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Neutron stars are one of the[br]most extreme things in the universe.

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They’re like giant atom cores.

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Kilometers in diameter,[br]unbelievably dense and violent.

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But how can something[br]like this even exist?

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The life of a star is dominated[br]by two forces being in balance.

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Its own gravity and the radiation[br]pressure of its fusion reaction.

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In the core of stars, hydrogen[br]is fused into helium.

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Eventually, the hydrogen[br]in the core is exhausted.

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If the star is massive enough,[br]helium is now fused into carbon.

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The cores of these massive[br]stars become layered like onions,

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as heavier and heavier atomic[br]nuclei build up at the center.

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Carbon is fused into neon, which leads[br]to oxygen, which leads to silicon.

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Eventually, the fusion reaction hits iron,[br]which cannot fuse into another element.

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When the fusion stops, the[br]radiation pressure drops rapidly.

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The star is no longer in balance,

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and if its core mass exceeds[br]about 1.4 solar masses,

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a catastrophic collapse takes place.

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The outer part of the core reaches[br]velocities of up to 70,000 km/s,

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as it collapses towards[br]the center of the star.

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Now, only the fundamental[br]forces inside an atom

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are left to fight the[br]gravitational collapse.

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The quantum-mechanical repulsion[br]of electrons is overcome,

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and electrons and protons[br]fuse into neutrons

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packed as densely as an atomic nucleus.

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The outer layers of the star[br]are catapulted into space

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in a violent supernova explosion.

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So, now we have a neutron star!

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Its mass is between 1 and 3 Suns,

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but compressed to an object[br]about 25 kilometers wide!

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And 500,000 times the mass[br]of Earth, in this tiny ball

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that’s roughly the diameter of Manhattan.

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It’s so dense that one cubic[br]centimeter of neutron star

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contains the same mass as an[br]iron cube 700 meters across.

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That’s roughly 1 billion tons,[br]as massive as Mount Everest,

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in a space the size of a sugar cube.

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Neutron star gravity[br]is pretty impressive too!

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If you were to drop an object from[br]1 meter over the surface,

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it would hit the star in one microsecond[br]and accelerate up to 7.2 million km/h.

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The surface is superflat, with[br]irregularities of 5 millimeters maximum,

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with a superthin atmosphere of hot plasma.

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The surface temperature[br]is about 1 million kelvin,

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compared to 5,800 kelvin for our Sun.

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Let’s look inside the neutron star!

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The crust is extremely hard[br]and is most likely made of

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an iron atom nuclei lattice with a sea[br]of electrons flowing through them.

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The closer we get to the core, the more[br]neutrons and the fewer protons we see

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until there’s just an incredibly dense[br]soup of indistinguishable neutrons.

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The cores of neutron stars[br]are very, very weird.

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We are not sure what their properties are,[br]but our closest guess is

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superfluid neutron degenerate matter

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or some kind of ultradense quark[br]matter called quark-gluon plasma.

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That does not make any sense[br]in the traditional way

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and can only exist in such an[br]ultraextreme environment.

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In many ways, a neutron star[br]is similar to a giant atom core.

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The most important difference is that atom[br]cores are held together by

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strong interaction[br]and neutron stars by gravity.

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As if all this wasn’t extreme enough,

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let’s take a look at[br]a few other properties.

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Neutron stars spin very, very fast,[br]young ones several times per second.

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And if there’s a poor star nearby[br]to feed the neutron star,

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it can rotate up to several[br]hundred times per second.

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Like the object PSRJ1748-2446ad.

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It spins at approximately[br]252 million km/h.

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This is so fast that the star has[br]a rather strange shape.

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We call these objects pulsars, because[br]they emit a strong radio signal.

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And the magnetic field of a neutron star

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is roughly 8 trillion times stronger[br]than the magnetic field of Earth.

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So strong that atoms get bent[br]when they enter its influence.

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Okay, I think we got the point across.

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Neutron stars are some[br]of the most extreme,

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but also some of the[br]coolest objects in the universe.

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Hopefully, we will one day send spaceships[br]to learn more about them

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and take some neat pictures!

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But we shouldn’t get too close!