Seeing Stars Horizon

Out there, hidden from the naked eye, is a universe we barely understand.

There are stars being born,

black holes, perhaps even new forms of life...

But now, astronomers are able to see the cosmos as never before.

They are creating a new breed of super-telescope of unprecedented power and clarity.

We have, at our disposal, tools that have never existed before in the history of mankind.

We're the first ones to get to look at this,

you know you don't actually realise how special a time this is.

This revolution in telescope construction promises a new age of discovery.

Right now is an extremely exciting time to be an astronomer, to be an engineer

building telescopes, because the questions keep multiplying.

The answers keep coming too, but the questions come even faster than the answers.

Engines start at 7.15, we'll taxi out at 7.25.

At the ends of the Earth, astronomers are trying to capture

light that has travelled from the farthest reaches of space.

So we're taking it to the Chajnantor Plateau.

The air density's about 50% of that at sea level.

So gloves on, hat on, oxygen happening...

more or less ready for the Chilean desert.

Together, they are reinventing what a telescope is and what it can do.

And they are rewriting the story of the universe.

The Atacama Desert, Chile.

Hardly any vegetation, moisture or life.

Mountains here have received no rain in living memory.

They reach up over one and a half miles into dry, cloudless skies.

Throughout history only death awaited those who ventured here.

Until now...

This is La Residencia.

But this is no luxury hotel...

and the people here no ordinary tourists.

This is the desert home from home for astronomers

hunting for the most mysterious and elusive objects in the Universe.

It's very exciting to be out here in the desert, and what we are actually doing here is,

we are looking for a very particular object in our own galaxy, we're looking for a black hole.

To locate this black hole, astronomers will be using

one of the most powerful telescopes ever built...

..the VLT - the very large telescope.

This, quite simply, is the most advanced optical instrument ever constructed.

The VLT is made up of four main telescopes.

Each contains identical glass ceramic mirrors -

the largest ever manufactured.

This is what it takes to spot a black hole.

But it's not going to be easy, even with the VLT.

A black hole...

the dense remains of a dead star...

has such a strong gravitational pull that nothing can escape... even light.

A black hole collects all the light

so from a certain distance from the black hole

no light can escape any more,

so in that sense you cannot observe a black hole, because it's black.

To locate it, astronomers will be searching for clues in infrared light...

light which lies just outside the visible part of the spectrum.

It is why the VLT is in the Atacama.

You need the most advanced facilities to observe this

and to do so, um, you need also very certain sites

that are dry for example and so this desert here

is just the perfect place for such research.

Dry air is vital...

atmospheric moisture filters out infrared light coming from space.

By building their telescope above the clouds on a desert mountain top,

astronomers hope for the clearest possible view.

It's now late afternoon.

Inside the four telescopes, engineers are preparing for the coming night's observations.

These 23-ton mirrors are fully automated...

and will be programmed in advance.

This 530 square-foot surface can observe objects

four billion times fainter than can be seen with the naked eye...

ideal for finding a distant black hole...

As the engineering shift ends, the black hole hunters' shift begins.

Gunther and his colleague Andreas will be working through to dawn.

To find the black hole, they need still, clear dry skies...

and this appears to be the perfect spot.

These are the clearest skies on Earth.

Here tens of thousands of stars can be seen twinkling overhead.

But if you're looking for a black hole this represents a problem...

Because in space, stars don't twinkle...

To find the black hole, the astronomers in the control room have to get rid of this distortion.

So what we see here is a stellar image and we see it hopping back and forth,

and that is because the light from the star, comes to us,

through the atmosphere of the Earth.

And we would like to ideally get rid entirely of this motion.

Here at the VLT, engineers have devised a way of doing this.

In the heart of the telescope they prepare to create a star of their own.

It will be used to calculate how atmospheric distortion affects the view of space.

A laser is fired into the upper atmosphere.

It interacts with sodium atoms,

creating an artificial star 60 miles above the desert.

