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Am Stars
An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc, strontium, zirconium, and barium, and deficiencies of others, such as calcium and scandium. The original definition of an Am star was one in which the star shows "an apparent surface underabundance of Ca (and/or Sc) and/or an apparent overabundance of the Fe group and heavier elements". The unusual relative abundances cause the spectral type assessed from the Calcium K lines to be systematically earlier than one assessed from other metallic lines. Typically, a spectral type judged solely from hydrogen lines is intermediate. This leads to two or three spectral types being given. For example, Sirius has been given a spectral type of kA0hA0VmA1, indicating that it is A0 when judged by the Calcium k line, A0V when judged by its hydrogen lines, and A1 when judged by the lines of heavy metals. There are oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemically Peculiar Star
In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual Metallicity, 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 star, metallic-lined (Am, CP1) * Ap and Bp stars, magnetic (Ap, CP2) * non-magnetic mercury-manganese star, mercury-manganese (HgMn, CP3) * Helium-weak star, 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 Calcium, Ca and/or Scandium, 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 sta ... [...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, 6.3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tau3 Gruis
Tau3 Gruis is a solitary star in the southern constellation of Grus. Its apparent magnitude is 5.71, which is bright enough to be visible to the naked eye as a dim, white-hued star. The star is located around distant from the Sun based on parallax, and it is drifting further away with a radial velocity of 6 km/s. This is an Am star with a stellar classification of kA5hA7mF2. This notation indicates the spectrum displays the calcium K-line of an A5 star, the hydrogen lines of an A7 star, and the metal lines of an F2 star. It has 2.9 times the Sun's radius and is radiating 27 times the luminosity of the Sun 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 ... from its photosphere at an effective temperature of around 7,735 K. References {{DEFAULTSORT ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2 Ursae Majoris
2 Ursae Majoris (2 UMa) is an Am star in the northern circumpolar constellation of Ursa Major, located 150 light-years from the Sun. It has the Bayer designation A Ursae Majoris; ''2 Ursae Majoris'' is the Flamsteed designation. It is visible to the naked eye as a faint white star with an apparent visual magnitude of 5.5. Currently 150 light years away, it is moving closer to the Earth with a heliocentric radial velocity of −17 km/s. Description 2 UMa has a stellar classification of kA3hA5mA7s, meaning it has hydrogen absorption lines typical of an A5 star, calcium K lines typical of an A3 star, and other metal absorption lines typical of an A7 star. This form of spectral type is used for Am stars, stars which show an over-abundance of metal lines in their spectrum due to slow rotation that allows stratification of elements within its photosphere. The 's' suffix indicates that the lines are sharp, another indicator of slow rotation. At an estimated age o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
μ Aurigae
Mu Aurigae, Latinized as μ Aurigae, is the Bayer designation for an unconfirmed binary star in the northern constellation of Auriga. It is visible to the naked eye with an apparent visual magnitude of +4.88. Based upon an annual parallax shift of as seen from Earth, is located 157 light-years from the Sun. This is an A-type main-sequence star with a stellar classification of A4 Vm; the 'm' suffix indicating that abnormal abundances of heavier elements appear in the star's spectrum, making this an Am star. It is 560 million years old with a projected rotational velocity of . It has double the mass of the Sun and is radiating 23 times the Sun's luminosity at an effective temperature of . A very close companion has been reported using speckle interferometry, but this remains unconfirmed. The separation at discovery in 1986 was and it was measured at in 1999. It was catalogued by ''Hipparcos'' as a problem binary, indicating that the measurements of its po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
π Virginis
Pi Virginis (π Vir, π Virginis) is a binary star in the zodiac constellation of Virgo. It is visible to the naked eye with an apparent visual magnitude of 4.64. The distance to this star, based upon parallax measurements, is roughly 380 light years. This is a spectroscopic binary system with a stellar classification of A5V. They have an orbital period of 283 days with an eccentricity of 0.27. The mass ratio of the two stars is about 0.47, with the primary having an estimated mass of around 2.2 times that of the Sun. The primary is a cool metallic-lined Am star An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc, strontium, zirconium, and barium, and deficiencies of others, such as ca .... References {{DEFAULTSORT:Pi Virginis Virginis, Pi Virgo (constellation) Spectroscopic binaries A-type main-sequence stars Virginis, 008 104321 058 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
