Show all your steps in detail.
A.) Suppose you want to construct a scale model of the Milky Way and Andromeda
galaxies using two frisbees. How far apart should you place the two frisbees? Would
they both fit in the classroom? How about a large lecture hall? A stadium?
B.) The light we receive from the Andromeda galaxy left it
approximately 2.4 million years ago. Assuming that Andromeda
is moving directly toward the Milky Way, and using the
information given by Croswell in Ch. 1, estimate how much
closer the Milky Way is to us *now* than it was when that light
left. What fraction of the total distance is this? In the
scale model above, how much closer would the two frisbees now
The rest wavelength of the
Alpha line of hydrogen is at λ
0= 656.28 nm. Suppose you
observe this line in the spectrum of the Andromeda galaxy but find that it is at
λ= 656.02 nm.
What can you conclude about the relative motion of the Milky Way and the
Andromeda galaxy? Are they moving together or apart? At what speed?
- At this rate, about how long might it be until the two
galaxies collide? Express your answer in seconds and in
years. Can you think of any reason the two galaxies might not
collide, at least not on the "next pass"? Explain.
(Feel free to compare your results
with p.8 of Croswell)
- C&O Problem 5.1 (Barnard's star)
- Hydrogen atom & Quantum Physics
- In what ways is the Bohr Model similar to the solar system,
and in what ways is it different? List as many as you can think of.
A.) Compute the energy of the photon that would be emitted if an electron dropped
from the n=6 to n=3 level.
B.) What wavelength would this photon have?
C.) Which "series" is this photon part of?
- C&O Problem 5.14 (White Dwarfs)
- Rotation of galaxies
Suppose you observe the H α line (rest wavelength = 656.3 nm) from an edge-on
spiral galaxy. You find that at the center of the galaxy the line is
at 656.5 nm. At a distance 50,000 ly from the center, the
H α line is at 656.0 nm and 657.0 nm on the
left and right sides, respectively.
A.) Is the galaxy moving toward or away from the Milky Way? How fast?
B.) How fast is the galaxy rotating?
The double star Albireo consists of two components, A and B, separated by about 35 arcseconds. Both stars have
parallaxes of 0.0085 arcseconds.
How far from the Sun is this binary star system?
Assuming the two stars are at exactly the same distance from the Sun,
compute the physical separation between Albireo A and B in AU.
Kepler's 3rd Law is very useful for binary star calculations.
Its general expression, derived by Newton is given in C&O ,
Eq. 2.37. A simpler form can be used if semimajor axis
is measured in AU and Period in Years:
P2 = a3/(M1+M2)
Prove these expressions are equivalent by looking up the values of
G, the AU and the Solar Mass given in your textbook, (all in MKS units),
to show that:
4π2/G = 1 yr2 MSUN /AU3