing your energy, so you're gonna be
spiraling in towards the center. And I guess why doesn't
(21:58):
it dissolve? Like why doesn't a neutron star just kind
of like under those conditions just kind of like break
apart or evaporate because it's super duper crazy dense, Like
a neutron star is pretty hard to break up. I mean,
what you have is a basically a wind of burning
plasma that's incident on the surface of this neutron star,
and so at that surface you get a lot of reaction,
(22:19):
but not enough to like break up a neutron star.
And the neutron star is a very tightly bound gravitational object.
You know, it's like putting a rock in a sandstorm
or something. And eventually what happens is you know, the
neutron star is also gravitationally very dense. It's just going
to gather more stuff around it. And so what starts
to happen is this really crazy reactions right at the
(22:40):
surface there where the neutron Star is super duper hot,
it starts burning the inside of the red super jump
because it's so much hotter. It's six hundred thousand degrees
versus four thousand degrees. Yeah, and and so you get
crazy stuff happening right there in the interior. And it's
also super heavy. So does it start to like kind
of suck out some of the red super Giant and
(23:00):
kind of build up in size as it's going in. Yeah,
and so what can happen is that it accumulates enough
stuff to trigger it to become eventually a black hole. Oh,
that would be some serious indigestion. Like if you like,
if you eat something and it turns into a black hole,
that's not good. Yeah, that's even more than Montezuma's revenge. Right,
(23:20):
it's like Nutron stars revenge it or your negative you see,
things never go well when you have to star parents, right,
they always end up fighting, Alright, So then one thing
that can happen is that it goes inside and it
becomes a black hole, and then it's kind of game
over for everybody, right, because then the black hole is
gonna suck in the Red super giant. Yeah, it can
(23:41):
suck in a lot of the mass of the Red supergiant,
but also a lot of it won't collapse. Remember, black
holes don't automatically suck in everything that's nearby. They're just
a powerful gravitational force. If you have enough rotational energy,
you can end up just in the accretion disk like
around the black hole. So basically the red supergiant just
because material for the accretion disc that's surrounding the black hole.
(24:04):
The black hole just kind of sucks up all of
the Red supergiant, yes, the center of it at least,
and then the outside becomes this like big swirling disk.
But you know, that's one possibility. Another possibility is that
you get crazy intense fusion and reactions at the surface
of the neutron star where it's embedded inside this other star,
and it creates a lot of energy flying out and
(24:26):
it basically disperses the Red supergiants like a new solar wind.
That's pushing out on the red supergiant and disperses it
back into basically a cloud of stuff. It's kind of
like dipping a hot poker into a bath of water,
Like it touches the water and then it just steams,
just explodes out and it just disrupts everything. And then
(24:50):
that stuff can do interesting things like form planets, and
so you might end up with like a crazy, big
spinning pulsar in the center surrounded by planets formed from
the depth of that red supergiant. Wow, crazy drama fusion
because you're making like a heavier element as it goes in. Yeah, yeah,
(25:13):
because that the surface of the neutron star, it's super hot.
And then you have all the materials you need for
fusion because there was fusion already happening inside the red Supergiant.
You just like supercharged it by bringing in all this
extra energy, all this extra heat. So then now suddenly
instead of a red giant and a neutron star, what
do you have? Then you have like a new solar system. Yeah,
(25:33):
you have a new solar system where the red supergiants
bones have been used to like supercharge the neutron star
and to form a bunch of planets, and so what
happens to the Red Supergiant just just activates, like it
just peters out and or does it just turns off. Well,
it's become diffused, and so it's no longer enough energy
and the conditions for fusion. But you know, this is
(25:56):
the fate of almost every star, right, especially these really
big ones. They will burn and then eventually their cores
will collapse and they will disperse. And so that's that's
just what happens anyway, that's the Red super Giant is
expecting that. It's not a surprise if it's one of
these thorn jit cob objects. It's and just sort of
gets accelerated by having a neutron star there in the middle. Well,
(26:19):
it's pretty amazing to think that you start out with
a star whose size it is the size of the
orbit of Jupiter, so it's huge, and then you have
this tiny little, you know, twenty kilometer wide bullet basically,
this little, tiny, superdense thing, and then it just it
just totally disrupts this whole ginormous star. I know, imagine
if Denver right was the downfall of the whole system.
(26:43):
That's pretty impressive, right, I mean, I like Denver. Denver's
got a lot of sway, but like that's pretty outsize
impact for a tiny little region. Yeah, yeah, well it
is a swing state, I think, so you know who knows, right,
it can totally tip the fate of the entire world. Yeah,
you could become a black hole or whatever. It's all
(27:03):
in the hands of those voters. It's all in the
hands of Denver's. All right, Well, let's get into how
you could tell if these things exist and if they
even are real out there in the universe. But first,
let's take a quick break. All right, Daniel red super
(27:33):
giant eating a neutron star. Sounds like they've worked it
out and it's totally possible and a lot of amazing
things would happen. So are they real and how could
we tell if we where they are? Well, that's sort
of the disappointing part about this thing is they had
this crazy idea. They were like, Wow, a neutron star
inside a red super giant. That would be awesome physics
(27:53):
deep inside the core. And then they asked, well, what
would it look like from the outside, right, Because we
don't get to like go inside red super giants and
take a box to see if there's a neutron star
or not. We only can observe these things, thankfully from
the outside. And you know, a red super giant again
is huge, and so seeing this neutron star inside of it,
(28:14):
like directly seeing it totally impossible, and mostly from the outside,
a thorn Chikov object looks just like a normal red
super giant. The differences are pretty subtle, really, But doesn't
it the little neutron star disrupted? Wouldn't we see it
kind of peter out suddenly or turn into a black
hole or turn into a solar system. Well, if you
(28:35):
could watch it over, you know, ten thousand or a
hundred thousand or a million years, then you you might
see these effects. We only get to see these things
in a snapshot, right You could ask like, does this
particular star have a neutron star inside of it? Right now?
So we don't get to see the time series evolution. Man,
I would love to look to take an object in
(28:55):
the sky and just like fast forward it for a
million years and back and forth and see what's gonna happen.
That to be amazing. I see It's like if you
see a dead red supergiant, it could be like, oh,
it could die from natural classes or maybe a shot
with a neutron star. It would be hard to tell. Yeah,
And and really the game is look at all the
red super giants out there right now, and ask do
(29:15):
we think any of them have a neutron star in
them right now? How would they look different if they did?