The ever-shifting image of the artificial star

is used to constantly correct the telescope optics

to create a stable view through the moving atmosphere.

Back in the control room, the black-hole hunters are still hard at work.

Theirs is a world fuelled by strong coffee.

Yes, to be here at, 4.30 local time, in the morning, is very exciting.

Er, because, um, this is what it is about to be an astronomer.

We are sitting here looking at the phenomenon we are interested in

and of course you have to go home to analyse your data, and to interpret the data.

And to try to understand what is going on.

But beyond that, you know, you simply see the phenomena.

And that is what all the excitement is about.

It might look like any other office, but here they're closing in on one

of the most powerful and elusive objects in space.

So here we have an image of the central region of the galaxy,

and it's actually taken in the infrared, its size is about 300 by 100 light years.

The stellar density is highest here, this is where the heart of the Milky Way is located,

that's what we're interested in, and we can now zoom into this region,

and this is actually a slice taken at the centre of the galaxy.

Over here you see a small cluster of high velocity stars,

they are orbiting this spot here.

These orbiting stars emit vast quantities of gas.

And it's the behaviour of this gas that holds the key to the location of the black hole.

If we have a massive black hole and gas coming towards it, it's going to

be accreted around the black hole and may form a so-called accretion disk.

So this is then hot gas orbiting the massive black hole.

So the light coming from that region, tell to us astronomers this actually here,

at the centre of the Milky Way,

this object is the location of a massive black hole.

It's a clever piece of detective work.

This insignificant-looking dot pinpoints the supermassive black hole at the very heart of our own galaxy.

It might not look like much

but these few pixels in reality cover an area about 27 million miles across.

The black hole they orbit is thought to be four million times heavier than our own Sun.

Well, studying black holes and doing astro physics, brings you basically to the limits of understanding.

It brings you to the limits of how we can describe the world that we're living in.

So in the process of understanding our world, telescopes are very important,

because they basically represent the eyes with which we look at the universe.

It's 7am, and the astronomers head down the mountain.

The power and optical resolution of these new supertelescopes

are revealing a previously invisible universe.

How many cups of coffee do you think you drank last night?

Um, indeed when one stays up so long, uh, one has to maintain your concentration

and so coffee is a good way to do so, so I had four or five cups of strong coffee.

First of all, I'm very happy because, uh, not only

the weather was very good now, but we also could see the black hole.

That was a very successful night, yes. It was exactly what we wanted.

Tired, Andreas?

Yeah. I'm actually tired.

So, I'm looking forward to having this breakfast and then go to bed.

Few people come off shift having seen the supermassive black hole at the centre of our galaxy.

Just over a decade ago such observations would

have been impossible as telescopes like the VLT simply didn't exist.

At 8,600 feet on top of this desert mountain

the VLT can capture vast amounts of infrared light from space.

But not all of it.

The atmosphere filters out the rest, even up here in this dry air.

To capture this missing light, astronomers have to get their

telescopes higher than this mountain top.

Much higher.

Palmdale, California.

If it's altitude you're after, there are few better place to come than here.

Flight 58. Another ten-hour jaunt Northwestern United States tonight.

It's the beginning of a long night for astronomer Professor Terry Herter.

Engines start at 7.15. We'll taxi out at 7.25 and take-off is planned for 7.45

and we'll land at approximately 6am.

-Aircraft status?

-Good, it's fuelled.

We do have the crew oxygen issue, but it's been checked.

Tonight, Terry and his team

will be trying to look inside distant nebulae...

the cosmic dust clouds where stars are born and die.

OK, so we're going to start with an old friend we've already observed this on a couple of flights.

This is Frosty Leo. This is a nebula in the Constellation Leo.

It's known as a Frosty Leo as it's got

ice lines at 43 and 63 microns.

To see into these mysterious places, the team will be hunting for infrared light.

