February 11, 2020 • 41 mins
Do rogue planets exist? Could they support life?
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Episode Transcript
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Speaker 1 (00:08):
Hey, Daniel, did you ever want to be an astronaut? Well, yes,
but I didn't because I'm terrified of the danger and
the adventure. Yeah, I'm not ready to travel in the
space until it's safe and routine. Yeah, it is pretty
dark and scary out there, But isn't that kind of
the point of space exploration to go out there and
discover and find new things hiding in the darkness. Yeah,
(00:29):
and I want other people to go out there take
those risks, and then I can just read about it
in the newspaper. Hi am or Handmay, cartoonist and the
(00:52):
creator of PhD Comics. Hi. I'm Daniel Whitson. I'm a
particle physicist, and I'm a stay at home adventurer of
the mind couch Explorer. I'd like to explore this vast
universe from the comfort of my office. But welcome to
our podcast, Daniel and Jorge Explain the Universe, a production
of I Heart Radio, in which we take you on
(01:13):
an exploration of all the amazing, crazy, monkers, beautiful, nasty, crazy,
weird things in this universe. Did I say crazy twice?
That's because the universe is that crazy. It's double crazy.
I feel like the things we're learning in science every year,
every decade, every generation are crazier than the things we
learned before. It's not just that we're learning more, but
(01:33):
the stuff we're revealing is just more bonkers than anything
we could have imagined. Don't you feel that way? Well,
do you think it's crazier than what we thought it
was before? You know, is it crazier than Greek gods
and Norse mythology? Well, I think it's maybe less creative,
but it's definitely crazier. Every generation has had to absorb
(01:54):
ideas which were very difficult to swallow because they completely
conflict with our view of the world. You know, the
universe is expanding, there is no sense of location and time.
You know, things are fundamentally random. Space curves like these
are hard things to get your mind around, and they
get harder and harder as we discover them. Yeah. We
are not the center of the universe, and the universe
(02:16):
is not like what we see around are where we are. Yeah,
and every time we look out into space we discover
new stuff, weird stuff. Places we thought were empty turned
out to be filled with interesting, fascinating, weird kinds of matter.
M Yeah, because that's kind of the history of humanity
and science. Right, Like, we look around and we assume
that the whole universe is kind of like where we're at. Right.
(02:39):
We thought the world was flat because everything seems flat
around us, And we thought that the Earth was the
center of the universe because everything seems to provolve around this.
But then as we learn more that we learn that
there are more and more different things out there. We
keep learning that the assumptions we make, that the generalizations
we make about what we learned here, cannot be applied everywhere.
(02:59):
And that's the exciting part. That's the moment of discovery,
when you realize, oh, I thought the universe was this way.
It turns out it's actually totally different in a way
I never imagine. We're intellectually maturing as a species by
discovering our universe and coming to grips with it. And
it's not always the way we liked it, but it
turns out to be quite fascinating to the other program
will be tackling one such idea that you know, maybe
(03:21):
a lot of people even today think is true, but
actually it turns out to be much more complex than that.
That's right, that darkness out there is more filled with
interesting stuff and rocks than you could have ever imagined. Yeah,
stuff that's out there hiding in the darkness, other worlds
out there looking at ours and wondering what would it
be like to be so close to a nice, warm,
(03:41):
toasty star. Yeah. So today on the program, we'll be
tackling the question are there planets without stars and not
just a movie stars? Right? We're talking about are there
places in the universe then don't have a son or
a star near them? I like the one you asked though, Like,
(04:03):
are their planets out there with only being C list actors?
That's right? Where everyone uh it only has five seconds
of fame. You can only be in one movie and
then your career is over. It's like turn limits for
for Hollywood actors. That's great, and then that'd be great
if we got rid of celebrity culture in our society. Yeah, well,
(04:27):
that won't appeal to any of our celebrity listeners, you know.
So Hey Brad Pitt, don't worry. You can still come
on the program. But apparently it works if you If
you speak badly about somebody don't want to come on
our show, then that's true. To defend themselves, maybe to
grab any kind of publicity they can. That's true. Stay
tuned for our episode in which science fiction authors come
(04:49):
on the show and respond to our critiques. And when
we're thinking about the broad universe, you know, you are
used to thinking about your planet is having one very
important feature, which is the on And every time you
think about a planet, you imagine, well, planets form around stars, right,
and so it's a bit mind bending to imagine that
the universe might be different. Yeah, a lot of people
(05:11):
might be surprised to learn that not every planet out
there is centered around the star. You may be shocked
to discover that rogue planets are not that rare. That
the universe may be chalk filled with these floating dark bodies. Yeah,
and that's the official physics name for them, right, like
a planet without a star. It's officially called a rogue planet. Yes,
(05:35):
but you will not be surprised to discover there is
some controversy about what exactly gets called a rogue planet.
Oh wow, physicists arguing about what to name something that's
so rare, not only arguing about whether something is a
good name, but like what exactly falls into this category?
You know, the whole Pluto, like is it a planet?
Is it not a planet? Thing? That's this same controversy
(05:57):
large interesting because I guess everything is sort of being
pulled by every star in the universe, So technically there
there isn't this a planet that's not being pulled by
a star. I like that. You're sort of saying every
planet is part of a sum solar system, even if
it's sort of distant from its star. Right, Well, technically, right,
don't all solar systems sort of overlap with each other?
(06:19):
Technically because the force of gravity is infinite has infinite reach. Yeah,
that's true. The force of gravity is infinite, but at
some point the force of gravity from these stars is
basically negligible and there's essentially no effect on these planets,
and they're more affected. Yeah, negligible, They're more affected by
the mass of the galaxy. So I think the distinction
(06:40):
is are you orbiting a star or are you orbiting
the center of the galaxy? All right, Well, I was
a little surprised to find out that there are road
planets out there, and that there are apparently not just
a few of them. But we were wondering how many
people out there knew the same fact that there are
planets out there in space without stars. So I walked
around campus a you see, Irvine, and I asked folks
(07:01):
what they thought and if they had a guess for
how many rogue planets there might be in the universe.
To think about it for a second, how many planets
out there in the universe? Would you, guys are out
there floating without a star. Here's what people had to say.
I have no clue how many there are. My guests
understanding from what I think I know is that they're
(07:22):
by one way or another of something flying by the
end up injected from the star that they'reth I have
not do you think does exists? I don't think. I
can't imagine that that would be not true, honestly, like
a lot of just like ten, I would have no
idea how to give a number, Um I would I
would actually have to say probably a lot, just because
(07:44):
gravity is so you can get a star really close
to another set of planets and then it throws them
off in space. So probably a lot, probably, I think.
So you think it's like seven or like a billion? Jeeus? Um, Well,
in a in a big universe, I don't know if
we could count. No, I think every planet. I think
(08:04):
interested pretty good mix of reactions. Yeah, a lot of
open minds. I love the people who say the universe
is so big you can never say no, you can
never say that something doesn't exist. I think that's a
great attitude because technically, in an infinite universe, anything can happen, right,
and anything is happening. Yeah, in an infinite universe, everything
(08:24):
that can happen eventually will happen and is happening somewhere.
So it's a good attitude. Now, we don't know the
universe is infinite, but it's definitely pretty big right somewhere
out there. There's a version of this podcast in which
you and I are the A List celebrities. That's not
this version. What are you saying? I don't I'm confused.
I think we're run out of letters letters. That's right
(08:49):
with the Triple A. We're the Triple We're Triple A celebrities,
which sounds good, but really, welcome to the minor the
Ego podcast, folks. Yeah, so, um, but people seem sort
of skeptical. I mean, some people said yes, but it
sort of seemed like yes, probably, but probably it's probably
(09:10):
not very common, that's right, and it's immediately a fascinating question.
It's the kind of thing you might not ever think about.
You think, oh, well, planet is of course they form
around stars, and that's reasonable because stars form from the
gravitational collapse of stuff, and plants do the same thing,
and so you should imagine they formed together. They're probably
associate with each other. You probably don't ever think that
(09:32):
there are dark bodies floating out there in between the stars.
But as soon as somebody suggested to you, then you
have to wonder, well do we know, how do we know?
Have we looked? Could we see them? And immediately it's
a question you need to know the answer to. Yeah,
because if it's a lot, then they would be pretty
uh interesting, I guess, or dangerous because what if one
(09:52):
of them hits us? Yeah, it's a little bit dangerous.
But also it just changes sort of your your view
of the universe. I mean, what if there are more
rogue planets out there than non rogue planets, then your
whole view of like what is a planet has to
all of a sudden change from oh, they're all around
stars to well, my sense of a planet is unusual
(10:13):
is a typical? Oh I see, it could be that
our kind of planet is the minority. Yeah, exactly, Just
like we discovered that our kind of matter is a
small fraction of all the matter in the universe. All
of a sudden, things we thought were typical are now weird.
It'd be like discovering their more continents out there. Or
you know, you grow up in your family eats a
dinner a certain way, and then you go to a
(10:34):
friend's house you discover, oh man, my family is weird.