And can we make the measurements to tell if one
of them does? So, how can we tell if they
did have a neutron star for a snack? Well, you know,
they have a really different interior, right they have this
crazy neutron star which is triggering this really intense reaction,
(29:35):
is burning at the core, and so that does have
some impact on what it looks like from the outside
in two important ways. One is that they are a
little brighter, get more effusion, and so you're producing more light.
And red supergiants are not famously bright. I mean, they're
ten thousand times or a hundred thousand times brighter than
the sun, But for that mass in that volume, it's
(29:57):
not a very intense source of light. So if you
see one that's like extra bright, unusually bright, then that's
a clue that maybe it's got a neutron star in
its core, because an intron star kind of creates new
kinds of reactions which would make it brighter. And then
there's a very specific kind of reaction that we think
(30:17):
could only happen inside one of these objects. That you
have to have a neutron star inside a red supergiant
for this even to work, and so you can look
for the very characteristic signs of that particular reaction. Interesting
involves elements cycling around from the surface of the red
supergiant down to the core where they get added protons
(30:38):
onto them, and then it's so hot they get shot
back up and they get to the surface. They come
back down and they get more protons, and they shot
back up and get to the surface. And remember, for
one of these objects, the core is much much hotter,
so it pushes these things out to the surface more.
See if it's something like this would make a particular
kind of element which we might be able to recognize
(31:00):
in the surface of these stars, that's right. And so
if it's a T c oh then you'd see much
more lithium and molybdenum and rubidium then you would see
a normal red supergiants. And so if we look at
these stars and we can tell that they have more
of this stuff on their surface and they're extra bright,
then it's a good sign that it might have a
neutron star hiding inside. It. Wouldn't a lot of lithium
(31:23):
make it more chill and more um more more calm.
You know, you can't take studies in humans and extrapolate
those two behaviors stars for a giant. We did this
study in mice, and so we're going to extrapolate, you know,
what would be the dose like for a lithium for
a red super using the mouse model to study this
(31:44):
giant supernova red supergiant totally works exactly, all right. So
there might be like if we see a red supergiant
and we see that it glows kind of in the
lithium range, then we're like, oh, maybe it has a
neutron star inside. Yeah, Actually it would be the that
doesn't glow in the lithium range because the opposite, because
if there's lithium on the surface, then the light is
(32:06):
going to be absorbed at certain characterists of frequencies that
lithium likes to eat, and so if there are dips
at certain characteristic frequencies that would indicate extra amounts of
those elements, So I see it means that that stuff
is there, which means that maybe there's a neutron star
in there exactly. So that's that's would be the signature
we're looking for. And so have we found any what's
(32:28):
kind of the likelihood of this this thing happening. Well,
there's a really fun story here because there's an awesome
scientist named Emily Lefek and she became an expert in
red supergiants because her research she was fascinated by how
they were made, how how they worked, and understanding this
whole process inside them. And then she got an email
from Anna Jikov saying, how would you be interested in
(32:50):
trying to figure out if any of these red supergiants
might be one of these weird objects that Kip Thorn
and I thought about years ago? And so that sounded
fun to Dr Levek, and so she surveyed all the
red supergiants she knew of and she found one. She
found this star which looked really weird with the dip
in lithium, like with the lithium signature on. Yeah, it
(33:12):
was weirdly bright and it had the dip at lithium
and libdenum and rubidium exactly the places you would expect
by one of these objects, unlike the other red supergiants
which didn't have these signatures exactly. And that's what she did.
She compared this red supergiant to like the broader population
of red supergiants, to find one that's unusual. And this
(33:35):
is the star that we've known about from more than
a hundred years, was discovered in nineteen o eight. It's
called HV two one two. It's from the Harvard Star Catalog.
It's in the small Magellanic cloud. And so this is
the paper that came out in two thousand fourteen saying,
oh my gosh, maybe we actually found one of these things.
That must have been a fun day. I bet she
(33:56):
was science blocked. And she said, what should I work
on next? I have no idea thing? Email from and Azikov?
Would you like to prove my concept? Right? She's like,
I'm on it. Sometimes when you don't know what to do,
you should just check your email, right, because sometimes people
literally email you good ideas. Wow. So she went out
and she found one of these and and for real
(34:18):
or what do they think? Well, you know, she was
very careful because she's a good scientist, and she called
it a candidate because it's really hard to know for sure, right,
And these calculations are hard to do. You have to
measure the brightness of the star, which means you have
to know how far away it is, and you have
to measure the spectra, which means you have to know
like how much the light is absorbed between here and there.
(34:38):
It's a candidate. It's a candidate. So then do the
people of Denver and now vote on it or did
they decide, Well, we're deciding whether or not to eject
Denver into the heart of that and that depends on
how they vote. Denver into a star, depending on how
they vote in the next election. Denver is a star.
Da It's always a star in my heart. But then
(34:59):
a other group of folks reanalyzed this in two thousand
eighteen with more data from this one candidate, and their
numbers disagree. They said, well, you know what, we don't
think it's as bright as you thought it was, and
we don't find these dips at those element lines as
convincing interesting using the same data well as updated data
(35:20):
and different analysis techniques. Yeah, so they actually used older data.
They went back into catalogs and found old data from
previous telecopes. They've been looking for something else and they
had this old data and they're like, oh, let's use
this to try to understand the behavior of this star
more deeply interesting. So that was sort of disappointing. But
it's one of these bad news good news situations. But
(35:42):
but also, I mean, either of them could be wrong
kind of you know, oh, yeah, either of them could
be wrong. Sounds like you need more studies. That's right. Well,
a third study that disagrees with both of them, and
they will be even more confused. But this two thousand
eighteen papers said that loves candidate maybe wasn't a t
c O, but they found a better candidate. They were like, well,
(36:02):
when we reanalyzed all the red supergiants, we found this
other one that has a very strong rubidium line and
it's very very bright. And so it's a question of like,
how well do we understand the population of red supergiants.
Maybe there's just weird behavior without having a neutron star
in the court. Maybe they just have latium on them
or rubidium, yeah, or maybe there are a lot of
(36:24):
these things. You know. They did some backup the envelope calculation.
They said, these things last like ten thousand or a
hundred thousand or a million years, and you can calculate
like the rate of which they are formed. Then you
can put together an estimate for like how many there
should be in the Milky Way right now? Wait, do
you mean how long do you expect once the neutron
star goes into the red Giant? How long do you
(36:46):
expect it to to live or to just act in
an unusual way? How long you expected to continue looking
like a red super giant before it like turns into
a black hole or blows the red super giant out
into just all are remnant. I see, there's no scenario
in which it just stays a red super giant like
once they once you shoot a neutron star and it's
(37:08):
it's game over for it. Yeah, well, game over meaning
like you know, ten thousand, a hundred thousand, maybe a
million years right game for star lifetimes, that's pretty short.
