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Pi Aquarii
Pi Aquarii, Latinized from π Aquarii, is the Bayer designation for a binary star in the equatorial constellation of Aquarius. This system has an apparent visual magnitude of a mean apparent magnitude of +4.57. Based upon parallax measurements, it is located at a distance of roughly from Earth. It is drifting further away with a radial velocity of . This is a binary star system with an orbital period of 84.1 days. The primary component is a B1 giant or subgiant star. This is a large star with nearly eleven times the mass and over six times the radius of the Sun. Pi Aquarii shines about 7,300 times as brightly as the Sun. This energy is being radiated from its outer atmosphere at an effective temperature of , giving it the blue-hued glow of a B-type star. It is spinning rapidly with a projected rotational velocity of . The nature of the secondary is unknown; some analyses have suggested it is an A- or F-type main-sequence star, but the possibility of a white dwarf ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquarius (constellation)
Aquarius is an celestial equator, equatorial constellation of the zodiac, between Capricornus and Pisces (constellation), Pisces. Its name is Latin for "water-carrier" or "cup-carrier", and its old astronomical symbol is (♒︎), a representation of water. Aquarius is one of the oldest of the recognized constellations along the zodiac (the Sun's apparent path). It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is found in a region often called the Sea (astronomy), Sea due to its profusion of constellations with watery associations such as Cetus the whale, Pisces (constellation), Pisces the fish, and Eridanus (constellation), Eridanus the river. At apparent magnitude 2.9, Beta Aquarii is the brightest star in the constellation. History and mythology Aquarius is identified as "The Great One" in the Babylonian star catalogues and represents the god Ea (god), Ea himself, who is commonly depic ... [...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] |
Zeta Aquarii
Zeta Aquarii (ζ Aquarii, ζ Aqr) is the Bayer designation for a triple star system, the central star of the "water jar" asterism in the equatorial constellation of Aquarius. The combined apparent visual magnitude of this system is 3.65, which is readily visible to the naked eye. Parallax measurements yield a distance estimate of around from Earth. Etymology In the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', this star was designated ''Achr al Achbiya'' (آخر ألأخبية - ''ākhir al-akhbiya''), which was translated into Latin as ''Postrema Tabernaculorum'', meaning ''the end of luck of the homes (tents)''. This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were ''al-Akḣbiya'' (الأخبية), the Tents. In Chinese, (), meaning ''Tomb'', refers to an asterism consisting of ζ Aquarii, γ Aquarii, η Aquarii and π Aquarii. Consequently, the Chinese name for ζ Aquarii itself is (, en, the First Star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Aquarii
Gamma Aquarii, or γ Aquarii, is a suspected binary star system in the constellation of Aquarius. It has an apparent visual magnitude of 3.849, making it one of the brighter members of the constellation. Based upon parallax measurements taken during the Hipparcos mission, this star is located at a distance of approximately from the Sun. It is drifting closer to the Sun with a radial velocity of −16 km/s. In 1998, Olin J. Eggen included this star as a candidate member of the Hyades Supercluster. Gamma Aquarii is the primary or 'A' component of a double star designated WDS J22217-0123. The secondary or 'B' component is UCAC2 31430071. Gamma Aquarii A's two purported components are therefore designated WDS J22217-0123 Aa and Ab. Gamma Aquarii is traditionally also called Sadachbia , a name now formally restricted to γ Aqr Aa. Nomenclature ''γ Aquarii'', Latinised to ''Gamma Aquarii'', is the system's Bayer designation. WDS J22217-0123 A is its designation in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rooftop (Chinese Constellation)
The Roof mansion () is one of the twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise The Black Tortoise () is one of the Four Symbols of the Chinese constellations. Despite its English name, it is usually depicted as a tortoise entwined together with a snake. The name used in East Asian languages does not mention either anima .... Asterisms References {{Chinese constellation Chinese constellations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Astronomy
Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categorized in the twenty-eight mansions have been found on oracle bones unearthed at Anyang, dating back to the mid-Shang dynasty. The core of the "mansion" (宿 ''xiù'') system also took shape around this period, by the time of King Wu Ding (1250–1192 BCE). Detailed records of astronomical observations began during the Warring States period (fourth century BCE) and flourished from the Han period onward. Chinese astronomy was equatorial, centered on close observation of circumpolar stars, and was based on different principles from those in traditional Western astronomy, where heliacal risings and settings of zodiac constellations formed the basic ecliptic framework. Joseph Needham has described the ancient Chinese as the most persistent and accurate obser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grotius
Hugo Grotius (; 10 April 1583 – 28 August 1645), also known as Huig de Groot () and Hugo de Groot (), was a Dutch humanist, diplomat, lawyer, theologian, jurist, poet and playwright. A teenage intellectual prodigy, he was born in Delft and studied at Leiden University. He was imprisoned in Loevestein Castle for his involvement in the intra-Calvinist disputes of the Dutch Republic, but escaped hidden in a chest of books that was transported to Gorinchem. Grotius wrote most of his major works in exile in France. Hugo Grotius was a major figure in the fields of philosophy, political theory and law during the 16th and 17th centuries. Along with the earlier works of Francisco de Vitoria and Alberico Gentili, he laid the foundations for international law, based on natural law in its Protestant side. Two of his books have had a lasting impact in the field of international law: ''De jure belli ac pacis'' 'On the Law of War and Peace''dedicated to Louis XIII of France and the '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: * Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. * Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of the Sun, for example, varies by about 0.1% over an 11-year solar cycle. Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. Of the modern astronomers, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emission Line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected ones of atoms and molecules, and are thus used to identify the atomic and molecular components of stars and planets, which would otherwise be impossible. Types of line spectra Spectral lines are the result of interaction between a quantum system (usually atoms, but sometimes molecules or atomic nucleus, atomic nuclei) and a single photon. When a photon has about the right amount of photon energy, energy (which is connected to its frequency) to allow a change in the energy state of the system (in the case of an atom this is usually an electron changing Electron configuration, orbitals), the photon is absorbed. Then the energy will be spontaneously ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Be Star
Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer emission lines. Definition and classification Many stars have B-type spectra and show hydrogen emission lines, including many supergiants, Herbig Ae/Be stars, mass-transferring binary systems, and B stars. It is preferred to restrict usage of the term Be star to non-supergiant stars showing one or more Balmer series lines in emission. These are sometimes referred to as classical Be stars. The emission lines may be present only at certain times. Although the Be type spectrum is most strongly produced in class B stars, it is also detected in O and A shell stars, and these are sometimes included under the "Be star" banner. Be stars are primarily considered to be main sequence stars, but a number of subgiants and giant stars are also inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Luyten in 1922. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
F-type Main-sequence Star
An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII and VIII. This temperature range gives the F-type stars a whitish hue when observed by the atmosphere. Because a main-sequence star is referred to as a dwarf star, this class of star may also be termed a yellow-white dwarf (not to be confused with white dwarfs, remnant stars that are a possible final stage of stellar evolution). Notable examples include Procyon A, Gamma Virginis A and B, and KIC 8462852. Spectral standard stars The revised Yerkes Atlas system (Johnson & Morgan 1953) listed a dense grid of F-type dwarf spectral standard stars; however, not all of these have survived to this day as stable standards. The ''anchor points'' of the MK spectral classification system among the F-type main-sequence dwarf stars, i.e. those standa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
