•
 •Question 2   (1 point) In my novel Star
 Dragon, the characters
 fly to a distant binary star system, SS Cygni. SS Cygni is a type of binary system in which a white dwarf star is consuming a main sequence K star. If
 the average separation
 of the stars is 1.5 million km, and the orbital period is 6.6 hours, what is the combined
 mass of the stars?
 (Hint: it will help to immediately convert 6.6 hours to years and 1.5 million km to
 AU.)
   a.0.6 solar masses.   
 •b.6 solar masses.  
 • c.1.8 solar masses.   
 •d.18 solar masses   
 •e.1.3 solar masses.    
 •Either
 solve from basic considerations (mass of KV star and white dwarf) or from Kepler’s
 Law:  Mass = a3/P2, with unit conversions to AUs and
 years.  Get 1.8 solar masses.  Cassandra should work on the
 board.
 •