What use are 21 cm radio waves to galactic astronomers?
A)They cut through the dusty cocoons to let us watch star birth.
B)We can reflect them off the core of the Galaxy.
C)Their Doppler shifts let us map the motions and locations of gas in the spiral arms.
D)They bounce off stars like our Sun to let us precisely measure their distances.
E)They pick up the cool, dark matter much better than can optical telescopes.

Question

Quizplus · Accepted Answer

21 cm radio waves can be used by galactic astronomers to map the motions and locations of gas in the spiral arms of galaxies through Doppler shifts. This information can provide insight into the dynamics and structure of the galaxy. The Doppler shifts of 21 cm radio waves allow galactic astronomers to map the motion and location of gas in the spiral arms of the galaxy.

What Use Are 21 Cm Radio Waves to Galactic Astronomers