Neutron Star

 Neutron Stars are one of the most extreme and

violent things in the Universe.

Giant atomic nuclei,

only a few kilometres in diameter,

but as massive as stars. And they owe their existence to

the death of something majestic

Stars exist because of a fragile balance.

The mass of millions of billions of trillions

of tons of hot plasma are being pulled inwards by

Gravity and squeeze material together with so much force

that nuclei fuse.

Hydrogen fuses into Helium.

This releases energy which pushes against gravity and tries to escape

As long as this balance exists,

stars are pretty stable

Eventually, the hydrogens will be exhausted

Medium stars like our Sun go to a Giant phase

where they burn Helium into Carbon and Oxygen

before they eventually turned into White Dwarfs.

But in stars many times the mass of our Sun,

things get interesting when the Helium is exhausted.

For a moment, the balance of pressure and radiation tips

and the gravity wins - squeezing the star tighter than before

The core burns hotter and faster while the outer layers

of the star swell by a hundreds of times,

fusing heavier and heavier elements.

Carbon burns to Neons for centuries,

Neon to Oxygen in a year, Oxygen to Silicone in months

and Silicone to Iron in a day

And then, death.

Iron is nuclear ash. It has no energy to give

and cannot be fused

The fusion suddenly stops, and the balance ends.

Without the outward pressure from fusion, the core is crushed

by the enormous weight of the star above it

What happens now is awesome and scary

Particles like electrons and protons

really don't want to be near each other

but the pressure of the collapsing star is so great

that electrons and protons fused into neutrons

which then get squeezed together as tightly as atomic nuclei

An iron ball the size of Earth is squeezed into

a ball of pure nuclear matter the size of a city

But not just the core, the whole star implodes

Gravity pulling the outer layers in

at 25% the speed of light

This implosion bounces off the Iron core

producing a shockwave that explodes outwards

catapults the rest of the star into space.

This is what we called a Supernova explosion

and it will outshine entire galaxy

What remains of the star, is now a Neutron star

Its mass is around a million times the mass of the Earth

but compressed to an object about 25 kilometres wide

It's so dense that the mass of all living humans

would fit into 1 cubic centimetre of Neutron star matter

That's roughly a billion tonnes

in a space a size of a sugar cube.

Put another way, that's Mount Everest

in a cup of coffee

From the outside, a Neutron star is unbelievably extreme

Its gravity is the strongest outside Black Holes,

and if it were any denser, it would become one

Light is bent around it - meaning you can see the front

and parts of the back

Their surfaces reach a million degree Celcius

compared to a measly 6,000 degrees for our Sun

Okay, let's look inside a Neutron star

Although these giant atomic nuclei are stars,

In many ways, they're also like planets

with solid crust over liquid core

The crust is extremely hard

The outermost layers are made of Iron leftover from the Supernova

squeezed together in a crystal lattice

with a sea of electrons flowing through them

Going deeper gravity squeezes nuclei

closer together

We find fewer and fewer protons as most merged to neutrons.

Until we reach the base of the crust

Here, nuclei are squeezed together so hard that they start to touch.

Protons and neutrons rearranged

making long cylinders or sheets

Enormous nuclei with millions of protons and neutrons

shaped like spaghetti and lasagne, which physicist called Nuclear Pasta

Nuclear Pasta is so dense,

that it maybe the strongest material in the Universe - basically unbreakable

Lumps of pasta inside a Neutron star can even make mountains

at most a few centimetres high

but many times as massive as the Himalayas

Eventually, beneath the pasta, we reach the core

We're not really sure what the properties of matter are

when they're squeezed this hard

Protons and neutrons might dissolve into an ocean of quarks

a so called quark-gluon plasma

Some of those quarks might turn into Strange quarks

making a sort of Strange matter, with properties

so extreme that we made a whole video about it

Or maybe they just stay protons and neutrons

No one knows for sure and that's why we do Science.

That's all pretty heavy stuff, literally

so let's go back out into Space

When neutron stars first collapse, they begin to spin very very fast

like a ballerina pulling her arms in

Neutron stars are cellestial ballerinas

spinning many times per second.

This creates pulses because their magnetic field creates a beam of

radio waves, which passes every time they spin

These radio pulsars are the best known type of Neutron star

about 2,000 are known of in the Milky Way

These magnetic fields are the strongest in the Universe

a quadrillion times stronger than Earth after they're born

They're called Magnetars until they calm down a bit

But the absolute best kind of neutron stars

are friends with other neutron stars

By radiating away energy as gravitational waves

ripples in space-time, their orbits can decay

and they can crush into and kill each other

in a Killnova explosion that spews out a lot of their guts.

When they do, the conditions become so extreme

that for a moment, heavy nuclei are made again

It's not fusion putting nuclei together this time,

but heavy neutron-rich matter falling apart

and reassembling

Only very recently, we've learnt that this is probably

the origin of most of the heavy elements in the Universe

like Gold, Uranium, and Platinum and dozens more

So then our two neutron stars collapsed and become a black hole

dying yet again

Not only does stars have to die to create elements,

they have to die twice.

Over millions of years, these atoms

will mix back into the Galaxy, but some of them end up in cloud

which gravity pulls together to form stars and planets

repeating the cycle

Our Solar System is one example, and the remains of those

neutron stars that came before us

are all around us

Our entire technological modern world was built

out of the elements neutron stars made in eons passed

sending these atoms on 13-billion-year journey

to come together and make us and our world

And that's pretty cool

Until then, we can look them on paper

The 12,020 year human space era calendar

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Get it for Christmas for your friends, families and kids

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