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My name is Stephanie Bernard
I'm a PhD student at the University of Melbourne, here in Melbourne
and I'm just going to talk to you today
a little bit about what I do as a PhD student
and I'm going to talk to you about our Solar System
and how we can find planets around other stars
apart from our own Sun.
A little bit about me...
as I said, I'm a PhD student at the University of Melbourne.
I grew up in Newcastle in New South Wales
which is at the top right of the screen
and when I was in primary school
I was really interested in maths and science
and especially in astronomy
so I wanted to know what are all the stars... out in sky.
We can see some planets in our sky
but also more further afield
are there other galaxies?
What do they look like?
What sort of stars do they have?
Is there life out there?
All these sorts of things.
I was lucky enough when I was in primary school
to go to Parkes, to the radio telescope there
which isn't shown on this map
it's a bit further north
and there there's a really, really big radio telescope
64 metres across...
and that was when I really decided I want to do astronomy,
I think this is really, really cool.
When I was in high school, I moved to Melbourne
and then when I finished high school
I went to university
and I studied physics.
Physics is... kind of how we look at the Universe, as a whole.
So we want to look at
what are the fundamental properties of the Universe?
What are all of the atoms that are in our bodies?
All of the electrons that give us electricity
how do they work, what's happening with them?
As we go out into the Universe
we want to know
what are the laws that govern
how everything in the Universe happens
like gravity, electromagnetism, all these sort of things.
So I thought physics was really cool at university
and I kept studying, I did a Masters
which is like a high level undergraduate degree
and then I started doing a PhD
which is where I do, basically just research,
so my work is on galaxies
and I'm looking at a very first galaxies that formed in the Universe.
If we look at galaxies at different distances from us
what we're actually seeing is galaxies that are further away.
We have this speed of light
which is really, really fast
but Space is really, really big
and we'll look into this a bit later with the Solar System.
So it takes time for light to reach us
so when we look at the very, very furthest things
we're actually seeing them really, really far back in time
and we can look at the first stars
which formed around 100 million years ago.
They're a little bit too far for us to see with current telescopes
We can see some of the very first galaxies
only 500 million years after the Big Bang
and you can see on the timeline here
from the Big Bang, which is the beginning of the Universe, to now
it's been 13.7 billion years
so we're really looking at baby galaxies in that very early Universe.
They're really, really small
but they're really hot and interesting to look at.
A bit closer to home
let's talk about our Solar System.
When we look at our Solar System
we have a number of different... what we call bodies, in it
and this is a little picture of what they all look like.
We have the Sun in the centre
and the Sun is our closest star.
Then from closest into furthest out, we have Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
and in the very edges of the Solar System,
it's not a planet anymore,
but we have Pluto.
When we look at the Solar System
we tend to classify the planets
into two different types.
We have the inner planet which are Mercury, Venus, Earth and Mars
and they're much smaller
you can kind of see in this image that they're really hard to see, actually.
They're made of rocks,
some of them have water like the Earth
and then as we go further out
the planets get to be a bit bigger
and they're made up of what we call gases
so they're not solid like the Earth is
they don't have a proper surface.
So they're much bigger,
they tend to have a lot more moons,
they also have rings.
So we know that Saturn...
this is a little one I brought from home...
has a beautiful ring system.
Actually, all of the outer planets have rings
most of them are just too faint for us to see with our eyes.
If we go into a bit more detail
and we look at our Sun.
Our Sun is our local star
it's a star like all the others in the sky
it's just really, really close to us
so we can see it really clearly
and we get a lot of light and heat from it
and actually, all the light and heat that we get from the Sun
is made in the core of it.
We can't see the core
it's really, really...
it's in the centre of the Sun.
What we see is its outer atmosphere
and we know that the Sun is really, really big.
It's around 100 times the diameter of the Earth
where the diameter is basically how far across it is.
So if you had our Sun...
and we have our Earth in the very corner...
you might not be able to see it
you can actually fit 100 Earths across the Sun.
Actually the Sun is really, really big.
If you fit them all inside
you could fit a million Earths inside.
