BOTH: Hello. Welcome to Herstmonceux Observatory in East Sussex,
with its collection of impressive
and elegant domes. They still have working telescopes here
and enjoy wonderful dark skies, so I'm told, when it's clear.
Well, we hope to enjoy those dark skies a little later with
the Wealden Astronomical Society, but until then,
we're going to talk about the lives and dramatic deaths of stars.
And the team are here too, having a tug-of-war.
We'll find out why later.
Herstmonceux was built after the Second World War
and became a Royal Observatory in 1958.
Many of the telescopes came from Greenwich,
where the London light pollution had become too much.
Sir Patrick Moore was a regular visitor
and supporter of the observatory, using the telescopes
to look at the moon. Here he is in 1984.
Of course, there are some features of the observatory
which everybody knows.
There is, for example, the time department.
And here, the atomic clocks
are now better timekeepers than the Earth itself.
And it's also from here that the six pips come out.
LOUD PIP
Then there are the telescopes of Herstmonceux,
which is another reason for our being here.
In its heyday, 200 astronomers worked here
and they looked at galaxies, nebula and even comets,
but the majority of their work was with the stars.
They mapped the stars in the sky, measured their distances, brightness
and studied the light to see what the stars are made of.
Stars make up a family and, like any family,
the members are different.
Some stars are big. Some small. Some bright. And some dim.
But they're all essentially the same.
They're vast balls of gas, mostly hydrogen.
But the best star to look at is our own - the sun.
And that's because, at the core of the sun, we know that
the temperatures and the pressures are almost unimaginably vast.
That means the atoms there are moving incredibly quickly.
And when they collide, they can fuse together and as a consequence
of the most famous equation - E=mc2 - matter is turned into light.
And that happens at a furious rate. In fact, the sun is losing
nearly 4 million tonnes of matter each and every second.
So that's 4 million tonnes gone.
And another 4 million tonnes gone.
And that's happening all the time, in every one
of the hundreds of billions of stars in our own galaxy.
In fact, as stars go, the sun's not much to write home about.
It's rather Mr Average. And so, it's time we met the rest of the family.
There are hundreds of billions of stars in our own galaxy,
but even from a good, dark spot,
you'll have to content yourself with seeing just a few thousand of them.
Even the largest telescopes won't show a star
as anything other than a point of light, but we do see colour.
Some stars are yellow, like our own sun,
some red, and some blue.
And it turns out that colour's important,
because it tells us how hot the stars are.
Lucie and I have come to a telescope
that's spent many a night staring at the stars.
Fantastic. So here we have the 1896 26-inch Thomson Refractor.
It's beautiful, isn't it? Fantastic.
Always good to see a proper refractor in a giant dome.
This is what observatories are supposed to look like.
And they used to do measurements of star positions from here.
And not just positions.
This telescope was used to measure the distances to the stars.
But that's not the most interesting thing about this telescope.
It does something really special. Let me show you. Come round here.
OK, I'm slightly nervous. SHE LAUGHS
When you start running for...for switches.
Hold onto your hats. OK. Here we go.
LOUD THUD, CHRIS LAUGHS
So we do not have to move the telescope. We go to the telescope.
This is the civilised way to get to your observing position.
Move the entire floor.
This is fabulous! LUCIE LAUGHS
But you need to watch out for your head, Chris. Right, thank you.
I've been told it stops automatically. I'm just going
to keep pressing until it does. Are you sure this stops?
I'm willing... Yes!
There we go. There we go. Perfect.
So what a civilised way to get up to do the observing. It's great.
And now, here we are and we can go look at the sky. Yeah, fantastic!
Over 100 years ago, astronomers were trying to make sense
of the assortment of stars in the night sky.
Two men - American Henry Russell and Dane Ejnar Hertzsprung -
realised that the key was showing
how the brightness of a star is related to its colour.
So what we've got here are the two things we know about stars.
