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Alcyoneus (galaxy)
Alcyoneus is a low-excitation, Fanaroff–Riley classification, Fanaroff–Riley class II radio galaxy located away from Earth, corresponding to the galaxy SDSS J081421.68+522410.0. It is located in the constellation Lynx (constellation), Lynx and it was discovered in Low-Frequency Array (LOFAR), Low-Frequency Array (LOFAR) data by a team of astronomers led by Martijn Oei. It has the largest extent of any radio galaxy identified, with lobed structures spanning across, described by its discoverers as the "largest known structure of galactic origin." For comparison, another similarly sized giant radio galaxy is 3C 236, with lobes 15 million light-years across. Aside from the size of its radio emissions, the central galaxy is otherwise of ordinary radio luminosity, stellar mass, and supermassive black hole mass. It is a standalone galaxy with an isophotal diameter at 25.0 r-mag/arcsec2 of about , with the nearest cluster located 11 million light years away from it. The galaxy was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low Frequency Array
The Low-Frequency Array, or LOFAR, is a large radio telescope, with an antenna network located mainly in the Netherlands, and spreading across 7 other European countries as of 2019. Originally designed and built by ASTRON, the Netherlands Institute for Radio Astronomy, it was first opened by queen Beatrix of The Netherlands in 2010, and has since been operated on behalf of the International LOFAR Telescope (ILT) partnership by ASTRON. LOFAR consists of a vast array of omnidirectional radio antennas using a modern concept, in which the signals from the separate antennas are not connected directly electrically to act as a single large antenna, as they are in most array antennas. Instead, the LOFAR dipole antennas (of two types) are distributed in stations, within which the antenna signals can be partly combined in analogue electronics, then digitised, then combined again across the full station. This step-wise approach provides great flexibility in setting and rapidly changing the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranus (mythology)
In Greek mythology, Uranus ( ), sometimes written Ouranos ( grc, Οὐρανός, , sky, ), is the personification of the sky and one of the Greek primordial deities. According to Hesiod, Uranus was the son and husband of Gaia (Earth), with whom he fathered the first generation of Titans. However, no cult addressed directly to Uranus survived into Classical times, and Uranus does not appear among the usual themes of Greek painted pottery. Elemental Earth, Sky, and Styx might be joined, however, in solemn invocation in Homeric epic. Uranus is associated with the Roman god Caelus and the Jewish god Yahweh. Etymology Most linguists trace the etymology of the name to a Proto-Greek form ''*Worsanós'' (), enlarged from *''ṷorsó-'' (also found in Greek ''()'' 'to urinate', Sanskrit ''varṣá'' 'rain', Hittite ''ṷarša-'' 'fog, mist'). Robert S. P. Beekes, ''Etymological Dictionary of Greek'', vol. 2 (Leiden: Brill, 2009), 1128–1129. The basic Indo-European root is '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hercules A
Hercules A is a bright astronomical radio source within the vicinity of the constellation Hercules corresponding to the galaxy 3C 348. Observation During a survey of bright radio sources in the mid-20th century, astronomers found a very bright radio source in the constellation Hercules. The radio source is strongest in the middle range frequency and emits synchrotron radiation, suggesting the source of radio emission may be gravitational interaction. In 1959, astronomers from the Radio Astronomy Group (later the Cavendish Astrophysics Group) detected the radio source using the Cambridge Interferometer of the Cavendish Observatory in Cambridge University in United Kingdom, including it in the Third Cambridge Catalogue of Radio Sources (3C) as 3C 348, the 348th object detected by the survey. Characteristics Galaxy The galaxy, 3C 348, is a supergiant elliptical galaxy. It is classified as type E3 to E4 of the updated Hubble–de Vaucouleurs extended galaxy morphological class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Largest Galaxies
This is a list of largest galaxies known, sorted by order of increasing major axis diameters. The unit of measurement used is the light-year (approximately 9.46 kilometers). Overview Galaxies are vast collections of stars, planets, nebulae and other objects that are surrounded by an interstellar medium and held together by gravity. They do not have a definite boundary by nature, and are characterized with gradually decreasing stellar density as a function of increasing distance from its center. Because of this, measuring the sizes of galaxies can often be difficult and have a wide range of results depending on the sensitivity of the detection equipment and the methodology being used. Some galaxies emit more strongly in wavelengths outside the visible spectrum, depending on its stellar population, whose stars may emit more strongly in other wavelengths that are beyond the detection range. It is also important to consider the morphology of the galaxy when attempting to measure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Jet
