The HR Diagram. Suppose we consider a main sequence "O star" much more massive than the sun. According to the formulae shown in lecture:

6. The HR Diagram. Suppose we consider a main sequence “O star” much more massive than the sun.  According to the formulae shown in lecture:

a. What is the luminosity of a main-sequence O star (in solar units, Lsun) of mass 100 solar masses? 

b. If the sun were a 100 solar mass main-sequence O star, how much brighter would it appear from the earth?

c. What is the hydrogen fusing lifetime of this star in years?

d. If the core of this star contains 5 solar masses, to what radius must the core shrink to become a black hole?