We've got their colour, but colour means temperature,
so the red stars are the coolest
and the blue, white ones are the hottest.
It's the opposite way round from bathroom taps.
Red is cool, blue is hot.
And the other piece of information is how bright the star is.
So faint ones go down here
and bright ones go up here.
So now all we need is to put some stars on our board
and, in fact, we've got some in our pocket.
And the first one that we can put on is the most familiar star - the sun.
And it turns out the sun goes bang in the middle of our diagram here.
Surface temperature of about 6,000 Kelvin,
so halfway along here and then, medium brightness as well.
We can also do the brightest star in the sky and that's Sirius.
And Sirius is a bit hotter and a bit brighter than our sun,
so that goes up here.
The nearest star system to our own is made up of Alpha Centauri.
A bit hotter, a bit brighter than the sun. That has a companion,
Alpha Centauri B, which is a bit fainter.
Put it down there. And then, the nearest star to the sun, Proxima,
red, much smaller, much fainter, so that goes down there.
And then, if we add a few more stars,
we begin to see that they fill in the gaps.
And actually, what's really clear is that all the stars lie along
one line in our diagram and that tells us something really important.
They're all fusing hydrogen to helium in their cores.
That's what's powering them.
It's what we astronomers call the main sequence.
But not all stars sit here.
There are hot bright stars called blue giants, like Deneb,
and then there are the red giants, like Arcturus,
which our sun will become in its old age.
These fuse helium at their core
causing them to swell to enormous proportions.
It's hard to get your head round the sizes of the stars,
but luckily, I've got an onion and I want you to imagine
that this onion is the size of the sun as it is today.
But the sun won't stay that size forever.
When it turns into a red giant 4,500 million years from now,
it will swell up from the size of the onion
to be the size of the dome and that will encompass the Earth's orbit.
And if that's not impressive enough, Betelgeuse,
one of the biggest of the stars,
is so large - ten times larger in fact - that Jupiter's orbit
would fit inside it.
Stars don't collapse because of pressure from the core,
pushing up against gravity.
As the star grows old, these two forces strain against each other,
rather like a tug-of-war.
JON CULSHAW, LIKE A BBC SPORTS COMMENTATOR: 'And you join us here
'for our stellar tug-of-war! We have two teams, Team Gravity,
'an ever present force, trying to pull everything inwards!
'And then, there is Team Star, which has energy and pressure on its side,
'resisting the pull of gravity. Team Star is nuclear!
'They are burning hydrogen and you can feel the heat!
'Team Gravity, though, they never give up.
'They are a force to be reckoned with!'
We stand a better chance of survival if we work together.
'Team Star, quite magnificent, producing just enough heat and light
'to balance gravity! Absolute stalemate here!
TEAMS GRUNT
'But Team Star running out of steam! The hydrogen has all but gone here!
'They are beginning to collapse!
'Team Gravity sensing success here, surely!'
LOUD GRUNTING
'But, but, hang on a minute, deep in the core, things are heating up here!
'Team Star are fighting right back. Suddenly, they're right back in it,
'burning helium, a surge in the energy! Team Star is now a red giant
'and the crowd love it!' CHEERING
'Gravity on the run here, you would have to say, Derek!
'But hold on a minute! Team Star has spent their fuel.
'They have burned up. They're all gone. Nothing left.
'And Gravity continues pulling in and the star collapses.
'It becomes a quite spectacular nebula
'with a tiny white dwarf at its heart.
'Gravity wins the day! Remarkable.'
Eventually, the outer layers of the sun will be expelled into space,
becoming a planetary nebula.
The core, called a white dwarf,
will be all that remains of our once mighty star.
We see lots of planetary nebulae in our night sky.
They are beautiful and ephemeral. The death of a star caught in time.
The most massive stars,
like hot blue Deneb, don't die quietly.
Once their fuel is consumed,
the star collapses
and the result is one of the most violent explosions in the universe.
We call it a supernova.
