In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages".
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology.
UDFy-38135539 is the Hubble Ultra Deep Field (UDF) identifier for a galaxy which was calculated as of October 2010 to have a light travel time of 13.1 billion years with a present proper distance of around 30 billion light-years.
UDFj-39546284 is a high-redshift Lyman-break galaxy discovered by the Hubble Space Telescope in infrared Hubble Ultra-Deep Field (HUDF) observations in 2009. The object, located in the Fornax constellation, was identified by G. Illingworth, R. Bouwens and the HUDF09 Team during 2009 and 2010. It was reported with a redshift of z~10 using Hubble and Spitzer Space Telescope photometric data, with later reports in 2012 suggesting a possibly higher redshift of z = 11.9 Although doubts were raised that this galaxy could instead be a low-redshift interloper with extreme spectral emission lines producing the appearance of a very high redshift source, later spectroscopic observations by the James Webb Space Telescope's NIRSpec instrument in 2022 confirmed the galaxy's high redshift to a spectroscopically confirmed estimate of z = 11.58.
MACS0647-JD is a galaxy with a redshift of about z = 10.7, equivalent to a light travel distance of 13.26 billion light-years. If the distance estimate is correct, it formed about 427 million years after the Big Bang.
z8_GND_5296 is a dwarf galaxy discovered in October 2013 which has the highest redshift that has been confirmed through the Lyman-alpha emission line of hydrogen, placing it among the oldest and most distant known galaxies at approximately 13.1 billion light-years (4.0 Gpc) from Earth. It is "seen as it was at a time just 700 million years after the Big Bang [...] when the universe was only about 5 percent of its current age of 13.8 billion years". The galaxy is at a redshift of 7.51, and it is a neighbour to what was announced then as the second-most distant galaxy with a redshift of 7.2. The galaxy in its observable timeframe was producing stars at a phenomenal rate, equivalent in mass to about 330 Suns per year.
The NIRSpec is one of the four scientific instruments flown on the James Webb Space Telescope (JWST). The JWST is the follow-on mission to the Hubble Space Telescope (HST) and is developed to receive more information about the origins of the universe by observing infrared light from the first stars and galaxies. In comparison to HST, its instruments will allow looking further back in time and will study the so-called Dark Ages during which the universe was opaque, about 150 to 800 million years after the Big Bang.
EGS-zs8-1 is a high-redshift Lyman-break galaxy found at the northern constellation of Boötes. In May 2015, EGS-zs8-1 had the highest spectroscopic redshift of any known galaxy, meaning EGS-zs8-1 was the most distant and the oldest galaxy observed. In July 2015, EGS-zs8-1 was surpassed by EGSY8p7 (EGSY-2008532660).
EGSY8p7 (EGSY-2008532660) is a distant galaxy in the constellation of Boötes, with a spectroscopic redshift of z = 8.68, a light travel distance of 13.2 billion light-years from Earth. Therefore, at an age of 13.2 billion years, it is observed as it existed 570 million years after the Big Bang, which occurred 13.8 billion years ago, using the W. M. Keck Observatory. In July 2015, EGSY8p7 was announced as the oldest and most-distant known object, surpassing the previous record holder, EGS-zs8-1, which was determined in May 2015 as the oldest and most distant object. In March 2016, Pascal Oesch, one of the discoverers of EGSY8p7, announced the discovery of GN-z11, an older and more distant galaxy.
GN-z11 is a high-redshift galaxy found in the constellation Ursa Major. It is among the farthest known galaxies from Earth ever discovered. The 2015 discovery was published in a 2016 paper headed by Pascal Oesch and Gabriel Brammer. Up until the discovery of JADES-GS-z13-0 in 2022 by the James Webb Space Telescope, GN-z11 was the oldest and most distant known galaxy yet identified in the observable universe, having a spectroscopic redshift of z = 10.957, which corresponds to a proper distance of approximately 32 billion light-years. Data published in 2024 established that the galaxy contains the most distant, and therefore earliest, black hole known in the universe, estimated at around 1.6 million solar masses.