This is our Earth...
and our Sun is behind me
so they're not to scale, as you can see
I've just told you that this is 100 times smaller than this...
and if we had a million of these we could fit them all inside the Sun.
Our Sun is made of gases like the outer planets
but because the Sun is making its own energy, on the inside
it's really, really hot so the surface of the Sun is around 5,000 degrees.
That's hot enough to melt metals
it's actually hot enough to vapourise some metals.
Usually you see metals in forms like my phone
where it's a solid
and so imagine this is just a gas
it's very, very hard to imagine
but the Sun can do that.
If we want to look at whether we can have life on planets
which is something that astronomers want to know about
well... planets that are closer in to the Sun they tend to be hotter
because they're getting more of the light that the Sun is emitting.
If we look at our closest planet in to the Sun, which is Mercury
I have a visual here...
On the screen is a video
which was taken by a satellite that's orbiting Mercury.
You can see that it's got lots of crater
which are... kind of pock marks on its surface
where rocks and asteroids have hit Mercury
over billions of years that it's been around.
Mercury is the closest planet to the Sun
and actually, it gets really, really hot because it's so close.
On the surface that's facing the Sun
it's around 450 degrees Celcius
it's really, really hot
and on the side that's not getting any Sun
it's actually really, really cold
because Mercury is too small to have an atmosphere.
Earth has an atmosphere, it's all the air we breathe
the clouds that are in the sky
all these sort of things
and that help to regulate the temperature of the planet
because the heat can travel from one side to the other
but Mercury doesn't have this
so it's both too hot on its side facing the Sun
and it's too cold on the side away from the Sun.
So we don't think it has life at all,
it just wouldn't be able to survive there.
If we go a little bit further out
we might think that it's... further away from the Sun
so it's not going to get as much light and heat
so it's probably going to be cooler.
Actually what we see is that Venus is really, really hot
it's even hotter than Mercury.
The reason for this is because it has a very, very thick atmosphere.
If you look on the left
we have a picture of Venus' surface
and you can see again some craters
you can also see some lines stretching through which are canyons on its surface
but actually what we usually see is the clouds on its surface.
Venus is covered in a very, very strong atmosphere
it has lots and lots of clouds
and they make these kind of... patterns on its surface.
The way that an atmosphere can keep heat in
is called the Greenhouse Effect.
It looks like this, so we have sunlight coming in from the Sun...
It comes out...like this...
and then when it hits Venus
the light can go through its clouds.
Some of it will get reflected, it will bounce straight off
but some of it goes in past the clouds and onto the surface.
When it hits the surface, the light can actually heat up the surface
and then the surface will emit some of the light
so it will send it back out into Space.
Because of the clouds...
the clouds will actually reflect this heat back onto the planet
rather than letting it all out into Space, like it does on Mercury.
So because the clouds are really, really thick
it actually keeps most of the heat that it takes in
and so it gets really, really hot.
So if you're cooking a pizza on Earth
you'd put it on, say 180 degrees Celcius
it would take you about... 20 minutes to get a nice crispy pizza
but if you were cooking it on Venus
you wouldn't even have to put it into an oven
you could just have it on the surface
it would take about nine seconds to cook
so it's really, really hot.
If we go a little bit further out
we get to our Earth, which is our favourite.
So we can see even in this picture that Earth has an atmosphere,
as I mentioned, it's got lots of clouds
it's got lots of water as well.
This is a little Earth ball.
We have planets in green... sorry... we have continents in green
and we have lots and lots of water in blue.
The Earth is really covered in liquid water
that's because it's far away enough from the Sun
that the water doesn't just boil off into Space
and it's far enough...sorry... it's close enough in that the water doesn't immediately freeze into ice.
This is due to our atmosphere.
Our atmosphere keeps the heat in
it means that, firstly, the water doesn't go out into Space
but also, we don't have a very big difference
between the temperature during the day and during the night.
It's only around 10 degrees, if that.
The problem is though,
that if we put more and more, what we call Greenhouse gases
which increase the amount of heat that we keep in
our Earth is going to keep warming and this is a really bad thing
because it will melt all the ice, like in beautiful Antarctica, down the bottom.
So this is something that scientists are working on at the moment.
