Question

1. When a variable star periodically changes its luminosity, each of the following also changes periodically except one. Which one does not change?
a) size
b) temperature
c) radial surface speed
d) rotation rate

2. Evidence for the conclusion that the longer-living gamma ray bursters are very distant comes from the
a) delay in the arrival of the visible pulse behind the gamma-ray pulse, caused by the passage of the light through optically thick intergalactic material
b) extreme redshift of emission lines in the visible spectrum detected after a gamma-ray burst
c) spread in arrival times of different gamma-ray photon energies, indicated a long passage through intergalactic gas
d) presence of absorption lines from intergalactic gas clouds in the spectrum of remnant visible light following the gamma-ray burst

3. A black hole can be thought of as
a) the point at the center of every star that provides the star's energy by gravitational collapse
b) a region with such a large mass density that even electromagnetic radiation cannot escape
c) a star with a temperature of 0 K, emitting no light
d) densely packed matter inside a small but finite volume

Answer 1

1) (c) radial surface speed

2) a) delay in the arrival of the visible pulse behind the gamma-ray pulse, caused by the passage of the light through optically thick intergalactic material

3) b) a region with such a large mass density that even electromagnetic radiation cannot escape