And you know, they did some estimates for how often
these things should happen, and they figured that, like, you know,
this happens at one every ten thousand years ish or so.
(37:30):
And if you do the calculations that tells you that
there should be something like twenty to two hundred of
these things at any given moment in the Milky Way. Wow,
it sounds like a lot, but the Milky Way is huge. Yeah,
there's like, you know, hundreds of billions of stars, and
so a twenty or two hundred of those would be
these weird category. That's not that many, but it's possible,
(37:52):
and it's kind of possible to spot them. Yeah, it's
totally possible. Theoretically, there's nothing preventing it from happening, and
so we think it might happen, and it's just a
question of finding one, and then you get to play
the fun game of like, well, it doesn't look like
we expected, which means maybe there's something different going on
inside red supergiants. You know, we're desperately curious about what's
(38:12):
going on in the inside of stars because that's where
all the critical stuff happens. That's where heavy metals are
man Currently, we don't have a great understanding, for example,
how lithium is made in the universe, and it might
be that this is an important component of the just
the manufacturing of lithium in the universe, and if so
it would change how we understand like lithium being made
(38:33):
in the Big Bang or the early universe, and so
this is really important stuff to try to get a
handle on. All Right, Well, it sounds like almost unbelievable scenario,
but it sounds like it's happening all the time right now,
Like right now, there's two hundred of these possibly red
supergiants being killed by a neutroun car right now. That's right,
And I hope it inspires a future generation of scientists
(38:55):
to think, like, hey, let's put three objects like these
guys had a stack of two rejects, have like a
neutron star inside a bigger star, and put that whole
thing inside a red super giant, and that whole thing
wrap it all up in a you know, tortilla, and
taco bell will sell it. Gordita and red super giant crunch,
putting on the toppings there. That's right, wrapping more cheese,
(39:18):
wrapping another layer of tortilla called something else. I think
Kip Thorns should maybe pitched his to Hollywood again as
a new movie called Interstellar Colon Star Snacks. It would
be great because it already has spinoffs in terms of merchandizing, right, yeah,
all right, Well I think it's just this again, just
(39:40):
how about how much we don't know about the universe.
You know, we think that we know these red super
giants out there, and we think we know what's going
on and how often they happen, um, but who knows.
You know, there's a lot we don't know going on
inside of him, and there's a lot going on that
can happen to them in the universe. Yeah, And a
big part of the exploration, big part of answering these
(40:01):
questions is internal, is starting with mental creativity, is just
thinking what could be out there. And a lot of
the progress we've made is because we've come up with
the right question, because we've had the right crazy idea.
And so if you're a person who likes science but
you're also creative, remember there's a lot of creativity necessary
to do good science. And don't forget to put it
(40:21):
in an email. That needs to be a critical step
in any good idea. Did anybody do science before there
was email? I don't even I don't think they did.
There's definitely a correlation with the amount of science papers
produced and then email scent so really negative or positive correlation,
some kind of correlation, that's all I'll say. Who knows
(40:43):
what the classation is a relationship exactly? All right, Well,
we hope you enjoyed that and think about you know,
next time you look up at this guy, think of
red giant stars, the size of this orbit of Jupiter
being killed by tiny little stars, the size of them.
You hope you ender a dad. See you next time.
(41:08):
Thanks for listening, and remember that. Daniel and Jorge Explain
the Universe is a production of I Heart Radio. For
more podcast For my heart Radio, visit the I Heart
Radio Apple Apple Podcasts, or wherever you listen to your
favorite shows.
Hey, Daniel, do physicists ever run out of crazy ideas? Well?
We all have our slow days. I mean I get
science blocks sometimes. Yeah. So what do you do then
to get fresh ideas? Well? Probably very similar to what
creative people do. You know, you just let ideas bounce
around in your head a little bit and see what happens.
I should try that. I usually just take an end.
(00:30):
All right, So what happens, Well, let's see, let's say,
let me try, let me see. Um, I'll just let
an idea bounce in my head. I'm thinking chocolate chip particles.
That a good physics idea. I don't know. We have
to go see if we can find those out there
in the universe. They could exist, They could exist chocolate chippos. Yeah,
I mean, if I just let ideas bounce around in
my head, I think of alien black holes. Is that
(00:53):
a black hole that's an alien or a black hole
made by alien? It's a bifurcated ideas that allows for
both possibilities. Well, does this ever work? This process? Does
it ever actually give you a good ideas? Yeah? You know,
the universe is pretty crazy, and so sometimes the crazy
idea that comes out of the head of a physicist
is something that's really out there. Okay, I got a
(01:13):
good one for you. Chocolate chip black Holes, where each
chocolate chip is actually an alien. Hi. I'm or Hammad,
(01:37):
cartoonists and the creator of PhD Comics. Hi. I'm Daniel.
I'm a particle of physicist and I'm the co author
of the book We Have No Idea together with Jorge,
a book all about the things we do know and
mostly the things we don't know about the universe. And
it's also a huge coincidence because we don't really have
an idea of what we're doing here. But welcome to
(01:58):
our podcast, Daniel and Horr Explain the Universe, a production
of I Heart Radio. Danie and Jorge make it up
as they go along. When it comes to podcastings, right
it does it called science improv No, But we try
to be honest about what we know and about what
science doesn't know, because it's on that edge of knowledge
that all the interesting questions lie. That's where the wonder is,
(02:18):
that's where the curiosity is, that's where the mental exploration is.
That's where people go when they want to get new
answers to questions about the universe. Things everybody wants to
know the answer to how our stars formed, how do
they die? Can they eat each other and start taste?
But yeah, it turns out there's a lot we don't
know about the universe. There's more that we don't know
(02:39):
than what we do know, kind of in a way,
And so it's interesting to sort of talk about that
because you know, I feel like people have the sense
that the scientists know everything that's going on in the
universe until they meet a scientist and then they realize, boy,
that guy is clueless. This one doesn't know anything that's right.
How can she call aselvel scientist if she doesn't understand
what most of the univer versus about. But actually, that's
(03:01):
a key step to being a scientist is understanding what
you don't know and then confronting that ignorance, because confronting
your ignorance is the first step in discovery. Is being
open to new ideas and asking questions about the things
you don't know. That's the best part of science, and
so that's why on our podcast we try to take
you to that forefront of knowledge, bring you up to
(03:22):
speed on the questions that scientists themselves are asking. Yeah,
because who knows what could be out there, what kinds
of crazy phenomenon that we've never seen before or even
thought about. It could be out there right now, happening
in the universe. And so to be on the podcast,
we'll be talking about one such kind of crazy idea
that has been proposed by a couple of famous scientists.