How do we stop the Earth from warming up too much?
Yeah.
If we go out to the further parts of the Solar System
we get Mars.
Mars is our beautiful red neighbour.
It's much smaller than Earth, it's only around half the size of the Earth
and because it's so small
it only has a very, very thin atmosphere
so it actually can't keep liquid water
but we know that it has ice water
so actually at its poles...
we can see on this little... inflatable version
we have some ice caps
and it's possible that during the past, when the Sun was hotter,
this ice might have been liquid.
So Mars might have had life on it at some point in the past.
As we go even further out
we get into the gas giants.
I've said that they don't have a solid surface that we can stand on.
What we actually see is that
they're really just made up of big balls of gas.
So they have clouds in their upper atmosphere
and this is a video taken by the Voyager satellite back in the 70s
and this shows you just how much is happening in the atmosphere of Jupiter.
We have big cyclones
and this, that you can see in the bottom part of the screen,
is actually the Great Red Spot
and this is... two or three times the size of the Earth
just a huge cyclone revolving around.
The other outer planets are similar
they're made up of gases
but they have lots and lots of moons
and what we think is that most of the moons now in that atmosphere...
and Jupiter has four very big ones
they have a layer of ice on them
because they're really, really far away from the Sun.
But actually under this ice they might have these... underground oceans
and so it's possible in these oceans that there might be life forming...bacterial...
But we do see life in very, very extreme conditions on Earth
like in really, really hot places
in the ocean, and also in really, really cold places
we still see life forming
so it's possible that, even though Jupiter the planet can't actually have life,
maybe its moons do.
Yeah, this is a...
we're sending satellites out to Jupiter
to look at both the planet and its moons
and we need to be really, really careful when we send satellites out there
that they actually don't hit the moons
because we don't want bacteria that might have escaped from Earth
to get onto these moons,
just in case there's something there that we could kill off with our nasty bacteria.
We have one more planet, well, one more body out in the Solar System
and this is called Pluto.
You might have heard of Pluto as being a planet
and up until 2006 it was
but actually it's really, really small.
If we put it next to the Earth
you can see that it's much, much smaller that the Earth
and actually it's only around the size of the moon.
So the New Horizons probe reached Pluto last year
and it took these beautiful pictures of its surface
which we couldn't see before because it's just so small
that even with our biggest telescopes like the Hubble Space Telescope
it was really, really hard to see
and we couldn't get any sort of idea of what it was actually like
but now we know that it's mostly made up of ice.
It's got some dirt on it
which you can see in the bottom part of the planet.
We also know that in the outer Solar System
there are lots and lots of bodies that are the same size as Pluto or even bigger.
So if we wanted to keep Pluto as a planet
we would have to add in all these other bodies as well...
as well as some asteroids like Ceres
which is in the asteroid belt between Mars and Jupiter
and it would just get very, very complicated
you would have to learn around the names of 20 planets
which is quite a lot.
OK, so we've looked at our Solar System
and we know that in our Solar System
Earth definitely has life because we're here
and then it's possible that Mars in the past might have had life
maybe some moons around Jupiter or even Saturn have life.
It's also possible there are planets around other stars
and so... in the night sky
if we look up we can see thousands of stars.
Actually with the naked eye you can see 10,000 stars
but you have to be in a really, really dark place.
This photo was taken at the Anglo-Australian Telescope in New South Wales
and this is our first...what we call Dark Sky site in Australia.
This means that there's very, very little what we call light pollution
from say street lights or houses that have lights on and these sorts of things
and you can see lots and lots of stars, you can also see the Milky Way
which is passing through the centre of the image
and so this is really our galaxy, where we live.
We're part of the Milky Way
and it's made up of billions of stars.
People started to think, well, our Sun is like a star, like any other
and there are billions of stars in the galaxy
so surely at least some of them have planets around them.
But until the 1990s no one had ever seen some... seen any, actually.
In the 1990s the first one was discovered
but it was really hard to see
and I'll tell you why it's really hard to see.
We can actually get an idea of how we could look for other planets
by using just our own Solar System.
We have the Sun which is letting out its own light
and we have Venus, which is much smaller
and it doesn't let its own light out
the only way that we see Venus is actually the light from the Sun
being reflected towards us.
