Why is 21-cm radiation so important to the study of interstellar ...

[sam.t96]

Why is 21-cm radiation so important to the study of interstellar matter and the Galaxy?
 
  A) It helps locate the galactic core in Sagittarius.
  B) Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy.
  C) Emitted by carbon monoxide, it passes through interstellar gas and lets us to see places rich in organic molecules around the Galaxy.
  D) It is emitted by most stars, enabling astronomers to map the entire Galaxy.
  E) It is emitted only in hot regions of star formation, so the pattern of the spiral arms of the Galaxy can be mapped.

Question 2

What is the accepted explanation for millisecond pulsars?
 
  What will be an ideal response?

[Melissahxx]

Answer to Question 1

B

Answer to Question 2

They are old neutron stars which have pulled matter off of a binary companion and in the process been spun up to very high rotational speeds.

[sam.t96]

Wow, this really help

[bassamabas]

Excellent