Unlike visible light, infrared can escape the dust that shrouds a nebula.

But to capture this light requires a most unusual telescope.

Meet SOFIA.

Suffice to say, this is no ordinary jumbo jet.

This plane has been given a one billion-dollar makeover.

What began as a conventional airliner is now the world's largest mobile

astronomical observatory, with an infrared telescope beneath the bulge.

That's all I got. Let's go! Thank you.

It's now late afternoon.

This is only the third major research observation flight for the team.

This is the first ever mission to be filmed for television.

On board, technicians are completing their preparations.

To capture the faintest infrared light they have to overcome a significant challenge.

They have to stop the telescope from observing itself.

When you operate in the infrared part of the spectrum, everything around you emits light.

And for our instrument to detect light from space,

we have to prevent it from basically seeing itself.

It emits light itself if it isn't very cold.

So essentially the colder something is, the less light it emits.

By super-cooling the telescope, the technicians will prevent it from blurring its own images.

They are making it about as cold as is scientifically possible.

Our instrument is actually being cooled down

to a temperature just four degrees above absolute zero,

about minus 273 degrees centigrade. Very, very cold.

With the telescope now cryogenically cooled, the team are getting close to take-off.

For Terry, it's a unique role - no other observatory like this exists.

Airborne observing is rather unique.

It's hard to explain quite how different it is to an astronomer

who's never been in this, been in this seat.

You don't want to waste any time, we're in the air burning fuel, you want to be as efficient as you can.

It's sort of funny, I don't get to worry about what goes right

usually, I'm worried about what's going wrong and how can I fix it.

By 7pm SOFIA is ready for take-off.

For the next 11 hours the team will be flying an arc-shaped course

as their celestial targets move across the sky with Earth's rotation.

'Three, two, one...'

'NASA 747 heavy contact Los Angeles, 127.1. You have a good flight!'

This mission is taking SOFIA far higher than jumbo jets usually fly.

SOFIA and her 17 ton-telescope is heading for the stratosphere.

132.6.

Here, nearly eight miles above the planet,

she will be above 99% of the water and gases in the atmosphere.

At this altitude, the star hunters can make infrared observations

which are impossible for ground-based telescopes.

This is, er, what shall I say? This is eye candy

for scientists that we're dealing with.

Tonight, the team are searching for infrared light telling the story of the origin and destiny of stars.

So we're actually looking at the case where a star is dying, and throwing out stuff away

from it. And so we're looking at the...what's called an outflow, or the dying stage of a star.

It's crucial research.

The way stars die will influence those born in their place.

The dots we're seeing on the screen right now is a star which is dying,

OK, the name of it is Frosty Leo.

It's called Frosty Leo because there's actually water ice associated with it.

So Frosty.

The specific nature of this research is what makes SOFIA's capabilities so important.

Detecting water out among the stars is actually not as easy as you might think.

It's very abundant, but because our atmosphere has so much water in it, it's hard to actually observe.

So that's why we're in an aeroplane above this, so we can detect some of those types of objects.

But the technical challenges don't end here.

Observing dying stars thousands of light years away

from the back of a moving aeroplane is easier said than done.

It requires the most sophisticated engineering.

This telescope is actually quite amazing, in the sense that we are flying in an aeroplane which

moves through the atmosphere, which shakes up and down and moves around.

But it can track on the sky and point to an object, and keep it fixed there,

with tremendous accuracy.

Once locked onto a celestial target, the telescope stays steady.

This isn't the telescope moving inside the plane

but the plane moving around the telescope.

Navigating this flying telescope is a unique challenge.

So we're going to go this way until we get to San Antonio, Texas.

As the Earth rotates, the apparent position of their celestial target is constantly changing.

They have to ensure SOFIA is always in the right spot to see it.

People ask, "Where, are you flying tonight? "And I say, "I don't know.

"The United States."

