If you ever thought about what makes a planet a planet,
is it just how big it is?
Or is there something more to it?
Right.
Well, today we're diving deep
into this whole world of planets.
We've got the familiar ones in our solar system,
but then some really out there planets you wouldn't believe.
Yeah, some really exotic ones out there.
Welcome to Cosmos in a Pod, Space and Astronomy series.
Get ready to go way beyond
the simple definition of a planet.
We're gonna explore how astronomers actually classify
all these crazy different worlds out there.
A question that's really puzzled astronomers,
I mean, for centuries really.
Let's start with our own solar system.
Okay.
Remember back in 2006, that whole Pluto thing?
Yeah, yeah.
That really stirred things up, what happened there?
So the International Astronomical Union, the IAU,
they decided we need like a stricter definition
for what is actually a planet.
Okay.
They came up with three key criteria.
Right.
First, it's gotta be orbiting the sun.
Yeah.
Second, it needs to be round, or at least nearly round,
because of its own gravity.
Basically, it has to be massive enough
for gravity to pull it into a round shape.
Okay.
And third, and this is the tricky one,
a planet has to have cleared its neighborhood.
Cleared its neighborhood.
What does that even mean?
So it means that a planet has become
the dominant gravitational force in its orbit, right?
It's either swept up or flung away
most of the other objects in its path.
Oh, okay.
And this is where Pluto fell short.
Yeah.
It shares its orbital space with a whole bunch
of other icy bodies in the Kuiper belt.
So Pluto got demoted,
because it's not like a gravitational bully, so to speak.
You could say that.
I mean, it's more about gravitational dominance.
And this definition, it works pretty well
within our solar system.
But when we start talking about exoplanets,
planets outside of our solar system,
things get a bit more complicated.
I can imagine.
Why is it harder to classify exoplanets?
Well, it's really tough to observe
those distant planetary systems in any detail.
I can't always tell if a planet has
cleared its neighborhood or not.
That makes sense.
So how do we even begin to classify
those distant worlds then?
Well, we rely on what we can observe, right?
So their mass, their size,
their composition, how far they are from their star,
this gives us some clues about their structure
and what they might be like.
So let's break down these different types of planets
that are out there.
Oh, right.
So we've got the familiar ones in our solar system.
Right.
You've got the rocky terrestrial planets,
like Earth, Mars, Venus, Mercury.
Right, and of course, Earth is the archetype here.
It's the only one we know of so far that can support life.
Right.
And then you have the gas giants, Jupiter and Saturn.
Massive planets composed mostly of hydrogen and helium.
And then there's the ice giants, Uranus and Neptune,
with their unique icy compositions.
Exactly.
Each type of these planets,
they have their own special characteristics
that help us classify them.
But then things get really wild
when we step outside of our solar system.
Right.
We start to find these planets,
these types of planets that we don't even have here.
Like tell me about these super Earths
and mini Neptunes I've been hearing about.
Ah, yes.
Those are categories that are specific to exoplanets.
Super Earths, as the name suggests,
they're rocky planets, but they're bigger than Earth,
but smaller than Neptune.
And then mini Neptunes,
they're like smaller versions of Neptune,
but they have these thick atmospheres.
You sound fascinating.
Can you give me some specific examples of those?
Sure, sure.
There's Kepler 452b.
Okay.
It's a super Earth.
It orbits a star, very similar to our sun,
and it sits within the habitable zone.
So that means it might have the right conditions
for liquid water to exist on its surface.
Wow.
A potentially habitable super Earth.
That's incredible.
What about mini Neptunes?
One really interesting one is TOI 270c.
And studying this mini Neptune,
it's helping us understand the transition
between rocky planets and gas giants.
So we're learning a lot about planet formation
from these distant worlds.
How eu-eu.
And then there are rogue planets.
Right.
These are planets that aren't bound to any star.
Right, yeah.
And they just kind of drift through space.
Yeah, they're just cruising through the galaxy
all by themselves.
Rogue planets.
They sound like lonely wanderers of the cosmos.
How do they even form?
Well, they were probably ejected
from their original solar systems when they were forming,
maybe through gravitational interactions
with other planets.
One example is PSO J3 18.522.
It's a rogue planet discovered back in 2013.
It's amazing to even think about.
So how common are these rogue planets?
You know, it's hard to say for sure,
but they might be more common than we think.
Oh, yeah.
They're just incredibly difficult to detect.
Right.
Because they don't emit much light.
Okay, so we've covered the familiar,
the somewhat familiar.
Yeah.
Now I'm ready for the truly weird stuff.
Bring on the exotic planet types.
