### What is the mass of Cygnus X-1?

Your professor has posed another challenge question to your introductory

astronomy class. The first student to come up with the correct answer
using good scientific methods and resources available on-line will be
excused from homework for the rest of the semester. You know there are
lots of things you would rather be doing on your weekends than homework,
so you are determined to get the answer first! The challenge question is:
What is the mass of Cygnus X-1?

You immediately think of three possible ways to go
about the problem. Choose one below to begin your investigation!