Packet 4: Tossup 8

A star’s core undergoes this process as it fuses heavier elements, causing the main sequence to have a nontrivial thickness. Objects undergoing this process maintain a roughly constant surface temperature if they are fully convective but increase in temperature if a radiative zone develops. This process is caused by a sudden [emphasize] decrease (-5[1])in opacity and pressure in a phase of the kappa mechanism. (10[1]-5[1])Hydrostatic equilibrium and nuclear equilibrium are maintained on a timescale of about [read slowly] “big-G times mass over the product of radius and luminosity,” which is 30 megayears for the Sun, during a mechanism for this process that is named after Kelvin and Helmholtz. (-5[5])Protostars slowly (-5[1])undergo this process accompanied (-5[1])by a decrease in luminosity (-5[1])as they move along the Hayashi (-5[1])track. (10[1]-5[1])For 10 points, name this phenomenon in which a star’s radius slowly (10[1])decreases (-5[1])due to gravity. (10[1])■END■ (10[12]0[7])

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