GN-z11 is a high-redshift galaxy found in the constellation Ursa Major. The 2015 discovery was published in a 2016 paper headed by Pascal Oesch and Gabriel Brammer (Cosmic Dawn Center). Up until the discovery of HD1 in 2022, GN-z11 was the oldest and most distant known galaxy yet identified in the observable universe,[4] having a spectroscopic redshift of z = 11.09, which corresponds to a proper distance of approximately 32billionlight-years (9.8billion parsecs).[5][note 1]
High-redshift galaxy that is the oldest and most distant known galaxy
GN-z11
GN-z11 superimposed on an image from the GOODS-North survey
The object's name is derived from its location in the GOODS-North field of galaxies and its high cosmological redshift number (GN + z11).[6] It is observed as it existed 13.4 billion years ago, just 400 million years after the Big Bang;[2][7][8] as a result, its distance is sometimes inappropriately[9] reported as 13.4 billion light-years, its light-travel distance measurement.[10][11]
The galaxy has such a high redshift that its angular diameter distance is actually less than that of some galaxies with lower redshift. This means that the ratio of its angular size to its size in light-years is greater.
Discovery
Artist's conception of GN-z11 galaxy
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).[12][13] The research team used Hubble's Wide Field Camera 3 to measure the distance to GN-z11 spectroscopically, measuring the redshift caused by the expansion of the universe.[14] The findings, which were announced in March 2016, revealed the galaxy to be farther away than originally thought, at the distance limit of what the Hubble Telescope can observe. GN-z11 is around 150million years older than the previous record-holder EGSY8p7,[6] and is observed (shortly after but) "very close to the end of the so-called Dark Ages of the universe",[14] and (during but) "near the very beginning" of the reionization era.[12]
Compared with the Milky Way galaxy, GN-z11 is 1⁄25 of the size, has 1% of the mass, and is forming new stars approximately twenty times as fast.[14] With a stellar age estimated at 40 million years, it appears the galaxy formed its stars relatively rapidly.[2] The fact that a galaxy so massive existed so soon after the first stars started to form is a challenge to some current theoretical models of the formation of galaxies.[12][14]
Animation showing the location of GN-z11
Hubble spectroscopically confirms farthest galaxy to date
At first glance, the distance of 32billionlight-years (9.8billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light-year is the distance light travels in a year, and where nothing can travel faster than the speed of light. However, because of the expansion of the universe, the distance of 2.66 billion light-years between GN-z11 and the Milky Way at the time when the light was emitted increased by a factor of (z+1)=12.1 to a distance of 32.2 billion light-years during the 13.4 billion years it has taken the light to reach us. See: Size of the observable universe, Misconceptions about the size of the observable universe, Measuring distances in expanding space, and Ant on a rubber rope.
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