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KBC Void
The KBC Void (or Local Hole) is an immense, comparatively empty region of space, named after astronomers Ryan Keenan, Amy Barger, and Lennox Cowie, who studied it in 2013. The existence of a local underdensity has been the subject of many pieces of literature and research articles. The underdensity is proposed to be roughly spherical, approximately 2 billion light-years (600 megaparsecs, Mpc) in diameter. As with other voids, it is not completely empty but contains the Milky Way, the Local Group, and the larger part of the Laniakea Supercluster. The Milky Way is within a few hundred million light-years of the void's center. It is debated whether the existence of the KBC void is consistent with the ΛCDM model. While Haslbauer et al. say that voids as large as the KBC void are inconsistent with ΛCDM, Sahlén et al. argue that the existence of supervoids such as the KBC void is consistent with ΛCDM. Galaxies inside a void experience a gravitational pull from outside the void, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amy Barger
Amy J. Barger (born January 18, 1971) is an American astronomer and Henrietta Leavitt Professor of Astronomy at the University of Wisconsin–Madison. She is considered a pioneer in combining data from multiple telescopes to monitor multiple wavelengths and in discovering distant galaxies and supermassive black holes, which are outside of the visible spectrum. Barger is an active member of the International Astronomical Union. Education and career Barger earned a Bachelor of Arts in astronomy-physics in 1993 from the University of Wisconsin-Madison. She was a Marshall scholar at King's College, University of Cambridge and received a doctor of philosophy in astronomy from the university in 1997. Barger holds positions as a Henrietta Leavitt Professor of Astronomy at the University of Wisconsin-Madison and as an affiliate graduate faculty member in the University of Hawaii Department of Physics and Astronomy. Notable research Barger's research discoveries concern distant Uni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Microwave Background
In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination when the first atoms were formed. With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark (see: Olbers' paradox). However, a sufficiently sensitive radio telescope shows a faint background brightness, or glow, almost uniform, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southern Local Supervoid
The Southern Local Supervoid is a tremendously large, nearly empty region of space (a void). It lies next to the Local Supercluster, which contains our galaxy the Milky Way. Its center is 96 megaparsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...s away and the void is 112 megaparsecs in diameter across its narrowest width. Its volume is very approximately 600 billion times that of the Milky Way. See volumes of similar orders of magnitude. See also * List of largest voids * KBC Void References Voids (astronomy) {{galaxy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northern Local Supervoid
The Northern Local Supervoid is a region of space devoid of rich clusters of galaxies, known as a void. It is the closest supervoid and is located between the Virgo (Local), Coma and Hercules superclusters. On the sky, it is located between Boötes, Virgo, and Serpens Caput constellations. It contains a few small galaxies (primarily spirals In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are: [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hubble Bubble (astronomy)
In astronomy, a Hubble bubble would be "a departure of the local value of the Hubble constant from its globally averaged value," or, more technically, "a local monopole in the peculiar velocity field, perhaps caused by a local void in the mass density." The Hubble constant, named for astronomer Edwin Hubble, whose work made clear the expansion of the universe, measures the rate at which expansion occurs. In accordance with the Copernican principle that the Earth is not in a central, specially favored position, one would expect that measuring this constant at any point in the universe would yield the same value. If, on the other hand, Earth were at or near the center of a very low-density region of interstellar space (a relative void), the local expansion of space would be faster due to the lack of nearby mass to slow it down. Thus, stars inside such a "Hubble bubble" would accelerate away from Earth much faster than the general expansion of the universe. This situation would pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Largest Cosmic Structures
This is a list of the largest cosmic structures so far discovered. The unit of measurement used is the light-year (distance traveled by light in one Julian year; approximately 9.46 trillion kilometres). This list includes superclusters, galaxy filaments and large quasar groups (LQGs). The list characterizes each structure based on its longest dimension. Note that this list refers only to coupling of matter with defined limits, and not the coupling of matter in general (as per example the cosmic microwave background, which fills the entire universe). All structures in this list are defined as to whether their presiding limits have been identified. There are some speculations about this list: *The Zone of Avoidance, or the part of the sky occupied by the Milky Way, blocks out light to several structures, making their limits imprecisely identified. *Some structures are far too distant to be seen even with the most powerful telescopes. Some factors are included to explain the st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observable Universe
