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Of the order 10000–100000 years. As an example of an old Supernova remnant, you can see the Vela SNR, estimated at 11,000–12,300 years old. Nasa describes the evolution of a remnant Initially, the shock wave expands freely, As it grows it sweeps up material from the interstellar medium which slows its expansion. Expansion causes adiabatic cooling (or the ...


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@ProfRob has already given a good answer to the question, but I wanted to add just a little more detail addressing the observational data side. As Rob already stated, the fundamental data often come (these days) from satellites like Kepler or TESS, which can measure a star's brightness with very high precision, over an uninterrupted period of many days. So ...


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Asteroseismology effectively measures the sound speed inside a star by finding the characteristic oscillation frequencies of a star. The sound speed depends on the composition because the pressure at a given temperature depends on the average mass of a particle in a gas. As the star gets older, it turns its hydrogen into helium, changing the composition, the ...


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