General Astronomy - Spring
2011
Homework #7 - due March 23
1. (3 pt) List three
different types of galaxies and
describe their stellar orbits and gas content.
2. (4 pt) Assuming
the Hubble constant is 60 km/s/Mpc, estimate the age of the
Universe. Explain your reasoning.
3. (4 pt) A galaxy has a measured recession velocity of 8,000
km/s. How
far away is it? (Assume that the Hubble constant is 71 km/s/Mpc.)
4. (4 pt) If the radius of the Sun suddenly decreased by a factor of 4,
by what factor would the rotation rate of the Sun increase?
5. (5 pt) Calculate the power output from a pulsar with a mass of one
solar mass and a radius of 14 km, with a spin down rate of -1×10-10
s-2 and an initial spin rate of 20 Hz.