(03:43):
That's right and maybe even discovered, Because there are several
ways to find weird new things in the universe. One
is to sort of stumble across them when you weren't looking, like, oh,
what's this thing, We've never seen it before. And the
other is to think of it first and say, I
wonder if you could make a black hole all out
of chocolate chips or whatever, you know, could you have
(04:06):
a planet the shape of a squirrel or something like that,
and then send experimentalists and astronomers out there to look
forward to see could this actually work? The planet in
the shape of a squirrel. That's just nuts, Daniel. But
today we'll be tackling one such crazy idea, And so
today on the episode we'll be asking the question, can
(04:30):
you have a star inside of another star? Sorry, I'm
still having your squirrel nuts joke. Let that play out. Yeah,
but This is a kind of a crazy question. I
don't even think I even understand it. How can you
have a star inside of another star? Well, you know,
some stars are really big and some stars are really small,
(04:51):
and you're used to thinking of stars is really far apart. Right,
our star is really far from other stars. But they
can get closer together, and you can imagine what might
happen if they get really close together, with one go
inside the other one. It would be a star on
star battle, they merged into one megastar. Yeah. So who
came up with this crazy idea star inside of another star?
(05:13):
Well it was from two scientists, Kip Thorne and Anna Zikkov,
and they had this idea that maybe you could have
one tiny, really dense little star called the neutron star
inside of a really big, puffy star called a red
super giant. And they were just wondering, hey, is it possible?
And they did some calculations and they thought, it doesn't
(05:35):
seem impossible. I wonder if it's also really I think
there were signs blocked when they came up with that
and just sat around drinking whiskey or eating chocolate chips,
and they're like, oh, what if you could have a
star inside of another star. Yeah. I bet they just
wrote a bunch of random things on the wall and
then threw darts at them, and they were like, all right,
neutron star, okay, red super giant. Hey, what if you
(05:59):
got one inside the there? You know, maybe they had
a hundred terrible ideas that day and this is the
best one. They're like, what if they're best friends? No,
not that. What if they're mortal enemies? Now? Not that?
What what if one is the evil twin of the other.
We need to that's been done. We need a better
plot twist. You see. There is something, though, there's a
deep connection between being creative in physics or in science
(06:22):
in general, and being creative when you're doing writing or whatever.
You just sort of let the ideas flow and and
think about what's been done before and then try to
find something new, Like has anybody thought about whether you
know these could actually be black holes reflected into this
dimension by some alien supercomputer whatever? Dot dot dot. You know,
you need to let your mind wander a little bit
(06:42):
when you're being scientifically creative. Sounds like there's a fine
line between science fiction and science for real. And I
tried to straddle that line. All right, Well, these things,
these stars inside of other stars, they have a name,
and they're called the thorn Jitkov objects. And so we
were wondering, as usual, how many people had heard of
(07:03):
these weird and crazy objects out there in the universe.
And so, as usual, Daniel went out there and pulled
the Internet for people to ask him this question. Yes,
so thanks to everybody who volunteered. If you'd like to
volunteer to answer random physics questions for a future episode,
please write to us at questions at Daniel and Jorge
(07:24):
dot com. All right, well here's what people had to say.
I think it is some type of a hybrid star
or something. I have no idea, Man, I have no idea.
I've never heard of that. Well, absolutely no idea. I
have no idea. Um, I have not heard of a
thorn site cow psit Co object. So I have no
(07:48):
idea what that is. No idea, I never heard of it.
The name looks like it might be something to do
with Kip Thorne, who is an astrophysicist, So I'm going
to guess it's something astrophysical. Al Right, not a lot
of name recognition. I feel like a lot of these
people maybe read our book We have no idea. We
stole our idea that we have no idea. That was
(08:10):
our idea being clueless. It was our idea not to
have an idea. I think that's that's an old human
kind idea. Yes, I think that's true, but also not
really much of an idea for how to pronounce this name?
And you know, I gave it to them in writing,
and it's sort of a strangely written name because it's
got a Z with a dot on top of it.
Why t k o W. But it's pronounced jitkov to
(08:33):
my best understanding, right right, And I guess if you're
googlly and you would have to type in z y
t k o W. Yeah. But Kip thorne Is is
sort of well known and he has kind of a
brand name in physics, he certainly does. He's also got
a Nobel Prize and he's worked on Interstellar the movie,
so he's sort of a celebrity and lots of different
arenas these days. And you know him, don't you. Yeah,
(08:54):
I do. I've met him a few times before. Super
nice guy and very cool. So so he came up
with this idea with Anna Zitkov. So let's dive into it, Daniel,
How can you have a star inside I don't even
know what that is or what that looks like. How
can you have a star inside of another star? Yeah? Well,
I think it's only possible for a couple of different
categories of stars, because what you need is one star
(09:15):
to be really really big and the other star to
be really really small, so it can sort of like
slip inside the other star. And so we've got to
like extreme categories of stars involved here. One is the
red super giant star, and the other is the neutron star,
and that's the really small one. And each of these
are like already fascinating just on their own, so you know,
(09:37):
you could write a whole science fiction movie about just
one of these. So combining the two of them together
it is like, hey, man, that's a bit too much,
but you know, hey, they're not limited in their scientific creativity. Okay,
so when you see a star instead of another star,
then you're talking kind of about specifically two kinds of
star that kind of come together, and then one of
them kind of eats the other one. Yeah, I mean,
I'm not sure which one you would describe as being active,
(10:00):
Like is the bigger one eating the other one? Or
is the smaller one sort of like boring into the
larger one? Or is it a poetic dance of two stars?
I'm not sure, but I guess that can happen, right,
because why not? Why can't a star fall into into
another star? Or why can't two stars kind of merge together?
(10:20):
That thing happens, right, Yeah, that kind of thing does happen.
And if the very different kinds of stars, like a
red super giant is very low density compared to a
neutron star, then the neutron star can enter the red
super giant without being disrupted, without blowing up, without you know,
being dispersed, and just merging into part of the red
super giant. But aren't sons like stars. Aren't they sort
(10:42):
of like giant explosions? You know, isn't there a lot
going on? How can something hold together inside of a star?
These are some of the largest stars in the universe. Like,
the largest red supergiant we've ever found has a radius
that's fourteen hundred times the radius of the Sun. Fourteen hunt,
you mean, if you take fourteen hundred of our sons,
you would get a super giant exactly. These things are ginormous,
(11:05):
like they make our Sun, which is already huge compared
to Jupiter, which is huge compared to the Earth, which
is huge compared to you write, this thing dwarfs our Sun.
