OK, I'm going to moon you.
Are you ready?
Close your eyes if you don't want
to see a big bright mooning.
Boom!
That's a moon.
That's Ganymede.
This is also a moon.
This is Phobos.
Cool, right?
Our moon is just called, "the moon,"
which is a bit presumptuous, actually.
But you could also call it Luna if you want.
That's Latin for moon, which some cultures use.
Just don't call it a planet.
This is the current International Astronomical
Union's definition of a planet.
So let's have a little thought experiment.
Let's say the moon were to fly off on its own.
Like, zoom out of the solar system.
Here on earth, of course, everybody dies.
But what happens to that little moon?
What does it become?
Because it's still not a planet, but it's not a moon either.
[VOCALIZING]
A new paper from earlier this year
has a name for this new non-planet moon.
And needless to say, I have questions.
Are you ready?
Because this is a great name.
It's not a planet, it's not a moon,
it's not an asteroid, or a meteor, or a celestial rogue.
The name for this thing is ploonet.
[MUSIC PLAYING]
[LAUGHS]
Oh, my God.
Hi, Moonies.
Pronx here-- uh, Trace here.
Thanks for watching Uno Dos of Trace.
I really love that you are here to learn along with me.
Welcome new subscribers.
25,000 subscribers.
My heart is soaring.
Thank you so much.
Phew, OK.
Recently, I read a paper in the Monthly Notices of The Royal
Astronomical Society from August of 2019,
and I was like, I have to tell everybody about this.
This is crazy.
Ploonets?
This is embarrassing for everyone involved.
And it's hilarious, and I love it.
It's not actually embarrassing, it's great.
How did we end up here, though?
I'll get there.
But first, I have to talk about how solar systems form.
I know, astronomy is a lot.
In the beginning, there was darkness and a lot of matter.
Slowly, over way more than a week,
a bunch of the atoms of hydrogen started to coalesce, like water
in a small bowl.
As more and more gas and dust fell together
joined by its shared gravity, it ignited, becoming a star!
[MUSIC PLAYING]
The gravity of this gas turned this mess of matter
into a protoplanetary disk, a fetal solar system.
Then more matters started to coalesce
into planets and asteroids, and everything else
in a solar planetary system!
[RIPPING SOUND]
Oh, sorry.
As new planets form in a protoplanetary disk,
some are going to float toward or away
from their original orbit in the cloud,
due to their gravitational forces.
This is called planetary migration.
Think about it like this.
This is the nice model of planetary migration,
and it says that Neptune and Uranus formed much closer
to the sun, and that Neptune was actually closer than Uranus
at one point.
But eventually, they both migrated outwards
to where they are in orbit today.
We've seen evidence of planetary migration
in other solar systems, like, Kepler-223,
where the planets are in resonance, i.e.,
for every orbit of one planet, a neighbor planet
will orbit twice.
Astronomers spotted this idea at Jupiter long ago,
and realized three of Jupe's moons are in resonance as well.
Seeing it elsewhere makes them think
that's our solar system used to have resonant orbits, too.
But for some reason, the larger gas giants
were knocked out of resonance to the orbits
that they have today.
The point here is that orbits can change.
So we've got planets.
They're forming in this cloud of protoplanetary debris.
And we've got orbits that can change over time,
remaking solar systems all over the universe.
Now we add in observations of exoplanets.
We've been looking at the stars and finding
so many alien planets that we haven't even been
able to study them all yet.
We've spotted over 4,000 planets around other stars so far,
and confirmed a lot of them.
What we haven't spotted yet are moons.
Exomoons, at least, not yet.
And I'm pretty sure you see where this is going.
Moons also formed from protoplanetary disks,
but they didn't gather enough material quick enough
to be a planet.
And instead, they were pulled or captured
by the gravity of nearby bodies and relegated
to be celestial sidekicks for now.
Keep that in mind.
Over billions of years, planets don't tend to float outwards,
away from their stars.
They don't disappear into the space around solar systems.
Instead, they tend to orbit inwards, falling
towards their stars, which is how some think we ended up
with hot Jupiters, a class of gas giant
exoplanets that orbit very close to their star,
like in less than 10 days, that's very close,
and they're very hot.
When a planet gets that close, this paper
theorizes it needs to shed its exomoons.
But where do those moons go?
What happens to them?
Do they leave the family and get their own franchise,
like Hydra and Sponde?
[MUSIC PLAYING]
Let's furiously fast forward to 2006.