We are and we don't use utensils at home or
whatever it is. You know, it's it's maturing in that
same way, right, It's expanding your horizon and your idea
of the universe. And that's why this is such a
fun opportunity to learn something new about the universe. All right,
so let's get into it. Daniel Wood exactly is a
(10:55):
rogue planet. Right, So let's begin with technical definitional stuff
that we could argue about easily for half an hour.
And and and very importantly, is there a first rogue
planet called rogue one? Well, the movie rights for that
one I've already been locked up, unfortunately. Yeah, Well they're
not definitely not making a sequel of that one. I
(11:18):
liked it. I liked it, but you know, Rogue two's
agent is not exactly getting a lot of traction in Hollywood.
But a rogue planet is a planet that's not orbiting
a star. And you said earlier, and you're right that
every planet feels the gravity from every star in the galaxy,
but you have to look at its motion, like the
motion of the Earth is that we are orbiting our star.
(11:39):
We're moving around our star. But if we were a
rogue planet, then our primary motion would just be around
the center of the galaxy. Would be the same category
as the stars, like our star orbits the center of
the galaxy. It's a planet that's not sort of trapped
by the gravitational well or pool of a star. Yeah,
(11:59):
we liked to in goo a Solar System as an
object because it's gravitationally bound that the dominant gravitational force
on every object in the Solar System is the Sun.
So it's like the Sun has its own little neighborhood
in which it's gravity is more powerful than any other gravity.
Or I guess maybe not not just that it's more powerful,
but it's powerful enough to to sort of trap things
(12:23):
in its vicinity. Yeah, it's a stable to let it
go exactly. But you know, the galaxy is big, and
there are a lot of stars, but they're not that many,
and so there's a lot of room out there between stars. Remember,
we're you know, light years away from the nearest star,
which makes a huge amount of space for stuff to
be floating between the stars. Oh, I see, So there's
(12:43):
a lot of room for you to be out there
without falling into the you know, the trap of the
gravitational pool of a star. Yeah, if you mapped the
Milky Way onto Earth, for example, you know, you have
like one house here in Los Angeles and another house
like in Kansas, and another house like in New York City,
and there'll be a lot of room between those that
(13:04):
you could rogue around it. Yeah, you can have a
rogue cabin in the woods and never have to get
close to anybody. And I guess more importantly, you could
be so far away from my house and your house
in Kansas, Dad, you wouldn't feel the need to sort
of go visit. Yeah, and you could largely ignore them.
You know, those stars would just be other slightly more
bright stars in the sky, and you wouldn't feel their
(13:25):
gravitational pull strongly enough to get sucked into one of them.
All right, So then what's the definition then that it's
it's a planet, meaning like a ball of stuff? Is
that what it means? What is exactly a planet? Yeah?
Well that's where it gets tricky, right. Um. These are
either things that were formed in other solar systems and
(13:46):
then ejected, or you could also think about stars that
never sort of got started, like failed stars. You know
what if a star never sort of turns on because
it's not big enough to burn, is that a rogue
planet or is that a failed star? Is a heated
debate in astronomy, But both of those things are out
there well in a way sort of Jube, isn't Jupiter
(14:08):
also kind of a failed star? Like it could have
been a star but it wasn't. Yeah, And if Jupiter
had formed far enough away from the Sun on its own,
if it was like the center of its own little
gravitational neighborhood, we would call it a sub brown dwarf star.
But because it formed around our star, we call it
a planet. And so there's a lot of energy spent
in astronomy arguing about these names and definitions. And wait,
(14:30):
you're saying that if Jupiter wasn't in our solar system,
if it was out there, it would be considered a
star even though it's not burning. Yeah, there's a whole
category of stars called brown dwarfs and sub brown dwarfs
that are just not big enough to ignite fusion and
to burn and to glow. But why still call them
a star if they're not ignited? I'm burning, see what
(14:50):
I mean. People have strong feelings about this, like you do.
Apparently in your mind you think, you think, if it's
got to be burning to be a star, right, Well,
other people think, oh know, it's a failed star. That's
a kind of star, all right, So that's kind of
the definition. It's a ball of stuff, or maybe the
definition is kind of fuzzy, but generally speaking, a rogue
planet is a ball of stuff. It could be gas.
Could be rock too, right, rocks or gas or you know,
(15:15):
it's compressed matter kind of um just to make it
different than a cloud. And it's floating out there in space,
not in the orbit of a star. Whatever that could mean.
That's right, it's a it's a dense blob of stuff.
Primarily orbiting the center of the galaxy instead of orbiting
another star. All right, let's get into how we can
(15:37):
see them even though it's dark out during space and
how many there are out there in the universe. But
first let's take a quick break. All right, I know
(15:57):
there are floating planets out there in the universe in
our galaxy that don't have a star. They're called road planets,
and there might be a lot of them. So first
of all, I guess, how do we even see them
if it's they're not burning bright and they're not near
a star for them to shine, Um, how do we
know they're there? It's tricky, right, These are dark objects.
(16:18):
They are not shining, they're not emitting light, and as
you say, they're not close enough to any star to
reflect light like like exoplanets are. So it's not easy
to spot them, which is why for a long time
we didn't even know that they existed. Um, but there
are two ways to see them. One is you get
really lucky, and one is close enough that we can
see them in the infrared. Remember, these things are not burning,
(16:42):
so they're not shining visible light, but they still have
some heat to them and everything in the universe that
has a temperature also radiates some energy, usually in the infrared,
and so sort of glowing in the infrared. And we
have infrared telescopes, I see, because we I think we're
used to thinking of like asteroids and things out there
(17:03):
in spaces being cold, but you could have, for example,
like the Earth is kind of warm by itself. The
Earth is kind of warm. And even if we were
ten or fifty kelvin. And I want to give props
to the person out there who wrote in to remind
me that it's not degrees kelvin, it's just kelvin. But
even if we were just ten or fifty kelvin, we
would still radiate. Everything that's above absolute zero radiates some energy.
(17:26):
It's called black body radiation. Oh, I see. It sort
of shines in the infrared. Yeah. And there's a telescope
called the Wise telescope w I S E, which is
really good at seeing this stuff, and it's really good
in the infrared. And so if it's close enough that
you can spot them directly with the Wise telescope, but
it has to be pretty close. So like if our
(17:46):
son suddenly went out and there was no more light
in our solar system, you could still maybe see the
Earth and all the other planets. Yeah, you could, precisely.
And we do this to study other solar systems. We
look at them in the visible light and we also
look at them in the infrared to try to get
a glimpse for like, what is the stuff out there
that's not blowing. It's still there, it's giving off different
(18:07):
kinds of radiation. So we have lots of different ways
of looking at the sky. The infrared, X ray, radio,
These are all just different kinds of light though. They're
all just different parts of the electromagnetic spectrum. But different
things out there glow in different parts of these spectrums.
So the most direct way is to look for them
in the infrared. But they have to be really close by,
Oh I see, because otherwise it would be too faint
(18:28):
to see them. Yeah, Because these things are small and
pretty faint, and so they're pretty hard to spot. The
best way to see these things is to look for
a little star eclipse. What well, if you have a
big dark object somewhere out there in the universe and
it passes between you and a star, then what happens
It blocks the light from that star momentarily like a
(18:49):
one time eclipse. Yes, like a one time eclipse, one
time ever eclipse, one time ever. Yeah. And so you
can see these things if you very carefully watch all
the stars in the sky and wait for a blip.
But there's something really fascinating because you might expect that,
like a star eclipse would dim the star, that it
would go out for a minute and then come back, right,
(19:10):
that's you'd expect, But this is really weird. Gravitational effect.
If the rogue planet or whatever it is alien ship
is big enough, then it has a gravitational lensing effect.
It acts like a big lens in space. Because remember
gravity is the bending of space. So gravity can change
the direction of light. We'll just block the light, they'll
(19:31):
bend the light. I mean that sort of happens here
on Earth too when there's an eclipse, right, doesn't the
light sort of go around the Moon when it's blocking
the sign a little bit? It does a little bit. Yeah,
And in this case it can actually enhance the strength
of that star because it acts like a lens. It
gathers more light and it focuses it all on the Earth.
So what actually happens when you get a micro lensing
(19:51):
event they call it, is that the star gets brighter,
not just a darker or like darker and lighter. Yeah,
it actually gets brighter. It gets enhanced, right, it gets
amplified by this micro lensing, and so the very center
of it is blocked out. But you're gathering light from
nearby and focusing it onto the earth. You actually get
more of the starlight when it goes by. It's an
(20:12):
eclipse that makes it the start look brighter. Yeah, recisely.
It's really fun. And the telescope to see these things
has a really awesome name. It's called the OGLE telescope.
I thought I thought it was already too much to
have a wise telescope. W I s e this one.
