Homework Set VIII (Review questions) 
 
This problem set is not to be handed in. It is essentially a study guide for the
second part of the course. Doing these problems may well help you on
the final exam, though it is not all encompassing.  You are
responsible for learning the material covered in the course.
You can find all the answers in your text book and in Jean Brodie?s notes. TA?s will
go through these questions during the review sections. 
 
 
1)    What observations did Hubble make to arrive at the famous ?Hubble relation? ?
    Is his result consistent with the cosmological principle ? 
 
2)    Name four different ?standard candles? used to find the distances to nearby
    galaxies. 
 
3)    What is the difference between Population I and Population II stars ? Where
    are they located inside our Galaxy ? What is their motion relative to the center
    of our Galaxy ?
 
4)    Define parallax and its cause. 
 
5)    What is the difference between absolute and apparent magnitude ? If you were
    to take a star and move it away from the Earth, what would happen to its apparent
    magnitude as it got further away ? and what would happen to its absolute
    magnitude ? 
 
6)    The three strongest pieces of evidence in support of the ?big-bang? theory
    are: 
           ·       The expansion of the universe;
           ·       The Cosmic Microwave Background Radiation;
           ·       Cosmic element abundances.
    Describe what each of these is and how each piece of evidence supports the
    ?big-bang? theory. 
     
7)    What is the spectral sequence of stars ? Which type represents the hottest
    stars ? and the coldest ? Which ones are red ? and which ones are blue ? 
 
8)    Draw a sketch of an elliptical, a spiral, and an irregular galaxy. What does
    each look like ? Are stars forming there ? Do they have gas and dust ? 
 
9)    What is the mass-luminosity relation ? If a star has a mass of 100 times the
    solar mass, what is the luminosity of this star as a function of the solar
    luminosity ? 
 
 
10)    Rank the following stars in order of apparent brightness from brightest to
    faintest (here m is the apparent magnitude and M is the absolute magnitude): 
           ·       Alpha centauri A,  m = 0.0   (M = +4.4)
           ·       Regulus,   m = + 1.4   (M = -0.6) 
           ·       Antares,   m = + 0.9   (M = -4.5) 
           ·       Canopus,   m = -0.7   (M = -3.1) 
           ·       Aldebaran,  m = +0.9   (M = -0.2) 
           ·       Sirius,   m = -1.4   (M = +1.4) 
 
11)    Describe what the 2.7 Kelvin microwave background radiation is: where it
    comes from and what it can tell us about the cosmological theories. 
 
12)    List at least two different methods that would help you to infer that
    globular clusters are the old objects in our Galaxy. What is the difference
    between globular and open clusters ? 
 
13)    What is the ?big-bang? ? Is it possible to locate the position of the ?big
    bang? relative to our actual position ? 
 
14)    There are three kinds of objects that stars can become when they end their
    life cycles: 
           ·       White dwarfs;
           ·       Neutron stars;
           ·       Black holes. 
    Which are the main differences among them ? 
 
15)    Describe what a quasar looks like from Earth and what it is in reality. 
 
16)    Make a rough sketch of our Galaxy seen from both the side and the top.
    Indicate the thickness of the disk and the total radius (in pc), the distribution
    of globular clusters, of open clusters, the distribution of gas and dust, the
    location of the Sun and its distance from the center, and the motion of the Sun
    with respect to the Galactic center.  
 
17)    What is the H-R diagram ? Describe the evolution of a low mass star and of a
    massive star in the H-R diagram.