Right now to let you know exactly where the aeroplane is, we are at 41,000 feet,

we are flying at point 0.85 mach, about 550 miles an hour and,

right now we're just over Jackson Hole, Wyoming and, er we're heading on a south-easterly heading

along our desired track to keep the celestial body of interest in the field view of the telescope.

It's now four o'clock in the morning.

Back in economy class the astronomers have observed

a stellar nursery in the direction of the constellation Cassiopeia.

What we're looking at here is a region where new stars are being born.

This region is a little over probably about 2,000 light years from us

in distance so we're looking at it in back about the time of the Romans,

that's when the light originated from here.

And what we see here are not only the stars themselves but there is

gas and dust left over from the birth of the stars.

This dust provides a crucial clue to how new stars might form.

The important part about this is basically that

the stars themselves when they're born affect their environment,

which in turn affects the next generation of stars.

And so this may help to create other stars in the area being born, or it may actually help

to keep them from being formed.

'NASA 747 full stop.'

That's affirmative.

Observing a distant nebula during a bumpy night-flight

in the back of a jumbo jet is a remarkable achievement.

SOFIA doesn't have the magnification power of the VLT, yet her ability to reach the stratosphere

means that she can capture certain infrared wavelengths that never make it to the ground.

But just like the VLT, she will never capture a complete picture

even at 41,000 feet infrared light coming from space can't be seen in its full intensity.

To observe this, astronomers have to take their telescopes to the final frontier.

'Three, two, one...'

April 24th 1990.

'Lift off of the Space Shuttle Discovery'

NASA's newest, most ambitious space telescope was launched.

'One minute thirty seconds into the flight.

'13 miles in altitude, 50 miles down range, travelling at almost 2,000 miles per hour.

Hubble was transported to near Earth orbit, 347 miles above the planet.

And it's still up there, sending back images that have changed our view of the universe.

But all this so nearly never happened.

After launch, Hubble's mirror was found to be faulty...

a problem only solved with repairs made from the space shuttle.

The inspiration and lessons

learned from Hubble couldn't be clearer for engineers in Los Angeles.

They're working on one of the most advanced telescopes ever - the James Webb Space Telescope,

possibly the ultimate exploration machine.

It will take infrared pictures to probe the biggest cosmological questions.

How do galaxies actually form,

how do they form those spiral shapes?

We don't know why.

Could life evolve in other places in the solar system?

Could life evolve in other places in the galaxy or in the universe?

Is there other life out there? I mean, how much bigger can you get than answering that question?!

The team's ambition is breathtaking.

But if controversies over the 6.5bn price tag

don't derail the project, their greatest discoveries might be those they least expect...

Certainly with the Hubble space telescope, the things that

we said, the reasons why we should do it and what we would find,

what we actually found blew the doors off anything that we had imagined before.

And with James Webb telescope, we're just creating a capability,

we're opening a door to view the cosmos that could never be opened any other way.

This time though there will be no second chances if things go wrong...

All right, are you guys ready?

Just watch out, all the edges. And make sure you're pulling correctly.

And just stop if you see anything, OK?

Because once launched, the telescope and its distinctive

3,200 square foot sun shield will be completely beyond reach.

The James Webb space telescope is actually being put in an orbit

at what we call an L2 orbit, or a Lagrange two orbit, and basically this is a point in space,

it's about a million miles away from Earth.

We're talking a long way away, we can't get to this one.

The telescope and its reflective sun shield will be located at the L2 point

so as to be far removed from sources of infrared light, which might blur its pictures.

The sun shield should protect the telescope from any infrared energy that remains.

What you're seeing here is one layer of the sun shield.

When it deploys out, it's about the size of a tennis court, but the thickness of it

is only about the thickness of a human hair, which is about one to two thousandths of an inch.

The finished product will consist of five layers, each coated

with silicon to reflect infrared energy away from the optics.

Nothing like this telescope has ever been attempted.

But perhaps even more remarkable is that the team behind it

aren't entirely sure what it might discover.