(20:32):
I want to look at things called the OGLE if
you want to sit on the couch and ogle the universe,
and you do it using the optical Gravitational Lensing Experiment OGL. Wow,
you guys probably pop some champagne when you came up
with that name. So those are the two ways you
can see him. You can see them either through micro
lensing or anti eclipses or directly through the infrared. And
(20:56):
so what do we know about them? Do we know
are they sort of round like our planets necessarily, or
do they look like giant asteroids or what do we
expect them to look like? Yeah, we expect that they're
mostly round because anything that's big enough gravity will make
it round. You know, gravity is powerful, and if you've
got a bit that's sticking out, eventually it's going to
(21:17):
roll down. And so you have something that's big enough
to have strong gravity, it's going to get around. Oh,
I see, And you expect these to be big, right,
I guess if you're If you're calling them planets, there's
a certain size associated with that name, isn't there? Like
Pluto got demoted because it wasn't big enough. Yeah, But
the really amazing part is that probably there's a whole
(21:38):
spectrum of sizes, from like things bigger than Jupiter down
to Earth size things down to just rocks, and the
number is probably inversely proportional to the size. So there
are a certain number of Jupiter sized ones, and they're
probably more Earth sized ones, and then probably like a
xillion times more just box out there. But at some
(22:01):
point they're just called rocks. You wouldn't call them planets, right,
At some point they're called planets and then dwarf planets,
and then yeah, just comets or rocks or dust. Right,
and you know, some of these things have come to
our solar system. Remember Omama and the comment that came
through UM in December. These are just rocks from other
solar system that flew through our Solar system. Wow, there
(22:23):
are Jupiter size planets out there, just floating in space,
not being bound to any star, just doing their own thing.
And that was the question when people first thought about this.
They thought, are they out there? Let's go look for them,
and so they started using these two approaches, and what
they found sort of boggled the mind. Right, they found
more than they expected. Yeah, they found that there's something
(22:45):
like around one Jupiter sized rogue planet for every star
in the Milky Way. So there's hundreds of millions of
these Jupiter size rogue planets out there. Yeah, more like
a hundred billion, yeah, because it's not about a hundred
billion stars in the Milky Way. And a few years
ago there was a really exciting result. Some people said
that there might be like two to four Jupiter size
(23:08):
rogue planets out there for every single star, so like
hundreds of billions, and everybody was like reacted just the
way you did, like what And then another experiment did
some measurements and they came back to everybody, calm down.
It looks like there's probably just about one jupiter size road.
And I was like, that's still crazy. I mean, I
was thinking like there might be ten in the whole galaxy.
(23:31):
Turns out there's billions and billions of these things, and
those are the Jupiter sized ones. The milky ways litter
with these. Yeah, they're everywhere, and if as you go
down the mass scale right like Earth size planets, there
might be ten or even a hundred times as many. Wow,
it's just traffic out there. It's pretty messages stuff. Nobody's
(23:55):
cleaned up, right. We formed all these solar systems and
that all the leftover base are just still out there.
But you know, it gets more and more uncertain. As
the size of the object we're talking about gets smaller,
it's harder to see, and so we've seen fewer of them,
so we're making more of an extrapolation with more uncertainty.
We're in early days of understanding this, and in five, ten,
(24:16):
fifty years we'll have a much better handle on it.
But right now it's pretty uncertain. Are they going to
keep on floating out there? Or will will all of
these planets eventually kind of fall into a star. Think
about what happens when a big Jupiter's eye planet approaches
a star. It's not that easy to fall into orbit. Remember,
orbit requires being in the right location, having the right direction,
(24:37):
and the right velocity. Much more likely is that you
come into a solar system and you just sort of
like mess it up. Yeah, you perturb the gravitational, the
nice cozy gravitational orbits of everybody that's been there for
billions of years, and you make more rogue planets like
you come in and you bust up a family. If
a Jupiter sized planet came into our solar system, we
(24:58):
would probably lose a planet or two. Well, I hope
it's not Earth. They can take Pluto, Neptune. You know,
we don't even we don't even care about those. Wow,
they haven't even arrived yet. And you're and you're already
at the negotiating table offering up our neighbors. What has
urine has done for me lately? Oh? Come on, it's
(25:21):
comic fodder. Urine is really I would give away Neptune first,
I see it's less funny. I see you need you
want you want to planet around you can make fun
of it. Yeah, exactly, some some planet has to be
the butt of all of our jokes. So okay, So
it's not likely because they're if they're already floating out there,
you know, careening through space, it's unlikely for them to
(25:41):
stop at any particular start. They'll just kind of bounce
around from solar system to solar system. It is possible,
it's possible for our start to capture a new planet,
and people wonder about the history of our Solar system,
you know, like some of our planets have weird orbits.
Is it possible they were captured? But if you just
shoot a planet at a star, most of the trajectories
(26:01):
will lead to it just being like whipped around and
shot out into space and probably losing some of its planets.
I guess. Then that gets us to the question of
how these planets even formed. If they are not in
a solar system, and they were, probably they can be
captured by a solar sism. Where did they even come from?
So let's tackle that question. But first let's take a
(26:23):
quick break, all right, So where do rogue planets come from.
Is there like a rogue planet factory somewhere? Is there
a rogue nation of planets where all of these planets
(26:45):
go rogue from their rogue nation. Well, it depends on
how you define a rogue planet. There is a big
population of them that were probably formed around a star,
just like Earth and Jupiter and all of our planets.
They were part of some big cloud out of gas
and dust and rocks which coalesced to form a star
and planets. But remember that's not like organized. Nobody planned
(27:07):
our Solar system, and so in the early days of
our Solar system, stuff was pretty chaotic. It's not like
everybody had cleared it up and say, everybody in this
lane become Earth and everybody over here. You had stuff
sort of bouncing around more. It was more disorganized, and
so stuff got ejected. So some planets that were formed
in the early days of our Solar system probably got
(27:28):
ejected are now out there and planets we have a
lost brother out there or sister. Yeah, we almost certainly do.
And it's almost certainly almost certainly we um. It's a
fun question to ask, like what fraction of planets end
up in stable orbits and what fraction get ejected? Um,
And you know we're looking at our Solar system billions
of years in. It's basically after everything has settled down,
(27:51):
you know, in our Solar system, people think, for example,
like Saturn and Jupiter might have once had different orbits
that might have been in a different order because we
had more things. Yeah, and that there was a third planet,
another icy giant, which got ejected from the Solar system.
Like you look at the organization of our Solar system
for clues, and you're like, this looks weird. You know,
(28:12):
would make more sense if this crazy thing happened. And
that's how we ended up with this configuration of our planets. Oh. Interesting,
that's right, because the Solar System didn't always look like
the Solar System. No. And remember Earth had a massive
collision with like a planet sized object which led to
the formation of the Moon. Where did that thing come from? Well,
probably our Solar system and so and now it's been obliterated. Okay.
(28:36):
So so that's one way you can create a rogue
planet out there in spaces. You it's born in a
Solar System along with other planets, but then the other
planets sort of get together and and kind of vote,
vote that planet out. That's right, planet survivor. But you know,
from that planets point of view, they're probably like, I
never wanted to be in a solar system anyway. It's
so much more exciting out here in the backwoods. I
(28:59):
see much cooler out here. It is much cooler out there. Um.
And it could also be, as we talked about earlier,
that something comes by and perturbs and nice stable solar system,
like a black hole comes near a solar system and
perturbs it and sucks out some of the planets, or
even just you know, another passing rogue planet. So solar
systems are not that stable. So so those are rogue
(29:20):
orphan planets I guess you could call um. Then you
can also have like true road planets or like uh,
independently formed road planets, feral planets, maybe we can say
native planets. These are the ones that you were saying
don't really count as a star, and they're called sub
brown dwarf stars, and they're just clumps of matter that
(29:43):
started to form together but didn't get enough to form
enough gravitational pressure that you would get hydrogen fusion at
the core of it, and so you never start to burn,
because you could just have dust out there and gas
and just have it. If there's nothing around it, it'll
just come together as a clump. It will come together
as a clump. Eventually gravity wins. Right. Gravity is so
(30:04):
weak but so patient, and it just pulls this stuff
together whatever you started with. And you know, you might
wonder like how does that start? And that's a whole
other fascinating topic. People think that these clouds of gas
and dust and maybe like a supernova shock wave passes
through it and that triggers the coalescing. Anyway, we'll talk
about that in another episode. But whatever you got around
(30:26):
you forms into a blob and if it's not bright
enough to burn into a star, then it becomes to
tonight to start fusion. Right, that's what you yeah, Because
you know, if you just have a rock out there,
it's not enough to start fusion. You need enough mass
that the gravity sort of takes over and you start
that star and then it's basically a sub brown dwarf star. Man,
(30:46):
I'm just gonna pass judgment right now, Daniel. I think
I don't think they should be called stars, alright, Just
climbing a sub brown dwarves or something. So would you
call them a rogue planet then? Yeah? Right? Independent? An
independent planet or yeah, why not? Is there an argument
against calling them a road planet? Well, some people think that,
(31:06):
you know, a planet is something that formed around a star,
and so that a rogue planet. I think the generally
acceptable term is that a rogue planet something was around
a star and then got lost. It went rogue. You
can't you can't be born rogue in astronomy, apparently, I
see if by planet you mean something that forms around
a star, then technically I think that doesn't form with
(31:29):
it around a star is not a planet. But this
is all semantics, but it's just what people decided to
call this thing, so they can have words that they
communicate with and all mean the same thing. Or maybe
they just like arguing about this stuff at meetings. That's
probably true also, or maybe if what do you mean
by star is just like celestial objects, um, then this
could be sort of a non shining star. Yeah, and
(31:50):
these things sort of go the same way as the
rogue planets. That is, when it comes to stars. We
know more about bigger stars because they burn bright and
we can see them. It's hard to spot brown dwarfs
and sub brown dwarfs because they don't shine like stars.
