-
Neutron stars are one of the
most extreme things in the universe.
-
They’re like giant atom cores.
-
Kilometers in diameter,
unbelievably dense and violent.
-
But how can something
like this even exist?
-
The life of a star is dominated
by two forces being in balance.
-
Its own gravity and the radiation
pressure of its fusion reaction.
-
In the core of stars, hydrogen
is fused into helium.
-
Eventually, the hydrogen
in the core is exhausted.
-
If the star is massive enough,
helium is now fused into carbon.
-
The cores of these massive
stars become layered like onions,
-
as heavier and heavier atomic
nuclei build up at the center.
-
Carbon is fused into neon, which leads
to oxygen, which leads to silicon.
-
Eventually, the fusion reaction hits iron,
which cannot fuse into another element.
-
When the fusion stops, the
radiation pressure drops rapidly.
-
The star is no longer in balance,
-
and if its core mass exceeds
about 1.4 solar masses,
-
a catastrophic collapse takes place.
-
The outer part of the core reaches
velocities of up to 70,000 km/s,
-
as it collapses towards
the center of the star.
-
Now, only the fundamental
forces inside an atom
-
are left to fight the
gravitational collapse.
-
The quantum-mechanical repulsion
of electrons is overcome,
-
and electrons and protons
fuse into neutrons
-
packed as densely as an atomic nucleus.
-
The outer layers of the star
are catapulted into space
-
in a violent supernova explosion.
-
So, now we have a neutron star!
-
Its mass is between 1 and 3 Suns,
-
but compressed to an object
about 25 kilometers wide!
-
And 500,000 times the mass
of Earth, in this tiny ball
-
that’s roughly the diameter of Manhattan.
-
It’s so dense that one cubic
centimeter of neutron star
-
contains the same mass as an
iron cube 700 meters across.
-
That’s roughly 1 billion tons,
as massive as Mount Everest,
-
in a space the size of a sugar cube.
-
Neutron star gravity
is pretty impressive too!
-
If you were to drop an object from
1 meter over the surface,
-
it would hit the star in one microsecond
and accelerate up to 7.2 million km/h.
-
The surface is superflat, with
irregularities of 5 millimeters maximum,
-
with a superthin atmosphere of hot plasma.
-
The surface temperature
is about 1 million kelvin,
-
compared to 5,800 kelvin for our Sun.
-
Let’s look inside the neutron star!
-
The crust is extremely hard
and is most likely made of
-
an iron atom nuclei lattice with a sea
of electrons flowing through them.
-
The closer we get to the core, the more
neutrons and the fewer protons we see
-
until there’s just an incredibly dense
soup of indistinguishable neutrons.
-
The cores of neutron stars
are very, very weird.
-
We are not sure what their properties are,
but our closest guess is
-
superfluid neutron degenerate matter
-
or some kind of ultradense quark
matter called quark-gluon plasma.
-
That does not make any sense
in the traditional way
-
and can only exist in such an
ultraextreme environment.
-
In many ways, a neutron star
is similar to a giant atom core.
-
The most important difference is that atom
cores are held together by
-
strong interaction
and neutron stars by gravity.
-
As if all this wasn’t extreme enough,
-
let’s take a look at
a few other properties.
-
Neutron stars spin very, very fast,
young ones several times per second.
-
And if there’s a poor star nearby
to feed the neutron star,
-
it can rotate up to several
hundred times per second.
-
Like the object PSRJ1748-2446ad.
-
It spins at approximately
252 million km/h.
-
This is so fast that the star has
a rather strange shape.
-
We call these objects pulsars, because
they emit a strong radio signal.
-
And the magnetic field of a neutron star
-
is roughly 8 trillion times stronger
than the magnetic field of Earth.
-
So strong that atoms get bent
when they enter its influence.
-
Okay, I think we got the point across.
-
Neutron stars are some
of the most extreme,
-
but also some of the
coolest objects in the universe.
-
Hopefully, we will one day send spaceships
to learn more about them
-
and take some neat pictures!
-
But we shouldn’t get too close!