December 24, 2020 • 41 mins
Centaurs are real, but not on Earth. Daniel and Jorge talk about the weird objects astronomers call a "space centaur"
Learn more about your ad-choices at https://www.iheartpodcastnetwork.com
See omnystudio.com/listener for privacy information.
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:08):
Hey, Daniel, do you think the universe is still capable
of surprising us? What do you mean? It's blowing my
mind all the time, that is what I mean. You're
always saying that we could discover anything out there. I
do say that, like, you know, there might be huge
purple dragons out there past the edge of the observable universe. Yeah,
but then what if we actually discover huge purple dragons?
(00:29):
Would you be like I saw that coming? No, I
would think like, wow, so cool. I wonder how we
could talk to dragons about business. But you don't think
there are actually dragons in space? Do you? Probably not?
But hey, some future astronomer listening today, we'll discover a
new kind of fiery star out there and call it
a space dragon. I guess you could say it be
(00:52):
in the night sky, you know, at night with the
k Sir Jorge, that is a terrible joke. Hi am
(01:12):
Orham made cartoonists and the creator of PhD Comics. Hi.
I'm Daniel, I'm a particle of physicist, and I really
do want to meet a space dragon. Welcome to our podcast,
Daniel and Jorge Explain the Universe, a production of I
Heart Radio in which We talk about all the things
that are out there in the universe, the things that
amaze us, the things that blow our minds, the things
that make us curious, and also the things that we
(01:34):
wonder if they are out there, the crazy hypothetical, the possible,
the things that will blow the minds of future generations.
And explain all of them to you. Is this Daniel
where science fiction meets fantasy is who has been a
tight connection between science and science fiction, and that connection
is the fantasy of science fiction authors thinking of crazy
(01:57):
stuff we might see one day. I mean, like agents
and space dragons. Yeah, exactly. And I think that there's
a lot of folks out there who are scientists or
read science fiction who also appreciate fantasy and crazy dragons
and magic and wizards and all that. Do you think
there's some science spaces for any of that. No, I
think it's all based in mythology. But it's all creative
(02:19):
and I like reading it. So we usually talk about
science fiction on this program, but I'm also a big
reader of fantasy novels. But yeah, we talk about all
the amazing things out there in the universe, all of
the weird and unexplained objects and there's a lot of
stuff out there in the universe and in space, floating
out there. Who knows what's out there. Yes, And the
more we look out there in space, the more we
(02:39):
discover that there are lots of different kinds of things
we never even imagined, and also that the distinctions between
the categories we thought were crisp and clear are a
little fuzzier than we understood. Yeah, there's a pretty big
diversity out there, because it's not just suns and planets
out in space floating out there and the darkness of
the cosmos. But there's other kinds of objects, and sometimes
(03:02):
they're kind of hard to categorize. That's right. The Solar
System is more than just a sun and a few
planets and a couple of moons. There's a huge spectrum
of stuff all the way down from space dust up
to the Sun itself and basically everything in between. And
where we draw the lines. What we call a planet,
what we call a brown dwarf, what we call a star,
(03:23):
what we call an asteroid, sometimes just has like a
historical basis more than a scientific one. So if there
are dwarf planets, Daniel or they're also elf planets, those
have been taken over by the dwarfs. That's all that's left.
The dwarves won that war, they leave for the West already.
That's right. There's a whole other set of solar systems,
deep deep in the galaxy where the elves have retreated to.
(03:45):
But I mean, this is sort of a continuing conversation
I feel with astronomers, like what counts as a planet,
as an asteroid, as a space rock, or even as
a sun. So it's hard to tell the difference between
a sun and a planet. Yeah, exactly, if Jupiter was bigger,
it would be right on that threshold where you might
argue like it's a really big planet, No it's a
failed star. No, it's a brown dwarf. And this isn't
(04:08):
just like astronomers being picky or astronomers coming up with
silly names for things. This just reflects how we look
out at the sky and see different kind of things
and try to make sense of them. You can't just say, hey,
there's lots of stuff out there. We can't categorize it
at all. You have to try to say, we're talking
about these kinds of stuff and that kind of stuff.
And when you face a bunch of messy observations. You
(04:29):
have to try to find categories and patterns. Yeah, So
today we'll be talking about one such object in the
Solar System, one that has a pretty mythic name to
be on the program. We'll be talking about what is
a space centaur and what happens when they do battle
with space dragons or space unicorns. That's that's the one
(04:52):
I want to right around in. Well, that is an
ancient rivalry unicorns versus centaurs. They do not get along really.
Oh man, can you have a space centaur with a horn?
Where would the horn go? Exactly? Based uni center? Would
it go on the forehead of the guy or the woman?
Where else would it go? I don't know. I mean
(05:15):
I guess it could come out of their chest? Yeah, exactly.
Like I have a lots of basic quests about centers,
like where is their belly button? You know, is it
sort of on the person part or all the way
down or like you know, anyway, a lot of interesting
questions you could talk about when it comes to centaurs. Well,
but that's a different podcast. That would be the Dungeons
and Space Dragons podcast. Daniel and Jorge explained the universe
(05:38):
of fantasy creatures. But yeah, there's is such a thing
as a space center, like this is actually something that
physicists talk about in conferences and in papers. That's right. Yeah,
it's something pretty awesome. And it came up on the
podcast a few weeks ago, just sort of obliquely when
we were talking about other things in the Solar System,
and we got a bunch of listeners right in saying,
(05:58):
what is that real? Are there actually space centaurs? And
so we thought we would dive into it into a
whole episode. They thought you were kidding or so they're
calling us out. They're calling us out, and we are
stepping up and explaining exactly what a space center actually think.
You didn't just make all this stuff up twenty minutes
before we started. No, this is not a fiction podcast.
(06:20):
This is real. But you know, sometimes in science we
borrow words from other fields, We borrow them from art
or from philosophy to try to describe some relationship we see,
to try to capture something about this new kind of
object that we can't describe in any other way. And
sometimes it seems creative and clever, and sometimes it seems
awkward and clunky. What percentage, Daniel, what percentage of physics
(06:41):
names you think are awkward versus right on? Well, I
would estimate that you would place it about clunky, But
I think there's some art to them, you know. I
think sometimes I see where they're going, even if they
didn't necessarily really hit the target. All right, Well, as usual,
we were wondering how many people out there had heard
of a space center or even knew what it could
(07:04):
possibly be. So Daniel went out there into the wild
to the internet to ask people what is a space centaur?
And thank you to everybody who volunteered to answer this
particularly strange question. If you are willing to put your baseless,
unresearched answers to difficult physics questions on the podcast, please
write to me at questions at Daniel and Jorge dot com.
(07:26):
You'll think about it for a second. Is someone approached
you and asked you what a space centaur is, what
would you say. Here's what listeners had to say. I
do not know what a space centauris, but I know
what a center is, so I'm guessing it's an astrological
phenomena that feels like magic, but it's actually a science.
(07:49):
I have no idea what that is. Uh, but it
sounds like a new kind of tesla, or maybe a
rocket of some kind. The space center is a NASA operate,
a museum where villites I engage with space science. If
it isn't a mythical beast that flies through the cosmos,
then I imagine it's a classification of some kind. I
have a memory of it being something to do with
(08:11):
maybe an unstable orbit or some kind of like collision
course in the future. I think I heard about these
things a few weeks ago Discovery. So I see a
rocky objects between Jupiter and Neptune. A space center sounds
(08:32):
like a constellation, maybe near Alpha cent Tori. If not that,
then some kind of nebula. Maybe A space center is
a child about human from Earth and a human born
in another planet, say Mars, for example. So I don't
know about you, but I feel like we got exceptionally
creative answers this week. A tesla, I think my favorite
(08:54):
is the child of a human from Earth and a
human born on another planet. What a great idea to
call that a space center. That is pretty good. It's
like the writing science fiction fantasy right now exactly. I
hope that sparked somebody to write their whole novel. Nobody
thought it was an actual center, and everyone sort of
assumed it's some kind of object in space. Yeah, but
it's such a weird thing that nobody heard of that
(09:15):
the guesses were pretty wide. I mean, one person was
guessing that it was a space center because I think
the idea of a centaur was so strange. They must
have thought I made a typo in the question a
space center does make more sense than a space center?
All right, well, let's jump into it, Daniel. I assume
the answer is going to be very magical and legendary,
(09:36):
but step us through it. What is a space center?
So to understand what a centaur is, you first have
to understand two other things, and that's asteroids and comets,
because that's what you're saying. Before you know, you look
out into space and you see lots of really weird
stuff out there, and the deeper you look, the more
weird stuff you see. And the more we learned that
there's a lot of objects out there in space. It's
(09:59):
not just planets and the Sun and a few moons.
There are zillions of asteroids, and there's lots of comets,
and then out there beyond Pluto, there's an enormous number
of frozen rocks. So astronomers are trying to come to
grift with this incredible number and variety of stuff by
giving them all names that describe roughly what they do.
Some of these names are like anchored in history because
(10:21):
they come from very early observations. Right, Astronomy is a
field that's hundreds or thousands of years old, So to
understand what a centaur is, you really need to understand
first what an asteroid is, and what a comet is.