We think that the number of these things grows very
quickly though, as you dial down the mass of the
object from bright star to sub brown dwarf to just
(32:12):
dark little blob. So there's a lot more sub brown
dwarfs out there than there are burning stars. There are
more failed stars and stars. Is that what you're saying?
Big surprise, right? There are more waiters than celebrities in Hollywood. Wow.
The analogies just keep keep on rewarding us here. It
(32:33):
turns out what we've learned here in Los Angeles does
apply to the rest of the universe. In this one case,
l A is the center of the universe. Obviously, it
has taught us something about template is a template for
the rest of the universe. That is terrifying. That is terrifying, alright, cool,
So it's pretty interesting to know, to understand, to to
have a sense that there are giant planets out there
(32:55):
floating in space without a home. You know, they're just
cruising through space like a like a spaceship. I guess, yeah,
And you have to wonder, like, what would it be
like to stand on the surface of that planet in
perpetual night. You have no seasons, you right, you could
do a lot of great astronomy, right because you have
no sun to interfere with your telescopes. You could have
a walk around that planet, go all the way around,
(33:18):
and you would only see the night sky with stars
in it. Yeah, but you could stay up all night long,
every night. You would never get a sunburn's right, that industry,
that industry would just not take off. Good for astronomers,
bad for practicing gamble. Yeah, and also makers a swimsuits,
(33:40):
probably because you know it'd be pretty cold. Right. We
rely on our Sun not just for sunlight but also
for the warmth, and it provides something like point nine
seven percent of the energy on the surface of the
Earth comes directly from the Sun. Really, but aren't there
planets in our Solar system that are like super hot
(34:00):
by themselves or is it all also from the Sun?
There are like Venus is super hot, but all that
energy comes from the Sun. And the reason it's super
hot is that has these thick clouds that trap that energy.
So all the surface energy from all the on all
the planets in our Solar system is almost all from
the Sun. But that's from on the surface, if you
wanted to live on the surface and have a view
of the night sky. But technically, could you in one
(34:23):
of these road planets, could you like evolve life inside
of it where where it is warm? You might because,
as you say, the core of our planet is warm,
and that's not from the Sun, that's from the gravitational pressure. Right,
the Earth is also being squeezed and melt the rock,
and from the radioactive decays that are happening inside that
rock that radiates a little bit of energy. And so
(34:45):
there is you know, there are hot spots underground. And
so if you're on one of these rogue planets safe
for example, the Earth went rogue, right, what would happen? Well,
their ocean good? Not good? Right? You throw away all
your sunscreen, Sorry about that, and the the oceans would
freeze and the atmosphere would like turn to snow and
just like accumulate on the surface of the Earth, which
(35:06):
would be crazy. But if you go down deep enough,
they would still be warmth, and so there might be
enough energy sort of bubbling up through the crust to
keep like a layer of water melted. Oh. Interesting, you
could have like underground oceans. Yeah, you could have underground
oceans that the Earth would be covered in layer of ice,
but a mile or maybe two miles down there could
(35:27):
still be water and it might be warm enough to
sustain life. So you would throw your sunscreen, but not
your swimsuit. Try to take your swimsuit or maybe your
wet suit, because I don't think it's going to be
very warm. But you could find like you know, cracks
in the Earth's mantle underground where there's geothermal energy, and
there are there is life the very bottom of the ocean,
(35:48):
clustered around these thermal vents. Yeah, and they don't have
any sunlight that you just live off of the hot
water from these events. They've been planning for this for
a long time. Yeah, they're ready for They're ready for Earth,
Bill Rode. They're the rogue life right there, ready to
take over when Earth goes rogue. There are the waiting
waiting to rise up. But I think what I what
I'm saying is that that that could happen in one
(36:08):
of these rogue planets out there. I mean, there could
be like a giant floating Jupiter out there in space.
It's actually like a spaceship full of life under the surface. Yeah,
and it doesn't have to be that life evolves on
a planet and then it goes rogue. I think you're saying, like,
could life evolve on a planet when it's a rogue
And I think the answer is yeah. You could have
a good water on a rogue planet and life could evolve,
(36:30):
and it could evolve under like a mile of ice
and never see the sky. Right, it might not even
be aware that the universe is larger than its ocean.
It would be like rogue life. And you have to wonder, like,
what kind of technology could you evolve? Like, could you
become intelligent? Could you evolve technology? Could you drill out
of the ice and then discover that? Imagine what that
(36:52):
would be like to be that kind of I want
to read a science fiction novel about life that evolves
on a rogue planet and develops the technology, drills as
of the ice, and then discovers Oh my gosh, the
university is so much bigger than we ever imagined. What
a moment. Right, There's a story that you and I
were talking earlier about. The writer thought Chiang, he has
a story I don't know if you read it, called
(37:13):
The Tower of Babel where that's kind of the plot
where they drill through the ceiling of heaven. Oh my gosh,
I want to read that story. That sounds awesome. Yeah. Alright,
So that that's kind of possible, is that there are
and and there are so many of these road planets
out there that it's it probably is maybe possible that
there is life and the life started in one of
these road planets. Yeah, it's very exciting for the possibility
(37:36):
of alien life, which you know, I'm a fan of.
You know, recently we've learned that there are a huge
number of planets around other stars. That was a big
moment just in astronomy in general, but also for us
who promote alien life, to realize that there are other
places for life in the universe around other stars. That
was exciting. Now we're learning that that's a tiny fraction
(37:56):
of all the planets out there, and that there's an
enormous number of these dark rogue planets, and I think
it's more challenging for life to form on a rogue planet,
but hey, you've got more opportunities also, right, there's a
there's like a hundred billion rogue planets the size of Jupiter. Yeah,
and maybe tend to a hundred times as many Earth
sized planets out there, and just in our solar systems,
(38:20):
I mean just in our galaxy that would be getting
kind of crowded. Just in our galaxy, I mean, I
mean the galaxy. There's hundreds and hundreds of billions of
these and and maybe there are hundreds of billions of galaxies.
So who knows, right there could be a rogue life
form out there. My money is that there is. I mean,
it just seems so much more likely. It seems so
(38:40):
impossible to imagine that nowhere out there, in any of
these planets has life begun. There's so many opportunities and
so many ways for life to happen we haven't even imagined.
I would definitely put my money on there being rogue
alien life. Can you imagine them bursting out of their
shell and be like WHOA what is this? Even crazier though,
is that like one of these rogue planets could pass
(39:01):
by our solar system, you know, within a few au
you know, just outside the edge of Pluto, and we
wouldn't even see it, and they might not even see us,
And so we could be like there could be like
cosmic neighbors and zooming by and we're not even paying attention.
And maybe, just maybe this happened a few billion years ago,
and maybe, just maybe an asteroid hit that road planet
(39:23):
and ejected a piece of rock with life that then landed.
I'm taking it too far, No, I like that. There
are a lot It's totally possible. It's possible for life
to have originated somewhere else and then come to Earth.
All right, Well, that's pretty interesting to know. It just
sort of makes you look at space and the night
sky differently. And in all those places where you only
(39:45):
see blackness, there could be planets out there, floating and
possibly with life. Yeah, and this life might not be
looking back at you. It might be hidden under two
miles of ice, looking up at the inside of its
ocean and wondering what l is out there? Right, that's
no interest in being famous like a star, only because
(40:05):
they don't even know it's possible. Once they get a
taste of it. Though, Once stay discovered television, it's all over.
Who doesn't want to be a star? All right, Well,
we hope you enjoyed that little tour into the blackness
of space and what could be out there. Waiting for
us to discover and as usual, you are in no
(40:25):
danger as you sit on your couch or sit in
the seat of your car and listen to us helping
you explore the universe. All right, We hope you enjoyed that.
See you next time. Before you still have a question
after listening to all these explanations, please drop us a line.