What are like some of the strangest planets out there?
Oh, get ready for some wild ones.
So there are ocean worlds.
Okay.
These are planets completely covered in water.
Think of a planet sized ocean.
Whoa.
Are there any real examples of those?
Well, there's Europa.
It's a moon of Jupiter.
And it's thought to have a vast ocean
beneath its icy surface.
Okay.
And then there's GJ 1214b.
It's an exoplanet.
And it shows strong evidence of being an ocean world.
Imagine the possibilities for life in those environments.
It's mind blowing.
What else is out there?
Then you've got lava worlds.
Okay.
Planets so close to their stars
that their surfaces are just molten rock.
55 Cancri E is a scorching example of this.
This sounds incredibly harsh.
How does scientists even study a place like that?
It's a challenge.
They have to rely on observing the planet's light
and how it interacts with its atmosphere
to try to learn about its composition and temperature.
It's like trying to study a volcano up close.
Wow, that's intense.
What other bizarre planets are on the menu?
Well, there's the hypothetical carbon planet.
Okay.
It's a world that's rich in carbon.
Some scientists think that these planets,
they could have surfaces made of graphite or even diamonds.
A diamond planet.
Now that's something I'd like to see.
Yeah.
Have we actually observed one yet?
We haven't observed one yet.
The theory is that they could form in star systems
that have a higher carbon to oxygen ratio than our own.
Okay, so maybe there's a whole blinged out solar system
out there somewhere.
What else we got?
How about puffy planets?
These are gas giants that are incredibly inflated
because of the heat from their star.
HATP67B is a good example.
Puffy planets, lava worlds, diamond planets.
This is wilder than any science fiction movie
you've ever seen.
I know, right?
It's mind blowing.
And then we have tidally locked planets.
So this is where one side permanently faces the star
and it results in these extreme temperature differences.
So eternal day on one side, eternal night on the other.
What would it even be like to live on a planet like that?
Oh, it would definitely make
for some unusual weather patterns.
Trappist-1M is a tidally locked planet
and it falls within the habitable zone of its star.
So it's a really intriguing target for study.
All these incredible discoveries must keep astronomers busy.
So how do they even find and classify all these exoplanets
in the first place?
There are three main methods.
There's the transit method.
There's radial velocity and direct imaging.
The transit method is the most commonly used one.
It involves looking for these tiny dips
in a star's brightness as a planet passes in front of it.
Kind of like a mini eclipse.
That sounds pretty ingenious.
What about radial velocity?
So radial velocity, that measures the wobble of a star
caused by the gravitational pull of an orbiting planet.
Ah, so we can detect planets
even if we can't see them directly.
Exactly, yeah.
And then there's direct imaging.
And that's literally taking a picture of a planet.
Wow.
But it's incredibly difficult.
Yeah, I bet.
Because planets are, they're so much fainter
than their stars.
Yeah, I can imagine that's quite a challenge.
Yeah.
What are we hoping to learn from
directly imaging exoplanet?
Oh, direct imaging, it can give us information
about a planet's atmosphere, its temperature,
and it might even allow us to search for signs of life.
This is all so fascinating.
But with so many new discoveries,
there have to be some areas where our understanding
is still evolving, right?
Oh, absolutely.
One of the biggest ongoing debates
is where we draw the line between planets and dwarf planets.
Right.
There are objects out there that blur the lines, you know?
And it makes classification tricky.
I guess the more we discover,
the more we realize how much we still don't know.
Exactly, and that's what makes this field so exciting.
You know, there are still so many unanswered questions
about the universe's incredible array of planets.
We've covered a lot of ground here.
I'm definitely ready for a little break
to let all this new information sink in.
Me too.
But stick with us because when we come back,
we'll be diving even deeper into the mysteries
of exoplanets and the search for life beyond Earth.
And don't forget to follow Cosmos in a Pod
and subscribe to our YouTube channel
for more exciting deep dives
into the mysteries of the universe.
We'll be back soon with more fascinating insights.
Welcome back to Cosmos in a Pod.
So we've been talking about all these different, you know,
types of planets, but I'm kind of curious,
are these classifications always so clear cut?
Are there like any cosmic objects
that just don't fit neatly into those categories?
Yeah, that's a great question.
And it really shows how like our understanding
of the universe is always changing, right?
Right.
Take brown dwarfs, for example.
They're fascinating, they kind of blur the line
between planets and stars.
Brown dwarfs, I've heard that term before,
but I'm not really sure what they are.
You can think of them as like failed stars.
Okay.
