Multiple Choice
In order to emit a 21-cm photon,an atom of neutral hydrogen in interstellar space must absorb energy to place it in the excited state (the parallel spin configuration) .What is the MOST likely mechanism to achieve this?
A) thermal energy
B) collisions
C) "falling" from an even higher energy state
D) cosmic rays
Correct Answer:
Verified
Correct Answer:
Verified
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