Original subtitles

Our Universe is violent, deadly.

Cosmic bombs are everywhere.

And the most crazy, intense, violent explosions

you can imagine are happening out there.

The Sun spits flares millions of miles high.

Magnetic monsters rip worlds apart.

Galactic flamethrowers

fire gamma rays halfway across the Universe.

It's like a cosmic blowtorch.

The energy of these things is unimaginable.

Mega-flares light up the Universe.

They illuminate hidden secrets.

They're also a threat.

If you're in the line of sight, watch out.

Our planet is under attack

from colossal, cosmic firestorms.

Do these deadly mega-flares threaten life on Earth?

How the Universe Works 2x04 Megaflares Original Air Date on August 1, 2012

== sync, corrected by elderman ==

An ordinary star field,

but home to one of the most extraordinary stars

in our galaxy.

8.7 light-years from Earth, this is UV Ceti.

This mysterious object

can grow five times brighter in less than a minute.

Any planet circling this star would be blasted by the heat,

quickly melting its frozen surface.

Then, just seconds later, the sun dims.

The planet retreats into icy darkness.

But UV Ceti is about to go way further.

The star begins to brighten, but this time, it doesn't stop.

A runaway inferno, in just 20 seconds,

it gets 75 times brighter than normal.

UV Ceti has unleashed a mega-flare...

...an immense explosion of energy on the star's surface.

If our Sun fired off a mega-flare like this...

...we'd be toast.

If you were standing on the surface of the Earth

and the Sun were to get 75 times brighter,

even for only a minute or two,

it would really probably be the last thing you'd ever see.

The temperature on the Earth would rise up.

We'd have huge fires. It would just basically cook everything.

Earth is a long way from UV Ceti.

We're safe from that particular star.

But the more stars we study...

...the more flares we find.

They fire in all directions...

...sometimes, directly at us.

The closer a star is to Earth, the greater the danger.

And one star is way closer than all the others.

Our Sun looks stable and calm.

But behind the glare...

...the Sun is a monster.

Solar observatories capture the violence.

Flares erupt across its surface...

...gigantic explosions on an unimaginable scale.

One flare, one of the most energetic flares

on the surface of the Sun would be equivalent

to over 200 million hydrogen atomic bombs.

It's enough energy

to power the entire human race's energy consumption

for something like 2 million years.

Each flare is as bright

as 400 billion trillion light bulbs.

But the visible light

is just a fraction of the energy it emits.

Radio waves...

Infrared heat...

Ultraviolet light...

even X-rays...

...unleashed in every flare at incredible intensities.

These are the biggest explosions in the solar system...

...yet the force behind them is simple...

...magnetism.

The Sun has an immense magnetic field.

The energy stored in this field powers solar flares.

Vast loops of magnetic force push toward the surface.

Huge magnetic arches rise out into space.

When two field lines cross,

it triggers a magnetic short circuit.

This is a solar flare.

All the energy trapped in the magnetic field

blasts out at 100 million degrees.

It can hurl hot gas

a billion miles out into space...

...an eruption 10 million times more powerful than a volcano.

Magnetism -- the same force that powers a simple compass

fuels the biggest explosions in the solar system.

Yet by cosmic standards, our Sun is puny.

As we look out into space, we see even more active stars,

even more intense magnetism,

and then things really start to get wild.

There are stars and objects

in our galaxy and in other galaxies

that produce flares of great intensity --

so great, they would literally destroy all life on Earth

if they were nearby.

Outside our solar system,

titanic explosions rock the cosmos

on a scale we can barely imagine.

Far beyond the sun, we enter the realm of mega-flares.

Our Sun is violent.

Flares explode with the force of billions of atomic bombs.

But travel out into the cosmos,

and the explosions get bigger.

Other stars have flares so huge, they're planet killers.

EV Lacertae is 16.5 light-years from Earth.

Every day, flares erupt on its surface.

But one mega-flare smashed every record.

The star blasted out 10,000 times more X-rays

than the sun's most powerful flare.

The ultraviolet light was so intense,

the star turned blue.

This stellar firestorm 100 trillion miles away

was visible from Earth with the naked eye.

If our sun flared like this, we'd be incinerated.

But EV Lacertae is a very different kind of star.

Compared to our sun, it is tiny.

This is a red dwarf.

Red dwarfs are stars that have much less mass than the Sun.

They could be a tenth to about four-tenths the mass of the Sun.

