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Helium-weak
Helium-weak stars are chemically peculiar stars which have a weak helium lines for their spectral type. Their helium lines place them in a later (i.e. cooler) spectral type then their hydrogen lines. List of helium-weak stars This is a non-extensive list of helium-weak stars. Helium-strong star A related class of stars have anomalously strong helium lines in their spectra, and are known as helium-strong stars. See also * Helium star * Extreme helium star An extreme helium star (abbreviated EHe) is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the Universe. Since there are no known conditions where stars devoid of hydrogen can be formed from molecular c ... References Star types {{stellar-astronomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 28843
HD 28843, also known as HR 1441 and DZ Eridani, is a star about 550 light years from the Earth, in the constellation Eridanus. It is a 5th magnitude star, so it will be faintly visible to the naked eye of an observer far from city lights. It is a variable star, whose brightness varies slightly from 5.70 to 5.84 during its 1.374 day rotation period. It is a member of the μ Tauri Association, a group of young stars within the larger Cassiopeia-Taurus Structure. In 1969 Mercedes Jaschek ''et al.'' determined that HD 28843 is a helium-weak star, based on its B-V color index being bluer (more negative) than would be expected for a star with its spectral type. In 1977, Robert Davis reported that the star has an overabundance of silicon. It is classified as a chemically peculiar star. Henning Jorgensen ''et al.'' reported that HD 28843 was a "suspected variable star" in 1971. The variability of the star was firmly established in 1977 by Holger Pedersen and Bjarne Thomse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helium-weak Stars
Helium-weak stars are chemically peculiar stars which have a weak helium lines for their spectral type. Their helium lines place them in a later (i.e. cooler) spectral type then their hydrogen lines. List of helium-weak stars This is a non-extensive list of helium-weak stars. Helium-strong star A related class of stars have anomalously strong helium lines in their spectra, and are known as helium-strong stars. See also * Helium star * Extreme helium star An extreme helium star (abbreviated EHe) is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the Universe. Since there are no known conditions where stars devoid of hydrogen can be formed from molecular c ... References Star types {{stellar-astronomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theta Hydri
Theta Hydri, Latinized from θ Hydri, is the Bayer designation for a blue-white hued star in the southern constellation of Hydrus. It is faintly visible to the naked eye with an apparent visual magnitude of +5.53. Based upon an annual parallax shift of as seen from Earth, is located approximately from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction of 0.10 due to interstellar dust. It is moving away from the Sun with a radial velocity of . A stellar classification of B8 III/IV suggests it is an evolving B-type star showing mixed traits of a subgiant or giant star. It is a PGa star – a sub-class of the higher temperature chemically peculiar stars known as mercury-manganese stars (HgMn stars). That is, it displays a rich spectra of singly-ionized phosphorus and gallium, in addition to ionized mercury and manganese. As such, Theta Hydri forms a typical example of this type. The absorption lines for these ionized eleme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
12 Canis Majoris
12 Canis Majoris is a variable star located 750 light years away from the Sun in the southern constellation of Canis Major. It has the variable star designation HK Canis Majoris; ''12 Canis Majoris'' is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07. It is moving away from the Earth with a heliocentric radial velocity of +16 km/s. This is the brightest star in the vicinity of the open cluster NGC 2287, although it is probably not a member based on its proper motion. This star has a stellar classification of B7 II/III, matching a B-type giant/bright giant hybrid. (Cidale et al. (2007) show a class of B5 V, which would indicate it is instead a B-type main-sequence star.) It is a magnetic Bp star of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the atmosphere. Samus et al ... [...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] |
20 Eridani
This is the list of notable stars in the constellation Eridanus, sorted by decreasing brightness. See also *List of stars by constellation All stars but one can be associated with an IAU constellation. IAU constellations are areas of the sky. Although there are only 88 IAU constellations, the sky is actually divided into 89 irregularly shaped boxes as the constellation Serpens is spli ... References * * * * * * {{DEFAULTSORT:List of stars in Eridanus *List Eridanus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SX Arietis Variable
