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Gigaparsec
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 is defined as the distance at which 1 au subtends an angle of one arcsecond ( of a degree). This corresponds to astronomical units, i.e. 1\, \mathrm = 1/\tan \left( \ \mathrm \right)\, \mathrm. The nearest star, Proxima Centauri, is about from the Sun. Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand. The word ''parsec'' is a portmanteau of "parallax of one second" and was coined by the British astronomer Herbert Hall Turner in 1913 to make calculations of astronomical distances from only raw observational data easy for astronomers. Partly for this reason, it is the unit preferred in astronomy and astrophysics, though the light-year remains prominent in popular sci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petametres
The following are examples of orders of magnitude for different lengths. __TOC__ Overview Detailed list To help compare different orders of magnitude, the following list describes various lengths between 1.6 \times 10^ metres and 10^metres. Subatomic scale Atomic to cellular scale Cellular to human scale Human to astronomical scale Astronomical scale Less than 1 zeptometre The ' ( SI symbol: ') is a unit of length in the metric system equal to . To help compare different orders of magnitude, this section lists lengths shorter than 10−21 m (1 zm). *1.6 × 10−5 quectometres (1.6 × 10−35 metres) – the Planck length (Measures of distance shorter than this do not make physical sense, according to current theories of physics.) *1 qm – 1 quectometre, the smallest named subdivision of the metre in the SI base unit of length, one nonillionth of a metre *1 rm – 1 rontometre, a subdivision of the metre in the SI base unit of length, one octilliont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unit Of Length
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units. Metric system SI The base unit in the International System of Units (SI) is the metre, defined as "the length of the path travelled by light in vacuum during a time interval of seconds." It is approximately equal to . Other SI units are derived from the metre by adding prefixes, as in millimetre or kilometre, thus producing systematic decimal multiples and submultiples of the base unit that span many orders of magnitude. For example, a kilometre is . Non-SI In the centimetre–gram–second system of units, the basic unit of length is the centimetre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial ''object'' is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures. Examples of astronomical objects include planetary systems, star clusters, nebulae, and galaxies, while asteroids, moons, planets, and stars are astronomical bodies. A comet may be identified as both body and object: It is a ''body'' when referring to the frozen nucleus of ice and dust, and an ''object'' when describing the entire comet with its diffuse coma and tail. History Astronomical objects such as stars, planets, nebulae, asteroids and comet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature Physics
''Nature Physics'' is a monthly peer-reviewed scientific journal published by Nature Portfolio. It was first published in October 2005 (volume 1, issue 1). The chief editor is Andrea Taroni, who is a full-time professional editor employed by this journal. Scope ''Nature Physics'' publishes both pure and applied research from all areas of physics. Subject areas covered by the journal include quantum mechanics, condensed-matter physics, optics, thermodynamics, particle physics, and biophysics. Abstracting and indexing The journal is indexed in the following databases: *Chemical Abstracts Service – CASSI *Science Citation Index *Science Citation Index Expanded *Current Contents – Physical, Chemical & Earth Sciences According to the ''Journal Citation Reports'', the journal has a 2021 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 (one million million, or billion in long scale). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year (365.25 days). Because it includes the time-measurement word "year", the term ''light-year'' is sometimes misinterpreted as a unit of time. The ''light-year'' is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist contexts and popular science publications. The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years) which derives from astrometry; it is the distance at which one astronomical unit subtends an angle of one second of arc. D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysics
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline said, Astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–''what'' they are, rather than ''where'' they are." Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, ''astrophysicists'' apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Egyptian astronomy, Egyptians, Chinese astronomy, Chinese, Maya civilization, Maya, and many anc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sirius
Sirius is the brightest star in the night sky. Its name is derived from the Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinized to Alpha Canis Majoris, and abbreviated Alpha CMa or α CMa. With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus, the next brightest star. Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years. Sirius appears bright because of its intrinsic luminosity and its proximity to the Solar System. At a distance of , the Sirius system is one of Earth's nearest neighbours. Sirius is gradually moving closer to the Solar System, so it is expected to increase in brightness slightly over the next 60,000 years, reaching a peak magnitude of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Charlier
Carl Vilhelm Ludwig Charlier (1 April 1862 – 4 November 1934) was a Swedish astronomer. His parents were Emmerich Emanuel and Aurora Kristina (née Hollstein) Charlier. Career Charlier was born in Östersund. He received his Ph.D. from Uppsala University in 1887, later worked there and at the Stockholm Observatory and was Professor of Astronomy and Director of the Observatory at Lund University from 1897. He made extensive statistical studies of the stars in our galaxy and their positions and motions, and tried to develop a model of the galaxy based on this. He proposed the siriometer as a unit of stellar distance. Charlier was also interested in pure statistics and played a role in the development of statistics in Swedish academia. Several of his pupils became statisticians, working at universities and in government and companies. Related to his work on galactic structure, he also developed a cosmological theory based on the work of Johann Heinrich Lambert. In the res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monthly Notices Of The Royal Astronomical Society
''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics. It has been in continuous existence since 1827 and publishes letters and papers reporting original research in relevant fields. Despite the name, the journal is no longer monthly, nor does it carry the notices of the Royal Astronomical Society. History The first issue of MNRAS was published on 9 February 1827 as ''Monthly Notices of the Astronomical Society of London'' and it has been in continuous publication ever since. It took its current name from the second volume, after the Astronomical Society of London became the Royal Astronomical Society (RAS). Until 1960 it carried the monthly notices of the RAS, at which time these were transferred to the newly established '' Quarterly Journal of the Royal Astronomical Society'' (1960–1996) and then to its successor journal '' Astronomy & Geophysics'' (since 1997). Until 1965, MNRAS wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbert Hall Turner
Herbert Hall Turner (13 August 1861 – 20 August 1930) was a British astronomer and seismologist. Biography Herbert Hall Turner was educated at the Leeds Modern School, Clifton College, Bristol and Trinity College, Cambridge. In 1884 he accepted the post of Chief Assistant at the Royal Greenwich Observatory and stayed there for nine years. In 1893 he became Savilian Professor of Astronomy and Director of the Radcliffe Observatory at Oxford University, a post he held for 37 years until his sudden death in 1930. He was one of the observers in the Eclipse Expeditions of 1886 and 1887. In seismology, he is credited with the discovery of deep focus earthquakes. He is also credited with coining the word ''parsec''. His 1897 Royal Society candidature citation read: " '' Secretary of the Royal Astronomical Society. Was Chief Assistant at the Royal Observatory, Greenwich 1884-1894. Author of various papers among which may be mentioned:- * "''On the correction of the Equilibrium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Portmanteau
A portmanteau word, or portmanteau (, ) is a blend of wordsGarner's Modern American Usage , p. 644. in which parts of multiple words are combined into a new word, as in ''smog'', coined by blending ''smoke'' and ''fog'', or ''motel'', from ''motor'' and ''hotel''. In , a portmanteau is a single morph that is analyzed as representing two (or more) underlying s. When portmanteaus shorte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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