WEBVTT FILE

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[Music]

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[Music]

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[Music] Narrator: Eta Carinae

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is the most massive star within 10,000 light-years.

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In the mid-nineteenth century, a tremendous eruption hurled

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enough gas into space to make at least 10 copies of the sun, creating

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an expanding nebula still visible today. New results from

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NASA satellites, ground-based telescopes, and theoretical models are

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providing astronomers with an improved understanding of the system.

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At the nebula's heart lie two giant stars. The smaller of the two

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is 30 times the mass of the sun and a million times brighter.

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The primary weighs 90 suns and shines 5 times brighter than

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its companion. Both stars produce powerful outflows called

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stellar winds, but the primary's is so dense it prevents astronomers

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from directly observing the star. The secondary's orbit

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is among the most eccentric known. Every five and a half years, when the

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two stars swing toward closest approach, or periastron, the come about

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as close to each other as Mars is from the sun.

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Eta Carinae's most recent periastron occurred in August 2014,

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and many of NASA's space-based telescopes, as well as ground-based

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observatories, looked on. Where the stellar winds collide,

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temperatures reach hundreds of degrees - hot enough to emit

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X-rays. But the X-ray emission shuts down near periastron,

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when the smaller star is swallowed up by the dense wind of its larger companion.

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The X-rays gradually recover after periastron,

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but they do so a bit differently each time, suggesting structural

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changes in the dueling winds. Recent observations have

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helped theorists refine computer models of this interaction. Here,

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darker colors indicate lower gas densities around the stars,

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while the stars themselves appear as black circles. When the stars are

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far apart, the winds collide head-on, creating a huge cavity

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surrounded by 50-million-degree gas. But near periastron,

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the secondary whips around the larger star, carving a tunnel though the primary's

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dense wind. The secondary star's rapid motion changes the

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collision zone from head...to tail. The smaller star's

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faster wind flows out along the cavity it created and then crashes into the

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outward-moving wind of its companion. From out perspective on Earth,

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the X-rays fade, then recover, as the stars move apart.

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New 3-D models of these simulations reveal the formation

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of finger-like protrusions along the cavity near periastron,

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features never before identified. Theorists now investigating

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the phenomenon suggest they may arise from instabilities developing in gas as

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it flows along the cavity wall. Astronomers also

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keep an eye on Eta Carinae with the Hubble Space Telescope.

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These images show a structure resembling a crab, formed by gas

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excited by the secondary star's intense UV light.

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This light dims near periastron, when the secondary passes through the thickest part of

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the primary's wind. The gas relaxes, settling into a lower-energy state.

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As a result, the crab appears in a different

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spectral line until the stars move apart and the UV light is restored.

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Eta Carinae is one of the closest and most

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massive colliding-wind binaries, and serves as a natural laboratory for

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studying these rare and important objects. While its past

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eruptions remain unexplained, astronomers think they have a handle on its current

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state--a claim to be tested at the next periastron in February

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2020. [Music]

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[Beeping]

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[Beeping]