Problem Set 1 

    Due date: Jan. 23
    Problem 3.1,
    Problem 3.2,
    Problem 3.5,
    Problem 3.7,
    Problem 3.10

    Problem Set 2 

    Due date: Feb.2

    Problem 3.4,
    Problem 3.8 (all parts),
    Problem 5.8,
    Problem 5.9,

    Problem Set 3 


    Due date: Feb.9

    Problem 5.1,
    Problem 7.4,
    Problem 7.6,
    Problem 7.7,
    Problem 8.15

    Problem Set 4 

    due Feb.21

    Problem 1. A proto-star gas cloud of mass MO formed a Sun-like star. Find the decrease of mass MO due to the gravitational compression. Assume: a) that all energy due to the compression was radiated away; b) constant mass densities. (15% of the total mark)
    Problem 2. 10.3
    Problem 3. 8.1     

    Optional Problem: Estimate pressure in the center of the Sun assuming linear decrease of the mass density from the center to zero near the surface. Compare with the result when the mass density is considered to be constant.

    Problem Set 5 

    Due date: March 9

    Problem 1. 10.12
    Problem 2. Due to gravitational compression, a Sun-like star can produce energy in today’s rate for ~107 years (the constant density assumption, example in class, or 10.3 in the textbook). Find how this prediction changes if we assume a linear radial dependency of the mass density (zero density on the surface). Hint: use the following formula for the linear dependence of the mass density \ro on the radius r: , where R is the star radius, M is its mass.

    You can derive this formula for the bonus.

  • Problem 3. Find how does the minimum temperature needed to spark the fusion (calculated in class as ~107K) change if helium is used for the fusion instead of hydrogen.

    • Problem 4. As you know, the phonic pressure inside the Sun is much lower than hydrodynamic (ideal gas) pressure. In the late stage of its evolution, the Sun passes through so-called helium flash. Temperature inside the Sun’s core is very high. Calculate hydrodynamic (ideal gas) and radiation pressure inside the core of a Sun-star right before the helium flash (density ~104g/cm3, T~108 K).

    Problem Set 6 

    Due date: March 23, 2006, Thursday, by the beginning of the class

    Problem 1. 10.15 of the textbook
    Problem 2.  10.16 of the textbook
    Problem 3.  Explain appearance of the red giants (not more than a few sentences). When do they form?
    Problem 4.  Explain the phenomenon of the helium flash (not more than a few sentences)

    Problem Set 7 

    Due date: Apr.4

    (try to be short and specific in your answers)

    Length of a star’s main sequence lifetime is determined by what?

    • Why does hydrogen fusion occur only in a star’s center?
    • What is the Sun’s future?
    • Why red giants are more luminous than white dwarfs?
    • What could be the mass of a white dwarf, why?
    • What could be the mass of a neutron star, why?
    • What is the main source of energy that powers a main sequence star?
    • When does a star move off the main sequence to become a red giant?
    • Why do stars of the lowest mass not become red giants?
    • What causes the core of a star to heat up after its hydrogen fusion ceases?
    • About how large will the Sun become when it reaches the red giant stage?
    • What happens to the size of a main sequence star when mass is added to it? What happens to the size of a white dwarf when mass is added to it?
    • What is the most massive element that can be formed by nuclear fusion with the liberation of energy?
    • What remains after a supernova type I,II?
    • What causes a planetary nebula to appear?
    • Temperature needed to fire the fusion, numerical?
    • Energy released in individual nuclear reaction.
    • Gravitational Energy.
    • Pressure inside stars.
    • Degenerate matter, degenerate pressure.

    Problem Set 8 

    Due date: April 24, 2006, Thursday, by the beginning of the class

    Problem 1.   22.1 of the textbook

    Problem 2.  22.19 (a) of the textbook

    Problem 3.  22.20 of the textbook

    Problem 4.  22.27 of the textbook

    Problem Set 9 

Due to April 27

Problem 1. A Cepheid star, appearing on the sky with an average apparent magnitude of 3, has oscillating luminosity with a period of 10 days. Using the period-magnitude relation (eq. 14.2), find distance to the star.

Problem 2. (Answer with one sentence to each of the questions below)

      • What is location of the Sun in our Galaxy?
      • Why people think that there is a massive black hole in the center of the Galaxy?
      • How people found necessity of dark matter in the galaxies?

Problem 3. What is the radius of the observed (visual) Universe in Mpc? Give the answer related to the Hubble constant.
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