Interstellar absorption lines are narrow primarily because:

Question

Quizplus · Accepted Answer

The narrowness of interstellar absorption lines is primarily due to the low temperature of the matter, which causes the atoms to have very little thermal motion and remain almost still. This produces sharp and narrow absorption lines. The other choices are not correct. Interstellar absorption lines are narrow primarily because interstellar matter is at a low temperature, and atoms are almost still. This lack of motion reduces the Doppler broadening of the absorption lines, resulting in narrow lines. The other options are not correct, as there is still a significant amount of interstellar matter even if it is not dense, molecules do not always produce narrow absorption lines, and ionized matter can produce broader lines due to the motions of charged particles.

Interstellar Absorption Lines Are Narrow Primarily Because