The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with
A)ground-based visible-light telescopes.
B)space-based ultraviolet telescopes.
C)X-ray telescopes.
D)radio telescopes observing at a wavelength of 21 centimeters.

Question

Quizplus · Accepted Answer

Atomic hydrogen emits radiation at a wavelength of 21 centimeters, which is in the radio part of the electromagnetic spectrum. Therefore, radio telescopes are the primary way to observe atomic hydrogen in the interstellar gas of the Milky Way.

The Primary Way That We Observe the Atomic Hydrogen That