They're smaller. They're cooler. These are dinky stars.

They burn so slowly that, unlike our Sun,

which will last 10 billion years,

some of them will last 10 trillion years.

They're also relatively cold.

Their surface is just 5,000 degrees Fahrenheit --

half the temperature of our Sun --

and 10,000 times dimmer.

Yet somehow, they're capable of staggering violence.

That's because red dwarfs are immensely magnetic.

The fields which form inside them are enormous,

much more powerful than our suns.

That means the magnetic-field energy

that can be released when those fields get twisted up

is incredibly intense.

And even though these objects are very dim in visible light,

they can produce flares

that are thousands of times more energetic

than those released by the Sun.

You wouldn't want to be near one of those when it went off.

All red dwarfs flare violently,

but EV Lacertae's flares are off the chart.

That's because it's young -- just 300 million years old...

...15 times younger than our Sun.

In one way, stars are a little bit like people.

They're hotheads when they're younger.

When stars are first born, they're spinning very rapidly,

and that actually helps generate magnetic fields, as well.

The result --

a star 100 times more magnetic than the Sun.

When its giant loops cross, the mega-flare is colossal...

...a torrent of radiation lasting 8 hours.

Big flares on our Sun

have the energy of billions of atomic bombs.

EV Lacertae's monster flare was 10,000 times more powerful.

Incredibly, even these massive flares

are just a flicker on the cosmic scale.

There are eruptions millions of times brighter...

...explosions that can light up a whole galaxy...

From a tiny star with unimaginable power.

This is the Australia telescope compact array --

a network of five radio dishes

constantly listening to the cosmos.

In 2004, they were struck by a massive blast of energy...

...evidence of a mega-flare.

But this was bigger than any we had witnessed before...

...the largest burst of power ever recorded from our galaxy.

The object behind it is truly bizarre --

a kind of star we didn't even know existed

until a mega-flare gave it away.

I've studied black holes. I've studied stars that explode.

I've talked about rogue planets wandering the galaxy.

For my money, the scariest single object in the galaxy

is a magnetar.

Magnetars are the most magnetic objects

in the Universe.

And this one beats them all.

Its magnetic field

is 1,000 trillion times stronger than our sun's.

If it came near our solar system,

the effects would be devastating.

The first thing you would notice is its magnetism

would wipe every credit card in your pocket.

As you start to get closer,

anything metal on you would be ripped away --

your earrings, your jewelry.

Once you got within a few million miles of the magnetar,

its magnetism would be so intense,

it would actually disrupt the electrical signals

in your nerves, and your heart would stop beating.

Get even closer, and the magnetism would be so intense,

it would rip apart every atom in your body.

Amazingly, this vast magnetic field

comes from an object no bigger than an asteroid.

Our Sun is close to a million miles across.

The magnetar, just 10.

But it's unimaginably dense.

It weighs more than the Sun. This is incredible.

Take the Sun and squeeze it down

not just to the size of the Earth,

but down to the size of Manhattan.

The entire mass of a gigantic star

packed into a space the size of a city.

You could almost walk around the star in a day,

except you couldn't, because the gravitational field

is so intense,

the density of material on these stars is so great,

that a teaspoonful of material

weighs several thousand billion tons.

You would be crushed beyond recognition in a moment.

Dense and compacted, the iron-rich crust

is under incredible magnetic pressure.

Something has to give.

Fissures rip across the surface.

The crust splits open --

a starquake.

It's like an earthquake on Earth,

except the crust literally moves a half an inch.

It's just a little, tiny shift,

but that is a huge amount of energy

because of this intense gravity.

It's like a magnitude-30 earthquake.

A flare erupts from the fracture.

A trillion-ton cloud of ultra-dense matter

blasts into space.

It lasts just a tenth of a second.

But it unleashes more energy

than the Sun emits over 250,000 years.

The energy emitted when one of these flares

from a magnetar is released --

in some cases, more than a billion times

the energy emitted by the Sun.

Mega-flares are time machines.

They show us events from long ago.

This magnetar is 50,000 light-years from Earth.

The flare we observed in 2004

actually happened 50,000 years ago.

It took that long for the light

to travel halfway across the galaxy

and slam into our atmosphere.

If a similar mega-flare exploded near Earth...

...we wouldn't even see it coming.

We would have no warning

if a magnetar were to have another flare like this.

