Some of these galaxies are about 11 billion light-years away and as dim as 30th magnitude, which is 6 billion times fainter than the human eye can see. The Wide Field and Planetary Camera 2 was the workhorse for the Hubble Deep Field north campaign in December 1995. For this program, astronomers pointed the telescope at a spot of sky near the Big Dipper. Astronomers took advantage of those capabilities, collecting optical, ultraviolet, and infrared light from faraway galaxies. The imaging spectrograph dissected light from a quasar 9.5 billion light-years from Earth.
Quasars are energetic beacons of light at the active cores of distant galaxies.
This light provides a powerful three-dimensional probe of the universe's hidden structure.