They're bigger than giant planets,
but they're not quite massive enough
to sustain nuclear fusion in their cores,
which is what powers, you know, stars.
They're kind of stuck in this awkward in-between phase.
Exactly, they're in this cosmic middle ground
and their classification, oh, it's been debated for years.
I can see how that would be a headache for astronomers.
What makes them so hard to categorize?
Well, their size and mass are big factors.
I mean, they can be as small as some giant planets,
but they can also be, you know, much bigger.
And their composition can vary a lot too.
So how do we tell if we're looking at a brown dwarf
or just a really big planet?
It's not always easy.
Astronomers have to look at things like their temperature,
their luminosity, and whether they show any signs
of nuclear fusion, even if it's just, you know, a tiny bit.
It sounds like a real cosmic detective story,
trying to figure these things out.
Oh, it really is.
And it reminds us that the universe is full of surprises,
and our understanding of it is always being refined
as we make new discoveries.
Speaking of refining our understanding,
I've been thinking about that,
that clearing its neighborhood criterion for planets.
Right.
It seems like that rule could be kind of subjective,
especially when we're talking about exoplanets
that, you know, we can't observe as clearly.
Yeah, that's a really good point.
And you're right, it's a point of a lot of debate
among planetary scientists.
There's actually a growing movement
to reconsider that criterion,
or maybe even, you know, get rid of it completely.
Really, why is that?
What are the arguments against it?
Well, for one thing,
it's just really hard to apply consistently.
As we talked about earlier,
it's much harder to observe distant exoplanetary systems
and know for sure if a planet has truly cleared its orbit.
So it's kind of biased towards planets in our solar system
that we can see better.
Yeah, some scientists argue that that's the case.
They think a planet should be defined by its own properties,
like its mass, its size, its composition,
and, you know, not by what's going on around it
in its orbit.
That makes sense to me.
I mean, a planet's a planet
regardless of its neighbors, right?
Exactly, and focusing on those intrinsic properties
might actually allow us to classify more objects
as planets, including some that are currently considered,
you know, dwarf planets.
So we're talking about a potential Pluto comeback,
justice for Pluto.
It's a possibility.
The debate's still going on,
and there's no clear consensus yet,
but it's a really cool example
of how our understanding of planets is constantly evolving.
This whole planet classification thing
is way more complex than I ever realized.
It really is.
It's like a reflection of the incredible diversity
of the universe itself.
There are so many different kinds of worlds out there,
and we're really just starting to scratch the surface.
Yeah, it makes you wonder what other strange
and wonderful planets are out there
just waiting to be discovered.
What new technologies are astronomers using
to kind of push the boundaries of our understanding?
Well, the James Webb Space Telescape,
it's been making some incredible discoveries
since it launched.
Right.
Its instruments are so powerful.
They let us study the atmospheres of exoplanets
in more detail than ever before.
That's right.
I remember those stunning first images from Webb.
Yeah.
But how does studying those exoplanet atmospheres
actually help us understand them better?
You can think of it like taking a planet's fingerprint.
Okay.
The composition of an atmosphere
can tell us a lot about a planet's history,
how it formed, its potential for life,
and maybe even whether it shows signs of life already.
So we could potentially detect signs of life
on other planets just by analyzing their atmospheres.
That's the hope.
We're looking for what we call biosignatures.
So those are gases like oxygen or methane
that could indicate there's some kind
of biological activity going on.
That would be groundbreaking.
Are there any planets that are particularly promising
for finding those biosignatures?
Absolutely.
The TRAPPIST-1 system is one
that has a lot of scientists excited.
Okay.
It's a nearby star system
with seven, count them, seven Earth-sized planets.
Wow.
And three of those are in the habitable zone.
Seven Earth-sized planets.
The possibilities are mind-boggling.
What else is coming up in the world
of exoplanet exploration?
There's some really cool missions in the works,
the European Space Agency's PLATO mission, for example.
It's designed to find and study Earth-like planets
around stars like our sun.
So potentially finding more planets
that could be like our own.
Exactly.
And then there's NASA's Nancy Grace Roman Space Telescope.
That one's gonna have a wide field of view,
which will let it search for exoplanets
using a technique called microlensing.
Microlensing.
That sounds interesting.
What is that exactly?
It's a little complicated,
but basically it uses the gravity of a star
to magnify the light from a more distant star.
Okay.
And if there's a planet orbiting that closer star,
it can cause a blip in that magnified light.
So it's like using gravity as a cosmic magnifying glass.
Precisely.
It's a really powerful technique
for finding planets that are further from their stars
or planets that are just too small
to detect using other methods.