ULAS J1342+0928 is the third-most distant known quasar detected and contains the second-most distant and oldest known supermassive black hole, at a reported redshift of z = 7.54. The ULAS J1342+0928 quasar is located in the Boötes constellation. The related supermassive black hole is reported to be "800 million times the mass of the Sun". At its discovery, it was the most distant known quasar. In 2021 it was eclipsed by QSO J0313-1806 as the most distant quasar.
HD1 is a proposed high-redshift galaxy, which is considered to be one of the earliest and most distant known galaxies yet identified in the observable universe. The galaxy, with an estimated redshift of approximately z = 13.27, is seen as it was about 324 million years after the Big Bang, which was 13.787 billion years ago. It has a light-travel distance of 13.463 billion light-years from Earth, and, due to the expansion of the universe, a present proper distance of 33.288 billion light-years.
SMACS J0723.3–7327, commonly referred to as SMACS 0723, is a galaxy cluster about 4 billion light years from Earth, within the southern constellation of Volans. It is a patch of sky visible from the Southern Hemisphere on Earth and often observed by the Hubble Space Telescope and other telescopes in search of the deep past. It was the target of the first full-color image to be unveiled by the James Webb Space Telescope (JWST), imaged using NIRCam, with spectra included, showing objects lensed by the cluster with redshifts implying they are 13.1 billion years old. The cluster has been previously observed by the Hubble Space Telescope (HST) as part of the Southern MAssive Cluster Survey (SMACS), as well as Planck and Chandra.
GLASS-z12 is a Lyman-break galaxy discovered by the Grism Lens-Amplified Survey from Space (GLASS) observing program using the James Webb Space Telescope's NIRCam in July 2022. Spectroscopic observations of GLASS-z12 by the Atacama Large Millimeter Array (ALMA) in August 2022 confirmed that the galaxy has a spectroscopic redshift of 12.117±0.012, making it one of the earliest and most distant galaxies ever discovered, dating back to just 350 million years after the Big Bang, 13.6 billion years ago. ALMA observations detected an emission line associated with doubly ionized oxygen at 258.7 GHz with a significance of 5σ, suggesting that there is very low dust content in GLASS-z12, if not the early universe as well. Also based on oxygen-related measurements, the age of the galaxy is confirmed.
CEERS-93316 is a high-redshift galaxy with a spectroscopic redshift z=4.9. Significantly, the redshift that was initially reported was photometric and would have made CEERS-93316 the earliest and most distant known galaxy observed.
JADES-GS-z13-0 is a high-redshift Lyman-break galaxy discovered by the James Webb Space Telescope (JWST) during NIRCam imaging for the JWST Advanced Deep Extragalactic Survey (JADES) on 29 September 2022. Spectroscopic observations by JWST's NIRSpec instrument in October 2022 confirmed the galaxy's redshift of z = 13.2 to a high accuracy, establishing it as the oldest and most distant spectroscopically-confirmed galaxy known as of 2023, with a light-travel distance of 13.4 billion years. Due to the expansion of the universe, its present proper distance is approximately 33 billion light-years.
F200DB-045 is a candidate high-redshift galaxy, with an estimated redshift of approximately z = 20.4, corresponding to 168 million years after the Big Bang. If confirmed, it would be one of the earliest and most distant known galaxies observed.
UHZ1 is a background galaxy containing a quasar. At a redshift of approximately 10.1, UHZ1 is at a distance of 13.2 billion light-years, seen when our universe was about 3 percent of its current age. This redshift made it the most distant, and therefore earliest known quasar in the observable universe as of 2023. To detect this object, astronomers working at the Chandra X-ray Observatory used the Abell 2744's cluster mass as a gravitational lens in order to magnify distant objects directly behind it. At the time of discovery, it exceeded the distance record of QSO J0313−1806.
UNCOVER-z13 is a high-redshift Lyman-break galaxy discovered by the James Webb Space Telescope (JWST) during NIRCam imaging for the JWST Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization (UNCOVER) project on November 14, 2023. UNCOVER-z13 is within Abell 2744 supercluster in the constellation Sculptor.