These cataclysmic stellar deaths can outshine an entire galaxy,
and, in 1987, we were treated to one in a galaxy on our cosmic doorstep -
in the nearby Large Magellanic Cloud.
The object, called Supernova 1987A,
has been studied in great detail ever since,
and astronomers have watched the glowing rings of material
spreading out into the cosmos.
You can see the remnants of supernovae in the night sky
with even a moderately-sized telescope.
Nearly 1,000 years ago,
a blue giant star exploded in the constellation of Taurus.
And we see it today as the Crab Nebula.
The astronomers at Herstmonceux studied these objects and many more.
'Chris North and I are going to see
'how they used to study the light from stars.'
Here, we've got the largest telescope on the site -
the 36 inch yapp reflector.
It's built in the 1930s, moved here in the '50s,
and it's quite a remarkable feat of engineering, isn't it?
It is wonderfully imposing to see it, really arresting as you walk in.
This, of course, adapted for spectroscopy,
so it can decode and specifically study starlight and really tell us
about the signature of stars and show us their uniqueness.
So you can do this with a prism, split the sun's light, or you can
even create the same effect using the back of a CD. Exactly.
But to see the light from other stars that are fainter than the sun,
you've actually got to use a telescope like this to
collect enough light, because they are so much fainter than the sun.
When we do that, we see something quite remarkable in the spectrum.
I imagine this would collect rather a lot of light. Yes.
And give us the chance that we could study it over here. Indeed.
Ah! There was one of these on Mr Dwyer's laboratory wall at school.
They're very decorative, but what do they tell us?
This is the sun, right?
So this is a representation of the light from the sun,
split out into its rainbow, its spectrum of colours.
But there are specific colours that appear much darker
and that's because those colours are absorbed by specific elements in the sun's atmosphere,
so this one, in the red end of the spectrum,
is absorbed by hydrogen in the sun's atmosphere
and there are other elements as well.
We can see that there's small amounts of calcium in the sun's atmosphere
and the small amounts of iron in the sun's atmosphere.
We can start to get a spectral fingerprint
of what the sun is made of. And the chart above.
Now, this is from a blue giant star.
Some of the lines are in a similar position,
but there's a lot that's different about it.
The first thing about the blue giant star is that
it's very bright in the blue, but it's very dim in the red
and that's because the star is much hotter.
The fact that the star's a lot hotter also means that
some of those elements in the atmosphere
are completely stripped of their electrons already.
so we don't see absorption lines, as these are called,
from iron and from calcium and that kind of thing.
We mainly just see hydrogen in the atmospheres of those stars.
So we had the diagram - the Hertzsprung-Russell diagram
that Chris and Lucie were showing us earlier -
and we had the sun right in the middle,
and the hot blue stars up on the top left,
then, down the bottom right, we had the cold red stars.
And this is one of those cooler red stars.
The spectrum's a lot busier.
There's an awful lot more lines in there.
And whereas the atmospheres of these stars, these warmer stars,
are dominated just by atoms in their atmospheres,
in cooler stars, you can have molecules. You can have chemistry.
This is atoms joined together. Molecules absorb light
at many, many more colours than just the pure atoms do.
And if you go to even colder temperatures too,
you get weather.
You certainly don't associate that taking place on a star
and this takes us to that strange world of the brown dwarf.
A very curious object, sort of like a duck-billed platypus, in a way.
Hard to classify exactly what they are.
LUCIE: Brown dwarves are a new addition to our star chart
and are the coolest and dimmest of stars.
Hertzsprung and Russell could only have dreamed
of these strange beasts.
Part of the difficulty has been seeing them,
because they don't shine brightly like our star.
To find them, we need infrared telescopes,
which can pick out cool objects
in the cold, dark parts of space.
We're hoping to see some brighter stars tonight.
Wealden Astronomical Society is resident here
and they've joined us to keep us company.
Gary Palmer likes studying my favourite star - our sun.
Pete's finding out why he enjoys solar observing so much.
