HUDF-JD2 (UDF 033238.7 -274839.8 or BBG 3179) is a distant, massive, post-

starburst galaxy 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 format ...

that was discovered with the

Hubble Ultra Deep Field The Hubble Ultra-Deep Field (HUDF) is a List of deep fields, deep-field image of a small region of outer space, space in the constellation Fornax, containing an estimated 10,000 galaxies. The original data for the image was collected by the Hub ...

(HUDF) image. It was the most distant galaxy identified in the HUDF, in 2005. It is located at in the constellation of

Fornax Fornax () is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus (constellation), Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Forna ...

. In a 2005 search for very red galaxies in the HUDF that were not detected at wavelengths shorter than the near-infrared J band, two objects were detected. The second, initially designated UDF033238.7-274839.8, displayed a high

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 ...

and showed characteristics of a post-starburst galaxy. The derived photometric redshift yielded ''z'' approximately equal to 6.5, which indicates it is most likely being viewed from a time when the Universe was only 830 million years old. The estimated bolometric luminosity of this galaxy is a trillion times the

solar luminosity The solar luminosity () is a unit of radiant flux (Power (physics), power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxy, galaxies and other celestial objects in terms of the output of ...

(the luminosity of the Sun) and it has a mass of approximately 600 billion

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

es. The

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

of this object indicates that most of its energy is being emitted by stars with three solar masses or less. Hence, as larger stars will exist for shorter periods, this galaxy has an age of more than 300 million years. The period of initial active star formation in this galaxy may have lasted less than 100 million years, during which the galaxy likely participated in the

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". ...

event. The unusually high mass estimate for this object may be explained by other factors. If it has an

active galactic nucleus An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

, this may reduce the mass estimate to half the current value. The estimate could also be affected by

gravitational lensing A gravitational lens is matter, such as a galaxy cluster, cluster of galaxies or a point particle, that bends light from a distant source as it travels toward an observer. The amount of gravitational lensing is described by Albert Einstein's Ge ...

, although it is too far away from the nearest visible object that could produce that effect: a foreground

spiral galaxy Spiral galaxies form a galaxy morphological classification, class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''

located 7.3 distant.

References

External links

*
Hubblesite HUDF.JD2
{{DEFAULTSORT:HUDF-JD2 Starburst galaxies Fornax Hubble Ultra-Deep Field Hubble Space Telescope

See also

References

External links