(40:46):
We'd love to hear from you. You can find us
on Facebook, Twitter, and Instagram at Daniel and Jorge That's
one word, or email us at Feedback at Daniel and
Jorge dot com. Thanks for listening and remember that Daniel
and Jorge, Hey, Explain the Universe is a production of
I Heart Radio. From more podcast from my Heart Radio
visit the i heart Radio app, Apple Podcasts, or wherever
(41:09):
you listen to your favorite shows. Yeah
Hey, Daniel, did you ever want to be an astronaut? Well, yes,
but I didn't because I'm terrified of the danger and
the adventure. Yeah, I'm not ready to travel in the
space until it's safe and routine. Yeah, it is pretty
dark and scary out there, But isn't that kind of
the point of space exploration to go out there and
discover and find new things hiding in the darkness. Yeah,
(00:29):
and I want other people to go out there take
those risks, and then I can just read about it
in the newspaper. Hi am or Handmay, cartoonist and the
(00:52):
creator of PhD Comics. Hi. I'm Daniel Whitson. I'm a
particle physicist, and I'm a stay at home adventurer of
the mind couch Explorer. I'd like to explore this vast
universe from the comfort of my office. But welcome to
our podcast, Daniel and Jorge Explain the Universe, a production
of I Heart Radio, in which we take you on
(01:13):
an exploration of all the amazing, crazy, monkers, beautiful, nasty, crazy,
weird things in this universe. Did I say crazy twice?
That's because the universe is that crazy. It's double crazy.
I feel like the things we're learning in science every year,
every decade, every generation are crazier than the things we
learned before. It's not just that we're learning more, but
(01:33):
the stuff we're revealing is just more bonkers than anything
we could have imagined. Don't you feel that way? Well,
do you think it's crazier than what we thought it
was before? You know, is it crazier than Greek gods
and Norse mythology? Well, I think it's maybe less creative,
but it's definitely crazier. Every generation has had to absorb
(01:54):
ideas which were very difficult to swallow because they completely
conflict with our view of the world. You know, the
universe is expanding, there is no sense of location and time.
You know, things are fundamentally random. Space curves like these
are hard things to get your mind around, and they
get harder and harder as we discover them. Yeah. We
are not the center of the universe, and the universe
(02:16):
is not like what we see around are where we are. Yeah,
and every time we look out into space we discover
new stuff, weird stuff. Places we thought were empty turned
out to be filled with interesting, fascinating, weird kinds of matter.
M Yeah, because that's kind of the history of humanity
and science. Right, Like, we look around and we assume
that the whole universe is kind of like where we're at. Right.
(02:39):
We thought the world was flat because everything seems flat
around us, And we thought that the Earth was the
center of the universe because everything seems to provolve around this.
But then as we learn more that we learn that
there are more and more different things out there. We
keep learning that the assumptions we make, that the generalizations
we make about what we learned here, cannot be applied everywhere.
(02:59):
And that's the exciting part. That's the moment of discovery,
when you realize, oh, I thought the universe was this way.
It turns out it's actually totally different in a way
I never imagine. We're intellectually maturing as a species by
discovering our universe and coming to grips with it. And
it's not always the way we liked it, but it
turns out to be quite fascinating to the other program
will be tackling one such idea that you know, maybe
(03:21):
a lot of people even today think is true, but
actually it turns out to be much more complex than that.
That's right, that darkness out there is more filled with
interesting stuff and rocks than you could have ever imagined. Yeah,
stuff that's out there hiding in the darkness, other worlds
out there looking at ours and wondering what would it
be like to be so close to a nice, warm,
(03:41):
toasty star. Yeah. So today on the program, we'll be
tackling the question are there planets without stars and not
just a movie stars? Right? We're talking about are there
places in the universe then don't have a son or
a star near them? I like the one you asked though, Like,
(04:03):
are their planets out there with only being C list actors?
That's right? Where everyone uh it only has five seconds
of fame. You can only be in one movie and
then your career is over. It's like turn limits for
for Hollywood actors. That's great, and then that'd be great
if we got rid of celebrity culture in our society. Yeah, well,
(04:27):
that won't appeal to any of our celebrity listeners, you know.
So Hey Brad Pitt, don't worry. You can still come
on the program. But apparently it works if you If
you speak badly about somebody don't want to come on
our show, then that's true. To defend themselves, maybe to
grab any kind of publicity they can. That's true. Stay
tuned for our episode in which science fiction authors come
(04:49):
on the show and respond to our critiques. And when
we're thinking about the broad universe, you know, you are
used to thinking about your planet is having one very
important feature, which is the on And every time you
think about a planet, you imagine, well, planets form around stars, right,
and so it's a bit mind bending to imagine that
the universe might be different. Yeah, a lot of people
(05:11):
might be surprised to learn that not every planet out
there is centered around the star. You may be shocked
to discover that rogue planets are not that rare. That
the universe may be chalk filled with these floating dark bodies. Yeah,
and that's the official physics name for them, right, like
a planet without a star. It's officially called a rogue planet. Yes,
(05:35):
but you will not be surprised to discover there is
some controversy about what exactly gets called a rogue planet.
Oh wow, physicists arguing about what to name something that's
so rare, not only arguing about whether something is a
good name, but like what exactly falls into this category?
You know, the whole Pluto, like is it a planet?
Is it not a planet? Thing? That's this same controversy
(05:57):
large interesting because I guess everything is sort of being
pulled by every star in the universe, So technically there
there isn't this a planet that's not being pulled by
a star. I like that. You're sort of saying every
planet is part of a sum solar system, even if
it's sort of distant from its star. Right, Well, technically, right,
don't all solar systems sort of overlap with each other?
(06:19):
Technically because the force of gravity is infinite has infinite reach. Yeah,
that's true. The force of gravity is infinite, but at
some point the force of gravity from these stars is
basically negligible and there's essentially no effect on these planets,
and they're more affected. Yeah, negligible, They're more affected by
the mass of the galaxy. So I think the distinction
(06:40):
is are you orbiting a star or are you orbiting
the center of the galaxy? All right, Well, I was
a little surprised to find out that there are road
planets out there, and that there are apparently not just
a few of them. But we were wondering how many
people out there knew the same fact that there are
planets out there in space without stars. So I walked
around campus a you see, Irvine, and I asked folks
(07:01):
what they thought and if they had a guess for
how many rogue planets there might be in the universe.
To think about it for a second, how many planets
out there in the universe? Would you, guys are out
there floating without a star. Here's what people had to say.
I have no clue how many there are. My guests
understanding from what I think I know is that they're
(07:22):
by one way or another of something flying by the
end up injected from the star that they'reth I have
not do you think does exists? I don't think. I
can't imagine that that would be not true, honestly, like
a lot of just like ten, I would have no
idea how to give a number, Um I would I
would actually have to say probably a lot, just because
(07:44):
gravity is so you can get a star really close
to another set of planets and then it throws them
off in space. So probably a lot, probably, I think.
So you think it's like seven or like a billion? Jeeus? Um, Well,
in a in a big universe, I don't know if
we could count. No, I think every planet. I think
(08:04):
interested pretty good mix of reactions. Yeah, a lot of
open minds. I love the people who say the universe
is so big you can never say no, you can
never say that something doesn't exist. I think that's a
great attitude because technically, in an infinite universe, anything can happen, right,
and anything is happening. Yeah, in an infinite universe, everything
(08:24):
that can happen eventually will happen and is happening somewhere.
So it's a good attitude. Now, we don't know the
universe is infinite, but it's definitely pretty big right somewhere
out there. There's a version of this podcast in which
you and I are the A List celebrities. That's not
this version. What are you saying? I don't I'm confused.
I think we're run out of letters letters. That's right
(08:49):
with the Triple A. We're the Triple We're Triple A celebrities,
which sounds good, but really, welcome to the minor the
Ego podcast, folks. Yeah, so, um, but people seem sort
of skeptical. I mean, some people said yes, but it
sort of seemed like yes, probably, but probably it's probably
(09:10):
not very common, that's right, and it's immediately a fascinating question.
It's the kind of thing you might not ever think about.
You think, oh, well, planet is of course they form
around stars, and that's reasonable because stars form from the
gravitational collapse of stuff, and plants do the same thing,
and so you should imagine they formed together. They're probably
associate with each other. You probably don't ever think that
(09:32):
there are dark bodies floating out there in between the stars.
But as soon as somebody suggested to you, then you
have to wonder, well do we know, how do we know?
Have we looked? Could we see them? And immediately it's
a question you need to know the answer to. Yeah,
because if it's a lot, then they would be pretty
uh interesting, I guess, or dangerous because what if one
(09:52):
of them hits us? Yeah, it's a little bit dangerous.
But also it just changes sort of your your view
of the universe. I mean, what if there are more
rogue planets out there than non rogue planets, then your
whole view of like what is a planet has to
all of a sudden change from oh, they're all around
stars to well, my sense of a planet is unusual
(10:13):
is a typical? Oh I see, it could be that
our kind of planet is the minority. Yeah, exactly, Just
like we discovered that our kind of matter is a
small fraction of all the matter in the universe. All
of a sudden, things we thought were typical are now weird.
It'd be like discovering their more continents out there. Or
you know, you grow up in your family eats a
dinner a certain way, and then you go to a
(10:34):
friend's house you discover, oh man, my family is weird.
