Neutron Stars – The Most Extreme Things that are not Black Holes

Neutron Stars – The Most Extreme Things that are not Black Holes


Neutron stars are one of the most extreme and violent things in the universe. Giant atomic nuclei, only a few kilometers in diameter, but as massive as stars. And they owe their existence to the death of something majestic. [Intro music] 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 hydrogen will be exhausted. Medium stars, like our Sun, go through a giant phase, where they burn helium into carbon and oxygen before they eventually turn 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 gravity wins, squeezing the star tighter than before. The core burns hotter and faster, while the outer layers of the star swell by hundreds of times, fusing heavier and heavier elements. Carbon burns to neon in centuries, neon to oxygen in a year, oxygen to silicon in months, and silicon 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 fuse into neutrons, which then get squeezed together as tightly as in atomic nuclei. An iron ball, the size of the 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 shock wave that explodes outwards and catapults the rest of the star into space. This is what we call a supernova explosion, and it will outshine entire galaxies. 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 kilometers wide. It’s so dense that the mass of all living humans would fit into one cubic centimeter of neutron star matter. That’s roughly a billion tons in a space the 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 1,000,000 degrees Celsius, 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 crusts over a liquid core. The crust is extremely hard. The outermost layers are made of iron left over 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 merge 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 rearrange, making long cylinders or sheets, enormous nuclei with millions of protons and neutrons shaped like spaghetti and lasagna, which physicists call nuclear pasta. Nuclear pasta is so dense that it may be the strongest material in the universe, basically unbreakable. Lumps of pasta inside a neutron star can even make mountains at most a few centimeters 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 celestial 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’s after they’re born. They’re called magnetars until they calm down a little. But the absolute best kind of neutron stars are friends with other neutron stars. By radiating away energy as gravitational waves, ripples in spacetime, their orbits can decay, and they can crash into and kill each other in a kilonova 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 learned that this is probably the origin of most of the heavy elements in the universe, like gold, uranium, and platinum, and dozens more. So there now two neutron stars collapse and become a black hole, dying yet again. Not only do 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 a 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 past, sending these atoms on a thirteen-billion-year journey to come together and make us and our world. And that’s pretty cool. Until then, we can look at them on paper. The 12,020 Human Space Era Calendar has arrived. You can order it now until we sell out, and then never again. Visit the cloudy cities of Venus, Dyson swarm assembly on Mercury, and cross the borders of our Solar System. Shipping from the US, and from Europe for the first time, but we deliver to every country all over the world. You could also get a plushie or hoodie or poster. We have some sweet deals for you. Get it for Christmas for your friends, families, and kids, or to distract yourself from the fact that there are 100 billion billion Earth-like planets in the habitable zone of Sun-like stars in the observable universe… …and you will never visit any of them. The last few years, we’ve sold them all, so no rush, but the clock is ticking. Getting stuff from our shop is one of the best ways to support Kurzgesagt. Because of you, we can keep this channel free for everyone, and make more beautiful things. A happy interstellar year 12,020. [Outro music]

100 thoughts on “Neutron Stars – The Most Extreme Things that are not Black Holes

  1. Get your 12,020 SPACE Calendar here: https://shop.kurzgesagt.org/
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  2. My imagination starts to wonder what happens to the billion degree neutron matter as it cools. Would it contract even further if it approached absolute zero? How would it be detected besides gravitational effects?

  3. I always love the space videos from Kurzgesagt, the others are very well made too but the space ones always stand out to me.

  4. What if there is a Galaxy that has us humans on the planet(s) and the planet(s) has a moon and sun but we don't know where it is since it is so far away??

    Maybe our bloodline is also on some other planet(s) but we don't know about it

    This world is endless and don't be scared of this right now because later or even today who knows there might be a nuke war, volcano eruption, A.I so many I can't even name them

    how can we believe nasa on what they says?

    we don't even know if the moon landing was real since it looked like the were cameras and wind and the "lost" the footage of the so called landing

    Don't believe in what you see because there is much more than all of this

  5. Neutron star: Ho Ho You're approaching me?

    Other neutron star: I can't create this universe without getting closer.

    Neutron star: then come as close as you like 😀

  6. I really want that calendar but my mom doesnt have enough money to buy it…😔😔😔. I wish my mom have enough money to buy it…..

  7. This is probably the best kurtgesagt video I have seen till date. Woweee that ending blew me away. So most elements weren't created during supernovas but during kilonovas . Stars had to die twice to form us. Woah

  8. I am sorry to interrupt you, but in your video about strange matter, you said that you if gravity wins it becomes a black hole. But in this video you says that it becomes a neutron star. I might have misunderstood, but currently I am confused and dont understand. If someone is willing to enlighten me I will be very grateful. Thank you for your amazing videos I really like your videos and I am sorry for bothering you.

  9. "Magnetars, until they calm down a little"

    "Damn it, Magnetar, go stand in the corner until you've learnt your lesson!"

  10. You used the wrong intro!
    This is a space video! You should have used the one of the galaxy zooming into the solar system zooming into earth
    And not an atom zooming out to molecules, cells, an embryo, then the earth.

  11. So it’s BIG CHUNGIS BUT it’s dencity is more than a qwantome beam or a laser that’s invisible but it’s so dense that it can cut through enything?

  12. Me at the end of video: So you are telling me that we are formed from the guts of zombified stars who died twice. Okay I can take that.

  13. I wish there were actual discussions in these comment sections about the actual video, rather than a bunch of lame jokes pandering for likes. Fascinating video, by the way.

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