If you put it in our solar system, it will
go all the way out to the orbit of Jupiter.
It's incredible. It's it's almost as big as our entire
solar system. Yeah, but it's not that much more massive, right,
(11:27):
So it's thousand times bigger and radius, which makes it,
you know, like a billion times bigger in volume, but
it's only about ten to forty times the mass of
the Sun. Oh. I see, it's like a thousand times
less dense than our Sun. More like ten over a
billion times less dense than the Sun. So it's millions
of times less dense than our Sun. Now it's still hot, right,
(11:50):
it's like thousands of degrees kelvin. It's not a place
you'd want to be. But compared to our Sun, it's
more like a cloud, right, It's more like a burning,
diffuse cloud. And so while it's a huge, burning ball
of gas and not a pleasant place to hang out
or have a picnic, it's not a hot, dense environment
like the center of our Sun. I see, it's just
kind of a hot cloud of stuff, but it's still
(12:11):
kind of igniting and burning, definitely burning, right. You have
a lot of pressure and temperature and a huge amount
of fusion is going on, and you've got light being admitted.
These things are big and they're glowing their ten thousand
or a hundred thousand times the luminosity of our Sun.
And they're pretty hot. You know, there's like four thousand
degrees kelvin on the surface. And there's one that you
(12:32):
can even see in the night sky. Wow, where yeh
Betel Juice. Betel Juice is a red supergiant in the
Orion constellation. You mean one of the one of the
points in the Orion Baiel Juice. And these stars have
fascinating histories because they started as a blue supergiant, like
the same size, but much hotter and more intense when
(12:54):
they were burning hydrogen. And then remember they burn that
hydrogen and they sort of start run out of hydrogen,
and as the temperature increases in the center, they start
to burn helium instead, and then near the end of
their life they turn into these red supergiants. They're cooled
off a little bit. It flipped red the sun. Yeah,
you know, yeah, it got more conservative in its older age.
(13:15):
I think that tends to happen. It's very brief period
of moderation in the middle, and then boom all the
way to the Fox News side, a Republican. Yeah. So
that's the red supergiant. That's like what is going into
And so you can imagine it's much easier to fall
inside a red super giant than it is like our
kind of sun, because it's so big, right, Yeah. And
(13:37):
so then the second kind of star for this to
sort of happen and stay happening, is that you need
a neutron star, which is almost like the opposite of
a red super giant. Yeah, exactly. It's super duper dense.
It's like the mass of our sun or the mass
of the Sun, but it's collapsed to like the size
of the city of den what like an object like
(13:59):
just like twenty kilometers. Why so the whole Sun the
size of Denver. Yeah, take the whole Sun, which is
already a hot, dense mess, and collapse it to something
that's you know, much much smaller than Earth. It's incredibly dense.
And this is what happens when a star collapses, like
at the very end of its life. It can go
(14:20):
black hole, or can go neutron star, or various other outcomes.
This is like the core remnant, the hard little nugget
that's left over after the collapse of a star. And
it's kind of almost almost at the point of a
black hole, right, Like it's so dense it could kind
of maybe easily tip into a black hole. Yeah. And
one way that you can get a supernova, at least
(14:41):
to a black holes, you start with something like a
neutron star and then you add a little bit more
gas and then it turns into a black hole. But
these things don't yet have enough gravitation of power to
overcome the neutron pressure. It's like a bunch of neutrons
all packed in together, really really really tightly. It's like
a bunch of people squeezed onto you know, the metro
(15:01):
in Mexico City at rush hour. Have you ever ever
done that? But it's a pretty intimate experience. It's a
big negative, as they would call it. And neutron stars
are fascinating because we only discovered them because we found
a particular type called a pulsar. This is the kind
that shoots a huge beam of light and rotates really quickly,
and so it appears on Earth like a flashing light.
(15:24):
And they discovered this in the night sky, you know,
several decades ago. And that's how we even know that
neutron stars exist. Because neutron stars don't have fusion inside them.
They're not fusing. They are emitting light in the same way.
They're not exploding. They just glow from all of the
compact stuff being squished together. Yeah, they glow because they're hot.
They're like six hundred thousand degrees kelvin. They're much hotter
(15:47):
than a hundred thousand degrees kelvin. It's pretty it's pretty hot.
They're smoking hot. It's much hotter than the inside of
a red super child. All right, So they're small but
super hot and supercompact, and so while the other one
is kind of big and fluffy. And so I'm starting
to get kind of the picture here what's going on,
And so let's get into how these things would happen
(16:09):
and what would happen and are they even real? But
first let's take a quick break, all right, Daniel, we're
talking about neutron stars being eaten up or invading the
(16:31):
space of red super giants, and so I think I'm
getting the picture here. Another, in order for this to
sort of happen, you need one big, fluffy star that's
kind of it's hot and it's a star, but it's
in a big and a kind of diffuse and then
you have one another one that's really compact and you know,
super duper hot, and then that can go inside of
the first one and exist there or an orbit there,
(16:54):
or what does it do once it gets eaten up. Yeah,
it's sort of like a bullet into a pillow. Right,
one can go into the other one. And there's a
few ways that this can happen. Like one way this
can happen is that they just bump into each other,
like you got a bunch of stars flying around and
these two things just sort of happened to hit each other.
That's not very likely because stars are typically very very
(17:16):
far apart. In some certain configurations, these things called globular clusters,
you have higher density of stars, it might happen, but
scientists think it's much more likely that these things already
started out near each other, like a binary star system,
a system where you have two stars like regular stars,
two regular stars, and you know, stars evolve, and so say,
for example, you have two stars and one of them
(17:39):
already is a red super giant, the other one is
a normal star. But then it goes supernova and at
the core it leaves a little neutron star. Well, that
little neutron star might not just stick around at the
center of the supernova. It might get a sideways kick
because these supernova aren't like totally symmetric, and so it
might get sort of shot into the red supergiant. Oh,
(18:01):
I see. Wow, it's like the relationship of alls. Yeah,
or that means that the supernova is like a neutron
star gun. It's like shoots out one huge crazy bullet
from the center of it, which goes right into the
red supergiant. Oh, it goes supernova and the jacksit center
which is a neutron star, which is a neutron star. Yeah,
(18:22):
what a way to go, And it goes into the
red giant super red giant. Remember, the red supergiant is enormous,
so it would be pretty hard to miss. It would
take up, you know, most of the sky from this
neutron star. So it just flies off roughly in that direction.
It's going to get captured by this red super giant.