I think what's really amazing is that you build this instrument,

you invent all these new technologies,

you have some of the most amazing people in the world contributing,

and once you have this instrument operating in space,

you have no idea what you're going to find.

I think it's fair to say that telescopes open up the unexpected.

That's the main reason we're sending this up there,

is to see what we don't know is out there.

We can never predict the magnitude of discoveries we can make as we go

and open up previously closed doors into the cosmos, into astronomy.

We're expecting to see the formation of stars, and galaxies,

and first light, and we have an idea of what this might look like,

models, but we don't really know,

and that's why we have to send this up there, because if we don't, we'll never know.

The latest infrared telescopes are ushering in a golden era in astronomy.

These observatories have already started to rewrite the story of the universe.

But despite their technical ability,

they will only ever contribute a single chapter, not the whole book.

To do this, requires telescopes that can capture other types of light,

and examine the clues that this light contains.

Back in the Atacama Desert, the quest for different forms of light

is driving one of the most ambitious science projects on Earth.

I think there's the potential to get a whole new window on the universe,

to get a way to see into the biggest mysteries and to start to probe

the ultimate origins of the universe.

The questions are as big as they come.

But the answers lie in the most inaccessible

and invisible parts of space.

Some of the biggest mysteries are the cold and dark places in space.

If you look right back to as close as we can see to the Big Bang,

those are the regions where the first galaxies are forming.

But it's very hard to see those regions

because of the gas and dust that they're actually forming from.

Very little light can escape these frozen dust clouds.

Yet some does make it through.

It is known as submillimetre radiation.

The problem for astronomers is that this form of light

has less energy than infrared, making it harder to spot.

To stand any chance, they need a radically different style of telescope.

Well, it's very difficult to capture submillimetre light,

because of the technology that's required, we need incredibly sensitive instruments to do it,

you need a large telescope because the radiation is, is very, very weak

and that radiation finds it very, very hard to get through the Earth's atmosphere,

and so we go to the highest, driest places on Earth to do that,

and it's one of those places that we're going to right now.

At 9,500 feet, on the side of a mountain

in the centre of the driest desert on Earth, Lewis and his team have built a telescope factory.

Here, they are manufacturing large quantities of giant antennas...

a necessity for capturing enough of the faint submillimetre light.

What's so special is the way that all these antennas will be used together.

But that won't happen here.

They now need to be moved.

This is, you might say, a pick-up truck or a jeep

is a 4x4 vehicle. This is a 28x28 vehicle.

It's 8am on a Monday.

The start of a busy week.

The science doesn't happen here.

Although we've got something like 20 antennas around us at the moment,

this isn't really where the observatory is.

The antennas themselves, in order to do astronomy, get taken 25km from here,

nearly two kilometres higher up than we are at the moment,

which gives us a fantastic view on the universe.

So we're taking it to the Chajnantor Plateau, which is very close

to the triple border point between Chile, Argentina and Bolivia.

The elevation is about 5,000 metres.

The air density's about 50% that of sea level,

so we're taking it to a place where

there's basically very good astronomical observatory conditions.

It will take three hours for the transporter to cover the 15 miles

up to the 16,500 ft high plateau.

For every foot gained in altitude, air density and temperature fall.

This is extreme astronomy.

Having now ascended 3,600 feet, the team are approaching a danger zone.

It's time to check their oxygen levels.

OK, we're on the way to the high site now, up at around about 4,000m,

and because of the altitude, my blood oxygen level will be dropping,

so I'm just going to stop and check

how that's going, I know it was about 95% saturation when we started off at the 3,000m site.

So it's actually pretty good now, it's at about 90, my pulse rate

is up a bit, but oxygen level at 90 is very good.

We try and always make sure that it stays above 80 as absolute minimum.

Mistakes made here could be fatal.

It can be very dangerous if your oxygen levels drop too low.

The biggest issue for us for the project is your ability to think clearly drops off.