SX Arietis variables are a class of variable stars. They are generally B-type main sequence stars of spectral types B0p to B9p— high-temperature analogues of Alpha2 Canum Venaticorum variables—and exhibit strong magnetic fields and intense He I and Si III spectral lines. They have brightness fluctuations of approximately 0.1 magnitudes with periods of about one day. The prototype of this class is 56 Arietis, which bears the variable star designation In astronomy, a variable star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constell ... ''SX Arietis''. List The following list contains selected SX Arietis variable that are of interest to amateur or professional astronomy. Unless otherwise noted, the given magnitudes are in the V-band. Notes References Samus N.N., Durlevich O.V., et al. ''Combined G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extreme Helium Star
An extreme helium star (abbreviated EHe) is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the Universe. Since there are no known conditions where stars devoid of hydrogen can be formed from molecular clouds, it is theorized that they are the product of the mergers of helium-core and carbon-oxygen core white dwarfs. Properties Extreme helium stars form a sub-group within the broader category of hydrogen-deficient stars. The latter includes cool carbon stars like R Coronae Borealis variables, helium-rich spectral class O or B stars, population I Wolf–Rayet stars, AM CVn stars, white dwarfs of spectral type WC, and transition stars like PG 1159. The first known extreme helium star, HD 124448, was discovered in 1942 by Daniel M. Popper at the McDonald Observatory near Fort Davis, Texas, United States. This star displayed no lines of hydrogen in its spectrum, but strong helium lines as well as the presence of carbon and oxygen. The se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helium Star
A helium star is a class O or B star (blue), which has extraordinarily strong helium lines and weaker than normal hydrogen lines, indicating strong stellar winds and a mass loss of the outer envelope. '' Extreme helium stars'' (EHe) entirely lack hydrogen in their spectra. Pure helium stars lie on or near a helium main sequence, analogous to the main sequence formed by the more common hydrogen stars. Previously, a ''helium star'' was a synonym for a B-type star, but this usage is considered obsolete. A ''helium star'' is also a term for a hypothetical star that could occur if two helium white dwarfs with a combined mass of at least 0.5 solar masses merge and subsequently start nuclear fusion of helium, with a lifetime of a few hundred million years. This may only happen if these two binary masses share the same type of envelope phase. It is believed this is the origin of the extreme helium stars. The helium star's great capability of transforming into other stellar objects has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orion (constellation)
Orion is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous and recognizable constellations in the night sky. It is named after Orion (mythology), Orion, a hunter in Greek mythology. Its brightest stars are the blue-white Rigel (Beta Orionis) and the red Betelgeuse (Alpha Orionis). Characteristics Orion is bordered by Taurus to the northwest, Eridanus to the southwest, Lepus to the south, Monoceros (constellation), Monoceros to the east, and Gemini to the northeast. Covering 594 square degrees, Orion ranks twenty-sixth of the 88 constellations in size. The constellation boundaries, as set by Belgian astronomer Eugène Joseph Delporte, Eugène Delporte in 1930, are defined by a polygon of 26 sides. In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between and . The constellation's three-letter abbreviation, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lepus (constellation)
Lepus (, ) is a constellation lying just south of the celestial equator. Its name is Latin for hare. It is located below—immediately south—of Orion (the hunter), and is sometimes represented as a hare being chased by Orion or by Orion's hunting dogs. Although the hare does not represent any particular figure in Greek mythology, Lepus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. History and mythology Lepus is most often represented as a hare being hunted by Orion, whose hunting dogs (Canis Major and Canis Minor) pursue it. The constellation is also associated with the Moon rabbit. Four stars of this constellation (α, β, γ, δ Lep) form a quadrilateral and are known as ''‘Arsh al- Jawzā''', "the Throne of Jawzā'" or ''Kursiyy al-Jawzā' al-Mu'akhkhar'', "the Hindmost Chair of Jawzā'" and ''al-Nihāl'', "the Camels Quenching Their Thirst" in Arabic. Features Stars There ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
