Question

question 10 of 19
which of the methods is used to detect regions of ionized hydrogen (hii) in the interstellar medium?
gamma rays
tracer particles, such as co (carbon monoxide)
hα lines
gravity waves
21 cm radiation
image credits: nasa/jpl - caltech/noao.

Explanation:

Ionized hydrogen (HII) regions emit strong Hα (Hydrogen - alpha) lines. Hα is a specific spectral line in the visible part of the electromagnetic spectrum that is characteristic of ionized hydrogen. Gamma - rays are not used for detecting HII regions. Tracer particles like CO are used to study molecular clouds, not HII regions. Gravity waves are not related to detecting HII regions, and 21 - cm radiation is associated with neutral hydrogen, not ionized hydrogen.

Answer:

Hα lines