3. Estimate the average number density of stars throughout the Milky Way, using the distribution n(r)=k*exp(-r/Rs)
a) Consider that within a 2pc radius of the Sun there are 5 stars.
b) Estimate based on the Galaxy's scale height of 330pc, and assuming an average stellar mass of half the mass of the Sun.
4. Determine the collision rate of the stars using the number density of the stars, the cross-section for a star, and the average velocity of the stars. How many stars will collide every year? Is the Sun likely to collide with another star?
Q2:
ReplyDeleteNice calculation! Try to use cgs units consistently — it will make your life easier! Also, note that, if we assume the two galaxies are currently at the farthest distance from each other, then semi-major axis should be *half* the current distance separating the two galaxies (800 kpc / 2).
4.5
Q3:
ReplyDeleteYour logic is correct but your results are a bit high! For a), check your volume calculation. For b), check your solar mass. Also, remember the galaxy scale height extends both above and below the mid plane!
4
Q4:
ReplyDeleteThis is a very high collision rate! I would be a little concerned! Look for a simple way to calculate collision rates given a particle density, cross-section area, and velocity, using dimensional analysis. Check solutions once they are posted.
2.5