This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Homework # 10 Solutions 1. Compute the deflection angle of a star whose light just grazes the limb of the Sun. Also compute the deflection angle of a star whose light just grazes the limb of a 1 . 4 M neutron star, if the neutron star was at the same distance from the Earth as the Sun. State assumptions. Assume that d Lens << d S , then = 4 G M / ( bc 2 ). b will be equal to the radius of the lens. For the Sun, we have = 4 G M R c 2 = 8 . 6 10 6 = 1 . 76 arcsec . For a neutron star, = 4 G M R c 2 = 0 . 98 = 56 . 4 . However, this assumes that the deflection angle is small, which is invalid for this case. A full calculation in GR yields a deflection about 21% larger! 2. Use the Plummer potential model, with a value of a = 100 kpc, together with the Viral theorem to infer a value for galaxy masses in Fig. 7.3 assuming that all the galaxies have the same mass. Do not include Stephans Quintet in this estimation....
View
Full
Document
 Spring '11
 Lattimer
 Galaxies

Click to edit the document details