How do we know that there are intergalactic clouds between a distant quasar and us?
A)We see hydrogen emission lines at redshifts smaller than that of the quasar.
B)We see hydrogen absorption lines at redshifts smaller than that of the quasar.
C)We see hydrogen emission lines at redshifts greater than that of the quasar.
D)We see hydrogen absorption lines at redshifts greater than that of the quasar.
E)We see that the emission lines from the quasar are lessened by intervening gas and dust.

Question

Quizplus · Accepted Answer

Hydrogen absorption lines at redshifts smaller than that of the quasar indicate the presence of intergalactic clouds that are absorbing light from the quasar. This is because the gas in the clouds is absorbing some of the light from the quasar, causing a decrease in the intensity of the light we receive.

How Do We Know That There Are Intergalactic Clouds Between