The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with _.
A)space- based ultraviolet telescopes
B)X- ray telescopes
C)ground- based visible- light 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 can be observed using radio telescopes. This is known as the 21-centimeter line, and it is the primary way that we observe the atomic hydrogen in the Milky Way. Choice A is incorrect because while ultraviolet telescopes can observe some types of interstellar gas, they are not the primary way that we observe atomic hydrogen. Choice B is incorrect because X-ray telescopes are more useful for observing high-energy phenomena such as black holes and supernovae, and they are not typically used to observe interstellar gas. Choice C is incorrect because interstellar gas is not typically visible in the visible-light portion of the electromagnetic spectrum.

The Primary Way That We Observe the Atomic Hydrogen That