Question

1. The Milky Way is about 30,000 kiloparsecs across and is shaped like a disk, and is about 600 parsecs thick. The typical distance between stars in the galaxy is about a parsec. Assume that most stars are about the size of the Sun. How many stars would it take to completely fill up the entire volume of the Galaxy? Compare that to the actual number of stars in the Milky Way. Discuss whether or not stars will ever hit each other.

Answer 1

VOLUME OF MILKY WAY = r2h

where, r = radius of the mily way disk

h = thickness/ height of milky way

V = 3.14 * (30000*103 / 2)2 * 600

V = 4239 * 1014 parsec3 = 1.245*1067 cubic metres

VOLUME OF OUR SUN, Vs = 1.4*1027 cubic metres

Number of stars to fill the entire galaxy = V/Vs = 1.245*1067 / 1.4*1027 = 8.89*1039 stars.

Number of actual stars in the galaxy = 4*1011 (on the high end)

This shows that, the universe is mostly empty and filled with void. Therefore, the probability of collision of 2 stars is very low.