According to what modern astronomers said, is that another mythical rivalry,
like unicorns, there's a centaurs asteroids versus commets. No asteroids
(10:42):
and comets get along. In fact, sometimes they mix and
form space centaurs or space mermaids. Oh my goodness, that's
the next level mermaids. Yeah, exactly. That would have been
even a better name, because makes sense for things to
swim through space rather than gallop through space with their
with an unknown bellyable location. Yeah, that's right. Maybe they
(11:03):
can swim through the sea of dark matter that's out
there using their dark matter tails and lure astronauts to
their doom. Alright, so it sounds like we need to
understand what asteroids and comets are, and I'm guessing many centaurs.
It's like a mix of the two or somewhere in between. Yeah, exactly.
So an asteroid is a really cool object. It's basically
(11:23):
just a big rock floating out in space that didn't
get gathered together into a moon or a planet. But
it has a really interesting history. The word asteroid basically
means not a star because it's something that early astronomers
saw out there in space. But it was too small
to look like a planet, right, You couldn't like see
a disk, but it moved the way a planet did.
(11:45):
It wasn't so far away, it didn't move like a star.
So it's this weird object that was discovered when they said, well,
it must be nearby because it moves like a planet,
but it's really really small and it looks like a star.
So they gave you this new name. Oh interesting. I
guess I hadn't thought about it that we would have
discovered asteroids before we had powerful telescopes, right, I guess
(12:07):
at the beginning, it was just like a strangely moving
pinpoint of light in the nights cut exactly. An Asteroids,
like planets, don't shine light right there, just big dark rocks,
but they can't reflect light, and so light goes from
the Sun and bounces off it and comes to Earth.
Then we can see them, and that's good because we'd
like to know where the asteroids are so that we
know they're not going to smash into the Earth. And
(12:28):
we identified a few of them very very early on.
It was like in the eighteen hundreds we had already
seen ten of them. These are the bigger ones, the
shinier ones, and so we could see that they were
out there and they were floating around the Solar System.
And for a long time, people like didn't even distinguish
between a planet and an asteroid. In science papers from
the eighteen hundreds, those two words are used interchangeably. It
(12:51):
just means like a floating object in space that reflects light. Yeah,
it's not a star. It's closer by, it's like orbiting
our Sun and it's reflecting light. And from that point
of view, what's the difference between Mars and a really
big asteroid. They're both just big rocks in space, right.
But then as you learn about these objects, you start
to distinguish them. He's like, well, planets move in their
(13:12):
own orbit and basically have cleared a path, whereas most
asteroids are in a big belt. And so you come
up with these ways of talking about things because they're related,
but they're also important differences between planets and asteroids. It's
not just a difference of size, like I would think
it would be like a size threshold that you have
to meet to be a planet. Isn't that what happened
to Pluto, Like it wasn't big enough, so they got downgraded. Yeah,
(13:34):
that is sort of what happened to Pluto. But it's
also context, Like Pluto we found and it's out there
and it's moving sort of like a planet. But then
we found that Pluto is actually just one example of
a lot of different objects that are deep out there
in the Solar System, and it's not even necessarily the biggest,
and so calling it a planet would mean you have
to call all those other ones a planet also. So
then yeah, they made an arbitrary distinction. They're like, sorry,
(13:56):
we're going to define a planet to be just bigger
than Pluto. The sort of get Pluto out the door?
Is that why? Because they didn't want to admit there
were a lot of planets in the Solar System. Yeah, well,
they didn't feel comfortable with the idea of having lots
and lots of planets in an unknown number of planets,
because out there past Pluto, there's an enormous number of
these things. These things are called trans Neptunian objects, and
(14:19):
some of them are called plutoids or plutinos. But there's
a huge number of these things out there, and if
you said Pluto is a planet, then you'd have to
call them all planets. And you know, planets have a
historically important name, you know, like we like to think
it's a special class of objects in the Solar System
that we call planets because we live on one. So yeah,
we could have gone with like there are many many planets,
(14:40):
but they wanted to make it special. They wanted to
reserve the name for special occasions. That was kind of
I guess it was like, you know, you have friends,
and you have best friends, and you could say, well,
all my friends are my best friends, or you could
acknowledge that some of your friends are actually closer than
other friends. Right, I do have a friend who calls
all of our friends best friends, and it's so confusing.
(15:03):
Something there you go exactly, So then what was the
rationale or what was the official excuse that they go
by size. The long saga of the definition of Pluto,
I think deserves its own episode. Um, we can go
through the details of that. But we were saying that
asteroids were discovered, you know, in the eighteen hundreds, we
have at ten of them, and then it rapidly cranked up.
We had like discovered a thousand asteroids by the early
(15:24):
nineteen hundreds, and by now we know that there are many,
many of these things that are like probably more than
a million asteroids, and a lot of them are floating
in this asteroid belt, which is this big chunk of
space between Mars and Jupiter, and some of them are
actually co orbiting with Jupiter, like Jupiter has its orbit
right this big circle, and in other places in that
(15:46):
same orbit where Jupiter isn't there are big blobs of asteroids,
big clumps of asteroids floating in the same path. They
can share the same orbit. Wouldn't they have a different
speed or something. They can share the same orbit, and
they have a cool name. They're called Upiter Trojans. Yes,
they really are called Jupiter trojans, and they get into
these weird gravitational resonances with Jupiter because Jupiter is having
(16:10):
a big influence on all the stuff that's going on
in the Solar System out there, So you can't just
ignore Jupiter. Jupiter is a huge gravitational attraction. Remember that
of the stuff in the Solar System is the Sun,
and of that remaining one percent, Jupiter is most of
it jupiters of that one percent, So the first approximation
the Solar System is just the Sun and Jupiter. So
(16:31):
if you're out there near Jupiter has a huge influence
on what's happening gravitationally, and some of these rocks get
tossed down into the inner Solar System by Jupiter, they
get disturbed, and some of them found these resonances where
they can stay happily in Jupiter's orbit. All right, Well
that's an asteroid, and so that's one half of the
space center puzzle. The other have our comments, which we'll
(16:54):
get into in a short bit, But first let's take
a quick break. All right, Danny, we're talking about space mermaids. Unicorns.
Man unicorns stand space unicorns. I guess maybe more like
(17:17):
space Vegas is too. That could be pretty cool. They're like,
have birds have courses? Right? Yeah? Or what about griffins?
Are those like half birds half lions? Right? Those would
be cool space griffins, space hippogriffs. That that's the next level.
Most of these things we just made up. But some
of these things are real and are out there in space.
But they're also just sort of funny names that astronomers
(17:39):
gives to things to try to show us the relationships
between what they've discovered. All right, So an asteroid is
a space rock. That's sort of the definition somewhere between
like a baseball and what like the size of the
Moon is what would be considered an asteroid. Yeah, they're
like between a meter and up to like five dred kilometers.
The biggest one called Vesta is like five hundred kilometers wide,
(18:01):
and they're mostly rocks, and they're mostly in the Inner
Solar System so they don't have a lot of ice,
so they can be pretty big and they're mostly rock
and they are in the Inner Solar System. Those are
the key points to be an asteroid. Really, what if
you're a big rock but you're outside of the Inner
Solar System, but bomb you might be a centaur. I see,
it's like a location. It's like a discriminating by where
(18:24):
you're from, all right, So that's one half of the puzzle.
The other half of our comets. Now, comets are different
than asteroids. Comets are different from asteroids. They come from
a different place in the Solar System. They come from
out beyond Neptune, the Kuiper Belt. This is huge collection
of rocky and icy objects. So that's the second key.
(18:45):
Comets come from deeper out either the Kuiper Belt or
the Orc Cloud, and they are made of different stuff.
They tend to have a lot more ice in them.
They're these big, dirty snowballs of ice and dust. And
there's a reason for that. There's more ice out in
the far edges of the Solar System because it was
colder out there. The water in the inner Solar System
got sort of blown out by the pressure from the
(19:06):
Sun out to the outer Solar System. So rocks that
coalesce out there deeper in space tend to have more
ice in them. So comets come from the Kuiper Belt
or the Arch Cloud, which is this hypothetical collection of
trillions of icy objects deep out there, and they tend
to be made more of ice, like water ice or
like messane ice, both kinds of ice or other kinds
(19:28):
of liquids, all kinds of ice. And don't get me
started on how planetarry geologists talk about ice like they
talk about the ice giants of Neptune, and they say
these things are filled with water ice, but they don't
actually mean these things are frozen water to them, like
a water ice. It's a whole category of states of
water that could be solid but could also be technically
a liquid, but are not actually frozen water. So the
(19:51):
whole idea of an ice is a very sort of
confusing in general topic which is badly named. But in general,
there is a lot of frozen water and a lot
of very areous organic ices out there in the deep
Solar system. All right, we won't get you started that, Daniel.
Although ice giants also sounds like a mythological creature, Well,
Neptune is reel and it's out there, and it's called
(20:12):
an ice giant even if it has a lot of
water and no ice. But these comets, they're also tend
to be smaller, like you know, they're not up to
five kilometers wide. They're like five to five miles wide,
and you can tell that they're made of different stuff
because when they plummet to the inner solar system, they
get a coma and they get a tail, like their
(20:33):
edges tend to be burned off by the sun the
solar pressure, it's frying the outside, and you get this
long tail of material. It's basically coming off of the comet.
