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Mercury-manganese Star
A mercury-manganese star (also HgMn star) is a type of chemically peculiar star with a prominent spectral line at 398.4 nm, due to absorption from ionized mercury. These stars are of spectral type B8, B9, or A0, corresponding to surface temperatures between about 10,000 and 15,000 K, with two distinctive characteristics: * An atmospheric excess of elements like phosphorus, manganese, gallium, strontium, yttrium, zirconium, platinum and mercury. * A lack of a strong dipole magnetic field. Their rotation is relatively slow, and as a consequence their atmosphere is relatively calm. It is thought, but has not been proven, that some types of atoms sink under the force of gravity, while others are lifted towards the exterior of the star by radiation pressure Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemically Peculiar Star
In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual metal abundances, at least in their surface layers. Classification Chemically peculiar stars are common among hot main-sequence (hydrogen-burning) stars. These hot peculiar stars have been divided into 4 main classes on the basis of their spectra, although two classification systems are sometimes used: * non-magnetic metallic-lined (Am, CP1) * magnetic (Ap, CP2) * non-magnetic mercury-manganese (HgMn, CP3) * helium-weak (He-weak, CP4). The class names provide a good idea of the peculiarities that set them apart from other stars on or near the main sequence. The Am stars (CP1 stars) show weak lines of singly ionized Ca and/or Sc, but show enhanced abundances of heavy metals. They also tend to be slow rotators and have an effective temperature between 7000 and . The Ap stars (CP2 stars) are characterized by strong magnetic fields, enhanced abundances of elements such as Si, Cr, Sr and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Pressure
Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is absorbed, reflected, or otherwise emitted (e.g. black-body radiation) by matter on any scale (from macroscopic objects to dust particles to gas molecules). The associated force is called the radiation pressure force, or sometimes just the force of light. The forces generated by radiation pressure are generally too small to be noticed under everyday circumstances; however, they are important in some physical processes and technologies. This particularly includes objects in outer space, where it is usually the main force acting on objects besides gravity, and where the net effect of a tiny force may have a large cumulative effect over long periods of time. For example, had the effects of the Sun's radiation pressure on the spacecraft of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iota Coronae Borealis
Iota Coronae Borealis, Latinized from ι Coronae Borealis, is a binary star system in the constellation Corona Borealis. It is visible to the naked eye with a combined apparent visual magnitude of is 4.96. Based upon an annual parallax shift of 10.46 mas as seen from the Earth, it is located about 312 light years from the Sun. This is a single-lined spectroscopic binary with an orbital period of 35.5 days and an eccentricity of 0.56. The visible member, component A, has a stellar classification of , indicating it is a chemically peculiar mercury-manganese star with narrow absorption lines. The secondary member, component B, appears to be an A-type star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 .... References {{DEFAULTSORT:Iota Coronae Bore ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi1 Bootis
''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yangtze River basin in China 13,500 to 8,200 years ago. ''Oryza sativa'' belongs to the genus ''Oryza'' of the grass family Poaceae. With a genome consisting of 430 Mbp across 12 chromosomes, it is renowned for being easy to genetically modify and is a model organism for the botany of cereals. Classification ''Oryza sativa'' contains two major subspecies: the sticky, short-grained ''japonica'' or ''sinica'' variety, and the nonsticky, long-grained ' rice variety. ''Japonica'' was domesticated in the Yangtze Valley 9–6,000 years ago, and its varieties can be cultivated in dry fields (it is cultivated mainly submerged in Japan), in temperate East Asia, upland areas of Southeast Asia, and high elevations in South Asia, while ''indica'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phi Herculis
Phi Herculis (φ Her) is a binary star system in the northern constellation of Hercules. Based upon an annual parallax shift of 15.99 mas as seen from Earth, it is located around 204 light years from the Sun. With a combined apparent visual magnitude of 4.24, it is bright enough to be seen with the naked eye. This is a single-lined spectroscopic binary star system with an orbital period of 564.8 days and an eccentricity of 0.526. The primary, component A, is a B-type main sequence star with a stellar classification of B9VspHgMn. It is a chemically peculiar star of the type called a mercury-manganese star. The star is tentatively catalogued as an Alpha2 Canum Venaticorum variable, with brightness variations of just 0.01 magnitudes. The secondary, component B, was first separated via interferometry in 2004. It is an A-type main sequence star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
γ Canis Majoris