The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion. There may be 2 trillion 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 isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe is a 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 to detect light or other information from an object, or whether there is anything to be detected. It refers to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Local Void
The Local Void is a vast, empty region of space, lying adjacent to the Local Group. Discovered by Brent Tully and Rick Fisher in 1987, the Local Void is now known to be composed of three separate sectors, separated by bridges of "wispy filaments". The precise extent of the void is unknown, but it is at least 45 Mpc (150 million light-years) across, and possibly 150 to 300 Mpc. The Local Void appears to have significantly fewer galaxies than expected from standard cosmology. Location and dimensions Voids are affected by the way gravity causes matter in the universe to "clump together", herding galaxies into clusters and chains, which are separated by regions mostly devoid of galaxies, yet the exact mechanisms are subject to scientific debate. Astronomers have previously noticed that the Milky Way sits in a large, flat array of galaxies called the Local Sheet, which bounds the Local Void. The Local Void extends approximately , beginning at the edge of the Loc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Void
The Giant Void (also known as the Giant Void in NGH, Canes Venatici Supervoid, and AR-Lp 36) is an extremely large region of space with an underdensity of galaxies and located in the constellation Canes Venatici. It is the second-largest-confirmed void to date, with an estimated diameter of 300 to 400 Mpc (1 to 1.3 billion light-years) and its centre is approximately 1.5 billion light-years away ( z = 0.116). It was discovered in 1988,"The Northern Cone of Metagalaxy" (Kopylov et al. 1988) and was the largest void in the Northern Galactic Hemisphere, and possibly the second-largest ever detected. Even the hypothesized "Eridanus Supervoid" corresponding to the location of the WMAP cold spot is dwarfed by this void, although the Giant Void does not correspond to any significant cooling to the cosmic microwave background. Inside this vast void there are 17 galaxy clusters, concentrated in a spherically shaped region 50 Mpc in diameter. Studies of the motion of these clusters sho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Void (astronomy)
Cosmic voids (also known as dark space) are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies. The cosmological evolution of the void regions differs drastically from the evolution of the Universe as a whole: there is a long stage when the curvature term dominates, which prevents the formation of galaxy clusters and massive galaxies. Hence, although even the emptiest regions of voids contain more than ~15% of the average matter density of the Universe, the voids look almost empty for an observer. Voids typically have a diameter of 10 to 100 megaparsecs (30 to 300 million light-years); particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. They were first discovered in 1978 in a pioneering study by Stephen Gregory and Laird A. Thompson at the Kitt Peak National Observatory. Voids are believed to have been formed by baryon acoustic oscillations in the Big Ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the ' is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations. Newton's law of universal gravitation, which describes classical gravity, can be seen as a prediction of general relativity for the almost flat spacetime geometry around stationary mass distributions. Some predictions of general relativity, however, are beyond Newton's law of universal gra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOND
Modified Newtonian dynamics (MOND) is a hypothesis that proposes a modification of Newton's law of universal gravitation to account for observed properties of galaxies. It is an alternative to the hypothesis of dark matter in terms of explaining why galaxies do not appear to obey the currently understood laws of physics. Created in 1982 and first published in 1983 by Israeli physicist Mordehai Milgrom,. . . the hypothesis' original motivation was to explain why the velocities of stars in galaxies were observed to be larger than expected based on Newtonian mechanics. Milgrom noted that this discrepancy could be resolved if the gravitational force experienced by a star in the outer regions of a galaxy was proportional to the ''square'' of its centripetal acceleration (as opposed to the centripetal acceleration itself, as in Newton's second law) or alternatively, if gravitational force came to vary inversely ''linearly'' with radius (as opposed to the inverse square of the radius, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