We are and we don't use utensils at home or
whatever it is. You know, it's it's maturing in that
same way, right, It's expanding your horizon and your idea
of the universe. And that's why this is such a
fun opportunity to learn something new about the universe. All right,
so let's get into it. Daniel Wood exactly is a
(10:55):
rogue planet. Right, So let's begin with technical definitional stuff
that we could argue about easily for half an hour.
And and and very importantly, is there a first rogue
planet called rogue one? Well, the movie rights for that
one I've already been locked up, unfortunately. Yeah, Well they're
not definitely not making a sequel of that one. I
(11:18):
liked it. I liked it, but you know, Rogue two's
agent is not exactly getting a lot of traction in Hollywood.
But a rogue planet is a planet that's not orbiting
a star. And you said earlier, and you're right that
every planet feels the gravity from every star in the galaxy,
but you have to look at its motion, like the
motion of the Earth is that we are orbiting our star.
(11:39):
We're moving around our star. But if we were a
rogue planet, then our primary motion would just be around
the center of the galaxy. Would be the same category
as the stars, like our star orbits the center of
the galaxy. It's a planet that's not sort of trapped
by the gravitational well or pool of a star. Yeah,
(11:59):
we liked to in goo a Solar System as an
object because it's gravitationally bound that the dominant gravitational force
on every object in the Solar System is the Sun.
So it's like the Sun has its own little neighborhood
in which it's gravity is more powerful than any other gravity.
Or I guess maybe not not just that it's more powerful,
but it's powerful enough to to sort of trap things
(12:23):
in its vicinity. Yeah, it's a stable to let it
go exactly. But you know, the galaxy is big, and
there are a lot of stars, but they're not that many,
and so there's a lot of room out there between stars. Remember,
we're you know, light years away from the nearest star,
which makes a huge amount of space for stuff to
be floating between the stars. Oh, I see, So there's
(12:43):
a lot of room for you to be out there
without falling into the you know, the trap of the
gravitational pool of a star. Yeah, if you mapped the
Milky Way onto Earth, for example, you know, you have
like one house here in Los Angeles and another house
like in Kansas, and another house like in New York City,
and there'll be a lot of room between those that
(13:04):
you could rogue around it. Yeah, you can have a
rogue cabin in the woods and never have to get
close to anybody. And I guess more importantly, you could
be so far away from my house and your house
in Kansas, Dad, you wouldn't feel the need to sort
of go visit. Yeah, and you could largely ignore them.
You know, those stars would just be other slightly more
bright stars in the sky, and you wouldn't feel their
(13:25):
gravitational pull strongly enough to get sucked into one of them.
All right, So then what's the definition then that it's
it's a planet, meaning like a ball of stuff? Is
that what it means? What is exactly a planet? Yeah?
Well that's where it gets tricky, right. Um. These are
either things that were formed in other solar systems and
(13:46):
then ejected, or you could also think about stars that
never sort of got started, like failed stars. You know
what if a star never sort of turns on because
it's not big enough to burn, is that a rogue
planet or is that a failed star? Is a heated
debate in astronomy, But both of those things are out
there well in a way sort of Jube, isn't Jupiter
(14:08):
also kind of a failed star? Like it could have
been a star but it wasn't. Yeah, And if Jupiter
had formed far enough away from the Sun on its own,
if it was like the center of its own little
gravitational neighborhood, we would call it a sub brown dwarf star.
But because it formed around our star, we call it
a planet. And so there's a lot of energy spent
in astronomy arguing about these names and definitions. And wait,
(14:30):
you're saying that if Jupiter wasn't in our solar system,
if it was out there, it would be considered a
star even though it's not burning. Yeah, there's a whole
category of stars called brown dwarfs and sub brown dwarfs
that are just not big enough to ignite fusion and
to burn and to glow. But why still call them
a star if they're not ignited? I'm burning, see what
(14:50):
I mean. People have strong feelings about this, like you do.
Apparently in your mind you think, you think, if it's
got to be burning to be a star, right, Well,
other people think, oh know, it's a failed star. That's
a kind of star, all right, So that's kind of
the definition. It's a ball of stuff, or maybe the
definition is kind of fuzzy, but generally speaking, a rogue
planet is a ball of stuff. It could be gas.
Could be rock too, right, rocks or gas or you know,
(15:15):
it's compressed matter kind of um just to make it
different than a cloud. And it's floating out there in space,
not in the orbit of a star. Whatever that could mean.
That's right, it's a it's a dense blob of stuff.
Primarily orbiting the center of the galaxy instead of orbiting
another star. All right, let's get into how we can
(15:37):
see them even though it's dark out during space and
how many there are out there in the universe. But
first let's take a quick break. All right, I know
(15:57):
there are floating planets out there in the universe in
our galaxy that don't have a star. They're called road planets,
and there might be a lot of them. So first
of all, I guess, how do we even see them
if it's they're not burning bright and they're not near
a star for them to shine, Um, how do we
know they're there? It's tricky, right, These are dark objects.
(16:18):
They are not shining, they're not emitting light, and as
you say, they're not close enough to any star to
reflect light like like exoplanets are. So it's not easy
to spot them, which is why for a long time
we didn't even know that they existed. Um, but there
are two ways to see them. One is you get
really lucky, and one is close enough that we can
see them in the infrared. Remember, these things are not burning,
(16:42):
so they're not shining visible light, but they still have
some heat to them and everything in the universe that
has a temperature also radiates some energy, usually in the infrared,
and so sort of glowing in the infrared. And we
have infrared telescopes, I see, because we I think we're
used to thinking of like asteroids and things out there
(17:03):
in spaces being cold, but you could have, for example,
like the Earth is kind of warm by itself. The
Earth is kind of warm. And even if we were
ten or fifty kelvin. And I want to give props
to the person out there who wrote in to remind
me that it's not degrees kelvin, it's just kelvin. But
even if we were just ten or fifty kelvin, we
would still radiate. Everything that's above absolute zero radiates some energy.
(17:26):
It's called black body radiation. Oh, I see. It sort
of shines in the infrared. Yeah. And there's a telescope
called the Wise telescope w I S E, which is
really good at seeing this stuff, and it's really good
in the infrared. And so if it's close enough that
you can spot them directly with the Wise telescope, but
it has to be pretty close. So like if our
(17:46):
son suddenly went out and there was no more light
in our solar system, you could still maybe see the
Earth and all the other planets. Yeah, you could, precisely.
And we do this to study other solar systems. We
look at them in the visible light and we also
look at them in the infrared to try to get
a glimpse for like, what is the stuff out there
that's not blowing. It's still there, it's giving off different
(18:07):
kinds of radiation. So we have lots of different ways
of looking at the sky. The infrared, X ray, radio,
These are all just different kinds of light though. They're
all just different parts of the electromagnetic spectrum. But different
things out there glow in different parts of these spectrums.
So the most direct way is to look for them
in the infrared. But they have to be really close by,
Oh I see, because otherwise it would be too faint
(18:28):
to see them. Yeah, Because these things are small and
pretty faint, and so they're pretty hard to spot. The
best way to see these things is to look for
a little star eclipse. What well, if you have a
big dark object somewhere out there in the universe and
it passes between you and a star, then what happens
It blocks the light from that star momentarily like a
(18:49):
one time eclipse. Yes, like a one time eclipse, one
time ever eclipse, one time ever. Yeah. And so you
can see these things if you very carefully watch all
the stars in the sky and wait for a blip.
But there's something really fascinating because you might expect that,
like a star eclipse would dim the star, that it
would go out for a minute and then come back, right,
(19:10):
that's you'd expect, But this is really weird. Gravitational effect.
If the rogue planet or whatever it is alien ship
is big enough, then it has a gravitational lensing effect.
It acts like a big lens in space. Because remember
gravity is the bending of space. So gravity can change
the direction of light. We'll just block the light, they'll
(19:31):
bend the light. I mean that sort of happens here
on Earth too when there's an eclipse, right, doesn't the
light sort of go around the Moon when it's blocking
the sign a little bit? It does a little bit. Yeah,
And in this case it can actually enhance the strength
of that star because it acts like a lens. It
gathers more light and it focuses it all on the Earth.
So what actually happens when you get a micro lensing
(19:51):
event they call it, is that the star gets brighter,
not just a darker or like darker and lighter. Yeah,
it actually gets brighter. It gets enhanced, right, it gets
amplified by this micro lensing, and so the very center
of it is blocked out. But you're gathering light from
nearby and focusing it onto the earth. You actually get
more of the starlight when it goes by. It's an
(20:12):
eclipse that makes it the start look brighter. Yeah, recisely.
It's really fun. And the telescope to see these things
has a really awesome name. It's called the OGLE telescope.
I thought I thought it was already too much to
have a wise telescope. W I s e this one.