θ1 Crucis
Theta1 Crucis (θ1 Cru, Theta1 Crucis) is a spectroscopic binary star system in the southern constellation of Crux. It is visible to the naked eye with an apparent visual magnitude of 4.30m. The distance to this star, as determined using parallax measurements, is around 235 light years. The pair orbit each other closely with a period of 24.5 days and an eccentricity of 0.61. The primary component is an Am star, which is a chemically peculiar A-type star that shows anomalous variations in absorption lines of certain elements. It has a stellar classification of A3(m)A8-A8. With a mass 157% times that of the Sun, it radiates 81 times the Sun's luminosity from its outer atmosphere at an 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 ... of 734 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ξ Cephei
Xi Cephei (ξ Cephei, abbreviated Xi Cep, ξ Cep) is a multiple star system in the constellation of Cepheus. It is approximately 86 light-years from Earth. It consists of two binary stars, designated Xi Cephei A and B, together with a more distant companion, Xi Cephei C. A's two components are themselves designated Xi Cephei Aa (officially named Kurhah , the traditional name of the system) and Ab. Nomenclature ''ξ Cephei'' ( Latinised to ''Xi Cephei'') is the system's Bayer designation. The designations of the three constituents as ''ξ Cephei A'', ''B'' and ''C'', and those of ''A's'' components - ''ξ Cephei Aa'' and ''Ab'' - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). Xi Cephei bore the traditional names ''Kurhah'', ''Alkirdah'' or ''Al Kirduh'', the name coming from Qazvini who gave ''Al Ḳurḥaḥ'' (''القرحة'' ''al-qurhah''), an Arabic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
α Cancri A
Alpha Cancri (α Cancri, abbreviated Alpha Cnc, α Cnc), also named Acubens , is a star system in the constellation of Cancer. Nomenclature ''α Cancri'' ( Latinised to ''Alpha Cancri'') is the star's Bayer designation. The traditional name ''Acubens'' (Açubens) is derived from the Arabic , 'the claws'. A second name, Sertan , derives from the Arabic ''al-saraṭān'', 'the crab'. The International Astronomical Union Working Group on Star Names (WGSN) choose 'Acubens' as the proper name for this star. Properties Alpha Cancri is a fourth-magnitude star with an apparent magnitude of 4.20, making it barely visible to the naked eye under good lighting conditions. Nevertheless, it is 23 times more luminous than the Sun. Its stellar classification is given as kA7VmF0/2III/IVSr, indicating an Am star with calcium K-lines similar to an A7 main sequence star and hydrogen lines more like an F0 giant or subgiant star. The distance of Alpha Cancri calculated from the Gaia Data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
α Volantis
Alpha Volantis (Alpha Vol), Latinized from α Volantis, is a binary star system located in the southern constellation Volans. It has an apparent visual magnitude of +4.00, which is bright enough to be seen with the naked eye. Based upon parallax measurements made with the Hipparcos spacecraft, it is located at a distance of 125 light years from the Sun. As of 2010, the two components of this system had an angular separation of 0.0318 ″ along a position angle of 286.9°. The magnitude difference between the two components is 0.1. It is considered a member of the Sirius supercluster. The primary component is an Am star with a stellar classification of kA3hA5mA5 V. This notation indicates the star has the weak calcium II K-line of an A3 star, and the hydrogen and metallic lines of an A5 star. It has an estimated age of 427 million years. In 1992, it was found to be emitting an infrared excess, suggesting the presence of a circumstellar disk A circumstellar d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
α Geminorum Ba
Castor is the second-brightest object in the zodiac constellation of Gemini. It has the Bayer designation α Geminorum, which is Latinised to Alpha Geminorum and abbreviated Alpha Gem or α Gem. With an apparent visual magnitude of 1.93, it is one of the brightest stars in the night sky. Castor appears singular to the naked eye, but it is actually a sextuple star system organized into three binary pairs. Although it is the 'α' (alpha) member of the constellation, it is fainter than 'β' (beta) Geminorum, Pollux. Stellar system Hierarchy of orbits in the Castor system Castor is a multiple star system made up of six individual stars; there are three visual components, all of which are spectroscopic binaries. Appearing to the naked eye as a single star, Castor was first recorded as a double star in 1718 by James Pound, but it may have been resolved into at least two sources of light by Cassini as early as 1678. The separation between the binary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
α Canis Majoris A
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] |
