(a) 6 marks (i) Explain the meaning of the Virial Theorem, i.e., E = -U/2, where E is the star's total energy while U is

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A 6 Marks I Explain The Meaning Of The Virial Theorem I E E U 2 Where E Is The Star S Total Energy While U Is 1 (108.04 KiB) Viewed 10 times

(a) 6 marks (i) Explain the meaning of the Virial Theorem, i.e., E = -U/2, where E is the star's total energy while U is its potential energy. (ii) Why does the Virial Theorem imply that, as a molecular cloud collapses to make a star, half of the energy generated must be radiated away? (iii) What is the characteristic timescale of stellar contraction during the pre-main sequence? (b) 6 marks (i) What is the mean molecular weight of a gas containing ionised hydrogen? Justify your answer. (ii) Will the mean molecular weight of a star increase or decrease as the star ages? Justify your answer. (iii) Why does a change in the composition of a star alter its hydrostatic equilibrium? (iv) Explain why hydrogen burning can take place at lower temperatures than helium burning.