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as an extended beam along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity. The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources. They likely arise from dynamic interactions within accretion disks, whose active processes are commonly connected with compact central objects such as black holes, neutron stars or pulsars. One explanation is that tangled magnetic fields are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide Jets may also be influenced by a general relativity effect known as frame-dragging. Most of the largest and most active jets are created by supermassive black holes ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Population
During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed that bluer stars were strongly associated with the spiral arms, and yellow stars dominated near the central galactic bulge and within globular star clusters. Two main divisions were defined as * Population I and * Population II, with another newer, hypothetical division called * Population III added in 1978; they are often simply abbreviated as Pop. I, Pop. II, and Pop. III. Among the population types, significant differences were found with their individual observed stellar spectra. These were later shown to be very important and were possibly related to star formation, observed kinematics, stellar age, and even galaxy evolution in both spiral and elliptical galaxies. These three simple population classes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Web
The observable universe is a Ball (mathematics), ball-shaped region of the universe comprising all matter that can be observation, observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these astronomical object, objects has had time to reach the Solar System and Earth since the beginning of the metric expansion of space, cosmological expansion. There may be 2 trillion galaxy, galaxies in the observable universe, although that number was reduced in 2021 to only several hundred billion based on data from ''New Horizons''. Assuming the universe is isotropy, isotropic, the distance to the edge of the observable universe is roughly equidistant, the same in every direction. That is, the observable universe is a sphere, spherical region centered on the observer and is unique for every unique observational position. The word ''observable'' in this sense does not refer to the capability of modern technology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Galactic Nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an "active galaxy". The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy. Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe, and as such can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on models of the cosmos. The observed characteristics of an AGN depend on several properties such as the mass of the central black hole, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Mass
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of the Sun. This equates to about two nonillion (short scale), two quintillion (long scale) kilograms or 2000 quettagrams: The solar mass is about times the mass of Earth (), or times the mass of Jupiter (). History of measurement The value of the gravitational constant was first derived from measurements that were made by Henry Cavendish in 1798 with a torsion balance. The value he obtained differs by only 1% from the modern value, but was not as precise. The diurnal parallax of the Sun was accurately measured during the transits of Venus in 1761 and 1769, yielding a value of (9 arcseconds, compared to the present value of ). From the value of the diurnal parallax, one can determine the distance to the Sun from the geomet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sloan Digital Sky Survey
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 and was named after the Alfred P. Sloan Foundation, which contributed significant funding. A consortium of the University of Washington and Princeton University was established to conduct a redshift survey. The Astrophysical Research Consortium (ARC) was established in 1984 with the additional participation of New Mexico State University and Washington State University to manage activities at Apache Point. In 1991 the Sloan Foundation granted the ARC funding for survey efforts and the construction of equipment to carry out the work.. Background At the time of its design, the SDSS was a pioneering combination of novel instrumentation as well as data reduction and storage techniques that drove major advances in astronomical observations, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supermassive Black Hole
A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, not even light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way has a supermassive black hole in its Galactic Center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars. Two supermassive black holes have been directly imaged by the Event Horizon Telescope: the black hole in the giant elliptical galaxy Messier 87 and the black hole at the Milky Way’s center. Description Supermassiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Jet
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as an extended beam along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity. The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources. They likely arise from dynamic interactions within accretion disks, whose active processes are commonly connected with compact central objects such as black holes, neutron stars or pulsars. One explanation is that tangled magnetic fields are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide Jets may also be influenced by a general relativity effect known as frame-dragging. Most of the largest and most active jets are created by supermassive black holes ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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