Our best measurements of the primordial deuterium abundance come from observations of hydrogen clouds backlit by quasars, extremely distant and bright beacons thought to be powered by black holes.

• 类星体一向被认为是由威力强大的黑洞所驱动的遥远而明亮的光源，测量太初氘丰度的最好方法就是观测那些后方有类星体照亮的氢云。