People can have acute problems, so certainly people do die of severe altitude sickness.

By midday, the team reach the plateau.

It's the perfect location for gathering submillimetre light.

The antennas here have over three miles less air to look through than if they were at sea-level.

But at this extreme altitude, oxygen is an immediate concern.

We've arrived at the high site now, we're on the Chajnantor Plateau, an altitude of 5,000 metres.

The oxygen levels here are around about half what they are at sea level,

so I can feel the difference now, it's pretty cold outside

but I can also feel that my oxygen levels are dropping.

Whoa!

It's freezing up here now!

I think the temperature's probably close to zero.

And there's a pretty strong westerly wind blowing.

So with the wind chill, that takes it well below zero.

My oxygen levels have been dropping down into the 70s, which is really not high enough.

Open the oxygen bottle, turn the flow rate down.

It'll help me to concentrate,

and help me think, and make me feel a bit better than I do just now,

then get the cannula in.

Not the best fashion accessory you've ever seen, but it works.

The whole team are now on oxygen.

Without it, operations of this complexity wouldn't be possible.

Placing the antenna on the pad is an intricate task requiring full concentration.

Those pads have precision ridges on them, three ridges,

and they'll lower the antenna onto those ridges, being very careful

about the positioning of the antenna.

The combination of the skill of the operator and precision of those ridges means

that we can locate this antenna to within around about a millimetre of a known position.

Precision is vital.

Each antenna is just a small part of a giant array, known as ALMA.

When it's finished, 66 dishes will operate as one -

the equivalent of an antenna ten miles across.

A vast area is needed to capture enough submillimetre light.

To enhance observations, the array can be reconfigured

by relocating individual antennas.

The effect will be like a camera zoom lens.

When we have the antennas spaced very close tougher, that gives us the ability to see large structures

in the sky. We can then move those antennas further out

onto different pads, and make a larger single telescope

comprised of those individual antennas,

and that gives us the ability to see finer and finer detail.

The complexity and scale of ALMA

is a measure of the soaring ambitions of 21st-century astronomy.

Never in human history

have we been able to see so far out into the universe with such accuracy.

I think there is something very special about what we get to observe

with these sorts of instruments.

They don't always produce pictures in the way that we think of the sky,

but they produce amazing insights into what's really out there

and they help us understand, not only how the universe

is created, but they also do really, I think, satisfy our sense of wonder about our place in that universe.

I'd really hope that in a few years' time, once ALMA's been in operation for a while,

that it will have started to reveal the key science

that we built it for, but I also am completely convinced

that what ALMA will do, like all great observatories, is that it will detect things

we haven't even predicted we'll be looking for.

It'll be those complete unknowns, I think, that'll revolutionise our understanding of the universe.

But despite the wonder they reveal, even the most advanced telescopes

like this can only provide a partial picture of space.

Astronomy now is becoming what we call a panchromatic science, really,

you have to combine the information from different wavelengths,

from different types of technologies and different observatories.

And that's really where the great advances of astronomy

and our understanding of the universe are going to come from.

Now, the very first panchromatic view of the Universe is coming together,

a breakthrough driven by the 21st-century renaissance in telescope construction.

This is our nearest galactic neighbour, Centaurus A,

seen in visible light.

It's a striking image, but an incomplete one.

When seen in the infrared, dust clouds begin to emerge.

In ultraviolet light, it's clear that these clouds are the nurseries

for thousands of bright young stars, all rotating around a central point.

But to understand this requires X-ray imaging,

which shows high-energy jets coming from the centre of the galaxy,

the location of a supermassive black hole.

But even here, the picture isn't complete.

This radio image shows how the jets energise particles deep in space,

creating vast radio pulses stretching out over millions of light years.

The invisible has been made visible by a combination of telescopes

working across the vast spectrum of light.

But to fully understand the universe takes more than this -

it requires a fundamental shift in what telescopes actually look for.

