Via the rotation curve method, we can estimate the mass of ...

[aabwk4]

Via the rotation curve method, we can estimate the mass of galaxies like M31 from
 
  a. Doppler shifts of material at the edge of its disk and computing P = 2r/v.
  b. the distances of the Doppler shift points from its center.
  c. Doppler shifts of material at the edge of its disk and computing P = 2r/v and the distances of the Doppler shift points from its center.
  d. It is impossible to estimate the mass of M31.

Question 2

A planetary nebula
 
  a. produces an absorption spectrum.
  b. produces an emission spectrum.
  c. is contracting to form planets.
  d. is contracting to form a star.
  e. is the result of carbon detonation in a 1- star.

[sylvia]

Answer to Question 1

c

Answer to Question 2

b

[aabwk4]

TYSM

[LVPMS]

Thanks for the timely response, appreciate it