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 Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

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 , which comes from 'herder, herdsman' or 'plowman' (literally, 'o ...

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

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 increase in frequency and e ...

of any known

galaxy A galaxy is a Physical system, system of stars, stellar remnants, interstellar medium, interstellar gas, cosmic dust, dust, and dark matter bound together by gravity. The word is derived from the Ancient Greek, Greek ' (), literally 'milky', ...

, 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).

Description

The redshift of EGS-zs8-1 was measured at z = 7.73, corresponding to a light travel distance of about 13.040 billion light years from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, 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 interstellar space—sometimes referred to as "stellar nurseries" or "star-forming regions"—Jeans instability, collapse and form stars. As a branch of astronomy, sta ...

, so it releases its peak radiation at the

vacuum ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of the ...

part of the

electromagnetic spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...

, 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 emitting the Lyman-alpha emission line. Because of the

cosmological redshift 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 a galaxy is from the Earth, the faster ...

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, ...

caused by the

expansion of the universe The expansion of the universe is the increase in proper length, distance between Gravitational binding energy, gravitationally unbound parts of the observable universe with time. It is an intrinsic and extrinsic properties (philosophy), intrins ...

, 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 that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

part of the

. The galaxy has a

comoving distance In standard cosmology, comoving distance and proper distance (or physical distance) are two closely related distance measures used by cosmologists to define distances between objects. ''Comoving distance'' factors out the expansion of the univ ...

of about 30 billion light years from Earth. EGS-zs8-1 was born 670 million years after the

Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...

, during the period of

reionization In the fields of Big Bang theory and physical cosmology, cosmology, reionization is the process that caused electrically neutral atoms in the primordial universe to reionize after the lapse of the "Timeline of the Big Bang#Dark Ages, dark ages". ...

, 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 or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

'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 Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the third-oldest institution of higher education in the United States, and one of the nine colonial colleges ch ...

astronomer Pascal Oesch spotted an unexpected bright object while looking at

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

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, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

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 increase in frequency and e ...

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

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

, 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 university, public Land-grant university, land-grant research university in Santa Cruz, California, United States. It is one of the ten campuses in the University of C ...

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 Ursa Major Boötes ? Dwarf galaxies

Description

Discovery

See also

References