So if we were in the centre and Venus went between us
it would block off some of the light of the Sun
which is actually what we see in this image.
We have the surface of the Sun
and we have this little kind of hole in the surface
and that's actually Venus getting between us and the Sun.
This is called a transit and it happens every couple of hundred years
when the orbit of Venus is lined up with the Sun.
This actually gives us the idea to look for planets around other stars.
We have to be very lucky though
because...if... we're where my head is
and the Sun is here and the planet is going around this way...
we're never going to see the planet
because it's not actually blocking any of the light from the Sun.
Whereas if it's edge on... like Venus is
then, as it passes across, it will block some of the light.
The most ambitious experiment to do this is called the Kepler Telescope
which is in Space and so the Kepler Telescope
looks at... patches of the sky, for a very long time
it looks at them for years and years
and it looks for... thousands of stars at the same time.
It looks for this signal, which is where a star has a particular brightness
and then as the planet goes across
the brightness of the star changes
and it changes a really small amount
because, as we know, stars are very big
whereas planets are very, very small.
So it's only, maybe a percent or something, that the brightness changes
but we can actually still see this if we look for a long enough time...
and Kepler has been really, really successful.
It's found thousand and thousands of planets around other stars
just using this method.
Most of the planets that it finds
are what we call gas giants, like Jupiter or Saturn
because these planets are bigger, they block out more of the light of the star
and we actually find them really, really close into the star
even closer than Mercury is
which isn't something that we thought would happen.
We thought that planets the size of Jupiter and Saturn
they would have to form out further from the star
than we see with these planets.
So this is a really interesting discovery that Kepler has made.
But it's so sensitive that it can start to find
planets as small as our Sun passing infront of other stars.
These are some examples...
these names are kind of... they don't really mean that much
but you can kind of see the sizes of them
and then compare them to Earth which is on the bottom left.
You can see that actually some of them are around the same size as Earth
but what we want to know is...
OK these planets are very small
but we don't really know what their atmosphere is like
just from this method where we look at the brightness of the Sun.
The next step in looking at what we call exoplanets or planets around other stars
is actually to get an idea of what the atmosphere of these planets is
and with the atmosphere we can look at things like
do they contain water?
Do they contain other chemicals that we know are essential to life?
We know that plants have particular chemicals like chlorophyll
which is used to transfer...carbon dioxide into energy.
So if we manage to see a planet that has some of these signs
then maybe, maybe these planets will have life around them.
Just to finish up, really excitingly...
just in the last couple of months...in August
we actually found that Proxima Centauri
which is the star that's closest to us
it also has a planet.
I say that Proxima Centauri is our closest neighbour
but it's actually trillions and trillions of kilometres away.
So it's not really easy to get there
because if we were going... kind of at the speed of our cars
it would take thousands and thousands of years to get there.
But actually there is a program called Breakthough Starshot
which is building these very, very small robots and satellites
and actually if you send out thousands of these small robots...
they're really, really small so you can make them go really, really fast.
You can make them go around a third of the speed of light.
Proxima Centauri is four light-years away
so if we go a third of the speed of light
it's going to take us around 12 to 20 years to get there.
So that's actually really, really fast.
We're going really, really far, across the Universe
to get to this... star and look at what the planet looks like.
This is kind of our best chance at maybe even...
being able to talk to other planets.
We don't think that there's any life there
because the star that it's around is actually really, really small.
It's smaller than our Sun and it actually lets off very, very large flares.
So if our Sun lets off flares then it can disrupt our electricity
it can let off harmful ultraviolet rays
which will give us... diseases.
So this star is actually probably not very hospitable to life
but it's really, really close
and it's a good way for us to look at other planets in our immediate area
apart from the ones that are in our Solar System.
That's it. Thanks!
Shooting stars are actually very small...
what we call meteoroids that are out in Space
they're really just like grains of sand, most of them.
When they hit the atmosphere
they get heated up really, really fast
and so they let off a lot light which is what we see as the shooting star.