It's a giant pillow the size of the sky. It's
kind of hard to miss exactly. And the other options,
(18:45):
the other order is that you have a neutron star
and it's got some partner star which becomes a red
supergiant because these stars can grow and you know, like
our sun is going to grow near the end of
its age. It's going to grow and grow and grow
and can do a large your radius. So the other
star can just sort of like grow and gradually engulf
(19:05):
drown star. You can just sort of like creep on
over and take over its space. But the one, the
other one needed to be a neutron star, right, yeah, okay,
And and these things just happen out there in the universe, right, Like,
you know, we're kind of used to this idea that
stars are really far apart because there aren't any stars
around us really close by, But there are places in
the universe where it's like a mess of stars. Yeah,
(19:26):
And it's actually much more common for stars to form
together because remember stars are formed sort of in bunches
when a big gas cloud collapses and so a lot
of stars are formed sort of near each other, and
it's more likely for stars to have a binary partner
than to be solo stars. Our son is unusual. In
the Milky way, binary stars are more common than solo really.
(19:47):
Uh yeah. Out there in the stellar dating field, almost
everybody's already married as somebody. Somebody needs to get our
Sun dating app or something. I'm sorry you want another star, like,
I just feel bad for our our son. I don't know.
Then we'd have like a step star and be a
weird relationship because it wasn't around when we were formed,
and it's trying to like boss us around gravitationally. I
(20:09):
think it'd be a big mess. They won't let us
go to the ball. But yeah, more family, that always
is always better. Yeah, I guess more family, more drama,
But I guess if that's what you're in for. But
I think this is what Kip Thorne and and a
Jikov we're thinking about, Like could you have these two
things end up inside each other. It's not that unlikely
because you have pairs of stars already, So if one
(20:31):
of them turns red super giant, or one of them
turns into a neutron star. Could they then fall into
each other, could they collapse into a single object and
could that work? What would it look like? Right, Yeah,
let's get into what happens. So we have one really
compact neutron star, super hot. It goes into the big
fluffy red supergiant and then what does it just keep
(20:52):
going because it come out the other end kind of
like a bullet, or does it you know, disintegrate that's
just going through or does it just kind of inside
kind of like a like eating a rock. Yeah, it
mostly stays inside. I mean, it depends a little bit
on its initial velocity. But you know, a red super
giant is still a lot of mass. These things are
ten or forty masses of the Sun, and so it's
(21:14):
a big gravitational Well, so most likely the neutron star
is just gonna spiral to the center of this red supergiant.
Oh what do you means spiral? Like? Um, it can't
just keep kind of orbiting around inside of the star
or does it eventually you're saying it eventually kind of
collapses into the middle. Yeah, you could orbit stably at
a fixed radius if you're not losing energy, and like,
(21:35):
you know, if you are a spaceship orbiting the Earth,
you can stay at the same altitude if there's no drag,
But if you're touching even a little bit of atmosphere,
then you're gonna be slowing down and spiraling back intowards
the Earth. If you're inside a red supergiant, then you're
definitely going to be dragging against the hot, burning plasma.
It's gonna be stealing your energy, so you're gonna be
spiraling in towards the center. And I guess why doesn't
(21:58):
it dissolve? Like why doesn't a neutron star just kind
of like under those conditions just kind of like break
apart or evaporate because it's super duper crazy dense, Like
a neutron star is pretty hard to break up. I mean,
what you have is a basically a wind of burning
plasma that's incident on the surface of this neutron star,
and so at that surface you get a lot of reaction,
(22:19):
but not enough to like break up a neutron star.
And the neutron star is a very tightly bound gravitational object.
You know, it's like putting a rock in a sandstorm
or something. And eventually what happens is you know, the
neutron star is also gravitationally very dense. It's just going
to gather more stuff around it. And so what starts
to happen is this really crazy reactions right at the
(22:40):
surface there where the neutron Star is super duper hot,
it starts burning the inside of the red super jump
because it's so much hotter. It's six hundred thousand degrees
versus four thousand degrees. Yeah, and and so you get
crazy stuff happening right there in the interior. And it's
also super heavy. So does it start to like kind
of suck out some of the red super Giant and
(23:00):
kind of build up in size as it's going in. Yeah,
and so what can happen is that it accumulates enough
stuff to trigger it to become eventually a black hole. Oh,
that would be some serious indigestion. Like if you like,
if you eat something and it turns into a black hole,
that's not good. Yeah, that's even more than Montezuma's revenge. Right,
(23:20):
it's like Nutron stars revenge it or your negative you see,
things never go well when you have to star parents, right,
they always end up fighting, Alright, So then one thing
that can happen is that it goes inside and it
becomes a black hole, and then it's kind of game
over for everybody, right, because then the black hole is
gonna suck in the Red super giant. Yeah, it can
(23:41):
suck in a lot of the mass of the Red supergiant,
but also a lot of it won't collapse. Remember, black
holes don't automatically suck in everything that's nearby. They're just
a powerful gravitational force. If you have enough rotational energy,
you can end up just in the accretion disk like
around the black hole. So basically the red supergiant just
because material for the accretion disc that's surrounding the black hole.
(24:04):
The black hole just kind of sucks up all of
the Red supergiant, yes, the center of it at least,
and then the outside becomes this like big swirling disk.
But you know, that's one possibility. Another possibility is that
you get crazy intense fusion and reactions at the surface
of the neutron star where it's embedded inside this other star,
and it creates a lot of energy flying out and
(24:26):
it basically disperses the Red supergiants like a new solar wind.
That's pushing out on the red supergiant and disperses it
back into basically a cloud of stuff. It's kind of
like dipping a hot poker into a bath of water,
Like it touches the water and then it just steams,
just explodes out and it just disrupts everything. And then
(24:50):
that stuff can do interesting things like form planets, and
so you might end up with like a crazy, big
spinning pulsar in the center surrounded by planets formed from
the depth of that red supergiant. Wow, crazy drama fusion
because you're making like a heavier element as it goes in. Yeah, yeah,
(25:13):
because that the surface of the neutron star, it's super hot.
And then you have all the materials you need for
fusion because there was fusion already happening inside the red Supergiant.