So they're not like as densely packed that they tend
to be more susceptible to the Sun. I guess further
out there, away from the Sun, it's more likely for
molecules to form into solids because it's colder, and so
(20:55):
there's just more things you can make rocks out of,
whereas maybe closer to the Sun, you know, there are
certain things like water or methane that evaporate. That's right.
Your distance to the Sun definitely changes the composition of
materials in the solar system, which are the basic building
blocks of everything we're talking about. And it's really fascinating.
And you know, we've only until recently seen one example
(21:16):
of a solar system ours, and now we're starting to
see other solar systems and we're looking at those and
we're saying Hey, are the patterns that are in our
Solar system also present in those? And we're finding really
surprising things, like we're finding huge planets like the size
of Jupiter really really close to the Sun, not just
in the outer Solar system. These are called hot Jupiters.
We actually did a whole fun podcast episode about this
(21:39):
is our Solar System weird and all the things we're
learning about our Solar system by looking at others. But
in general what you say is corrected. That tend to
be different kinds of things deeper in the Solar System
than closer in, and this affects how these objects come together.
And it's one reason why comets are different from asteroids
because they're made of different stuff because they come from
further app interesting, can we see asteroids and comets and
(22:02):
other solar systems yet? And b wouldn't it be cool
to have a novel about bix space war between our
centaurs and there are unicorns and another solar systems mermaids
that would I want to read a book called Exo
Mermaids would be pretty cool mermaids. No, we think we
(22:23):
have seen a comment from another solar system, but we
can't see them in their solar system. We think that
oh muamua, that weird cigar shaped object that came through
our solar system a couple of years ago wasn't exo mermaid.
It was probably a lost comment from another solar system,
but we don't know. It came through really fast, and
we only spotted it when it was halfway through the
solar system, so we only got like good pictures as
(22:45):
it was on its way out. So there's still a
lot of questions about what exactly OMMA was. But most
likely it was something from another solar system's equivalent of
the Orc cloud that got lost and ejected into space
and drifted over here. But we can't see these things
from other solar systems because they're so small. Like if
we wanted to point your telescope at another star, we
(23:06):
can just barely detect the planets, which are these huge masses.
So we're very far from being able to see exo
asteroids or exo commets or exo mermaids. All right, So
those are commets, And now the comets have sized restrictions too,
or do they also range from like small to gigantic.
They tend to be smaller than asteroids and that's because
they form deeper out and they just haven't gathered together
(23:27):
into larger objects, and Neptune tends to keep these things small.
Like Neptune is also a really big planet, and so
it's gravity tends to break stuff up because of tidal forces,
and so anything in the Kuiper Belt that would gather
together into a larger object generally gets torn apart by Neptune.
It's like the big bully on the playground out there
and doesn't want anything to challenge its supremacy. So they
(23:49):
tend to be up to about like twenty five miles wide.
Do we think, wow, So there's an active effort not
to have more planets. That's right. It's a good old
boys club, you know, and it's old worth something. If
it's exclusive, you can keep people out. That tunes the bouncer,
it's the enforcer exactly, all right. So that those are
asteroids in comments, And now I'm guessing that a space
(24:13):
center is like a mix of the two. Is it
like half asteroid half commet Like the top half is one,
the bottom half is another. Where do you put the
horn on the space center exactly? Or the belly button right?
And the asteroids half belly buttons due depends on how
they are born. Deep mystery of science, they have multiple
belly bons. Well, you're sort of right. A space center
(24:36):
is half asteroid half comet, but not in the sense
that a centaur is. It's not like you take an asteroid,
cut it in half and slap it onto the half
of a comet and this weird hybrid object you would
call a centaur. That would be pretty cool, but like
the tail trailing, that would be like a pretty killer commet. There. Yeah,
it's sort of like punk, you know, like shave half
your head and have the other half long or something,
(24:57):
or maybe it's like a mullet. This is in the
front rocking the front party in the back. Anyway, a
centaur is not an actual mix of an asteroid and
a comet. It's an object which has some of the
characteristics of both, so it doesn't fall neatly into either category.
And this is what I was saying earlier, is that
as we look deeper into the Solar system and catalog
(25:19):
more and more stuff, we find that the transitions between
our categories are kind of fluid and fuzzy and in
the end kind of arbitrary, you know. We have to
make categorizations so we can talk about stuff. You know,
when you go to a meeting of astronomers and you say,
I'm studying the planets, you don't want to every time
have to define what you mean by a planet, so
that you've got to have words we can all agree on,
(25:40):
even if they are arbitrary. So what we've discovered is
that there is a population of rocks out there which
don't fall nicely into either the category of asteroid or
of comet. So the solution was give it a cool name,
and now everyone's happy, and now everyone's happy. But now
everyone said arguing about whether or not account as a
(26:00):
space center or not. Yeah, exactly. And so these things
are fun because they're sort of like comets because we
think they come from deeper in the Solar System than asteroids.
They're on these sort of longer elliptical orbits. Their orbits
go out to like between Jupiter and Neptune. All the
asteroids are in the inner Solar System, but the space
(26:20):
centers they go out all the way to Neptune sometimes,
so there's sort of like comets because they also they
have some of these commas, like you can see these
sort of fuzz around them that's getting blown off by
the Sun. So they seem sort of like comets because
they come from deeper in the Solar System and they
have this fuzz. But they're also like asteroids because they're
(26:42):
really really big. Some of them are way too big
to be considered comets. And they also they cross the
paths of these giant planets like comets and unlike asteroids.
So there really are sort of a mix of the
characteristics of the two different things. So wait, these are
objects that they have like a tail, like comments like
they have you know, like a trail of stuff facing
(27:04):
away from the sun of like melted water or liquid.
They don't have a tail to have a coma. What's
the difference. So a tail usually comes if you have
like stuff that can be vaporized, like water or other
things which can be vaporized, and dusk coma is more
like you know, the little bits of stuff on it
are sort of floating around it. These things are big
(27:25):
enough that they can have their own gravity, so they
can sort of hold onto these things. In fact, one
of them is so big is has its own ring system,
like you know Saturn has rings. What there's this one centaur.
It's called charik Low and it's three hundred kilometers wide.
It's the biggest known centaur and it orbits between Saturn
and Urineus and it has rings around it. That's how
(27:47):
big it is. It has its own gravity. Wow, what
do you call the moon of a centaur? Daniel, I'm
gonna have to defer to the official astronomy naming department,
Like a fairy, a space ferry, I think, so us,
a nymph maybe ego? Right, So it's it's like it
has an entourage. It's not just the rock. It's like
a rock with some fuzz, yeah, And that tells you
(28:09):
a little bit about what it's made out of. That
there's a big component of sort of space dust in there,
not just like big deposits of metal and rock like
an asteroid, more like space dust like a comet. And
so that makes it more like a comet and less
like an asteroid. But it doesn't have ice, or does it?
Some of them? Maybe? I see these things are much
more rare than the other ones, and so they're not
(28:31):
as well studied. There's only like two hundred and fifty
of them that have actually been identified. But you know,
we can only really see the bigger ones. So the
estimates range from like forty thousand of these things too,
there might be ten million of these things out there
in the Solar System. Okay, so then it's like an asteroid,
you said, because of its size, but also it's orbit. Yeah,
(28:52):
it's it's like an asteroid because it's really really big,
and it's sort of unlike an asteroid because of its orbit.
Like asteroids tend to stay either in the asteroid belt
or in Jupiter's orbit. These Jupiter trojans that we talked
about before, these guys tend to be more stable than
a comet, right, But they have these orbits that are
really long and elliptical, and they pass the giant planets.
(29:14):
They're like cross over the orbits of the giant planets.
Sometimes they're further out than Jupiter. Sometimes they're closer in
than Jupiter. So that sort of makes them more like
a comet. But then again they're sort of big, lack
an asteroid. Interesting. I don't know, I'm not getting a
big comet vibe from these, you know what I mean,
Like it feels like maybe just like a rogue asteroid
or something. All right, Well, you know, on the common
(29:35):
side of it. They have these big elliptical orbits and
we think that maybe they came from the Kuiper Belt,
Like these things don't look like the same kind of
material that makes up asteroids. They're made it more of
the same stuff that comments are made out. So I
guess this is the kind of argument that astronomers would
have a conferences. They're like, oh, but it's big, so
it must be an asteroid. No, it has this weird orbit,
(29:57):
so it must be a comment. So that's why they
came up with the name. Yeah, yeah, exactly. And of
course nobody even agrees on what the definition of a
space center is. There's like seven different definitions of a
space center for real, for real, Like JPL has one,
the Jet Propulsion Lab in Pasadena down here in southern California.
