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[Music throughout] Now and then, an obscure star briefly

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flares up, brightening up to a million times. It’s an event

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called a nova. The star V906 Carinae

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erupted as a nova in 2018. Observations from

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three satellites provide new insights into what happened.

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NASA’s Fermi mission has seen 14 novae since 2010.

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Before then, astronomers didn’t think novae could glow in gamma rays,

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the highest-energy light. When a white dwarf pulls

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material from a companion star, the gas forms a thickening layer

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that eventually erupts in a thermonuclear fireball. A nova

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is born. Led by a team from Michigan State University, 

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astronomers studied V906 Carinae using high-energy data from Fermi,

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NASA’s NuSTAR X-ray telescope, and in

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visible light from a Canadian satellite named BRITE-Toronto.

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Shaped by the orbital motion of the stars, the explosion debris

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first forms a thick expanding ring around the system.

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Then, after 10 days or so, fast outflows — likely

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driven by residual fusion on the white dwarf — strike the ring.

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The resulting shockwaves produce gamma-ray and optical flares

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that radiate away most of the nova’s energy. These

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observations provide the first direct evidence that shock waves

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can power most of a stellar explosion’s visible light.

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Figuring out how they work in nearby novae will help us understand

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more powerful events much deeper in the cosmos.

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Explore: solar system & beyond.  NASA