Hello and welcome to the Cool Worlds Channel
I'm Hannah Wakeford and I'm going to
talk to you about the exotic clouds of planetary
atmospheres and how you can get clouds
made of rubies. Now, we all here on the
Earth know that it can be cloudy from
time to time
I'm British so I actually love clouds
which is quite helpful but actually
every single planet in our solar system
which has a stable atmosphere has clouds
of some kind
now that can be from sulfuric acid
clouds of Venus which would melt your
skin and it's not a very nice place to
go all the way out to Jupiter's ammonia
clouds swirling around creating storms
that we can see through our telescopes and even
Pluto, the second largest dwarf planet
in our solar system which the New
Horizons spacecraft flew by in 2015 and
saw that it had an atmosphere and in that
atmosphere there were clouds. So it comes
as no surprise that there are clouds
absolutely everywhere. Our question then
comes to exoplanets. What are their
atmospheres like, what are they made off
and do they have clouds of their own? Now you'd think
that that's a normal question. We have
clouds in every atmosphere so why don't
they
now the difference between our planets
and some of the planets that were
looking at is that they're very very
alien indeed. Now one of these planets
that we look at is called a hot Jupiter. Now
to imagine this I want you to think of
Jupiter, the largest planet in our solar
system, it's mostly made of hydrogen helium
it's a gas giant 11 times the size of the Earth
Now what I want you to do is I want you
to put that planet, that giant planet, right
next to the Sun, 20 times closer to the
Sun than the Earth is. That means that
one side of the planet is incredibly hot
in fact it's so close to its star that
it becomes tightly locked. There is a
permanent day side and a permanent night
side we see the same thing with our Moon.
The Moon is tidally locked to the Earth, we only ever see
one side of it. So it's this kind of rotation
that we're seeing with these planets: a
permanent day side and a permanent night side.
So in these atmospheres can you see clouds at all?
What are their atmospheres going to look
like?
To do this we use a method called
transmission spectroscopy which is
looking at the starlight that is filtered
through that planet's atmosphere before it reaches our telescopes. So we can see
this here on Earth when an astronaut on
the International Space Station takes a
really beautiful picture of our planet
and the Sun is behind the Earth. Now this is the light that is being
filtered through the atmosphere - that's
essentially what we're doing with
transmission spectroscopy. We're looking
at that star's light as it filters through its
planet's atmosphere before it reaches
our telescopes. Now the best way to do
this is with the Hubble Space Telescope
and that's because it's outside of our
own atmosphere so you are not having to
look through the Earth's clouds to see
anything. So what we're doing is we're
looking at the transmission spectrum
of the light filtered through the planet's
atmosphere across multiple wavelengths
over multiple colors to build up a
picture of what they're made of. And what
we're finding is absolutely astonishing
every single planet is different and
that's because light interacts with
different materials in different ways
and different environments change how
those materials react to the light. So
if there's a cloud in the atmosphere it's
going to scatter the light in a very
specific way and that's its fingerprint,
that it's fingerprint on the spectrum
and that's what we're looking for.
Now in these really hot planets, over
2,500 degrees in the atmosphere, that's hotter
than sitting under a rocket when it
takes off, at that temperature everything
should be a gas so how can clouds form?
Clouds made of liquids or solids so
we're looking for this light being
scattered what we're finding is that
even in these very hot atmospheres there
are clouds. And that's really interesting
because that narrows down what they might be
made of. One of the coolest things that
they can be made of one of the hottest
materials that will form a cloud is
something called corundum. It's an
aluminium oxide which actually forms
the basis of rubies and sapphires here
on Earth. So imagine that clouds in an
atmosphere of a giant planet close to its
star made of rubies!
Now these rubies essentially scatter
light in a very specific way which we
are able to measure with Hubble and in
the future with the James Webb Space
Telescope, which launches in 2018, we'll be
able to see
these fingerprints of these different
materials in the atmosphere and actually
be able to prove, or give a better
indication, of exactly what those
materials like. And there's a whole host
of other strange materials making up
clouds and exoplanet atmospheres all the
way through to liquid glass raining down in
some exoplanets and down to these
sulphur-based yellowish materials. So
there's so many alien planets and
atmospheres out there there's a huge
amount for us to explore and I'm really
excited for the future of exoplanet cloud studies. So thank
you for watching and if you want to do
anything to do astronomy then please
subscribe to the Cool Worlds channel.
And! Hannah forgot to say that you should
also check out the exocast podcast, which
Hannah runs, which has all the latest news about exoplanets in the Universe. So check that out!