(30:19):
They define a space center in one way. And then
there's another group called the Minor Planet Center, which is
an important institution in astronomy, and they have a different
definition for what a space center is. And the differences
in like how you measure the orbit details doesn't matter
if you cross Neptune or if you cross Jupiter, and
these are just like totally arbitrary, but conflicting definitions of
(30:41):
what a space centaur is. I guess there's such a
weird variety of stuff out there that, you know, you
kind of need more names to be able to talk
about all these things. And it gets tricky when you
try to put things into bins. Or you could just
be inclusive and say, hey, there's just sort of stuff
out there, and they're all my best friends, and they're
all a little bit different, and you can categorize them by,
(31:02):
you know, their orbit and their composition and not get
so hung up on names. I guess space stuff, planet stars,
everything in between is just space stuff. It's all just
particles to me, right, Like this is a big collection
of particles, a little collection of particles. What's the difference
two particle physicists. I guess all five percent of the
universe looks like a particle. All right, let's get into
(31:24):
where they actually come from and if we have actually
set ined some with our very own eyes. But first
let's take another quick break. All right, Daniel, we're talking
(31:46):
about space centaurs, which are a mix of asteroids and
comets that are like you know, space giant space rocks
that are kind of in between. They're big and rocky,
but they also have these weird orbits that make them
sort of like commets. Yeah, and so there's sort of
a mix between the two different things. And some things
(32:07):
are called comets, some things are called asteroids, some things
are called centaurs, and then you have these weird objects
that nobody agrees about because they fall sort of like
in between the definitions from different organizations. So there's an object,
for example, called Chiron, which some folks classify as a comet,
some folks classify as an asteroid, and some folks classify
(32:27):
as a space centaur. So it's a little bit of everything. Wow. Yeah,
I guess there's no agreed upon a set of definitions,
Like there's no International Space Stuff Naming Committee. No. I
think the problem is there are too many of those
committees and they don't agree with each other. And so
I think this like controversy about Pluto and is it
a planet or is it a dwarf planet or whatever,
(32:50):
it's just the tip of the iceberg. It's just the
tip of the frozen comet. When it comes to like
the naming controversies we're gonna be facing in the future
as we discover more and more stuff out are in
the Solar System, and people are gonna be arguing like
should you name stuff based on where it is now
or where you think it was formed, or what it's
made out of, or it's possible history or its gravitational
(33:11):
role in the Solar System. And there's lots of like
philosophical differences about how you categorize this stuff that I
think we're gonna be hearing more and more about in
the future. I guess maybe some naming groups are like
you know, committees, some of them are groups, some of
them are centers, so they're just sort of a naming
war for those two. That's true, Yeah, exactly, the naming
(33:32):
centaur wars. All right, well, step of three, or where
can we see one and what what do they look like?
So we've never actually photographed one up close, like we've
identified them in telescopes. We see these things, we can
tell that they're they're they're reflected light, but we've never
liked passed a space probe by one to get a
close up picture of the way we have of asteroids
and of comets, and of course of planets and dwarf
(33:55):
planets and all those other kinds of things. So space
centers or one of those last things that are really
unexplored in our Solar system. And there's some really fascinating
questions about what they are and where they come from.
Like question number one is why do they have their
weird colors? Like they have colors. There's different colored space centaurs. Yeah,
there are two different kinds of space centaurs at least,
(34:18):
and they range from very very red sort of like
the surface of Mars too much more blue sort of
like Urinus. And so that's fascinating that there's these two camps.
There's like two kinds of centaurs. I don't know which
ones are the good ones and which ones are the
evil ones or if it's much more nuanced than that,
but there are red and there are blue centers. Thing. Wait, um,
(34:38):
so we don't have a photograph of them, but we
can tell from the light that they they reflect what
color they are, Like they look like pin points, but
like a red pin point and a blue pin point sometimes. Yeah,
just like when you look at the night sky, you
can tell which planet is Mars because it actually looks
red to the naked eye, even though your naked eye
can't really like see the size of Mars. You can
(35:01):
still measure the light that comes from a pin prick,
and that's the limitation of our knowledge about space center.
So far. We basically just see them as pin pricks
in telescopes because we've never done a close up fly by.
And now there's also a little bit of controversy about
these objects, yeah, because the color is an important clue.
Like one question we'd like to ask is where did
(35:22):
these things come from? Where were they made? Because remember,
we're interested in studying the Solar System not just because
stuff out there in space is cool it is, but
because we think it tells us a story about how
the Solar System was formed and what happened and where
everything came from and whether it was unusual. And we
think that a lot of these objects can tell us
about that story based on where they are now and
(35:44):
the way we do that as we build a complete
model of how the Solar System was formed and we
try to compare what that predicts to what we actually
see out there in space, and where there's something we
don't understand that tells us that something in our model
is wrong, and so we're interested in, like where did
these space guitars form? Do they form with the asteroids
and then get sort of knocked out into weirder, longer orbits,
(36:06):
or did they form with the comets and somehow get
preferentially selected and pulled into the inner Solar system somehow?
And so one great way to do that is to
look at their composition. And we can't really do that
without sampling them, but we can get a clue by
looking at their light, so looking at whether they reflect
red or blue light and comparing that to what we
(36:26):
see from other parts of the Solar system. Like you
might think, well, if these things are red and blue,
what else out there is red and blue? And if
you look at the Kuiper Belt, where we think that
these things might come from, we find that those objects
are not actually by colored. There aren't red and blue
objects out there in the Kuiper Belt. Wait, if something
is red and blue, would it be purple? Can there
(36:50):
be purple centaurs? If not purple purple dragons? No, we
mean that the Kuiper Belt doesn't necessarily have like a
distribution of colors the way we see in centaurs, like
centers tend to be red or blue. You don't have
an individual center that's red and blue. You have red
centaurs and blue centaurs, but if you look out in
the Kuiper Belt, you don't see red objects and blue objects.
(37:12):
So it suggests that that maybe they don't come from
the Kuiper Belt. Maybe they come from somewhere else, like
maybe they are not evenly distributed, like maybe they come
from one of two places, yeah, Or maybe there's some
process which is related to their composition which preferentially selects them.
And there's this whole other group of objects out there.
The Kuiper Belt is part of this set of objects
(37:34):
we called trans neptunity and objects basically anything out there
past Neptune. And in that group of stuff, there's a
group of objects called plutinos, which are basically the category
of objects that Pluto is in. You know, dwarf planets
out there really far in the Solar System, and those
things tend to have interesting colors. Like you remember when
(37:56):
we did that fly by Pluto. One of the big
shocks was frankly, how interesting Pluto was to look at.
Are we sorry we downgraded it now they're like, oh,
you're kind of cooler than we thought. We're sorry we
kick you out of our club. Yeah, I think that's
what happens when you kick somebody at your best friends
club and then you discover they actually really talented and
you wish you had stayed friends with them. That Pluto
(38:17):
has these really interesting features. It's really interesting colors, and
it has this heart shaped pattern on it. It's a
pretty beautiful planet, actually non planet, non planet, thank you
very much, as a dwarf planet. And a lot of
these plutinos out there have interesting colors, and so those
things tend to have both red and blue colors. So
it might be that these centaurs used to be plutinos
(38:38):
that used to be objects out there past Pluto and
somehow got knocked in words by some process we don't understand. Now,
can I actually see uspace on center with my naked eye,
Like if I look out into the night sky, is
it possible that I might see one going by? No,
they tend to be further out and they're too small,
so you definitely need a telescope to see one, the
(38:59):
same way that you and see asteroids with your naked eye.
And asteroids are sometimes even bigger than space centers and
it's closer in, So if you see one with your
naked eye. It means we're in trouble. Runaway, runaway to Mars. Maybe, Yeah,
quick build that ship. All right, Well, that is what
a space center is. It's um a sort of a
(39:21):
half asteroid, half common but not really. It makes just
sort of like a fuzzy object that falls in between
the two. And so we see that the stuff out
there in the Solar System can't be nicely categorized into
little bins. That makes sense. There's stuff out there that,
you know, might be a planet, might be a star,
might be a dwarf planet. But there's an incredible variety
of stuff out there for us to identify and to
(39:43):
learn from. Yeah, I think the cool thing is that
there are still things out there, even in our Solar
System that kind of defied definition or that still kind
of surprises or still has this talking about what's out
there and how it all came to be. Yeah, and
the far reaches of the Solar System are not very
well explored. This trans Neptunian objects and stuff out there
past Pluto is too far for us to see most
(40:05):
of it, and we haven't sent very many probes, and
so we're constantly surprised whenever we learned about them, and
I think there are a lot more surprises out there
waiting for us. And you know, even further out the
Orc cloud. Remember that's something we've never actually seen. It's
just theoretical. And when it's just theoretical, that means there
are definitely surprises waiting for us. Oh yeah, what could
(40:26):
there be? There could be interesting new things and maybe
some of our listeners could discover one day armies of
elves waiting to take back the Solis. Yeah. Yeah, what
do you call a half common half planet, Daniel or
a half moon have planetoid? I call it an ambush
waiting to happen. They call it a future Nobel prize
for somebody that's listening to this. All right, Well, the
(40:48):
next time you look up at the night guy, think
about it. There might be a Centaurs out there, or
even new undiscovered objects at b B you could name,
or at least fantasized about naming. And please be responsible
with your future astronomical namings because we might have to
cover it on the podcast. Yep. All right, Well we
hope you enjoyed that. Thanks for joining us, see you
(41:09):
next time. Thanks for listening, and remember that Daniel and
Jorge Explain the Universe is a production of I Heart
Radio or more podcast from my heart Radio. Visit the
i heart Radio app, Apple Podcasts, or wherever you listen
(41:29):
to your favorite shows.