It's the perfect thing for the public,
cos it's during the day. That's right, yeah. It's also nicer for me,
cos I keep warmer, so, um... LAUGHTER
No, I've seen some of your pictures and they are spectacular.
You've been looking at the sun today, haven't you? Yeah.
It's been really interesting today. There's some nice detail on there.
There was a nice flare
that came off the edge of the sun earlier on,
and gradually developed into a nice loop prominence. Oh, really?
They're fantastic! It was really nice, yeah, lovely to watch.
And also, a lot of sunspots,
so it seems like there's a lot of activity starting again.
Do you think the sun's starting to wake up a bit? I think so.
About time. Yeah, it's very, very late.
It's a little bit like our summer this year.
JON: So, Paul and Pete, what of the stars in the June sky at the moment?
We're waiting for the clouds to co-operate. It looks like
more are blowing in. It doesn't look promising. Not at the moment,
but at least June is the time for the noctilucent clouds. Ah, yes.
We like those. We do. Pete's obsessed with them.
They're great, because the nights in June are really, really short,
so these are things that are easy to see, if they're there.
They glow with an electric blue light,
like a network of clouds in the night sky.
They're really high altitude clouds, they're picking up
the light reflecting off them from the sun, which is below the horizon.
They're something which are unique to the summertime.
And June also the time of the moon's perigee,
the super moon, as they call it. That's right.
The moon is going to be
a tiny fraction of a bit larger in the sky.
It's actually 23rd of June and it's because the moon
is at the closest point in its orbit. Perigee.
And that coincides with it being full moon this time.
It has the name super moon. That's actually an astrological term.
We won't have such things here! Astrologers brought it in.
Don't mention them again! Let's say perigee moon.
Well, spectacular as that moon will be,
hopefully it won't wash the stars out too much.
So which particular ones should we be looking out for in June?
Well, the lives and deaths of stars, something we've looked at on the programme.
We've got those in the summer night sky,
so let's start with star clusters and the wild duck cluster,
M11, is a good one, isn't it? Lovely, actually.
That's at the bottom of Aquila the eagle.
A little curve of stars points to it.
When you look at it through a telescope...
Even a small telescope will show a beautiful smattering of stars there.
We also have a nice globular cluster.
It's low down in the constellation of Sagittarius.
This is in your teapot asterism, isn't it? That's right.
It's at the heart of Sagittarius,
which sort of marks the region where the centre of the Milky Way is.
It looks exactly like a teapot. Not exactly! Oh, it does!
It's exactly like a teapot. But if you imagine where steam would
rise out of the spout of the teapot, loads of stuff around there.
You've got the Lagoon Nebula, which is one of only two
areas of nebulosity you can see with the naked eye in the night sky.
You've got the Trifid Nebula, which is a beautiful thing
to look at through a telescope. Three dark lanes cuts it into three.
And then, you've also got M22, which is the brightest globular cluster
which can be seen from the northern hemisphere,
and you've got M25, which is another beautiful cluster.
A deep sky treasure trove. It is, absolutely.
Well, there's a fine thing to look out for. June full of promise.
And, hopefully, some clear skies. Yes!
Many fine objects to observe in June, so long as the weather co-operates
and you can use Pete's sky charts to help locate them,
including the teapot and its steam, if you like.
Just go to our website...
We have had no luck with the weather and it's even starting to rain.
Wealden Astronomical Society are packing up.
Let's hope, next time, we come and enjoy Herstmonceux's dark skies.
In the meantime, it's just the ducks and us that are left behind
to enjoy this beautiful and atmospheric observatory.
We've had a great time here at Herstmonceux.
It's been wonderful to see these lovely old telescopes.
And when we come back next month, we'll be celebrating
the summer solstice by launching our Moore Moon Marathon.
We've selected some easy-to-find features on the moon
for you to tick off during those warm summer nights.
And so, until next month...
ALL: Good night.
Subtitles by Red Bee Media Ltd