prob_set - Introduction to Astrophysics 0321.3108 Problems...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Introduction to Astrophysics 0321.3108 Problems Set 1. The virial theorem states that for a star in hydrostatic equilibrium < P > = - 1 3 E gr V , where < P > is the volume average pressure, V is the volume, and E gr is the gravitational potential energy. a. For a star supported by thermal gas pressure P = nk B T , what is the relationship between the internal energy E K and E gr . b. Assume the Sun is supported by thermal gas pressure and is composed entirely of ionized hydrogen. Estimate the typical (virial) temperature < T > in the Sun. c. For a star dominated by radiation pressure, what is the relationship between E k and E gr ? What is the total E tot in this case? d. Find an expression for the mass of a star at which radiation pressure begins to domi- nate. Don’t worry about numerical factors, express your answer in terms of the physical constants c, h, G and m H . 2. Kelvin-Helmholtz time Derive an expression for the Kelvin Helmholtz time for which the Sun could be shining at its present luminosity due to the release of gravitational energy. Calculate this time in years.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

prob_set - Introduction to Astrophysics 0321.3108 Problems...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online