Hey, Daniel, do you think the universe is still capable
of surprising us? What do you mean? It's blowing my
mind all the time, that is what I mean. You're
always saying that we could discover anything out there. I
do say that, like, you know, there might be huge
purple dragons out there past the edge of the observable universe. Yeah,
but then what if we actually discover huge purple dragons?
(00:29):
Would you be like I saw that coming? No, I
would think like, wow, so cool. I wonder how we
could talk to dragons about business. But you don't think
there are actually dragons in space? Do you? Probably not?
But hey, some future astronomer listening today, we'll discover a
new kind of fiery star out there and call it
a space dragon. I guess you could say it be
(00:52):
in the night sky, you know, at night with the
k Sir Jorge, that is a terrible joke. Hi am
(01:12):
Orham made cartoonists and the creator of PhD Comics. Hi.
I'm Daniel, I'm a particle of physicist, and I really
do want to meet a space dragon. Welcome to our podcast,
Daniel and Jorge Explain the Universe, a production of I
Heart Radio in which We talk about all the things
that are out there in the universe, the things that
amaze us, the things that blow our minds, the things
that make us curious, and also the things that we
(01:34):
wonder if they are out there, the crazy hypothetical, the possible,
the things that will blow the minds of future generations.
And explain all of them to you. Is this Daniel
where science fiction meets fantasy is who has been a
tight connection between science and science fiction, and that connection
is the fantasy of science fiction authors thinking of crazy
(01:57):
stuff we might see one day. I mean, like agents
and space dragons. Yeah, exactly. And I think that there's
a lot of folks out there who are scientists or
read science fiction who also appreciate fantasy and crazy dragons
and magic and wizards and all that. Do you think
there's some science spaces for any of that. No, I
think it's all based in mythology. But it's all creative
(02:19):
and I like reading it. So we usually talk about
science fiction on this program, but I'm also a big
reader of fantasy novels. But yeah, we talk about all
the amazing things out there in the universe, all of
the weird and unexplained objects and there's a lot of
stuff out there in the universe and in space, floating
out there. Who knows what's out there. Yes, And the
more we look out there in space, the more we
(02:39):
discover that there are lots of different kinds of things
we never even imagined, and also that the distinctions between
the categories we thought were crisp and clear are a
little fuzzier than we understood. Yeah, there's a pretty big
diversity out there, because it's not just suns and planets
out in space floating out there and the darkness of
the cosmos. But there's other kinds of objects, and sometimes
(03:02):
they're kind of hard to categorize. That's right. The Solar
System is more than just a sun and a few
planets and a couple of moons. There's a huge spectrum
of stuff all the way down from space dust up
to the Sun itself and basically everything in between. And
where we draw the lines. What we call a planet,
what we call a brown dwarf, what we call a star,
(03:23):
what we call an asteroid, sometimes just has like a
historical basis more than a scientific one. So if there
are dwarf planets, Daniel or they're also elf planets, those
have been taken over by the dwarfs. That's all that's left.
The dwarves won that war, they leave for the West already.
That's right. There's a whole other set of solar systems,
deep deep in the galaxy where the elves have retreated to.
(03:45):
But I mean, this is sort of a continuing conversation
I feel with astronomers, like what counts as a planet,
as an asteroid, as a space rock, or even as
a sun. So it's hard to tell the difference between
a sun and a planet. Yeah, exactly, if Jupiter was bigger,
it would be right on that threshold where you might
argue like it's a really big planet, No it's a
failed star. No, it's a brown dwarf. And this isn't
(04:08):
just like astronomers being picky or astronomers coming up with
silly names for things. This just reflects how we look
out at the sky and see different kind of things
and try to make sense of them. You can't just say, hey,
there's lots of stuff out there. We can't categorize it
at all. You have to try to say, we're talking
about these kinds of stuff and that kind of stuff.
And when you face a bunch of messy observations. You
(04:29):
have to try to find categories and patterns. Yeah, So
today we'll be talking about one such object in the
Solar System, one that has a pretty mythic name to
be on the program. We'll be talking about what is
a space centaur and what happens when they do battle
with space dragons or space unicorns. That's that's the one
(04:52):
I want to right around in. Well, that is an
ancient rivalry unicorns versus centaurs. They do not get along really.
Oh man, can you have a space centaur with a horn?
Where would the horn go? Exactly? Based uni center? Would
it go on the forehead of the guy or the woman?
Where else would it go? I don't know. I mean
(05:15):
I guess it could come out of their chest? Yeah, exactly.
Like I have a lots of basic quests about centers,
like where is their belly button? You know, is it
sort of on the person part or all the way
down or like you know, anyway, a lot of interesting
questions you could talk about when it comes to centaurs. Well,
but that's a different podcast. That would be the Dungeons
and Space Dragons podcast. Daniel and Jorge explained the universe
(05:38):
of fantasy creatures. But yeah, there's is such a thing
as a space center, like this is actually something that
physicists talk about in conferences and in papers. That's right. Yeah,
it's something pretty awesome. And it came up on the
podcast a few weeks ago, just sort of obliquely when
we were talking about other things in the Solar System,
and we got a bunch of listeners right in saying,
(05:58):
what is that real? Are there actually space centaurs? And
so we thought we would dive into it into a
whole episode. They thought you were kidding or so they're
calling us out. They're calling us out, and we are
stepping up and explaining exactly what a space center actually think.
You didn't just make all this stuff up twenty minutes
before we started. No, this is not a fiction podcast.
(06:20):
This is real. But you know, sometimes in science we
borrow words from other fields, We borrow them from art
or from philosophy to try to describe some relationship we see,
to try to capture something about this new kind of
object that we can't describe in any other way. And
sometimes it seems creative and clever, and sometimes it seems
awkward and clunky. What percentage, Daniel, what percentage of physics
(06:41):
names you think are awkward versus right on? Well, I
would estimate that you would place it about clunky, But
I think there's some art to them, you know. I
think sometimes I see where they're going, even if they
didn't necessarily really hit the target. All right, Well, as usual,
we were wondering how many people out there had heard
of a space center or even knew what it could
(07:04):
possibly be. So Daniel went out there into the wild
to the internet to ask people what is a space centaur?
And thank you to everybody who volunteered to answer this
particularly strange question. If you are willing to put your baseless,
unresearched answers to difficult physics questions on the podcast, please
write to me at questions at Daniel and Jorge dot com.
(07:26):
You'll think about it for a second. Is someone approached
you and asked you what a space centaur is, what
would you say. Here's what listeners had to say. I
do not know what a space centauris, but I know
what a center is, so I'm guessing it's an astrological
phenomena that feels like magic, but it's actually a science.
(07:49):
I have no idea what that is. Uh, but it
sounds like a new kind of tesla, or maybe a
rocket of some kind. The space center is a NASA operate,
a museum where villites I engage with space science. If
it isn't a mythical beast that flies through the cosmos,
then I imagine it's a classification of some kind. I
have a memory of it being something to do with
(08:11):
maybe an unstable orbit or some kind of like collision
course in the future. I think I heard about these
things a few weeks ago Discovery. So I see a
rocky objects between Jupiter and Neptune. A space center sounds
(08:32):
like a constellation, maybe near Alpha cent Tori. If not that,
then some kind of nebula. Maybe A space center is
a child about human from Earth and a human born
in another planet, say Mars, for example. So I don't
know about you, but I feel like we got exceptionally
creative answers this week. A tesla, I think my favorite
(08:54):
is the child of a human from Earth and a
human born on another planet. What a great idea to
call that a space center. That is pretty good. It's
like the writing science fiction fantasy right now exactly. I
hope that sparked somebody to write their whole novel. Nobody
thought it was an actual center, and everyone sort of
assumed it's some kind of object in space. Yeah, but
it's such a weird thing that nobody heard of that
(09:15):
the guesses were pretty wide. I mean, one person was
guessing that it was a space center because I think
the idea of a centaur was so strange. They must
have thought I made a typo in the question a
space center does make more sense than a space center?
All right, well, let's jump into it, Daniel. I assume
the answer is going to be very magical and legendary,
(09:36):
but step us through it. What is a space center?
So to understand what a centaur is, you first have
to understand two other things, and that's asteroids and comets,
because that's what you're saying. Before you know, you look
out into space and you see lots of really weird
stuff out there, and the deeper you look, the more
weird stuff you see. And the more we learned that
there's a lot of objects out there in space. It's
(09:59):
not just planets and the Sun and a few moons.
There are zillions of asteroids, and there's lots of comets,
and then out there beyond Pluto, there's an enormous number
of frozen rocks. So astronomers are trying to come to
grift with this incredible number and variety of stuff by
giving them all names that describe roughly what they do.
Some of these names are like anchored in history because
(10:21):
they come from very early observations. Right, Astronomy is a
field that's hundreds or thousands of years old, So to
understand what a centaur is, you really need to understand
first what an asteroid is, and what a comet is.
According to what modern astronomers said, is that another mythical rivalry,
like unicorns, there's a centaurs asteroids versus commets. No asteroids
(10:42):
and comets get along. In fact, sometimes they mix and
form space centaurs or space mermaids. Oh my goodness, that's
the next level mermaids. Yeah, exactly. That would have been
even a better name, because makes sense for things to
swim through space rather than gallop through space with their
with an unknown bellyable location. Yeah, that's right. Maybe they
(11:03):
can swim through the sea of dark matter that's out
there using their dark matter tails and lure astronauts to
their doom. Alright, so it sounds like we need to
understand what asteroids and comets are, and I'm guessing many centaurs.
