Who first determined that the energy/s emitted by (luminosity of) ...

[roselinechinyere27m]

Who first determined that the energy/s emitted by (luminosity of) Cepheid variable stars is larger the longer their period of variation is?
 
  a. Henrietta Leavitt
  b. Edwin Hubble
  c. John Glenn
  d. Carl Sagan
  e. Harlow Shapley

Question 2

How does an H-R diagram make it clear that giant stars are larger than main-sequence stars of the same temperature?
 
  What will be an ideal response?

[joanwhite]

Answer to Question 1

a

Answer to Question 2

The relationship among luminosity, radius, and temperature tells us that luminosity is proportional to the surface area and to the temperature. The H-R diagram shows the luminosity vs. temperature, and the giant stars are in the top left corner, meaning greater luminosity and lower temperature. So their surface areas, and therefore radii, must be larger.

[roselinechinyere27m]

Thanks for the timely response, appreciate it

[cdmart10]

Gracias!