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
[Kurzgesagt intro]
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
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Get it for Christmas for your friends, families and kids
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12,020
