Why planets around dead stars rain diamonds

HostWhen we look up at the night sky, we usually think of planets as big balls of rock or gas, kind of like the ones in our own backyard. But out in the deep dark, there are worlds that sound like they belong in a storybook rather than a science lab.

HostThere's one place in particular that's basically a giant, glowing gem circling the remains of a dead star. How does a world like that even come to be?

GuestIt really starts with a bit of a cosmic heist. This isn't a normal planet that formed from a cloud of dust like Earth did. It's actually the leftover heart of a star that got bullied by its neighbor. Imagine two stars living close together. One of them dies and becomes what we call a pulsar, which is this tiny, heavy ball that spins incredibly fast and shoots out beams of energy like a lighthouse. That pulsar starts sucking the life out of the second star, peeling away its outer layers of gas like skin off an onion.

HostSo the pulsar is basically eating its partner? That sounds less like a neighborly chat and more like a total takeover.

GuestIt's pretty brutal. The pulsar has such a strong tug that it strips away all the light stuff, like hydrogen and helium. What you're left with is the inner core of that second star. Because that star was older, its core was mostly made of carbon and oxygen. Once the outer layers are gone, that core just sits there, circling the pulsar. It's not a star anymore because it can't burn fuel, but it's way too heavy to be a normal planet. We call it a diamond planet because of what happens to all that leftover carbon under so much weight.

HostI mean, we know carbon from things like pencil lead or charcoal. How do we get from a pile of soot to a planet sized jewel?

GuestIt's all about the squeeze. Even though this world is only a few times bigger than Earth, it weighs as much as Jupiter. Think about taking something the size of a giant gas world and crushing it down until it fits inside a small marble. The pressure inside that leftover core is so high that the carbon atoms have no choice but to link up in a very tight, very hard pattern. That pattern is exactly what a diamond is. Deep down, the whole thing is likely one massive, sparkling structure.

HostThat's hard to even wrap my head around. But I have heard that it doesn't just sit there being shiny. People talk about it raining diamonds too. Is that actually happening in the sky of a dead star?

GuestWell, the rain part is a bit different than a storm on Earth. On a world like this, or even on giant gas planets closer to home, the air is full of carbon. High up in the sky, the heat and the weight of the air can turn that carbon into solid chunks. So you would've these tiny gems or flakes of diamond forming in the clouds and then falling down through the sky. But here is the wild part. As they fall further down, it gets so hot and the pressure gets so intense that those diamonds might actually melt. You could've a layer of the planet where it's literally raining liquid diamond into an ocean of melted carbon.

HostWait, I thought diamonds were the hardest thing there is. You're telling me it gets so hot that they turn into a puddle?

GuestIn those extreme spots, yeah. Heat can break down almost anything if you have enough of it. And since this planet is so close to a pulsar, it's getting blasted with energy. Plus, it still holds onto a lot of the heat from back when it was a real star. So you have this strange mix of a solid, icy gem core and these layers where carbon is acting like water.

HostSo it's glowing, it's raining jewels, and it's made of solid diamond. If we could actually see it, what would it look like? Does it look like a giant engagement ring floating in the dark?

GuestIt probably wouldn't look like a clear diamond you see in a shop. It would likely be very dark, maybe a deep, glassy gray or black because of the way the light hits it. But it would glow. It would give off its own dim, steady light from all that trapped heat. And when the beams from the pulsar hit it, the surface might shimmer in ways we can't really imagine. But you could never actually go there to see it.

HostBecause of the heat?

GuestThat, and the gravity would crush you into a pancake before you even touched the ground. And the pulsar itself is shooting out so much radiation that it would be like standing inside a giant X-ray machine. It's a beautiful, sparkling graveyard, but it's one of the most dangerous places in the whole woods.

HostIt's amazing to think that something as pretty as a diamond is really just the result of a star being squeezed to death.

GuestThe universe has a way of turning the most violent ends into the most orderly and strange new things, like a star that dies only to leave behind a gem the size of a world.

HostThe next time I look at a ring, I'll probably think less about the jewelry store and more about those lonely, crushed stars spinning in the dark.