The event is so sudden on the surface

and it creates so much energy,

it blasts out at the speed of light,

and nothing can travel faster than light.

So, basically, this just happens, and that's it.

Any life within 10 light-years of the blast

would be vaporized.

Thankfully, even the closest magnetar

is too distant to threaten us.

We can't see them,

even with the strongest telescope.

We've only detected these stars in the flash of a mega-flare.

Yet these explosions are dwarfed

by an even more powerful monster.

Second only to the Big Bang in scale,

this is the ultimate mega-flare.

7.5 billion years ago,

many galaxies away...

...a supergiant star is in trouble.

Its nuclear core has run out of energy.

It's about to implode.

For a few seconds, the colossal blast shines

a million times brighter than our entire galaxy.

This is the most extreme explosion in the Universe...

...a gamma-ray burster.

Gamma-ray bursters are so powerful

that they can be seen across the entire universe,

second only to creation itself.

Two intense jets of energy shoot out.

These two beams of gamma rays are the ultimate mega-flare.

The energy of these things is just unimaginable.

It's the entire power

that the Sun puts out over its entire 10-billion-year lifetime,

focused into just these two things

that last for maybe a few seconds.

It's like a cosmic blowtorch of gamma rays and matter

that march across the Universe.

The most high-energy, intense light

is gamma rays.

Gamma rays are naturally produced

by things that are billions of degrees hot.

There will never be a hotter type of flare.

This is where it stops. Gamma rays is it.

7.5 billion years

after the explosion actually happened,

we see it in our skies...

March 2008.

A flare from halfway across the entire Universe

shines even more brightly than the closest star.

Something blew up 7 billion light-years away

that you could see with your unaided eye on a dark night.

That should tell you something.

It is the biggest flare ever witnessed.

But it is also a sign...

of the birth of the most destructive entity

in the Universe.

A black hole has formed

in the core of the collapsing star.

It consumes the star from the inside out.

When the star finally explodes in a catastrophic supernova,

all that remains is a newborn black hole.

Usually when we look in outer space,

we see old black holes --

black holes that have been around for millions of years.

But to see a baby black hole being born --

that is an incredible event,

and that's what we think is a gamma-ray burster.

Amazingly, these gigantic explosions are common.

We see more than 350 a year.

We see them every day.

Our satellites detect them every few hours

in all directions outside the Milky Way galaxy.

Gamma-ray mega-flares reveal

one of the Universe's most awesome secrets --

a new black hole is born every single day.

Most of these explosions happened a long time ago,

far away from Earth.

But if one went off inside our galaxy...

...it could be catastrophic.

If you were to put a gamma-ray burst

100 light-years from the Earth...

...it would be like igniting a one-megaton nuclear bomb

over every square mile of the surface

of the Earth facing that event.

You would be blowing up millions and millions of nuclear weapons

over the planet.

It would be the end of all life on Earth as we know it forever.

Gamma-ray bursts

are the most powerful mega-flares in existence,

but not the most dangerous for us.

The greatest threat to Earth sits terrifyingly close,

right at the heart of our own solar system.

We were once blissfully ignorant,

safe in our solar system.

Now we know Earth sits in a cosmic firing range.

Monster mega-flares are everywhere we look.

But the deadliest cosmic weapon of all

is right on our doorstep...

...our Sun.

We're lulled into thinking that the Sun is static,

it's benevolent, and is our friend.

Wrong.

The Sun is dynamic.

In some sense, it's alive.

It creates magnetism on a scale

that we can only begin to comprehend.

And its most powerful weapon is this --

a coronal mass ejection, or CME.

A colossal solar explosion rips a chunk of the star away

and torpedoes it out into space.

Coronal mass ejections are related to flares,

but they're even larger.

You can sort of think of it

as a solar flare being like a tornado --

very powerful, very intense, very short-lived.

And a coronal mass ejection is like a hurricane --

much more energy, much bigger, and can last for days and days.

CMEs start with a magnetic short circuit.

Magnetic arcs emerge from the surface...

...glowing with trapped solar matter.

The loops cross, triggering a firestorm of energy.

The Sun erupts.

Solar matter explodes from the surface out into space...

...a monstrous cloud

of super-hot gas and electric particles.

When one of these huge prominences is shot out,

an energy equivalent of about 10%

of the entire luminosity of the Sun for a second

is released towards the Earth.

Over 10 billion tons of material is shot out

at a speed of over a million miles an hour.