It's like a mix of the two or somewhere in between. Yeah, exactly.
So an asteroid is a really cool object. It's basically
(11:23):
just a big rock floating out in space that didn't
get gathered together into a moon or a planet. But
it has a really interesting history. The word asteroid basically
means not a star because it's something that early astronomers
saw out there in space. But it was too small
to look like a planet, right, You couldn't like see
a disk, but it moved the way a planet did.
(11:45):
It wasn't so far away, it didn't move like a star.
So it's this weird object that was discovered when they said, well,
it must be nearby because it moves like a planet,
but it's really really small and it looks like a star.
So they gave you this new name. Oh interesting. I
guess I hadn't thought about it that we would have
discovered asteroids before we had powerful telescopes, right, I guess
(12:07):
at the beginning, it was just like a strangely moving
pinpoint of light in the nights cut exactly. An Asteroids,
like planets, don't shine light right there, just big dark rocks,
but they can't reflect light, and so light goes from
the Sun and bounces off it and comes to Earth.
Then we can see them, and that's good because we'd
like to know where the asteroids are so that we
know they're not going to smash into the Earth. And
(12:28):
we identified a few of them very very early on.
It was like in the eighteen hundreds we had already
seen ten of them. These are the bigger ones, the
shinier ones, and so we could see that they were
out there and they were floating around the Solar System.
And for a long time, people like didn't even distinguish
between a planet and an asteroid. In science papers from
the eighteen hundreds, those two words are used interchangeably. It
(12:51):
just means like a floating object in space that reflects light. Yeah,
it's not a star. It's closer by, it's like orbiting
our Sun and it's reflecting light. And from that point
of view, what's the difference between Mars and a really
big asteroid. They're both just big rocks in space, right.
But then as you learn about these objects, you start
to distinguish them. He's like, well, planets move in their
(13:12):
own orbit and basically have cleared a path, whereas most
asteroids are in a big belt. And so you come
up with these ways of talking about things because they're related,
but they're also important differences between planets and asteroids. It's
not just a difference of size, like I would think
it would be like a size threshold that you have
to meet to be a planet. Isn't that what happened
to Pluto, Like it wasn't big enough, so they got downgraded. Yeah,
(13:34):
that is sort of what happened to Pluto. But it's
also context, Like Pluto we found and it's out there
and it's moving sort of like a planet. But then
we found that Pluto is actually just one example of
a lot of different objects that are deep out there
in the Solar System, and it's not even necessarily the biggest,
and so calling it a planet would mean you have
to call all those other ones a planet also. So
then yeah, they made an arbitrary distinction. They're like, sorry,
(13:56):
we're going to define a planet to be just bigger
than Pluto. The sort of get Pluto out the door?
Is that why? Because they didn't want to admit there
were a lot of planets in the Solar System. Yeah, well,
they didn't feel comfortable with the idea of having lots
and lots of planets in an unknown number of planets,
because out there past Pluto, there's an enormous number of
these things. These things are called trans Neptunian objects, and
(14:19):
some of them are called plutoids or plutinos. But there's
a huge number of these things out there, and if
you said Pluto is a planet, then you'd have to
call them all planets. And you know, planets have a
historically important name, you know, like we like to think
it's a special class of objects in the Solar System
that we call planets because we live on one. So yeah,
we could have gone with like there are many many planets,
(14:40):
but they wanted to make it special. They wanted to
reserve the name for special occasions. That was kind of
I guess it was like, you know, you have friends,
and you have best friends, and you could say, well,
all my friends are my best friends, or you could
acknowledge that some of your friends are actually closer than
other friends. Right, I do have a friend who calls
all of our friends best friends, and it's so confusing.
(15:03):
Something there you go exactly, So then what was the
rationale or what was the official excuse that they go
by size. The long saga of the definition of Pluto,
I think deserves its own episode. Um, we can go
through the details of that. But we were saying that
asteroids were discovered, you know, in the eighteen hundreds, we
have at ten of them, and then it rapidly cranked up.
We had like discovered a thousand asteroids by the early
(15:24):
nineteen hundreds, and by now we know that there are many,
many of these things that are like probably more than
a million asteroids, and a lot of them are floating
in this asteroid belt, which is this big chunk of
space between Mars and Jupiter, and some of them are
actually co orbiting with Jupiter, like Jupiter has its orbit
right this big circle, and in other places in that
(15:46):
same orbit where Jupiter isn't there are big blobs of asteroids,
big clumps of asteroids floating in the same path. They
can share the same orbit. Wouldn't they have a different
speed or something. They can share the same orbit, and
they have a cool name. They're called Upiter Trojans. Yes,
they really are called Jupiter trojans, and they get into
these weird gravitational resonances with Jupiter because Jupiter is having
(16:10):
a big influence on all the stuff that's going on
in the Solar System out there, So you can't just
ignore Jupiter. Jupiter is a huge gravitational attraction. Remember that
of the stuff in the Solar System is the Sun,
and of that remaining one percent, Jupiter is most of
it jupiters of that one percent, So the first approximation
the Solar System is just the Sun and Jupiter. So
(16:31):
if you're out there near Jupiter has a huge influence
on what's happening gravitationally, and some of these rocks get
tossed down into the inner Solar System by Jupiter, they
get disturbed, and some of them found these resonances where
they can stay happily in Jupiter's orbit. All right, Well
that's an asteroid, and so that's one half of the
space center puzzle. The other have our comments, which we'll
(16:54):
get into in a short bit, But first let's take
a quick break. All right, Danny, we're talking about space mermaids. Unicorns.
Man unicorns stand space unicorns. I guess maybe more like
(17:17):
space Vegas is too. That could be pretty cool. They're like,
have birds have courses? Right? Yeah? Or what about griffins?
Are those like half birds half lions? Right? Those would
be cool space griffins, space hippogriffs. That that's the next level.
Most of these things we just made up. But some
of these things are real and are out there in space.
But they're also just sort of funny names that astronomers
(17:39):
gives to things to try to show us the relationships
between what they've discovered. All right, So an asteroid is
a space rock. That's sort of the definition somewhere between
like a baseball and what like the size of the
Moon is what would be considered an asteroid. Yeah, they're
like between a meter and up to like five dred kilometers.
The biggest one called Vesta is like five hundred kilometers wide,
(18:01):
and they're mostly rocks, and they're mostly in the Inner
Solar System so they don't have a lot of ice,
so they can be pretty big and they're mostly rock
and they are in the Inner Solar System. Those are
the key points to be an asteroid. Really, what if
you're a big rock but you're outside of the Inner
Solar System, but bomb you might be a centaur. I see,
it's like a location. It's like a discriminating by where
(18:24):
you're from, all right, So that's one half of the puzzle.
The other half of our comets. Now, comets are different
than asteroids. Comets are different from asteroids. They come from
a different place in the Solar System. They come from
out beyond Neptune, the Kuiper Belt. This is huge collection
of rocky and icy objects. So that's the second key.
(18:45):
Comets come from deeper out either the Kuiper Belt or
the Orc Cloud, and they are made of different stuff.
They tend to have a lot more ice in them.
They're these big, dirty snowballs of ice and dust. And
there's a reason for that. There's more ice out in
the far edges of the Solar System because it was
colder out there. The water in the inner Solar System
got sort of blown out by the pressure from the
(19:06):
Sun out to the outer Solar System. So rocks that
coalesce out there deeper in space tend to have more
ice in them. So comets come from the Kuiper Belt
or the Arch Cloud, which is this hypothetical collection of
trillions of icy objects deep out there, and they tend
to be made more of ice, like water ice or
like messane ice, both kinds of ice or other kinds
(19:28):
of liquids, all kinds of ice. And don't get me
started on how planetarry geologists talk about ice like they
talk about the ice giants of Neptune, and they say
these things are filled with water ice, but they don't
actually mean these things are frozen water to them, like
a water ice. It's a whole category of states of
water that could be solid but could also be technically
a liquid, but are not actually frozen water. So the
(19:51):
whole idea of an ice is a very sort of
confusing in general topic which is badly named. But in general,
there is a lot of frozen water and a lot
of very areous organic ices out there in the deep
Solar system. All right, we won't get you started that, Daniel.
Although ice giants also sounds like a mythological creature, Well,
Neptune is reel and it's out there, and it's called
(20:12):
an ice giant even if it has a lot of
water and no ice. But these comets, they're also tend
to be smaller, like you know, they're not up to
five kilometers wide. They're like five to five miles wide,
and you can tell that they're made of different stuff
because when they plummet to the inner solar system, they
get a coma and they get a tail, like their
(20:33):
edges tend to be burned off by the sun the
solar pressure, it's frying the outside, and you get this
long tail of material. It's basically coming off of the comet.
So they're not like as densely packed that they tend
to be more susceptible to the Sun. I guess further
out there, away from the Sun, it's more likely for
molecules to form into solids because it's colder, and so
(20:55):
there's just more things you can make rocks out of,
whereas maybe closer to the Sun, you know, there are
certain things like water or methane that evaporate. That's right.