It sounds like the future of exoplanet discovery
is incredibly bright.
But before we get lost in all the excitement,
I think it's time to kind of shift gears a bit.
Okay.
We've talked about the science of planet classification,
the search for life, and the amazing technology
that's helping us make those discoveries.
But what about the ethical side of space exploration?
It seems like there's some big questions
we need to be asking as we venture
further out into the cosmos.
Yeah, you're absolutely right.
As we explore the universe
and potentially even encounter extraterrestrial life,
we need to be thinking carefully about our responsibilities.
It's a conversation we need to start having now
before we actually face those challenges head on.
Yeah.
I'm definitely intrigued and maybe a little nervous
to delve into those ethical considerations.
It's understandable.
We're talking about potentially encountering life
as we don't know it.
And that raises all sorts of questions
about how we should interact, what our responsibilities are.
This deep dive has taken us
from the familiar planets in our solar system
to the most bizarre worlds imaginable,
and now to some really profound ethical questions.
I can't wait to explore this next chapter.
Me neither.
Join us after the break as we contemplate
the philosophical implications of our journey
into the cosmos.
And remember to follow Cosmos in a Pod
and subscribe to our YouTube channel
for more exciting deep dives
into the mysteries of the universe.
We'll be right back.
Welcome back to Cosmos in a Pod.
So we've been on this incredible journey,
exploring all these different planets across the universe.
But now let's think about something a bit deeper.
Like the ethics of it all.
The ethical side of space exploration.
It's exciting and kind of daunting at the same time.
It's definitely something we need to think about carefully.
As we go further out there,
the chances of us actually bumping
into extraterrestrial life, well, they become more real.
And that brings up a whole bunch of ethical dilemmas
that we need to be ready for.
Like what kind of challenges are we talking about?
What are some examples?
Well, one of the biggest worries is contamination.
Like if we send probes or even people to other planets,
there's a chance, right,
that we could accidentally bring earth microbes with us.
And those could be harmful to any life
that might already be there.
So we could accidentally wipe out alien life
before we even know it exists.
It would be a huge loss, scientifically and ethically.
And then there's also the flip side.
We gotta think about those extraterrestrial organisms
potentially contaminating earth.
We don't know how our biosphere would react to alien life.
It sounds like something straight out of a sci-fi movie.
I know, right.
But it's a real possibility we need to consider.
What are scientists doing to try and minimize those risks?
Well, planetary protection protocols.
Those are like a super important part of any space mission.
Probes in spacecraft, they go through
this intense sterilization process
to reduce the risk of contamination.
So it's like washing your hands before dinner,
but on a cosmic scale.
Exactly.
And there are very strict rules for handling any samples
that come back from other planets.
Like the Mars sample return mission, for example.
Yeah, makes sense.
Better safe than sorry, especially when we're dealing with
things we don't even understand.
But what about if we actually do find
intelligent alien life?
Like how do we even begin to talk to them
to interact with them?
Oh, that's where things get really tricky.
There are a lot of discussions happening right now
about how to create a universal language
or some kind of protocol for communicating
with extraterrestrial intelligence.
I mean, it's hard enough to communicate with people
from different cultures here on Earth.
Imagine trying to bridge that gap with beings
from a whole other planet.
It would be an immense challenge.
We'd have to completely rethink how we understand language,
how we communicate.
And then there are the questions of rights
and responsibilities.
Do extraterrestrial beings have the same rights as humans?
How do we make sure they're safe?
What if their values, what if their goals
are totally different from ours?
It's like a whole new frontier, not just in science,
but in ethics and philosophy too.
Absolutely, it's crucial to have these conversations now
before we're actually in these situations.
We need to approach space exploration with responsibility
and respect for the universe
and everything that might be out there.
I couldn't agree more.
This deep dive has really changed
how I see exploring the cosmos.
It's not just about scientific discoveries.
It's about understanding our place in the universe
and our responsibilities as citizens of the cosmos.
Well said.
It's a humbling and awe-inspiring endeavor.
It really requires careful thought and consideration.
It's been an amazing journey,
going from those familiar planets in our own solar system
to the most bizarre worlds we can imagine.
And it's clear we've only just scratched the surface.
The universe is full of wonders,
just waiting for us to discover them.
Who knows what incredible planets
and life forms are out there?
It's truly mind-blowing.
Well, that's all the time we have for today's deep dive
into the world of planets, but that the exploration continues.
Don't forget to follow Cosmos in a pod
and subscribe to our YouTube channel
for more exciting deep dives
into the mysteries of the universe.
Until next time, keep looking up
and never stop exploring those wonders of the cosmos.