You observe a distant galaxy.You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum.What can you conclude?
A)The galaxy is moving away from you.
B)The galaxy is moving towards you.
C)The galaxy has very weak gravity.
D)The galaxy is made purely of hydrogen.

Question

Quizplus · Accepted Answer

The fact that the hydrogen spectral line is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum indicates that the galaxy is moving away from us. This is known as a redshift, which occurs due to the Doppler effect, where the wavelength of light gets stretched and appears longer when the source is moving away from us.

You Observe a Distant Galaxy