Your distance to the Sun definitely changes the composition of
materials in the solar system, which are the basic building
blocks of everything we're talking about. And it's really fascinating.
And you know, we've only until recently seen one example
(21:16):
of a solar system ours, and now we're starting to
see other solar systems and we're looking at those and
we're saying Hey, are the patterns that are in our
Solar system also present in those? And we're finding really
surprising things, like we're finding huge planets like the size
of Jupiter really really close to the Sun, not just
in the outer Solar system. These are called hot Jupiters.
We actually did a whole fun podcast episode about this
(21:39):
is our Solar System weird and all the things we're
learning about our Solar system by looking at others. But
in general what you say is corrected. That tend to
be different kinds of things deeper in the Solar System
than closer in, and this affects how these objects come together.
And it's one reason why comets are different from asteroids
because they're made of different stuff because they come from
further app interesting, can we see asteroids and comets and
(22:02):
other solar systems yet? And b wouldn't it be cool
to have a novel about bix space war between our
centaurs and there are unicorns and another solar systems mermaids
that would I want to read a book called Exo
Mermaids would be pretty cool mermaids. No, we think we
(22:23):
have seen a comment from another solar system, but we
can't see them in their solar system. We think that
oh muamua, that weird cigar shaped object that came through
our solar system a couple of years ago wasn't exo mermaid.
It was probably a lost comment from another solar system,
but we don't know. It came through really fast, and
we only spotted it when it was halfway through the
solar system, so we only got like good pictures as
(22:45):
it was on its way out. So there's still a
lot of questions about what exactly OMMA was. But most
likely it was something from another solar system's equivalent of
the Orc cloud that got lost and ejected into space
and drifted over here. But we can't see these things
from other solar systems because they're so small. Like if
we wanted to point your telescope at another star, we
(23:06):
can just barely detect the planets, which are these huge masses.
So we're very far from being able to see exo
asteroids or exo commets or exo mermaids. All right, So
those are commets, And now the comets have sized restrictions too,
or do they also range from like small to gigantic.
They tend to be smaller than asteroids and that's because
they form deeper out and they just haven't gathered together
(23:27):
into larger objects, and Neptune tends to keep these things small.
Like Neptune is also a really big planet, and so
it's gravity tends to break stuff up because of tidal forces,
and so anything in the Kuiper Belt that would gather
together into a larger object generally gets torn apart by Neptune.
It's like the big bully on the playground out there
and doesn't want anything to challenge its supremacy. So they
(23:49):
tend to be up to about like twenty five miles wide.
Do we think, wow, So there's an active effort not
to have more planets. That's right. It's a good old
boys club, you know, and it's old worth something. If
it's exclusive, you can keep people out. That tunes the bouncer,
it's the enforcer exactly, all right. So that those are
asteroids in comments, And now I'm guessing that a space
(24:13):
center is like a mix of the two. Is it
like half asteroid half commet Like the top half is one,
the bottom half is another. Where do you put the
horn on the space center exactly? Or the belly button right?
And the asteroids half belly buttons due depends on how
they are born. Deep mystery of science, they have multiple
belly bons. Well, you're sort of right. A space center
(24:36):
is half asteroid half comet, but not in the sense
that a centaur is. It's not like you take an asteroid,
cut it in half and slap it onto the half
of a comet and this weird hybrid object you would
call a centaur. That would be pretty cool, but like
the tail trailing, that would be like a pretty killer commet. There. Yeah,
it's sort of like punk, you know, like shave half
your head and have the other half long or something,
(24:57):
or maybe it's like a mullet. This is in the
front rocking the front party in the back. Anyway, a
centaur is not an actual mix of an asteroid and
a comet. It's an object which has some of the
characteristics of both, so it doesn't fall neatly into either category.
And this is what I was saying earlier, is that
as we look deeper into the Solar system and catalog
(25:19):
more and more stuff, we find that the transitions between
our categories are kind of fluid and fuzzy and in
the end kind of arbitrary, you know. We have to
make categorizations so we can talk about stuff. You know,
when you go to a meeting of astronomers and you say,
I'm studying the planets, you don't want to every time
have to define what you mean by a planet, so
that you've got to have words we can all agree on,
(25:40):
even if they are arbitrary. So what we've discovered is
that there is a population of rocks out there which
don't fall nicely into either the category of asteroid or
of comet. So the solution was give it a cool name,
and now everyone's happy, and now everyone's happy. But now
everyone said arguing about whether or not account as a
(26:00):
space center or not. Yeah, exactly. And so these things
are fun because they're sort of like comets because we
think they come from deeper in the Solar System than asteroids.
They're on these sort of longer elliptical orbits. Their orbits
go out to like between Jupiter and Neptune. All the
asteroids are in the inner Solar System, but the space
(26:20):
centers they go out all the way to Neptune sometimes,
so there's sort of like comets because they also they
have some of these commas, like you can see these
sort of fuzz around them that's getting blown off by
the Sun. So they seem sort of like comets because
they come from deeper in the Solar System and they
have this fuzz. But they're also like asteroids because they're
(26:42):
really really big. Some of them are way too big
to be considered comets. And they also they cross the
paths of these giant planets like comets and unlike asteroids.
So there really are sort of a mix of the
characteristics of the two different things. So wait, these are
objects that they have like a tail, like comments like
they have you know, like a trail of stuff facing
(27:04):
away from the sun of like melted water or liquid.
They don't have a tail to have a coma. What's
the difference. So a tail usually comes if you have
like stuff that can be vaporized, like water or other
things which can be vaporized, and dusk coma is more
like you know, the little bits of stuff on it
are sort of floating around it. These things are big
(27:25):
enough that they can have their own gravity, so they
can sort of hold onto these things. In fact, one
of them is so big is has its own ring system,
like you know Saturn has rings. What there's this one centaur.
It's called charik Low and it's three hundred kilometers wide.
It's the biggest known centaur and it orbits between Saturn
and Urineus and it has rings around it. That's how
(27:47):
big it is. It has its own gravity. Wow, what
do you call the moon of a centaur? Daniel, I'm
gonna have to defer to the official astronomy naming department,
Like a fairy, a space ferry, I think, so us,
a nymph maybe ego? Right, So it's it's like it
has an entourage. It's not just the rock. It's like
a rock with some fuzz, yeah, And that tells you
(28:09):
a little bit about what it's made out of. That
there's a big component of sort of space dust in there,
not just like big deposits of metal and rock like
an asteroid, more like space dust like a comet. And
so that makes it more like a comet and less
like an asteroid. But it doesn't have ice, or does it?
Some of them? Maybe? I see these things are much
more rare than the other ones, and so they're not
(28:31):
as well studied. There's only like two hundred and fifty
of them that have actually been identified. But you know,
we can only really see the bigger ones. So the
estimates range from like forty thousand of these things too,
there might be ten million of these things out there
in the Solar System. Okay, so then it's like an asteroid,
you said, because of its size, but also it's orbit. Yeah,
(28:52):
it's it's like an asteroid because it's really really big,
and it's sort of unlike an asteroid because of its orbit.
Like asteroids tend to stay either in the asteroid belt
or in Jupiter's orbit. These Jupiter trojans that we talked
about before, these guys tend to be more stable than
a comet, right, But they have these orbits that are
really long and elliptical, and they pass the giant planets.
(29:14):
They're like cross over the orbits of the giant planets.
Sometimes they're further out than Jupiter. Sometimes they're closer in
than Jupiter. So that sort of makes them more like
a comet. But then again they're sort of big, lack
an asteroid. Interesting. I don't know, I'm not getting a
big comet vibe from these, you know what I mean,
Like it feels like maybe just like a rogue asteroid
or something. All right, Well, you know, on the common
(29:35):
side of it. They have these big elliptical orbits and
we think that maybe they came from the Kuiper Belt,
Like these things don't look like the same kind of
material that makes up asteroids. They're made it more of
the same stuff that comments are made out. So I
guess this is the kind of argument that astronomers would
have a conferences. They're like, oh, but it's big, so
it must be an asteroid. No, it has this weird orbit,
(29:57):
so it must be a comment. So that's why they
came up with the name. Yeah, yeah, exactly. And of
course nobody even agrees on what the definition of a
space center is. There's like seven different definitions of a
space center for real, for real, Like JPL has one,
the Jet Propulsion Lab in Pasadena down here in southern California.
