ISP 205, Section 3, Spring 1997

Quiz #3

Tuesday, April 15, 1997

						    Name: ________________________



						    Student Number: ______________
1. (4 points) On the blank graph below, sketch the relationship between the distance of galaxies from us and the speed at which they are moving away from us.

2. (3 points) You are observing a massive, young main-sequence star. Which component of the Milky Way is this likely to be located in?

(a) The Nuclear Bulge.
(b) A globular cluster.
(c) A spiral arm in the Disk.
(d) An old open cluster.
(e) The Halo.

3. (4 points) You have observed the spectra of stars in two different galaxies, Fornax I and Leo II. From the Doppler shift of these spectra, you know that stars in Fornax I are orbiting much faster than the stars in Leo II. Which galaxy is more massive?

Fornax I _More Massive

Leo II   ____________

 
Explain exactly how you drew this conclusion.

F = m a
lambdapeak=3x107 / T
P2=a3
m1 + m2 = a3/P2
E = m c2
D=1/p


Stars orbiting faster means they are accelerated more which must be
due to a larger force of gravity which is produced by more mass in the
galaxy.


If stars move faster, they will complete one orbit in less time, so their
period will be smaller.  From Kepler's Third Law then the mass will be
greater.
4. (3 points) Quasars are compact, extremely luminous sources of light. All of their redshifts are large. How is this information usually interpreted in terms of galaxian evolution?

(a) Quasars are found only far away and in the past, so they are a stage of evolution galaxies went through when they were young.
(b) Quasars are rare and far apart, so none are found close to us.
(c) The Milky Way was once a quasar.
(d) Quasars are extremely massive, young stars ejected from the Milky Way at high speeds.
(e) Quasars are "quasi-stellar objects," believed to be produced by super-massive black holes in the center of galaxies.
Visions of the Universe
Beth Hufnagel's home page, email: hufnage4@pilot.msu.edu
Bob Stein's home page , email: steinr@pilot.msu.edu