You just like supercharged it by bringing in all this
extra energy, all this extra heat. So then now suddenly
instead of a red giant and a neutron star, what
do you have? Then you have like a new solar system. Yeah,
(25:33):
you have a new solar system where the red supergiants
bones have been used to like supercharge the neutron star
and to form a bunch of planets, and so what
happens to the Red Supergiant just just activates, like it
just peters out and or does it just turns off. Well,
it's become diffused, and so it's no longer enough energy
and the conditions for fusion. But you know, this is
(25:56):
the fate of almost every star, right, especially these really
big ones. They will burn and then eventually their cores
will collapse and they will disperse. And so that's that's
just what happens anyway, that's the Red super Giant is
expecting that. It's not a surprise if it's one of
these thorn jit cob objects. It's and just sort of
gets accelerated by having a neutron star there in the middle. Well,
(26:19):
it's pretty amazing to think that you start out with
a star whose size it is the size of the
orbit of Jupiter, so it's huge, and then you have
this tiny little, you know, twenty kilometer wide bullet basically,
this little, tiny, superdense thing, and then it just it
just totally disrupts this whole ginormous star. I know, imagine
if Denver right was the downfall of the whole system.
(26:43):
That's pretty impressive, right, I mean, I like Denver. Denver's
got a lot of sway, but like that's pretty outsize
impact for a tiny little region. Yeah, yeah, well it
is a swing state, I think, so you know who knows, right,
it can totally tip the fate of the entire world. Yeah,
you could become a black hole or whatever. It's all
(27:03):
in the hands of those voters. It's all in the
hands of Denver's. All right, Well, let's get into how
you could tell if these things exist and if they
even are real out there in the universe. But first,
let's take a quick break. All right, Daniel red super
(27:33):
giant eating a neutron star. Sounds like they've worked it
out and it's totally possible and a lot of amazing
things would happen. So are they real and how could
we tell if we where they are? Well, that's sort
of the disappointing part about this thing is they had
this crazy idea. They were like, Wow, a neutron star
inside a red super giant. That would be awesome physics
(27:53):
deep inside the core. And then they asked, well, what
would it look like from the outside, right, Because we
don't get to like go inside red super giants and
take a box to see if there's a neutron star
or not. We only can observe these things, thankfully from
the outside. And you know, a red super giant again
is huge, and so seeing this neutron star inside of it,
(28:14):
like directly seeing it totally impossible, and mostly from the outside,
a thorn Chikov object looks just like a normal red
super giant. The differences are pretty subtle, really, But doesn't
it the little neutron star disrupted? Wouldn't we see it
kind of peter out suddenly or turn into a black
hole or turn into a solar system. Well, if you
(28:35):
could watch it over, you know, ten thousand or a
hundred thousand or a million years, then you you might
see these effects. We only get to see these things
in a snapshot, right You could ask like, does this
particular star have a neutron star inside of it? Right now?
So we don't get to see the time series evolution. Man,
I would love to look to take an object in
(28:55):
the sky and just like fast forward it for a
million years and back and forth and see what's gonna happen.
That to be amazing. I see It's like if you
see a dead red supergiant, it could be like, oh,
it could die from natural classes or maybe a shot
with a neutron star. It would be hard to tell. Yeah,
And and really the game is look at all the
red super giants out there right now, and ask do
(29:15):
we think any of them have a neutron star in
them right now? How would they look different if they did?
And can we make the measurements to tell if one
of them does? So, how can we tell if they
did have a neutron star for a snack? Well, you know,
they have a really different interior, right they have this
crazy neutron star which is triggering this really intense reaction,
(29:35):
is burning at the core, and so that does have
some impact on what it looks like from the outside
in two important ways. One is that they are a
little brighter, get more effusion, and so you're producing more light.
And red supergiants are not famously bright. I mean, they're
ten thousand times or a hundred thousand times brighter than
the sun, But for that mass in that volume, it's
(29:57):
not a very intense source of light. So if you
see one that's like extra bright, unusually bright, then that's
a clue that maybe it's got a neutron star in
its core, because an intron star kind of creates new
kinds of reactions which would make it brighter. And then
there's a very specific kind of reaction that we think
(30:17):
could only happen inside one of these objects. That you
have to have a neutron star inside a red supergiant
for this even to work, and so you can look
for the very characteristic signs of that particular reaction. Interesting
involves elements cycling around from the surface of the red
supergiant down to the core where they get added protons
(30:38):
onto them, and then it's so hot they get shot
back up and they get to the surface. They come
back down and they get more protons, and they shot
back up and get to the surface. And remember, for
one of these objects, the core is much much hotter,
so it pushes these things out to the surface more.
See if it's something like this would make a particular
kind of element which we might be able to recognize
(31:00):
in the surface of these stars, that's right. And so
if it's a T c oh then you'd see much
more lithium and molybdenum and rubidium then you would see
a normal red supergiants. And so if we look at
these stars and we can tell that they have more
of this stuff on their surface and they're extra bright,
then it's a good sign that it might have a
neutron star hiding inside. It. Wouldn't a lot of lithium
(31:23):
make it more chill and more um more more calm.
You know, you can't take studies in humans and extrapolate
those two behaviors stars for a giant. We did this
study in mice, and so we're going to extrapolate, you know,
what would be the dose like for a lithium for
a red super using the mouse model to study this
(31:44):
giant supernova red supergiant totally works exactly, all right. So
there might be like if we see a red supergiant
and we see that it glows kind of in the
lithium range, then we're like, oh, maybe it has a
neutron star inside. Yeah, Actually it would be the that
doesn't glow in the lithium range because the opposite, because
if there's lithium on the surface, then the light is
(32:06):
going to be absorbed at certain characterists of frequencies that
lithium likes to eat, and so if there are dips
at certain characteristic frequencies that would indicate extra amounts of
those elements, So I see it means that that stuff
is there, which means that maybe there's a neutron star
in there exactly. So that's that's would be the signature
we're looking for. And so have we found any what's
(32:28):
kind of the likelihood of this this thing happening. Well,
there's a really fun story here because there's an awesome
scientist named Emily Lefek and she became an expert in
red supergiants because her research she was fascinated by how
they were made, how how they worked, and understanding this
whole process inside them. And then she got an email
from Anna Jikov saying, how would you be interested in
(32:50):
trying to figure out if any of these red supergiants
might be one of these weird objects that Kip Thorn
and I thought about years ago? And so that sounded
fun to Dr Levek, and so she surveyed all the
red supergiants she knew of and she found one. She
found this star which looked really weird with the dip
in lithium, like with the lithium signature on. Yeah, it
(33:12):
was weirdly bright and it had the dip at lithium
and libdenum and rubidium exactly the places you would expect
by one of these objects, unlike the other red supergiants
which didn't have these signatures exactly. And that's what she did.
She compared this red supergiant to like the broader population
of red supergiants, to find one that's unusual. And this
(33:35):
is the star that we've known about from more than
a hundred years, was discovered in nineteen o eight. It's
called HV two one two. It's from the Harvard Star Catalog.
