How are rotation curves of spiral galaxies determined beyond ...

[rlane42]

How are rotation curves of spiral galaxies determined beyond radii where starlight can be detected?
 
  A) by extrapolation
  B) through observations of the 21 cm line of atomic hydrogen
  C) through observations of spectral lines of dark matter
  D) by watching the galaxies rotate over a period of years
  E) by measuring the broadening of absorption lines

Question 2

Approximately how far is the Sun from the center of the galaxy?
 
  A) 27 light-years
  B) 270 light-years
  C) 2,700 light-years
  D) 27,000 light-years
  E) 27 million light-years

[wergv]

Answer to Question 1

B

Answer to Question 2

D

[rlane42]

Excellent

[flexer1n1]

Thanks for the timely response, appreciate it