Most people think that astronomy is about collecting light,

but actually it's a lot more than that.

Millard County, Utah.

I think we are getting into an age

where the old astronomical observatories, the classical ones

that we're all familiar with, with optical telescopes - although they'll continue on,

will gradually simply become part of a much larger set of instruments.

Astronomers have always been collecting light,

they're making bigger mirrors to look further into the universe.

But there's another way to go, and that is to look at

other kinds of energy that the universe is producing.

Here, Professor Pierre Sokolsky has built a new kind of observatory.

It's designed not to look for light, but subatomic particles.

So here we are in the middle of this desert

full of mosquitoes, and we're approaching what appears to be

a rusty hospital bed, really kind of a piece of junk if you look at it,

and yet it's part of a multimillion dollar experiment

that consumes the passions of hundreds of scientists.

It might not look like it, but this is a telescope.

Part of one, at least.

So we have an array of these detectors, they're about 500,

507 of them exactly, they're spaced by about 1.2km,

and it's a rectangular array which covers this whole basin.

The detectors lie in wait for an elusive particle

first seen by astronauts on their historic first mission to the Moon.

'Tranquillity Base, Houston.

'Roger, go ahead. You're cleared for take off.

'Roger, understand. We're number one on the runway.'

21st July, 1969.

Neil Armstrong and Buzz Aldrin blast off from the Moon.

They now face a long and perilous journey back home.

'Roger, we got you coming home...'

Only 24 men in history have been this far from Earth.

Nearly all of them reported what Armstrong and Aldrin saw next.

Here, beyond Earth's protective magnetic field,

the astronauts started seeing stars.

Even with their eyes shut.

Bizarre dots and flashes of light rippled through their vision.

Only later did scientists work out that these phenomena

were probably caused by particles called cosmic rays

passing through the vitreous humour, the gel between the lens and retina

in the astronauts' eyes.

One of the marvellous things about cosmic rays

is that they're really messengers -

they're actually pieces of matter from distant galaxies,

so they're a marvellous gift to us to study.

These intergalactic messengers are constantly bombarding our entire planet.

But to this day, an essential mystery remains unsolved -

nobody knows which objects in the universe produce cosmic rays.

To find out, astronomers here aren't trying to catch one directly -

they're trying to spot its effects.

So when a cosmic ray hits the atmosphere, it produces what's called an air shower.

That's a bundle of billions of particles that travel very near the speed of light,

across the atmosphere and hit the ground, and this is actually what these detectors detect.

Under the metal cover is a plastic layer...

the equivalent of the vitreous humour in the astronauts' eyes.

It absorbs then releases energy from the air shower

as a detectable flash of light.

But it's one thing to observe the arrival of a cosmic ray,

quite another to pinpoint its origin.

It's very difficult to track down the origin of cosmic rays

just with this equipment, and the reason is

that we're looking at the very tail end of this shower of particles

produced by the cosmic ray.

So it's a bit like describing an elephant by looking at its tail,

you really have to see the whole object, and to see the whole object,

we need to look high in the atmosphere

and see what's happening as that cosmic ray travels through the atmosphere.

To achieve this, Professor Sokolsky is relying on another type of detector.

This is an air fluorescence telescope.

It captures the flicker of ultraviolet light

which is produced as cosmic rays travel through the atmosphere.

So we have three such detectors, one here, one twenty kilometres

in this direction, one twenty kilometres in this direction.

So by triangulating the position of this cosmic ray, we can then figure out what angle it came from

and extrapolate that direction back onto the sky, to see -

is there an object that it came from?

The current theory is that cosmic rays

come from jets streaming from the region around supermassive black holes.

When you're looking at that, at those edges, at those frontiers, you very often discover

the inadequacies of your understanding,

and in that process learn something new about the laws of nature.

So, revolutions occur very often in step with revolutions in technology,

revolutions in scientific thought.