So because these are so small
they're literally just the size of grains of sand, most of them,
they completely burn up in the atmosphere
and... all of the molecules and atoms that would have made them
become part of our atmosphere.
Each individual one is not really... going to affect our atmosphere too much
but actually we pass through tonnes and tonnes of these little grains of sand every day.
Because our Earth is so big
even these tonnes and tonnes of meteorites
that we pass through, they're really not affecting us too much.
Yeah, they're very pretty
but they're not going to harm us at all.
[laughs]
[Voice off screen] Would they leave anything behind in the atmosphere
when they burn up?
[Stephanie] Yeah, I think they would leave aside
whatever they're made of, so usually it's just iron and carbon
and things that are already on the Earth to begin with.
I think it's really interesting.
I like to do research, I get to look at pictures of galaxies most of the day
which is really, really cool
and I also get to look at some of the questions that want to know.
So where did galaxies like our Milky Way come from
because the galaxies that we see in the very early Universe
we think that they merge over time
to become bigger and bigger
and eventually they become galaxies like our own.
Also it's really, really cool to be able to get your problem
and figure out all the different pieces.
Problem solving is really a big part of being a scientist
and especially an astronomer.
So if you like... doing maths
and you get to sit down with the maths problem
and... figure out all the pieces, then that's really good
but even... being more creative...thinking
OK, if I know this, how does that relate to this other thing that I've got?
Being able to think creatively is a really important part as well.
Yeah, I get to use really big telescopes as well...
[Voice off screen] I understand you use computer programming
quite a bit in your work as well.
[Stephanie] Yes, computer programming
is a really big part of doing physics
but also most science, it's really useful to know.
Learning how computers work
and how we can use them to make our lives easier
is a really big part of it.
If I wanted to take...
I have several gigabytes of pictures of galaxies
and I want to know, how do I get the information
from these gigabytes of pictures as efficiently as possible?
I don't want to look at each single pixel of each image
to work out what it's got in it.
I want the computer to be able to look at it and say
OK, this is what you've got
this is what's interesting, let's have a bit of a further look.
Yeah, so it's made of... silicon,
it's made of carbon
it's made of iron
it's made of lots of different metals.
All these things... get mix together in the core
and our core is like the core of the Sun
it's very, very dense and very, very hot.
As we go out in the Earth...
we have this layer called the mantle
which is where all the magma is
and magma comes out of volcanoes, it's lava.
All this silicon and carbon and iron and other metals...
it eventually... gets out onto the surface of the Earth
and then it hardens and becomes rocks.
Different types of volcanoes produce different types of rocks
and also when the... continents shift apart
we get rocks forming there.
All of these are made of slightly different things
depending on... the time that they formed in the Earth's history
yeah, lots of different things
but it's mostly these heavier kind of elements.
[Voice off screen] I've heard that we're actually made out of
an old star, like an exploded star.
[Stephanie] Yes, absolutely... [voice] Is that true?
[Stephanie] Yes, in the beginning, at the Big Bang
there was only hydrogen and helium
and so these are the lightest elements
and we know that, we ourselves are made of carbon
and we're made of oxygen and... iron and all those sort of things
so to get from hydrogen we actually have to have stars
because stars are the only things in the Universe
that are big enough and hot enough
to actually take these very light hydrogen atoms
and they fuse them together to helium.
Helium can fuse into carbon.
Carbon can fuse into oxygen
and so we build up these heavier and heavier elements inside stars, actually.
Once the star dies,
it will let out all of these new elements out into the Universe
and then these new elements get formed into new stars
and eventually into planets like our own.
I said that our galaxy, The Milky Way, contains billions of stars
and we think that, actually, most stars will have planets around them.
Based on what Kepler has found around other stars
we actually think that...
most stars will have at least one planet and probably more.
We know that our own star has eight planets around it.
So in our galaxy there are probably tens of billions of planets
and then our galaxy isn't the only one in the Universe.
In the Universe, there are billions and billions of galaxies
and so each of them is made up of billions of stars
so there are just a huge number of planets in the Universe
and any one of them...
most of them are not hospitable for life
even in our own Solar System
we only know of one that definitely has life
but... even if there's a very small chance
out of billions and billions of planets
and billions and billions of galaxies
it's very likely that there'll be a few that will have some life on them.