(20:32):
I want to look at things called the OGLE if
you want to sit on the couch and ogle the universe,
and you do it using the optical Gravitational Lensing Experiment OGL. Wow,
you guys probably pop some champagne when you came up
with that name. So those are the two ways you
can see him. You can see them either through micro
lensing or anti eclipses or directly through the infrared. And
(20:56):
so what do we know about them? Do we know
are they sort of round like our planets necessarily, or
do they look like giant asteroids or what do we
expect them to look like? Yeah, we expect that they're
mostly round because anything that's big enough gravity will make
it round. You know, gravity is powerful, and if you've
got a bit that's sticking out, eventually it's going to
(21:17):
roll down. And so you have something that's big enough
to have strong gravity, it's going to get around. Oh,
I see, And you expect these to be big, right,
I guess if you're If you're calling them planets, there's
a certain size associated with that name, isn't there? Like
Pluto got demoted because it wasn't big enough. Yeah, But
the really amazing part is that probably there's a whole
(21:38):
spectrum of sizes, from like things bigger than Jupiter down
to Earth size things down to just rocks, and the
number is probably inversely proportional to the size. So there
are a certain number of Jupiter sized ones, and they're
probably more Earth sized ones, and then probably like a
xillion times more just box out there. But at some
(22:01):
point they're just called rocks. You wouldn't call them planets, right,
At some point they're called planets and then dwarf planets,
and then yeah, just comets or rocks or dust. Right,
and you know, some of these things have come to
our solar system. Remember Omama and the comment that came
through UM in December. These are just rocks from other
solar system that flew through our Solar system. Wow, there
(22:23):
are Jupiter size planets out there, just floating in space,
not being bound to any star, just doing their own thing.
And that was the question when people first thought about this.
They thought, are they out there? Let's go look for them,
and so they started using these two approaches, and what
they found sort of boggled the mind. Right, they found
more than they expected. Yeah, they found that there's something
(22:45):
like around one Jupiter sized rogue planet for every star
in the Milky Way. So there's hundreds of millions of
these Jupiter size rogue planets out there. Yeah, more like
a hundred billion, yeah, because it's not about a hundred
billion stars in the Milky Way. And a few years
ago there was a really exciting result. Some people said
that there might be like two to four Jupiter size
(23:08):
rogue planets out there for every single star, so like
hundreds of billions, and everybody was like reacted just the
way you did, like what And then another experiment did
some measurements and they came back to everybody, calm down.
It looks like there's probably just about one jupiter size road.
And I was like, that's still crazy. I mean, I
was thinking like there might be ten in the whole galaxy.
(23:31):
Turns out there's billions and billions of these things, and
those are the Jupiter sized ones. The milky ways litter
with these. Yeah, they're everywhere, and if as you go
down the mass scale right like Earth size planets, there
might be ten or even a hundred times as many. Wow,
it's just traffic out there. It's pretty messages stuff. Nobody's
(23:55):
cleaned up, right. We formed all these solar systems and
that all the leftover base are just still out there.
But you know, it gets more and more uncertain. As
the size of the object we're talking about gets smaller,
it's harder to see, and so we've seen fewer of them,
so we're making more of an extrapolation with more uncertainty.
We're in early days of understanding this, and in five, ten,
(24:16):
fifty years we'll have a much better handle on it.
But right now it's pretty uncertain. Are they going to
keep on floating out there? Or will will all of
these planets eventually kind of fall into a star. Think
about what happens when a big Jupiter's eye planet approaches
a star. It's not that easy to fall into orbit. Remember,
orbit requires being in the right location, having the right direction,
(24:37):
and the right velocity. Much more likely is that you
come into a solar system and you just sort of
like mess it up. Yeah, you perturb the gravitational, the
nice cozy gravitational orbits of everybody that's been there for
billions of years, and you make more rogue planets like
you come in and you bust up a family. If
a Jupiter sized planet came into our solar system, we
(24:58):
would probably lose a planet or two. Well, I hope
it's not Earth. They can take Pluto, Neptune. You know,
we don't even we don't even care about those. Wow,
they haven't even arrived yet. And you're and you're already
at the negotiating table offering up our neighbors. What has
urine has done for me lately? Oh? Come on, it's
(25:21):
comic fodder. Urine is really I would give away Neptune first,
I see it's less funny. I see you need you
want you want to planet around you can make fun
of it. Yeah, exactly, some some planet has to be
the butt of all of our jokes. So okay, So
it's not likely because they're if they're already floating out there,
you know, careening through space, it's unlikely for them to
(25:41):
stop at any particular start. They'll just kind of bounce
around from solar system to solar system. It is possible,
it's possible for our start to capture a new planet,
and people wonder about the history of our Solar system,
you know, like some of our planets have weird orbits.
Is it possible they were captured? But if you just
shoot a planet at a star, most of the trajectories
(26:01):
will lead to it just being like whipped around and
shot out into space and probably losing some of its planets.
I guess. Then that gets us to the question of
how these planets even formed. If they are not in
a solar system, and they were, probably they can be
captured by a solar sism. Where did they even come from?
So let's tackle that question. But first let's take a
(26:23):
quick break, all right, So where do rogue planets come from.
Is there like a rogue planet factory somewhere? Is there
a rogue nation of planets where all of these planets
(26:45):
go rogue from their rogue nation. Well, it depends on
how you define a rogue planet. There is a big
population of them that were probably formed around a star,
just like Earth and Jupiter and all of our planets.
They were part of some big cloud out of gas
and dust and rocks which coalesced to form a star
and planets. But remember that's not like organized. Nobody planned
(27:07):
our Solar system, and so in the early days of
our Solar system, stuff was pretty chaotic. It's not like
everybody had cleared it up and say, everybody in this
lane become Earth and everybody over here. You had stuff
sort of bouncing around more. It was more disorganized, and
so stuff got ejected. So some planets that were formed
in the early days of our Solar system probably got
(27:28):
ejected are now out there and planets we have a
lost brother out there or sister. Yeah, we almost certainly do.
And it's almost certainly almost certainly we um. It's a
fun question to ask, like what fraction of planets end
up in stable orbits and what fraction get ejected? Um,
And you know we're looking at our Solar system billions
of years in. It's basically after everything has settled down,
(27:51):
you know, in our Solar system, people think, for example,
like Saturn and Jupiter might have once had different orbits
that might have been in a different order because we
had more things. Yeah, and that there was a third planet,
another icy giant, which got ejected from the Solar system.
Like you look at the organization of our Solar system
for clues, and you're like, this looks weird. You know,
(28:12):
would make more sense if this crazy thing happened. And
that's how we ended up with this configuration of our planets. Oh. Interesting,
that's right, because the Solar System didn't always look like
the Solar System. No. And remember Earth had a massive
collision with like a planet sized object which led to
the formation of the Moon. Where did that thing come from? Well,
probably our Solar system and so and now it's been obliterated. Okay.
(28:36):
So so that's one way you can create a rogue
planet out there in spaces. You it's born in a
Solar System along with other planets, but then the other
planets sort of get together and and kind of vote,
vote that planet out. That's right, planet survivor. But you know,
from that planets point of view, they're probably like, I
never wanted to be in a solar system anyway. It's
so much more exciting out here in the backwoods. I
(28:59):
see much cooler out here. It is much cooler out there. Um.
And it could also be, as we talked about earlier,
that something comes by and perturbs and nice stable solar system,
like a black hole comes near a solar system and
perturbs it and sucks out some of the planets, or
even just you know, another passing rogue planet. So solar
systems are not that stable. So so those are rogue
(29:20):
orphan planets I guess you could call um. Then you
can also have like true road planets or like uh,
independently formed road planets, feral planets, maybe we can say
native planets. These are the ones that you were saying
don't really count as a star, and they're called sub
brown dwarf stars, and they're just clumps of matter that
(29:43):
started to form together but didn't get enough to form
enough gravitational pressure that you would get hydrogen fusion at
the core of it, and so you never start to burn,
because you could just have dust out there and gas
and just have it. If there's nothing around it, it'll
just come together as a clump. It will come together
as a clump. Eventually gravity wins. Right. Gravity is so
(30:04):
weak but so patient, and it just pulls this stuff
together whatever you started with. And you know, you might
wonder like how does that start? And that's a whole
other fascinating topic. People think that these clouds of gas
and dust and maybe like a supernova shock wave passes
through it and that triggers the coalescing. Anyway, we'll talk
about that in another episode. But whatever you got around
(30:26):
you forms into a blob and if it's not bright
enough to burn into a star, then it becomes to
tonight to start fusion. Right, that's what you yeah, Because
you know, if you just have a rock out there,
it's not enough to start fusion. You need enough mass
that the gravity sort of takes over and you start
that star and then it's basically a sub brown dwarf star. Man,
(30:46):
I'm just gonna pass judgment right now, Daniel. I think
I don't think they should be called stars, alright, Just
climbing a sub brown dwarves or something. So would you
call them a rogue planet then? Yeah? Right? Independent? An
independent planet or yeah, why not? Is there an argument
against calling them a road planet? Well, some people think that,
(31:06):
you know, a planet is something that formed around a star,
and so that a rogue planet. I think the generally
acceptable term is that a rogue planet something was around
a star and then got lost. It went rogue. You
can't you can't be born rogue in astronomy, apparently, I
see if by planet you mean something that forms around
a star, then technically I think that doesn't form with
(31:29):
it around a star is not a planet. But this
is all semantics, but it's just what people decided to
call this thing, so they can have words that they
communicate with and all mean the same thing. Or maybe
they just like arguing about this stuff at meetings. That's
probably true also, or maybe if what do you mean
by star is just like celestial objects, um, then this
could be sort of a non shining star. Yeah, and
(31:50):
these things sort of go the same way as the
rogue planets. That is, when it comes to stars. We
know more about bigger stars because they burn bright and
we can see them. It's hard to spot brown dwarfs
and sub brown dwarfs because they don't shine like stars.
