Multiple Choice
Why has the 21 cm emission line been especially useful for studying the structure of the Milky Way galaxy?
A) Stars emit very strongly at 21 cm
B) The 21 cm radiation travels to us at the speed of light
C) Twenty-one cm emission is produced only in the core of the galaxy
D) Twenty-one cm radiation is unaffected by interstellar dust
Correct Answer:
Verified
Correct Answer:
Verified
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