Duke Intro to Astro                                                homework 4 (assignment 5)
                                                                                due Tuesday, August 1, 2006

1) text, question 20(34)

     The question is expecting you to answer with differences than can be observed. 
      I am hoping for at least 2 differences, but please don't stop at 2!

2) a) use the web images of HH30  (a Herbig Haro object) to determine the speed of the jet
          (km/s would be a nice unit)

    b) then use this speed to determine the age of the jet in HH1 on page 453 of the text

3) text, questions 20(39) and 22(41); do they give roughly the same answers?

4) text, question 20(32)

    (the nebula is sufficiently far away that we cannot actually see it expand over time)

5) Find the age of the Pleiades star cluster (figure 20-18, page 457) using the
    procedure we learned in class.  How different is your answer from the one given
    in the caption?

6) The Sirius binary system is the fifth nearest star system to us.  The binary
    consists of

    an A1 V main sequence star of mass 2.0 solar masses

    a white dwarf star with a mass of 0.5 solar masses

a) what is paradoxical (in terms of stellar evolution theory) about this system?

b) explain your way out of this paradox

c) what is the oldest age this system could be  (assuming that the A1 V star's mass
    has not changed since it was born)?