The most distant objects found so far are galaxies. Often, these distant galaxies are found because they are forming hot stars at a rapid rate, causing them to be very bright. Or, they may contain active galactic nuclei (AGN) or quasi-stellar objects (QSOs), which are extremely bright gravitational engines powered by supermassive black holes.

The most distant galaxies measured to date are at redshifts of about 10, which puts them slightly more than thirteen billion light-years away. Since the distance to the cosmic horizon is 13.7 billion light-years, that means that astronomers have looked more than 90 percent of the distance out to the edge of the observable universe.