When I was your age, as I mentioned,
I went to the Parkes Radio Telescope
and they were playing a video on quasars.
Quasars are...
you know what a black hole is?
It's something that's so dense that even light can't escape.
We know that every galaxy, almost, has a black hole in its centre.
Our galaxy has a black hole in its centre
and that's got the same mass in it as billions of stars
so it's really, really big.
Ours isn't eating anything at the moment
it's what we call passive
it's just kind of quiet and it doesn't do anything
but some galaxies they're actually eating up gas and stars and things around them
and they let out lots and lots of light
and so they had this video on how this happens
and I thought it was so cool
and I was like... there's these things in the Universe
that are just eating up whole stars and gas
and they let out light and we can see them
and so I think that was...
why I decided I wanted to do astronomy. [laughs]
Yes, that's a good question.
Back in the 1990s when I was a kid
we did actually think that...
it was a very plausible possibility that the Big Bang would happen
and the Universe expands
and then if there's enough matter in the Universe
then eventually it would actually start to collapse
so gravity would take over and it would come back in
and cause this big crunch.
Of course in this... the Earth and the Sun would get crushed up as well
and then it might become a new Big Bang
so it might rebound and become a new Universe.
Since then we've actually discovered this thing called dark energy
which is some sort of force in the Universe that's... pulling everything apart.
So the expansion of the Universe is actually accelerating
so rather than going like this.... where it accelerates at a time
it actually starts off small and then it goes...
much, much faster than we thought it was
and in this case, actually, we don't think that there's enough matter in the Universe
in all the stars and galaxies and this thing that's called dark matter
which is most of actually what the matter in the Universe is...
that actually, there's not enough of this
to make it pull back in and become a big crunch
which is a shame because it's a nice idea about how the Big Bang happened.
At the moment we really don't know why the Big Bang happened
all that we know is that
the evidence that we have strongly suggests that we had this Big Bang, in the past,
we just don't know why.
The first telescopes were made in the 1600s.
Galileo was one of the first people to use a telescope
and he discovered moons around Jupiter
Really, kind of, since even the ancient Greeks
we've know that Space is quite large
during that time actually people thought that
the Sun and the other planets and the stars orbited around the Earth
rather than the other way around
where the Earth orbits around the Sun.
But even then...yeah... they knew that
the distance from the Sun to the Earth was really large.
They could work out how big the Earth was
just using trigonometry
which you guys will learn in maths in high school
and just using shadows and how... you know...
how long shadows were at different times of the day
at different times of the year.
Yes, so even 2000 years ago we kinda knew
some of the basic things about the Universe.
Dark matter is... this thing we don't really know what it's made of
but we can see its effect on the Universe.
We can see that... it's certainly affected by gravity
it doesn't really interact with matter
like the atoms in our bodies, or in stars or galaxies.
But we know that when we look at galaxies
there's too much matter in them
so they're rotating faster than they should be...
and we can see actually in galaxy clusters as well
the properties that they have, implies that they have
lots and lots of dark matter in them.
So we can't see it
but we, kind of, can see what it does to the Universe
and we have some ideas what it might be
it might actually be very small black holes.
It might be... planets that we just can't see because they're very, very faint.
Or it might be... more interesting things like
what we call subatomic particles
like smaller than atoms...
even the ones that make up our cells and everything
and that's what... particle colliders
in Europe and the US are trying to find actually.
They send very, very high energy protons at each other
and they look at, is there any kind of mass
that they don't detect from this...
because then they think that maybe
they've actually created dark matter in their colliders.
My favourite planet is Saturn
because it's got these beautiful big rings
and if you get to look at it through a telescope
it actually looks like a picture.
It looks like it's got this... yellow planet
in the centre and it's surrounded by these beautiful rings
and actually, if you have a big enough telescope
you can see there's this gap in the rings
which is formed by some of the moons around it
and it's just very pretty.
[laughs]
It's a bit of a mystery as well
we don't really know exactly how these rings formed.
We thing that they actually must still be forming... as we speak.
Yeah, it's a very interesting planet, I think.
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