A pair of stars orbit around one another in an elliptical orbit ...

[Marty]

A pair of stars orbit around one another in an elliptical orbit with a semi-major axis, a, of 1 AU with an orbital period, P, of 1 year. What is the mass of the pair of stars?
 
  a. 1 solar masses
  b. 2 solar masses
  c. 4 solar masses
  d. 8 solar masses
  e. 16 solar masses

Question 2

An ordinary glass lens forms an image by ____________ of light.
 
  a. reflection
  b. refraction
  c. diffraction

[phuda]

Answer to Question 1

a

Answer to Question 2

b

[Marty]

TYSM

[peter]

Thanks for the timely response, appreciate it