GN-z11 is a high-redshift galaxy found at the constellation Ursa Major, and is currently the oldest and most distant known galaxy in the Universe. GN-z11 has a spectroscopic redshift of z = 11.1 which corresponds to a comoving distance of about 32 billion light-years away from the Earth. GN-z11 is observed as it existed 13.4 billion years ago, just 400 million years after the Big Bang.
The galaxy was identified by a team studying data from the Hubble Space Telescope's Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and Spitzer Space Telescope's Great Observatories Origins Deep Survey-North (GOODS-North). The research team used Hubble's Wide Field Camera 3 to measure the distance to GN-z11 spectroscopically, by splitting the light into its component colors to measure the redshift caused by the expansion of the universe. The findings, which were announced in March 2016, revealed the galaxy to be farther away than originally thought, at the distance limit of what Hubble can observe. GN-z11 is around 150 million years older than the previous record-holder EGSY8p7, and is observed (shortly after but) "very close to the end of the so-called Dark Ages of the universe", and (during but) "near the very beginning" of the reionization era.
GN-z11 is twenty-five times smaller than the Milky Way, has 1% of the Milky Way galaxy's mass, and is forming stars at a rate about twenty times faster than the Milky Way galaxy does today. With a stellar age estimated at 40 million years, it appears the galaxy formed its stars relatively rapidly. The fact that a galaxy so massive existed so soon after the first stars started to form is a challenge for some current theoretical models for the formation of galaxies.
source: Wikipedia
