EGS-zs8-1 is a high-redshift Lyman-break galaxy found at the northern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellation ...

Boötes Boötes ( ) is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from la, Boōtēs, which comes from grc-gre, Βοώτης, Boṓtē ...

. In May 2015, EGS-zs8-1 had the highest

spectroscopic Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in fr ...

of any known

galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System ...

, meaning EGS-zs8-1 was the most distant and the oldest galaxy observed. In July 2015, EGS-zs8-1 was surpassed by

EGSY8p7 __NOTOC__ EGSY8p7 (EGSY-2008532660) is a distant galaxy in the constellation of Boötes, with a spectroscopic redshift of ''z'' = 8.68 (photometric redshift 8.57), a light travel distance of 13.2 billion light-years from Earth. Therefore ...

(EGSY-2008532660).

Description

The redshift of EGS-zs8-1 was measured at z = 7.73, corresponding to a

light travel distance Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe. They are often used to tie some ''observable'' quantity (such as the luminosity of a distant quasar, the ...

of about 13.040 billion light years from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

, and age of 13.04 billion years. The galaxy shows a high rate of

star formation Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

, so it releases its peak radiation at the

vacuum ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

part of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

, near the Lyman-alpha emission line due to the intense radiation from newly formed blue stars, hence it is classified as a Lyman-break galaxy; high-redshift

starburst galaxies A starburst galaxy is one undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies. For example, the star formatio ...

emitting the Lyman-alpha emission line. Because of the cosmological redshift

effect Effect may refer to: * A result or change of something ** List of effects ** Cause and effect, an idiom describing causality Pharmacy and pharmacology * Drug effect, a change resulting from the administration of a drug ** Therapeutic effect, a ...

caused by the

metric expansion of space The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not ex ...

, the peak light from the galaxy has become

ed and has moved into the

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

part of the

. The galaxy has a

comoving distance In standard cosmology, comoving distance and proper distance are two closely related distance measures used by cosmologists to define distances between objects. ''Proper distance'' roughly corresponds to where a distant object would be at a spec ...

(light travel distance multiplied by the

Hubble constant Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving ...

, caused by the metric expansion of space) of about 30 billion light years from Earth. EGS-zs8-1 was born 670 million years after the

Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...

, during the period of

reionization In the fields of Big Bang theory and cosmology, reionization is the process that caused matter in the universe to reionize after the lapse of the " dark ages". Reionization is the second of two major phase transitions of gas in the universe (t ...

, and it's 15 percent the size of the Milky Way. The galaxy was found to be larger than its other neighbors in that period when the universe was still very young. Its mass at the time the light was emitted is estimated to have been about 15% of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

's current mass. The galaxy was making new stars at roughly 80 times the rate of the current Milky Way, or equivalent to 800 worth of material turning to stars every year. The light reaching Earth was made by stars in EGS-zs8-1 that were 100 million to 300 million years old at the time they emitted the light. The age of EGS-zs8-1 places it in the

phase of creation, a time when hydrogen outside the galaxies was switching from a neutral to ionized state. According to the galaxy's discoverers, EGS-zs8-1 and other early galaxies were likely the causes of reionization.

Discovery

In 2013,

Yale Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the wor ...

astronomer Pascal Oesch spotted an unexpected bright object while looking at

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

images. He then confirmed the existence of the object using the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, ...

Redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in fr ...

calculations, using the Multi-Object Spectrometer for Infrared Exploration (MOSFIRE) equipment at the W.M. Keck Observatory in

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

, were then performed to precisely determine the age of the galaxy. Oesch and his colleagues at Yale and the

University of California, Santa Cruz The University of California, Santa Cruz (UC Santa Cruz or UCSC) is a public land-grant research university in Santa Cruz, California. It is one of the ten campuses in the University of California system. Located on Monterey Bay, on the ed ...

announced the find, which was named EGS-zs8-1, in May 2015 surpassing the previous record for oldest galaxy by about 30 million years.

References

{{2015 in space Boötes Galaxies ? Dwarf galaxies

Description

Discovery

See also

References