It's in the small Magellanic cloud. And so this is
the paper that came out in two thousand fourteen saying,
oh my gosh, maybe we actually found one of these things.
That must have been a fun day. I bet she
(33:56):
was science blocked. And she said, what should I work
on next? I have no idea thing? Email from and Azikov?
Would you like to prove my concept? Right? She's like,
I'm on it. Sometimes when you don't know what to do,
you should just check your email, right, because sometimes people
literally email you good ideas. Wow. So she went out
and she found one of these and and for real
(34:18):
or what do they think? Well, you know, she was
very careful because she's a good scientist, and she called
it a candidate because it's really hard to know for sure, right,
And these calculations are hard to do. You have to
measure the brightness of the star, which means you have
to know how far away it is, and you have
to measure the spectra, which means you have to know
like how much the light is absorbed between here and there.
(34:38):
It's a candidate. It's a candidate. So then do the
people of Denver and now vote on it or did
they decide, Well, we're deciding whether or not to eject
Denver into the heart of that and that depends on
how they vote. Denver into a star, depending on how
they vote in the next election. Denver is a star.
Da It's always a star in my heart. But then
(34:59):
a other group of folks reanalyzed this in two thousand
eighteen with more data from this one candidate, and their
numbers disagree. They said, well, you know what, we don't
think it's as bright as you thought it was, and
we don't find these dips at those element lines as
convincing interesting using the same data well as updated data
(35:20):
and different analysis techniques. Yeah, so they actually used older data.
They went back into catalogs and found old data from
previous telecopes. They've been looking for something else and they
had this old data and they're like, oh, let's use
this to try to understand the behavior of this star
more deeply interesting. So that was sort of disappointing. But
it's one of these bad news good news situations. But
(35:42):
but also, I mean, either of them could be wrong
kind of you know, oh, yeah, either of them could
be wrong. Sounds like you need more studies. That's right. Well,
a third study that disagrees with both of them, and
they will be even more confused. But this two thousand
eighteen papers said that loves candidate maybe wasn't a t
c O, but they found a better candidate. They were like, well,
(36:02):
when we reanalyzed all the red supergiants, we found this
other one that has a very strong rubidium line and
it's very very bright. And so it's a question of like,
how well do we understand the population of red supergiants.
Maybe there's just weird behavior without having a neutron star
in the court. Maybe they just have latium on them
or rubidium, yeah, or maybe there are a lot of
(36:24):
these things. You know. They did some backup the envelope calculation.
They said, these things last like ten thousand or a
hundred thousand or a million years, and you can calculate
like the rate of which they are formed. Then you
can put together an estimate for like how many there
should be in the Milky Way right now? Wait, do
you mean how long do you expect once the neutron
star goes into the red Giant? How long do you
(36:46):
expect it to to live or to just act in
an unusual way? How long you expected to continue looking
like a red super giant before it like turns into
a black hole or blows the red super giant out
into just all are remnant. I see, there's no scenario
in which it just stays a red super giant like
once they once you shoot a neutron star and it's
(37:08):
it's game over for it. Yeah, well, game over meaning
like you know, ten thousand, a hundred thousand, maybe a
million years right game for star lifetimes, that's pretty short.
And you know, they did some estimates for how often
these things should happen, and they figured that, like, you know,
this happens at one every ten thousand years ish or so.
(37:30):
And if you do the calculations that tells you that
there should be something like twenty to two hundred of
these things at any given moment in the Milky Way. Wow,
it sounds like a lot, but the Milky Way is huge. Yeah,
there's like, you know, hundreds of billions of stars, and
so a twenty or two hundred of those would be
these weird category. That's not that many, but it's possible,
(37:52):
and it's kind of possible to spot them. Yeah, it's
totally possible. Theoretically, there's nothing preventing it from happening, and
so we think it might happen, and it's just a
question of finding one, and then you get to play
the fun game of like, well, it doesn't look like
we expected, which means maybe there's something different going on
inside red supergiants. You know, we're desperately curious about what's
(38:12):
going on in the inside of stars because that's where
all the critical stuff happens. That's where heavy metals are
man Currently, we don't have a great understanding, for example,
how lithium is made in the universe, and it might
be that this is an important component of the just
the manufacturing of lithium in the universe, and if so
it would change how we understand like lithium being made
(38:33):
in the Big Bang or the early universe, and so
this is really important stuff to try to get a
handle on. All Right, Well, it sounds like almost unbelievable scenario,
but it sounds like it's happening all the time right now,
Like right now, there's two hundred of these possibly red
supergiants being killed by a neutroun car right now. That's right,
And I hope it inspires a future generation of scientists
(38:55):
to think, like, hey, let's put three objects like these
guys had a stack of two rejects, have like a
neutron star inside a bigger star, and put that whole
thing inside a red super giant, and that whole thing
wrap it all up in a you know, tortilla, and
taco bell will sell it. Gordita and red super giant crunch,
putting on the toppings there. That's right, wrapping more cheese,
(39:18):
wrapping another layer of tortilla called something else. I think
Kip Thorns should maybe pitched his to Hollywood again as
a new movie called Interstellar Colon Star Snacks. It would
be great because it already has spinoffs in terms of merchandizing, right, yeah,
all right, Well I think it's just this again, just
(39:40):
how about how much we don't know about the universe.
You know, we think that we know these red super
giants out there, and we think we know what's going
on and how often they happen, um, but who knows.
You know, there's a lot we don't know going on
inside of him, and there's a lot going on that
can happen to them in the universe. Yeah, And a
big part of the exploration, big part of answering these
(40:01):
questions is internal, is starting with mental creativity, is just
thinking what could be out there. And a lot of
the progress we've made is because we've come up with
the right question, because we've had the right crazy idea.
And so if you're a person who likes science but
you're also creative, remember there's a lot of creativity necessary
to do good science. And don't forget to put it
(40:21):
in an email. That needs to be a critical step
in any good idea. Did anybody do science before there
was email? I don't even I don't think they did.
There's definitely a correlation with the amount of science papers
produced and then email scent so really negative or positive correlation,
some kind of correlation, that's all I'll say. Who knows
(40:43):
what the classation is a relationship exactly? All right, Well,
we hope you enjoyed that and think about you know,
next time you look up at this guy, think of
red giant stars, the size of this orbit of Jupiter
being killed by tiny little stars, the size of them.
You hope you ender a dad. See you next time.
(41:08):
Thanks for listening, and remember that. Daniel and Jorge Explain
the Universe is a production of I Heart Radio. For
more podcast For my heart Radio, visit the I Heart
Radio Apple Apple Podcasts, or wherever you listen to your
favorite shows.
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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