WEBVTT - How Can a Star Become a Giant Crystal?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works, Hey, brain Stuff,

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<v Speaker 1>Lauren Vogel bomb Here. Our Sun may look like an

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<v Speaker 1>eternal miasma of incandescent plasma, but one day it will die.

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<v Speaker 1>This may sound like a bummer, especially for anything that's

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<v Speaker 1>living on Earth in a few billion years, but there

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<v Speaker 1>is a bright side to the solar doom. According to

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<v Speaker 1>research published in the journal Nature, this very month, our

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<v Speaker 1>dead star will leave behind a shimmering legacy. It'll turn

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<v Speaker 1>into a massive crystal. Before we start talking about supersized

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<v Speaker 1>stellar crystals, we first need to understand how stars like

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<v Speaker 1>our Sun live and die. The Sun is fueled by

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<v Speaker 1>nuclear fusion. It's massive gravity crushes hydrogen atoms together in

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<v Speaker 1>its core to create helium, and the vast quantities of

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<v Speaker 1>energy released by these fusion processes push outward, maintaining a

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<v Speaker 1>happy equilibrium. So long as there's plenty of hydrogen fuel

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<v Speaker 1>feeding this process, the core remains about the same side

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<v Speaker 1>as in temperature around fifteen million kelvin, producing energy that

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<v Speaker 1>radiates throughout the Solar system, ultimately nurturing the evolution of

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<v Speaker 1>life on a certain habitable planet. This hydrogen burning phase

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<v Speaker 1>of a star's life will last of the lifetime of

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<v Speaker 1>our Sun. The period of stellar life is known as

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<v Speaker 1>the main sequence. We're currently about four point five billion

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<v Speaker 1>years into our Sun's main sequence days, or approximately halfway

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<v Speaker 1>through its life. So what happens when that hydrogen is

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<v Speaker 1>all used up? Things start to get a little wild,

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<v Speaker 1>to put it mildly. Without the outward pressure of the

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<v Speaker 1>energy created by fusing hydrogen, the Sun's gravity overwhelms the core,

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<v Speaker 1>crushing it into a smaller space and boosting its temperature tenfold.

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<v Speaker 1>That's okay, though, the heavier helium nuclei will begin to

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<v Speaker 1>fuse together, creating the outward pressure once again to maintain equilibrium.

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<v Speaker 1>It's predicted that this will start happening in about five

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<v Speaker 1>billion years, marked with a sudden outbrush of energy known

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<v Speaker 1>as a helium flash. As the helium fuses, carbon and

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<v Speaker 1>oxygen are formed and the temperature of the core rises

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<v Speaker 1>yet again. Soon after, even heavier elements also begin to fuse,

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<v Speaker 1>and the Sun on the whole will start looking a

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<v Speaker 1>bit worse for the wear. It will begin to swell,

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<v Speaker 1>blasting into planetary space with savage solar winds that will

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<v Speaker 1>begin to strip away its upper layers. Though our Sun

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<v Speaker 1>isn't massive enough to explode as a supernova, it will

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<v Speaker 1>turn into a red giant star, possibly expanding beyond the

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<v Speaker 1>orbit of Earth. Our planet will be toast. After the

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<v Speaker 1>death of our star, it will leave behind whispy remains

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<v Speaker 1>of solar plasma, creating a beautiful planetary nebula, enriched with

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<v Speaker 1>newly formed heavy elements that will go on to create

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<v Speaker 1>the next generation of stars and planets, And in its

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<v Speaker 1>core will be a hot stellar remnant known as a

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<v Speaker 1>white dwarf, a tiny dense star shimmering brightly, a testament

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<v Speaker 1>to the Sun that used to be in its place.

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<v Speaker 1>White dwarfs can sustain themselves for billions of years before

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<v Speaker 1>fizzing out in dimming forever. But this isn't the end

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<v Speaker 1>of the story. Using observations by the European GUIA mission,

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<v Speaker 1>which is currently making precision measurements of stars throughout our galaxy,

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<v Speaker 1>researchers at the University of Warwick in the UK have

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<v Speaker 1>stumbled on a white dwarf secret that has remained hidden

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<v Speaker 1>until now. Soon after forming, white dwarfs are extremely hot,

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<v Speaker 1>radiating the intense energy that was once held in the

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<v Speaker 1>core of the main sequence star that came before them.

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<v Speaker 1>Over billions of years. After forming, white dwarves slowly cool

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<v Speaker 1>and at a certain point the oxygen and carbon they

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<v Speaker 1>contain will go through a phase transition akin to liquid

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<v Speaker 1>water freezing and turning into solid ice, only at much

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<v Speaker 1>more extreme temperatures and pressures, and they'll solidify to form

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<v Speaker 1>a huge crystal. Pierre Emmanuel Tremblay, from the University of

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<v Speaker 1>Warwick's Department of Physics and leader of the study, said

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<v Speaker 1>in a press release. All white dwarves will crystallize at

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<v Speaker 1>some point in their evolution, although more massive white dwarfs

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<v Speaker 1>go through the process sooner. This means that billions of

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<v Speaker 1>white dwarfs in our galaxy have already completed the process

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<v Speaker 1>and are essentially crystal spheres in the sky. The sum

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<v Speaker 1>itself will become a crystal white dwarf in about ten

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<v Speaker 1>billion years. Tremblay's team analyzed the Gaia observations to measure

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<v Speaker 1>the luminosities and colors of fifteen thousand white dwarves within

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<v Speaker 1>three d light years of Earth. What they found was

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<v Speaker 1>an excess in the population of stars of specific colors

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<v Speaker 1>and brightness. They realized that this group of stars represented

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<v Speaker 1>a similar phase instellar evolution where the conditions are right

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<v Speaker 1>for this phase transition to occur, causing a delay in cooling,

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<v Speaker 1>thus slowing down the aging process. The researchers found that

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<v Speaker 1>some of these stars had extended their lifespan by up

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<v Speaker 1>to two billion years. Tremblay said in the statement, this

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<v Speaker 1>is the first direct evidence that white dwarfs crystallize or

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<v Speaker 1>transition from liquid to solid. It was predicted fifty years

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<v Speaker 1>ago that we should observe a pile up in the

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<v Speaker 1>number of white dwarves at certain luminosities and colors due

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<v Speaker 1>to crystallization, and only now has this been observed. Stalized

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<v Speaker 1>white dwarfs aren't just a stellar curiosity. Their quantum makeup

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<v Speaker 1>is unlike anything we can recreate in the laboratory. As

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<v Speaker 1>the white star material crystallizes, its material becomes ordered on

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<v Speaker 1>a quantum level nuclei aligning themselves in a complex lattice

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<v Speaker 1>with a metallic oxygen core and an outer layer enriched

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<v Speaker 1>with carbon. So it turns out that after stars like

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<v Speaker 1>our sun die, their stories aren't over all. White dwarfs

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<v Speaker 1>will go through this crystallization process, littering the galaxy with

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<v Speaker 1>massive diamond like stellar remnants. Today's episode was written by

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<v Speaker 1>Ian O'Neil and produced by Tyler Claying for iHeart Media

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<v Speaker 1>and How Stuff Works. For more on this and lots

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<v Speaker 1>of other shining topics, visit our home planet, how stuff

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<v Speaker 1>Works dot com