(30:19):
They define a space center in one way. And then
there's another group called the Minor Planet Center, which is
an important institution in astronomy, and they have a different
definition for what a space center is. And the differences
in like how you measure the orbit details doesn't matter
if you cross Neptune or if you cross Jupiter, and
these are just like totally arbitrary, but conflicting definitions of
(30:41):
what a space centaur is. I guess there's such a
weird variety of stuff out there that, you know, you
kind of need more names to be able to talk
about all these things. And it gets tricky when you
try to put things into bins. Or you could just
be inclusive and say, hey, there's just sort of stuff
out there, and they're all my best friends, and they're
all a little bit different, and you can categorize them by,
(31:02):
you know, their orbit and their composition and not get
so hung up on names. I guess space stuff, planet stars,
everything in between is just space stuff. It's all just
particles to me, right, Like this is a big collection
of particles, a little collection of particles. What's the difference
two particle physicists. I guess all five percent of the
universe looks like a particle. All right, let's get into
(31:24):
where they actually come from and if we have actually
set ined some with our very own eyes. But first
let's take another quick break. All right, Daniel, we're talking
(31:46):
about space centaurs, which are a mix of asteroids and
comets that are like you know, space giant space rocks
that are kind of in between. They're big and rocky,
but they also have these weird orbits that make them
sort of like commets. Yeah, and so there's sort of
a mix between the two different things. And some things
(32:07):
are called comets, some things are called asteroids, some things
are called centaurs, and then you have these weird objects
that nobody agrees about because they fall sort of like
in between the definitions from different organizations. So there's an object,
for example, called Chiron, which some folks classify as a comet,
some folks classify as an asteroid, and some folks classify
(32:27):
as a space centaur. So it's a little bit of everything. Wow. Yeah,
I guess there's no agreed upon a set of definitions,
Like there's no International Space Stuff Naming Committee. No. I
think the problem is there are too many of those
committees and they don't agree with each other. And so
I think this like controversy about Pluto and is it
a planet or is it a dwarf planet or whatever,
(32:50):
it's just the tip of the iceberg. It's just the
tip of the frozen comet. When it comes to like
the naming controversies we're gonna be facing in the future
as we discover more and more stuff out are in
the Solar System, and people are gonna be arguing like
should you name stuff based on where it is now
or where you think it was formed, or what it's
made out of, or it's possible history or its gravitational
(33:11):
role in the Solar System. And there's lots of like
philosophical differences about how you categorize this stuff that I
think we're gonna be hearing more and more about in
the future. I guess maybe some naming groups are like
you know, committees, some of them are groups, some of
them are centers, so they're just sort of a naming
war for those two. That's true, Yeah, exactly, the naming
(33:32):
centaur wars. All right, well, step of three, or where
can we see one and what what do they look like?
So we've never actually photographed one up close, like we've
identified them in telescopes. We see these things, we can
tell that they're they're they're reflected light, but we've never
liked passed a space probe by one to get a
close up picture of the way we have of asteroids
and of comets, and of course of planets and dwarf
(33:55):
planets and all those other kinds of things. So space
centers or one of those last things that are really
unexplored in our Solar system. And there's some really fascinating
questions about what they are and where they come from.
Like question number one is why do they have their
weird colors? Like they have colors. There's different colored space centaurs. Yeah,
there are two different kinds of space centaurs at least,
(34:18):
and they range from very very red sort of like
the surface of Mars too much more blue sort of
like Urinus. And so that's fascinating that there's these two camps.
There's like two kinds of centaurs. I don't know which
ones are the good ones and which ones are the
evil ones or if it's much more nuanced than that,
but there are red and there are blue centers. Thing. Wait, um,
(34:38):
so we don't have a photograph of them, but we
can tell from the light that they they reflect what
color they are, Like they look like pin points, but
like a red pin point and a blue pin point sometimes. Yeah,
just like when you look at the night sky, you
can tell which planet is Mars because it actually looks
red to the naked eye, even though your naked eye
can't really like see the size of Mars. You can
(35:01):
still measure the light that comes from a pin prick,
and that's the limitation of our knowledge about space center.
So far. We basically just see them as pin pricks
in telescopes because we've never done a close up fly by.
And now there's also a little bit of controversy about
these objects, yeah, because the color is an important clue.
Like one question we'd like to ask is where did
(35:22):
these things come from? Where were they made? Because remember,
we're interested in studying the Solar System not just because
stuff out there in space is cool it is, but
because we think it tells us a story about how
the Solar System was formed and what happened and where
everything came from and whether it was unusual. And we
think that a lot of these objects can tell us
about that story based on where they are now and
(35:44):
the way we do that as we build a complete
model of how the Solar System was formed and we
try to compare what that predicts to what we actually
see out there in space, and where there's something we
don't understand that tells us that something in our model
is wrong, and so we're interested in, like where did
these space guitars form? Do they form with the asteroids
and then get sort of knocked out into weirder, longer orbits,
(36:06):
or did they form with the comets and somehow get
preferentially selected and pulled into the inner Solar system somehow?
And so one great way to do that is to
look at their composition. And we can't really do that
without sampling them, but we can get a clue by
looking at their light, so looking at whether they reflect
red or blue light and comparing that to what we
(36:26):
see from other parts of the Solar system. Like you
might think, well, if these things are red and blue,
what else out there is red and blue? And if
you look at the Kuiper Belt, where we think that
these things might come from, we find that those objects
are not actually by colored. There aren't red and blue
objects out there in the Kuiper Belt. Wait, if something
is red and blue, would it be purple? Can there
(36:50):
be purple centaurs? If not purple purple dragons? No, we
mean that the Kuiper Belt doesn't necessarily have like a
distribution of colors the way we see in centaurs, like
centers tend to be red or blue. You don't have
an individual center that's red and blue. You have red
centaurs and blue centaurs, but if you look out in
the Kuiper Belt, you don't see red objects and blue objects.
(37:12):
So it suggests that that maybe they don't come from
the Kuiper Belt. Maybe they come from somewhere else, like
maybe they are not evenly distributed, like maybe they come
from one of two places, yeah, Or maybe there's some
process which is related to their composition which preferentially selects them.
And there's this whole other group of objects out there.
The Kuiper Belt is part of this set of objects
(37:34):
we called trans neptunity and objects basically anything out there
past Neptune. And in that group of stuff, there's a
group of objects called plutinos, which are basically the category
of objects that Pluto is in. You know, dwarf planets
out there really far in the Solar System, and those
things tend to have interesting colors. Like you remember when
(37:56):
we did that fly by Pluto. One of the big
shocks was frankly, how interesting Pluto was to look at.
Are we sorry we downgraded it now they're like, oh,
you're kind of cooler than we thought. We're sorry we
kick you out of our club. Yeah, I think that's
what happens when you kick somebody at your best friends
club and then you discover they actually really talented and
you wish you had stayed friends with them. That Pluto
(38:17):
has these really interesting features. It's really interesting colors, and
it has this heart shaped pattern on it. It's a
pretty beautiful planet, actually non planet, non planet, thank you
very much, as a dwarf planet. And a lot of
these plutinos out there have interesting colors, and so those
things tend to have both red and blue colors. So
it might be that these centaurs used to be plutinos
(38:38):
that used to be objects out there past Pluto and
somehow got knocked in words by some process we don't understand. Now,
can I actually see uspace on center with my naked eye,
Like if I look out into the night sky, is
it possible that I might see one going by? No,
they tend to be further out and they're too small,
so you definitely need a telescope to see one, the
(38:59):
same way that you and see asteroids with your naked eye.
And asteroids are sometimes even bigger than space centers and
it's closer in, So if you see one with your
naked eye. It means we're in trouble. Runaway, runaway to Mars. Maybe, Yeah,
quick build that ship. All right, Well, that is what
a space center is. It's um a sort of a
(39:21):
half asteroid, half common but not really. It makes just
sort of like a fuzzy object that falls in between
the two. And so we see that the stuff out
there in the Solar System can't be nicely categorized into
little bins. That makes sense. There's stuff out there that,
you know, might be a planet, might be a star,
might be a dwarf planet. But there's an incredible variety
of stuff out there for us to identify and to
(39:43):
learn from. Yeah, I think the cool thing is that
there are still things out there, even in our Solar
System that kind of defied definition or that still kind
of surprises or still has this talking about what's out
there and how it all came to be. Yeah, and
the far reaches of the Solar System are not very
well explored. This trans Neptunian objects and stuff out there
past Pluto is too far for us to see most
(40:05):
of it, and we haven't sent very many probes, and
so we're constantly surprised whenever we learned about them, and
I think there are a lot more surprises out there
waiting for us. And you know, even further out the
Orc cloud. Remember that's something we've never actually seen. It's
just theoretical. And when it's just theoretical, that means there
are definitely surprises waiting for us. Oh yeah, what could
(40:26):
there be? There could be interesting new things and maybe
some of our listeners could discover one day armies of
elves waiting to take back the Solis. Yeah. Yeah, what
do you call a half common half planet, Daniel or
a half moon have planetoid? I call it an ambush
waiting to happen. They call it a future Nobel prize
for somebody that's listening to this. All right, Well, the
(40:48):
next time you look up at the night guy, think
about it. There might be a Centaurs out there, or
even new undiscovered objects at b B you could name,
or at least fantasized about naming. And please be responsible
with your future astronomical namings because we might have to
cover it on the podcast. Yep. All right, Well we
hope you enjoyed that. Thanks for joining us, see you
(41:09):
next time. Thanks for listening, and remember that Daniel and
Jorge Explain the Universe is a production of I Heart
Radio or more podcast from my heart Radio. Visit the
i heart Radio app, Apple Podcasts, or wherever you listen
(41:29):
to your favorite shows.
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
Popular Podcasts
United States of Kennedy
United States of Kennedy is a podcast about our cultural fascination with the Kennedy dynasty. Every week, hosts Lyra Smith and George Civeris go into one aspect of the Kennedy story.
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
Dateline NBC
Current and classic episodes, featuring compelling true-crime mysteries, powerful documentaries and in-depth investigations. Follow now to get the latest episodes of Dateline NBC completely free, or subscribe to Dateline Premium for ad-free listening and exclusive bonus content: DatelinePremium.com