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Atria (star)
Alpha Trianguli Australis ( Latinised from α Trianguli Australis, abbreviated Alpha TrA, α TrA), officially named Atria , is the brightest star in the southern constellation of Triangulum Australe, forming an apex of a triangle with Beta Trianguli Australis and Gamma Trianguli Australis that gives the constellation its name ( Latin for southern triangle). Nomenclature ''α Trianguli Australis'' (Latinised to ''Alpha Trianguli Australis'') is the star's Bayer designation. The historical name ''Atria'' is a contraction. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Atria'' for this star. In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, (), meaning '' Triangle'', refers to an asterism co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangulum Australe
Triangulum Australe is a small constellation in the far Southern Celestial Hemisphere. Its name is Latin for "the southern triangle", which distinguishes it from Triangulum in the northern sky and is derived from the acute, almost equilateral pattern of its three brightest stars. It was first depicted on a celestial globe as Triangulus Antarcticus by Petrus Plancius in 1589, and later with more accuracy and its current name by Johann Bayer in his 1603 '' Uranometria''. The French explorer and astronomer Nicolas Louis de Lacaille charted and gave the brighter stars their Bayer designations in 1756. Alpha Trianguli Australis, known as Atria, is a second-magnitude orange giant and the brightest star in the constellation, as well as the 42nd-brightest star in the night sky. Completing the triangle are the two white main sequence stars Beta and Gamma Trianguli Australis. Although the constellation lies in the Milky Way and contains many stars, deep-sky objects are not promi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Language
Chinese (, especially when referring to written Chinese) is a group of languages spoken natively by the ethnic Han Chinese majority and many minority ethnic groups in Greater China. About 1.3 billion people (or approximately 16% of the world's population) speak a variety of Chinese as their first language. Chinese languages form the Sinitic branch of the Sino-Tibetan languages family. The spoken varieties of Chinese are usually considered by native speakers to be variants of a single language. However, their lack of mutual intelligibility means they are sometimes considered separate languages in a family. Investigation of the historical relationships among the varieties of Chinese is ongoing. Currently, most classifications posit 7 to 13 main regional groups based on phonetic developments from Middle Chinese, of which the most spoken by far is Mandarin (with about 800 million speakers, or 66%), followed by Min (75 million, e.g. Southern Min), Wu (74 million, e.g. Shangh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flare Star
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to the magnetic energy stored in the stars' atmospheres. The brightness increase is across the spectrum, from X-rays to radio waves. The first known flare stars ( V1396 Cygni and AT Microscopii) were discovered in 1924. However, the best-known flare star is UV Ceti, first observed to flare in 1948. Today similar flare stars are classified as UV Ceti type variable stars (using the abbreviation UV) in variable star catalogs such as the General Catalogue of Variable Stars. Most flare stars are dim red dwarfs, although recent research indicates that less massive brown dwarfs might also be capable of flaring. The more massive RS Canum Venaticorum variables (RS CVn) are also known to flare, but it is understood that these flares are induced by a companion star in a binary system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Star
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar System" and "solar system" structures in theinaming guidelines document. The name is commonly rendered in lower case ('solar system'), as, for example, in the ''Oxford English Dictionary'' an''Merriam-Webster's 11th Collegiate Dictionary''. is the gravity, gravitationally bound system of the Sun and the objects that orbit it. It Formation and evolution of the Solar System, formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The solar mass, vast majority (99.86%) of the system's mass is in the Sun, with most of the Jupiter mass, remaining mass contained in the planet Jupiter. The four inner Solar System, inner system planets—Mercury (planet), Mercury, Venus, Earth and Mars—are terrest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never far from the Sun, either as morning star or evening star. Aside from the Sun and Moon, Venus is the brightest natural object in Earth's sky, capable of casting visible shadows on Earth at dark conditions and being visible to the naked eye in broad daylight. Venus is the second largest terrestrial object of the Solar System. It has a surface gravity slightly lower than on Earth and has a very weak induced magnetosphere. The atmosphere of Venus, mainly consists of carbon dioxide, and is the densest and hottest of the four terrestrial planets at the surface. With an atmospheric pressure at the planet's surface of about 92 times the sea level pressure of Earth and a mean temperature of , the carbon dioxide gas at Venus's surface is in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Radius
Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: :1\,R_ = 6.957\times 10^8 \hbox is approximately 10 times the average radius of Jupiter, about 109 times the radius of the Earth, and 1/215th of an astronomical unit, the distance of the Earth from the Sun. It varies slightly from pole to equator due to its rotation, which induces an oblateness in the order of 10 parts per million. Measurements The unmanned SOHO spacecraft was used to measure the radius of the Sun by timing transits of Mercury across the surface during 2003 and 2006. The result was a measured radius of . Haberreiter, Schmutz & Kosovichev (2008) determined the radius corresponding to the solar photosphere to be . This new value is consistent with helioseismic estimates; the same study showed that previous estimates using inflection poin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve (as a function of wavelength) is not known. When the star's or planet's net emissivity in the relevant wavelength band is less than unity (less than that of a black body), the actual temperature of the body will be higher than the effective temperature. The net emissivity may be low due to surface or atmospheric properties, including greenhouse effect. Star The effective temperature of a star is the temperature of a black body with the same luminosity per ''surface area'' () as the star and is defined according to the Stefan–Boltzmann law . Notice that the total (bolometric) luminosity of a star is then , where is the stellar radius. The definition of the stellar radius is obviously not straightf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Luminosity
The solar luminosity (), is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal solar luminosity is defined by the International Astronomical Union to be . This does not include the solar neutrino luminosity, which would add , or , i.e. a total of (the mean energy of the solar photons is 26 MeV and that of the solar neutrinos 0.59 MeV, i.e. 2.27%; the Sun emits photons and as many neutrinos each second, of which per m2 reach the Earth each second). The Sun is a weakly variable star, and its actual luminosity therefore fluctuates. The major fluctuation is the eleven-year solar cycle (sunspot cycle) that causes a quasi-periodic variation of about ±0.1%. Other variations over the last 200–300 years are thought to be much smaller than this. Determination Solar luminosity is related to solar irradiance (the solar c ... [...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 geometry o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Main Sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. Stars on this band are known as main-sequence stars or dwarf stars. These are the most numerous true stars in the universe and include the Sun. After condensation and ignition of a star, it generates thermal energy in its dense core region through nuclear fusion of hydrogen into helium. During this stage of the star's lifetime, it is located on the main sequence at a position determined primarily by its mass but also based on its chemical composition and age. The cores of main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. The strong dependence of the rate of energy ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects show a larger parallax than farther objects when observed from different positions, so parallax can be used to determine distances. To measure large distances, such as the distance of a planet or a star from Earth, astronomers use the principle of parallax. Here, the term ''parallax'' is the semi-angle of inclination between two sight-lines to the star, as observed when Earth is on opposite sides of the Sun in its orbit. These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder. Parallax also affects optical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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