Moons are round.
Generally, they've cleared their orbit.
But they don't orbit the sun, they orbit a planet.
So under the IAU definition, they are not planets.
But what if a moon isn't orbiting its planet anymore?
What happens if one of those moons
gets fed up with cats jumping over it and playing
second fiddle, and they just want to go solo?
We never actually observed this happening,
but we know that it can happen.
So we need a name for this specific scenario.
And that name, as weird as it may be, is ploonet.
Ploonets may get their own franchise,
but it all comes back to family.
So even though they haven't been seen,
we know that ploonets could exist.
The problem is, ploonets are not long for this universe.
Once a moon has been spun off from its host planet,
it can be torn apart by tidal forces of other planets,
eaten by another gas giant, or even the star itself.
It could even be tossed entirely out of the solar system,
into interstellar space.
Become like a rogue moon.
That said, there are some ploonets
that are theorized to last for several million years
and gather new dust and gas still available
from the leftovers of the protoplanetary disk.
And if they do that, they might be able to upgrade themselves
to a capital P planet!
And now, you see the problem.
Astronomers need specificity.
This isn't a moon being destroyed by its planet friend.
It's not a rogue moon.
It's something different.
And it needs to go on to have a new life as a planet,
but scientists needed a new word to describe these orphaned
celestial bodies.
You could feel however you want about the word
that they proposed-- ploonet.
[CHUCKLES]
But these astronomers are saying we
call them ploonets because they are not a moon anymore,
and they might someday get to be a planet.
Although, it's kind of unlikely.
And again, we've never actually seen
one of these things in the universe.
What we have seen, though, is a bunch
of strange anomalies in other solar systems with planet
spotting space telescopes like Kepler.
And those anomalies, they think might
be explained by these moons.
Well, ploonets--
[CHUCKLES]
--that have been destroyed, or they're
messing with the gravitational interactions of the planets
around distant stars we can see.
Now, I can understand what these astronomers
are doing with ploonets.
Hopefully you can, too.
It's a mix of planet and moon.
But couldn't we mix a cooler word, like, moon and asteroid?
Wouldn't that be better?
It gives us some way cooler rombinations, like, masterioid!
It's like an asteroid, but it's a former moon,
with a heart of vengeance!
[ROCK MUSIC PLAYING]
Moonsteroid--
Ah, yeah!
--it's neither a moon, nor an asteroid.
And it's terrorizing its planetary system
until a planet arrives to put it in its place!
[UPBEAT MUSIC]
[CLASSICAL MUSIC]
Asteroon, that special time in going to galactic day, when
we all sit and have a lovely spot of tea and martian
cucumber sandwiches.
Any of these words--
[CHUCKLES]
--are better.
So I'm going to go ahead and tweet a poll
and see what people think.
But in the end, moons are weird, right?
When you really think about it, moons
are relegated to the second class celestial body.
Planets, they get all the press.
But moons can be very planet-like,
and sometimes that makes them even more interesting.
We love to talk about life on Mars, which is a planet.
But it's far more likely that we're
going to find life on Europa, which
is just a little old moon.
Titan is actually larger than Mars,
and it has more atmosphere than Earth.
It's also just a moon, so it's not as interesting.
Ganymede is larger than both the planet Mercury and the dwarf
planet Pluto.
It's only a bit smaller than the planet Mars.
And yet, it's still just a moon, so, meh.
Moons are amazing.
And they deserve our love and respect,
and they deserve to be explored.
Exomoons, too.
Exomoons haven't even been spotted yet.
They're really small.
But once we do, if the moons in our own solar system
are any example, then we are going
to find some amazing things.
In the end, whatever we want to call them,
ploonets are showing us that solar systems are not as
unchanging as we would think.
When you look at those wire models, where
all the planets are in stationary orbits, remember,
that's not real.
Things change, planets shift, moons
get thrown hither and thither, nothing lasts forever.
You know, except our curiosity.
Curiosity is at the center of everything I do.
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So it's actually a double-win.
Thanks.
OK, so, ploonets.
[LAUGHS]
Make sure you fill out that pole.
Thank you so much for watching Uno Dos of Trace,
I really appreciate it.
Thank you for subscribing, for sharing the channel.
I think in 2020, we're really going to blow this thing out
of the water.
Even if the ploonets thing was not the best name,
let me know what you think the best name is in the comments.
I'm a big fan of moonsteroid.
Kind of sounds like a cool band.
OK, I'll see you in the future.