The power of a coronal mass ejection

is sort of mind-numbing.

It takes our probes years to get from the Earth to the Sun.

A coronal mass ejection

can cross that distance in a couple of days,

sometimes in only a couple of hours or even faster than that.

So these are tremendously powerful events.

Powerful, but also deadly.

Because sometimes, the Sun shoots a CME

straight toward the Earth.

The crackling, charged cloud

plays havoc with our electronics.

It melts power grids, blows fuses,

and disrupts communications.

But that's nothing compared to the damage

that a really big CME could do.

They can wipe out satellites, GPS, the Internet.

All sorts of havoc can take place

when this huge Tsunami hits the Earth.

The damage to satellites alone

would total $100 billion.

Think of a blackout that hits not just one city,

but hundreds of cities around the planet Earth.

Property damage would be about $2 trillion.

We're talking about perhaps

a collapse of modern-day civilization.

We can be thrown back perhaps 50, 100 years into the past

into a world without electricity.

Big solar storms are rare.

On average, a massive CME strikes Earth

every 500 years.

But it's happened before...

And it will happen again.

In 2003, we had one of the largest

coronal mass ejections ever recorded,

but fortunately, it missed the Earth.

One of these days, it's gonna hit the Earth.

One of these days, one of these rifle bullets

will be aimed right at the Earth,

and at that point, watch out.

Our planet is under attack...

...not just from mega-flares in deep space...

...but from our own star.

The Sun fires billions of tons

of hot gas and electric particles

into space every day...

...deadly solar weapons...

...sometimes pointing straight at us.

What I find amazing is the fact

that the Earth is in the middle of a shooting gallery.

But we have survived this onslaught.

We are protected.

The earth has a magnetic field.

It's incredibly weak, but enough to keep us safe.

Think of an ordinary magnet

that you use on your refrigerator.

That has more magnetism than the Earth's magnetic field.

Without our magnetic shield,

every CME would strip away Earth's atmosphere,

and we'd be fried by solar radiation.

How do we know?

Because it happened to one of our neighbors.

Look at Mars.

Mars is an example of what happens

to a planet without a magnetic field.

Mars is a frozen desert

with an atmosphere

only 1% the atmospheric density of the Earth.

It's because it lacks a magnetic field.

Over billions of years, these particles

have actually stripped away Mars' air,

and that's why it has a very thin atmosphere now.

Here on Earth, we have a magnetic field, and we have air.

This is not a coincidence.

So we can breathe because of our magnetic field.

From Earth's surface,

safe beneath our magnetic umbrella,

we see the power of our violent Sun

in the northern and southern lights.

Trillions upon trillions of electric particles

strike the earth every second.

The magnetic shield funnels them to the poles.

They energize gas molecules in our atmosphere,

making them glow --

a chemical light show.

Oxygen shines green.

Nitrogen, blue or red.

The aurorae are evidence of a battle between magnetic fields.

The Sun's field creates CMEs.

Earth's field shields us from them.

Magnetism is nature's most mysterious force.

Only now are we beginning to understand

how it shapes the cosmos.

Mega-flares make magnetism visible.

They shine a light

on the incredible power of magnetic fields...

...fields that play a fundamental role

in the Universe.

They impose order on chaos.

They weave their way

through the spiral shapes of galaxies...

...fields hundreds of thousands of light-years across,

yet 100,000 times weaker than Earth's.

Smaller magnetic fields exist inside galaxies.

They organize matter into clouds of molecules --

spectacular nebulae.

These stellar nurseries are where new stars are born.

Now we've discovered magnetic fields

even permeate empty space...

...fields created in the Big Bang

with just one quadrillionth the strength of Earth's.

This is a magnetic universe.

What's amazing is this thing

that's invisible -- magnetic fields --

play such an important role in every aspect of the Universe,

protecting us from the radiation from the Sun

to explosions and red dwarfs, to magnetars,

and to the most energetic, violent processes

in the entire Universe -- gamma-ray bursts.

Magnetism plays a role on every scale of the Universe,

changing the dynamics of objects

and making the universe a violent and interesting place.

Mega-flares light up the cosmos.

They show us things we can't otherwise see

from the other side of the Universe...

...or from billions of years in the past.

A black hole is born.

A star dies.

Distant events and hidden mysteries.

In a flash, flares reveal them...

...illuminating the awesome secrets of the Universe.

== sync, corrected by elderman ==

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