We think that the number of these things grows very
quickly though, as you dial down the mass of the
object from bright star to sub brown dwarf to just
(32:12):
dark little blob. So there's a lot more sub brown
dwarfs out there than there are burning stars. There are
more failed stars and stars. Is that what you're saying?
Big surprise, right? There are more waiters than celebrities in Hollywood. Wow.
The analogies just keep keep on rewarding us here. It
(32:33):
turns out what we've learned here in Los Angeles does
apply to the rest of the universe. In this one case,
l A is the center of the universe. Obviously, it
has taught us something about template is a template for
the rest of the universe. That is terrifying. That is terrifying, alright, cool,
So it's pretty interesting to know, to understand, to to
have a sense that there are giant planets out there
(32:55):
floating in space without a home. You know, they're just
cruising through space like a like a spaceship. I guess, yeah,
And you have to wonder, like, what would it be
like to stand on the surface of that planet in
perpetual night. You have no seasons, you right, you could
do a lot of great astronomy, right because you have
no sun to interfere with your telescopes. You could have
a walk around that planet, go all the way around,
(33:18):
and you would only see the night sky with stars
in it. Yeah, but you could stay up all night long,
every night. You would never get a sunburn's right, that industry,
that industry would just not take off. Good for astronomers,
bad for practicing gamble. Yeah, and also makers a swimsuits,
(33:40):
probably because you know it'd be pretty cold. Right. We
rely on our Sun not just for sunlight but also
for the warmth, and it provides something like point nine
seven percent of the energy on the surface of the
Earth comes directly from the Sun. Really, but aren't there
planets in our Solar system that are like super hot
(34:00):
by themselves or is it all also from the Sun?
There are like Venus is super hot, but all that
energy comes from the Sun. And the reason it's super
hot is that has these thick clouds that trap that energy.
So all the surface energy from all the on all
the planets in our Solar system is almost all from
the Sun. But that's from on the surface, if you
wanted to live on the surface and have a view
of the night sky. But technically, could you in one
(34:23):
of these road planets, could you like evolve life inside
of it where where it is warm? You might because,
as you say, the core of our planet is warm,
and that's not from the Sun, that's from the gravitational pressure. Right,
the Earth is also being squeezed and melt the rock,
and from the radioactive decays that are happening inside that
rock that radiates a little bit of energy. And so
(34:45):
there is you know, there are hot spots underground. And
so if you're on one of these rogue planets safe
for example, the Earth went rogue, right, what would happen? Well,
their ocean good? Not good? Right? You throw away all
your sunscreen, Sorry about that, and the the oceans would
freeze and the atmosphere would like turn to snow and
just like accumulate on the surface of the Earth, which
(35:06):
would be crazy. But if you go down deep enough,
they would still be warmth, and so there might be
enough energy sort of bubbling up through the crust to
keep like a layer of water melted. Oh. Interesting, you
could have like underground oceans. Yeah, you could have underground
oceans that the Earth would be covered in layer of ice,
but a mile or maybe two miles down there could
(35:27):
still be water and it might be warm enough to
sustain life. So you would throw your sunscreen, but not
your swimsuit. Try to take your swimsuit or maybe your
wet suit, because I don't think it's going to be
very warm. But you could find like you know, cracks
in the Earth's mantle underground where there's geothermal energy, and
there are there is life the very bottom of the ocean,
(35:48):
clustered around these thermal vents. Yeah, and they don't have
any sunlight that you just live off of the hot
water from these events. They've been planning for this for
a long time. Yeah, they're ready for They're ready for Earth,
Bill Rode. They're the rogue life right there, ready to
take over when Earth goes rogue. There are the waiting
waiting to rise up. But I think what I what
I'm saying is that that that could happen in one
(36:08):
of these rogue planets out there. I mean, there could
be like a giant floating Jupiter out there in space.
It's actually like a spaceship full of life under the surface. Yeah,
and it doesn't have to be that life evolves on
a planet and then it goes rogue. I think you're saying, like,
could life evolve on a planet when it's a rogue
And I think the answer is yeah. You could have
a good water on a rogue planet and life could evolve,
(36:30):
and it could evolve under like a mile of ice
and never see the sky. Right, it might not even
be aware that the universe is larger than its ocean.
It would be like rogue life. And you have to wonder, like,
what kind of technology could you evolve? Like, could you
become intelligent? Could you evolve technology? Could you drill out
of the ice and then discover that? Imagine what that
(36:52):
would be like to be that kind of I want
to read a science fiction novel about life that evolves
on a rogue planet and develops the technology, drills as
of the ice, and then discovers Oh my gosh, the
university is so much bigger than we ever imagined. What
a moment. Right, There's a story that you and I
were talking earlier about. The writer thought Chiang, he has
a story I don't know if you read it, called
(37:13):
The Tower of Babel where that's kind of the plot
where they drill through the ceiling of heaven. Oh my gosh,
I want to read that story. That sounds awesome. Yeah. Alright,
So that that's kind of possible, is that there are
and and there are so many of these road planets
out there that it's it probably is maybe possible that
there is life and the life started in one of
these road planets. Yeah, it's very exciting for the possibility
(37:36):
of alien life, which you know, I'm a fan of.
You know, recently we've learned that there are a huge
number of planets around other stars. That was a big
moment just in astronomy in general, but also for us
who promote alien life, to realize that there are other
places for life in the universe around other stars. That
was exciting. Now we're learning that that's a tiny fraction
(37:56):
of all the planets out there, and that there's an
enormous number of these dark rogue planets, and I think
it's more challenging for life to form on a rogue planet,
but hey, you've got more opportunities also, right, there's a
there's like a hundred billion rogue planets the size of Jupiter. Yeah,
and maybe tend to a hundred times as many Earth
sized planets out there, and just in our solar systems,
(38:20):
I mean just in our galaxy that would be getting
kind of crowded. Just in our galaxy, I mean, I
mean the galaxy. There's hundreds and hundreds of billions of
these and and maybe there are hundreds of billions of galaxies.
So who knows, right there could be a rogue life
form out there. My money is that there is. I mean,
it just seems so much more likely. It seems so
(38:40):
impossible to imagine that nowhere out there, in any of
these planets has life begun. There's so many opportunities and
so many ways for life to happen we haven't even imagined.
I would definitely put my money on there being rogue
alien life. Can you imagine them bursting out of their
shell and be like WHOA what is this? Even crazier though,
is that like one of these rogue planets could pass
(39:01):
by our solar system, you know, within a few au
you know, just outside the edge of Pluto, and we
wouldn't even see it, and they might not even see us,
And so we could be like there could be like
cosmic neighbors and zooming by and we're not even paying attention.
And maybe, just maybe this happened a few billion years ago,
and maybe, just maybe an asteroid hit that road planet
(39:23):
and ejected a piece of rock with life that then landed.
I'm taking it too far, No, I like that. There
are a lot It's totally possible. It's possible for life
to have originated somewhere else and then come to Earth.
All right, Well, that's pretty interesting to know. It just
sort of makes you look at space and the night
sky differently. And in all those places where you only
(39:45):
see blackness, there could be planets out there, floating and
possibly with life. Yeah, and this life might not be
looking back at you. It might be hidden under two
miles of ice, looking up at the inside of its
ocean and wondering what l is out there? Right, that's
no interest in being famous like a star, only because
(40:05):
they don't even know it's possible. Once they get a
taste of it. Though, Once stay discovered television, it's all over.
Who doesn't want to be a star? All right, Well,
we hope you enjoyed that little tour into the blackness
of space and what could be out there. Waiting for
us to discover and as usual, you are in no
(40:25):
danger as you sit on your couch or sit in
the seat of your car and listen to us helping
you explore the universe. All right, We hope you enjoyed that.
See you next time. Before you still have a question
after listening to all these explanations, please drop us a line.
(40:46):
We'd love to hear from you. You can find us
on Facebook, Twitter, and Instagram at Daniel and Jorge That's
one word, or email us at Feedback at Daniel and
Jorge dot com. Thanks for listening and remember that Daniel
and Jorge, Hey, Explain the Universe is a production of
I Heart Radio. From more podcast from my Heart Radio
visit the i heart Radio app, Apple Podcasts, or wherever
(41:09):
you listen to your favorite shows. Yeah
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Daniel Whiteson
Kelly Weinersmith
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