Problem set 6 for ASTR 221: Stars and Planets

Due 5pm, Fri Nov 21.

Kutner problems P5.17, P5.20, P5.24

Read Kutner sections 6.3 thru 6.6.

Kutner questions Q6.3, Q6.7, Q6.13

Kutner problem P6.5

(8) (a) At what rate is the Sun's mass decreasing due to nuclear reactions? express your answer in solar masses per year. (b) Compare this to the mass loss rate due to the solar wind. (c) Assuming that the solar wind mass loss rate remains constant, will either of these processes significantly effect the Sun's mass over its main-sequence lifetime?

(9) Assuming that 10 eV could be released by every atom in the Sun through chemical reactions, estimate how long the Sun could shine at its current rate due to chemical reactions alone. For simplicity, assume that the Sun is entirely hydrogen.

(10) Estimate the hydrogen-burning lifetimes of stars near the lower and upper ends of the main sequence. The lower end of the main sequence occurs near 0.072 M_sun, with log10(L/L_sun)=-4.3. An 85 M_sun star near the top of the main sequence has a luminosity of log10(L/L_sun)=6.006. Assume that the 0.072 M_sun star is fully convective, so that, through convective mixing, all of its hydrogen, not just its inner 10%, becomes available for nucleosynthesis.