Gamma Canis Majoris (γ Canis Majoris, abbreviated Gamma CMa, γ CMa), also named Muliphein , is a star in the constellation of Canis Major. It is unclear exactly why this relatively faint star was given the ' gamma' designation, but possibly because it is in the same part of the constellation as Sirius ( alpha) and Mirzam ( beta). Nomenclature ''γ Canis Majoris'' ( Latinised to ''Gamma Canis Majoris'') is the star's Bayer designation. It bore the traditional name ''Muliphein'', not to be confused with ''Muhlifain'', which is Gamma Centauri; both names derive from the same Arabic root, محلفين ''muħlifayn''. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name ''Muliphein'' for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names. Properties Gamma Canis Majoris is a blue-white B-type bright giant with a st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
χ Lupi
Chi Lupi (Chi Lup, χ Lupi, χ Lup) is a spectroscopic binary star in the constellation of Lupus. It has an apparent visual magnitude of approximately 3.957. The primary star in the binary is a mercury-manganese star of spectral type B9.5V; the secondary is a metallic-lined star of type A2Vm. This system is a proper motion member of the Upper Scorpius sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. The Upper Scorpius subgroup contains thousands of stars with an average age of 11 million years old at mean distances of 145 parsec 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, an ...s (470 light years). References {{Stars of Lupus Lupus (constellation) B-type main-sequence ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
20 Tauri
Maia , designated 20 Tauri (abbreviated 20 Tau), is a star in the constellation of Taurus. It is a blue giant of spectral type B8 III, a chemically peculiar star, and the prototype of the Maia variable class of variable star. Maia is the fourth-brightest star in the Pleiades open star cluster (Messier 45), after Alcyone, Atlas and Electra. It is surrounded by one of the brighter reflection nebulae within the Pleiades, designated NGC 1432 and sometimes called the Maia Nebula. Nomenclature The name ''Maia'' originates with the el, Μαῖα and la, Maia. Maia is one of the seven daughters of Atlas and Pleione in Greek mythology—stars which are also included in the Pleiades star cluster. 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 incl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
γ Corvi
Gamma Corvi (γ Corvi, abbreviated Gamma Crv, γ Crv) is a binary star and the brightest star in the southern constellation of Corvus, having an apparent visual magnitude of 2.59. The system's two components are designated Gamma Corvi A (officially named Gienah , traditionally the name of the system)) and Gamma Corvi B, whose magnitude is 9.7 and which is 1.1 arcseconds away from Gamma Corvi The distance to this system has been measured directly using the stellar parallax, parallax technique, yielding an estimated from the Sun. Nomenclature ''γ Corvi'' ( Latinised to ''Gamma Corvi'') is the system's Bayer designation. The designation of the components – ''Gamma Corvi A'' and ''B'' – derives from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). Gamma Corvi bore the traditional name of ''Gienah'' derived from Arabic, from Ulugh Beg's الجناح الغراب ال ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
α Andromedae
Alpha Andromedae (α Andromedae, abbreviated Alpha And or α And), officially named Alpheratz , is 97 light-years from the Sun and is the brightest star in the constellation of Andromeda when Beta Andromedae undergoes its periodical dimming. Immediately northeast of the constellation of Pegasus, it is the upper left star of the Great Square of Pegasus. Although it appears to the naked eye as a single star, with overall apparent visual magnitude +2.06, it is actually a binary system composed of two stars in close orbit. The chemical composition of the brighter of the two stars is unusual as it is a mercury-manganese star whose atmosphere contains abnormally high levels of mercury, manganese, and other elements, including gallium and xenon.Alpheratz, Kaler Star2/14/2013 It is the brightest mercury-manganese star known. Nomenclature ''α Andromedae'' ( Latinisation of names, Latinised to ''Alpha Andromedae'') is the star's Bayer designation. Ptolemy consi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apparent Visual Magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer. The word ''magnitude'' in astronomy, unless stated otherwise, usually refers to a celestial object's apparent magnitude. The magnitude scale dates back to the ancient Roman astronomer Claudius Ptolemy, whose star catalog listed stars from 1st magnitude (brightest) to 6th magnitude (dimmest). The modern scale was mathematically defined in a way to closely match this historical system. The scale is reverse logarithmic: the brighter an object is, the lower its magnitude number. A difference of 1.0 in magnitude corresponds to a brightness ratio of \sqrt /math>, or about 2.512. For example, a star of magnitude 2.0 is 2.512 times as bright as a star of magnitude 3.0, 6. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SIMBAD
SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data) is an astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de Strasbourg (CDS), France. SIMBAD was created by merging the Catalog of Stellar Identifications (CSI) and the Bibliographic Star Index as they existed at the Meudon Computer Centre until 1979, and then expanded by additional source data from other catalogues and the academic literature. The first on-line interactive version, known as Version 2, was made available in 1981. Version 3, developed in the C language and running on UNIX stations at the Volgograd Observatory, was released in 1990. Fall of 2006 saw the release of Version 4 of the database, now stored in PostgreSQL, and the supporting software, now written entirely in Java. JP11 is a star catalogue containing about 4,000 objects. Currently it exists only as a part of the SIMBAD database. , SIMBAD contains info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