Since Galileo first turned his telescope

to the heavens four centuries ago,

new technology has driven our understanding of the cosmos.

It's a tradition that continues today,

even in the most unlikely locations.

The world of telescopes doesn't get much stranger than this.

Here in France, astronomers are beginning to redefine what a telescope actually is.

Dr Paschal Coyle is sailing for one of the most unusual telescopes in existence.

We're just now leaving the port of Toulon in the South of France,

the telescope is located 40 kilometres off shore.

The Pourqois Pas is heading for ANTARES, a telescope designed

to spot the most elusive and mysterious cosmic particles of all -

neutrinos.

Neutrinos are a bizarre elementary particle,

they have no charge, they essentially have very little mass,

so they interact very little with matter.

So we have to build telescopes which are enormous to have even

the smallest chance to detect just a handful of neutrinos.

Detecting a virtually invisible particle is a real challenge.

But if the team's telescope can spot one, and work out where it came from,

they might rewrite the rules of the universe.

So the boat has now reached the site of the telescope,

and it's located 2.5km below the boat.

Everybody is preparing the submarine to be deployed.

A telescope on the bottom of the ocean might sound strange,

but that's only the start.

Because the telescope this remotely-operated submarine is heading for

doesn't look up into the Mediterranean skies,

but down through the planet.

It's all due to the incredible properties of the neutrinos themselves.

Somewhere far out in the universe, we expect there are sources of very high-energy neutrinos.

The distances are enormous, they can be millions and billions of light years away.

If we're lucky, some of these neutrinos will come close to the Earth, and pass through

the atmosphere, in Australia, pass right through the centre of the Earth, through the core of the Earth

without really even noticing it's there.

Having passed through the entire planet, the neutrino will bump

into an atom of seawater, causing a flash of light.

The telescope, strings of light-sensitive detectors suspended in the ocean,

will spot this light.

Or so the astronomers hope.

The name of the game with neutrino telescopes is to essentially make

a neutrino sky map of the universe.

This search for the slippery cosmic neutrino represents a significant scientific challenge.

Their slipperyness is what makes them so valuable.

They pass through cosmic obstacles, revealing the hidden universe beyond.

Observing one requires not only immense scientific and engineering prowess,

but also a large helping of luck.

And today, luck is in short supply.

A cable connector here on the telescope on the seabed is jammed.

Normally a broken connector isn't such a major problem.

When it happens 2.5km under the sea, it's almost a disaster.

It's a long night for the team in the control room.

But despite their best efforts, the connector remains jammed.

Another mission will be needed.

Beneath the waves, the telescope is still operational.

But in over three years of searching, the neutrino hunters haven't found a single cosmic neutrino.

Yet their enthusiasm and optimism remains undimmed.

We are convinced that these elusive neutrinos are there, we don't really know how big a detector

we actually need to be able to find them, so maybe it'll happen that we

won't find any, in that case we will try to build a bigger ANTARES,

so we have plans to build a new detector which will be 50 times bigger than Antares.

This is the story of how great discoveries happen.

Nobody really knows what the team might end up discovering.

History has shown that every time we look at the universe in a new way,

we have had expectations of what we might see, but in fact

the most interesting things were the things we didn't expect.

This is the true power of telescopes.

Many no longer look like telescopes,

but their ability to change our view of the universe places them

among the most intellectually explosive instruments ever made.

The 21st-century renaissance in telescope construction

will answer the greatest questions in cosmology,

and pose new ones.

It's very exciting to be an astronomer right now.

We have telescopes in space, we have telescopes at mountaintops,

we have telescopes in airplanes.

I certainly can't imagine a time when we would be done asking questions.

I can't imagine that as human beings we'd ever be there.

I know sometimes people feel insignificant or small

when they think about astronomy, and they think about the cosmos.

And I think it's amazing that we are the people,

we are the species who are able to understand how we got here.

And that's not small, that's pretty amazing.

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