|
Helium-strong Star
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 than their hydrogen lines. Helium-weak star Helium-weak stars are mid-to-late B-class stars with weaker than normal spectral lines of neutral helium, compared to normal stars with similar hydrogen line strengths. These are considered to be an extension of the Ap/Bp chemically-peculiar stars with slightly hotter temperatures. They often show similar increased abundances of heavy elements. The mechanism of atmospheric stratification of elements is though to be responsible for both types of chemical peculiarity. 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. These are the more massive stars with classes of B1 to B3, compared to the helium-weak stars with classes of B5 ... [...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 four 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 st ... [...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 Thoms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
V761 Centauri
HD 125823, also known as V761 Centauri or a Centauri, is a variable star in the constellation Centaurus. It is a blue-white star that is visible to the naked eye with a mean apparent visual magnitude of +4.41. The distance to this star is approximately 460 light years based on parallax measurements. It is a member of the Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association. In 1965, W. P. Bidelman discovered that the intensities of the star's neutral helium lines had varied on photographic plates taken over the period 1908 to 1911. This variation was confirmed by A. D. Thackeray in 1966. The star ranges from a helium-strong B2 class to a helium-weak B8 with a period of 8.82 days. Radial velocity measurements during the 1970s showed differing velocity variations for helium and other elements. The magnetic field strength peaks at a negative maximum in phase with the maximum helium line strength. Weak emission has been detected in the singly-i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
V2052 Ophiuchi
V2052 Ophiuchi, also known as HR 6684, is a star about 920 light years from Earth in the constellation Ophiuchus. It is a 5th-magnitude star, making it faintly visible to the naked eye of an observer far from city lights. V2052 Ophiuchi is a Beta Cephei variable (β Cep) star, varying slightly in brightness from magnitude 5.81 to 5.84 over a period of about 3.4 hours. In 1972, Mikolaj Jerzykiewicz announced that HR 6684 is a variable star, based on his observations using the 0.6 meter Air Force Telescope on Mauna Kea. He classified the star as a β Cep variable with period of 0.13989 days, He further noted that if confirmed, it would be the least luminous and shortest period β Cep star known up to that date. Spectroscopic and photometric observations by D. Harold McNamara and Bruce Bills in 1973 confirmed Jerzykiewicz's results. In 1973, HR 6684 was given the variable star designation V2052 Ophiuchi. In 1994, Henryk Cugier ''et al.'' determined that V2052 Ophiuchi pulsa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sigma Lupi
Sigma Lupi, Latinized from σ Lupi, is a star in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.4. Based upon an annual parallax shift of 5.67 mas as seen from Earth, it is located about 580 light years from the Sun. It is a member of the Upper Centaurus–Lupus subgroup of the nearby Sco OB2 association. D. vander Linden and Christiaan L. Sterken discovered that the star is a variable star, based on data obtained in 1984, and announced their discovery in 1987. This is a B-type main sequence star with a stellar classification of B1/B2 V. Sigma Lupi is a Helium strong star with an enhanced abundance nitrogen and an underabundance of carbon. Jerzykiewicz and Sterken (1992) showed a small amplitude variability with a period of 3.02 days. This suggests it is a close binary system forming a rotating ellipsoidal variable, although other causes such as rotational modulation can not be ruled out. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HR 7355
HR 7355 is a star in the southern constellation of Sagittarius. It is faintly visible to the naked eye with an apparent visual magnitude of 6.03. The star is located at a distance of approximately 760 light years based on parallax measurements. The radial velocity of the star is poorly constrained, but it appears to be receding at the rate of +4 km/s. The stellar classification of HR 7355 is B2Vnn, indicating this is a B-type main-sequence star. The 'nn' notation indicates "nebulous" lines caused by rapid rotation. It is spinning on its axis with a period of 0.52 days. The projected rotational velocity is 310 km/s, for an estimated equatorial rotation rate of 358 km/s. This is 89% of the star's critical velocity, giving the star an equatorial bulge that is 20% larger than the polar radius. The star is subject to significant gravity darkening, with an effective temperature at the pole of 19,751 K compared to 15,740 K at the equator. In 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 144941
HD 144941 is a massive helium-strong star in the southern constellation of Scorpius. With an apparent visual magnitude of 10.1, it requires a telescope to view. Based on parallax measurements, it is located at a distance of approximately 4,900 light years from the Sun. The star is drifting closer with a radial velocity of −44 km/s. Observations In 1960, a study of stellar spectra of the southern sky taken at Cerro Tololo showed this to be a helium rich, hydrogen deficient star. Spectra taken from La Silla Observatory in 1973 showed an under abundance of nitrogen and carbon by a factor of ten compared to normal B-type stars. Helium shows a number abundance ten times that of hydrogen. The metallicity of the star is very low, which may explain why it displays no radial pulsations like those found in similar helium stars. Most extreme helium stars can be explained based on an evolutionary stage past the asymptotic giant branch. However, HD 144941 has too high a su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 37017
HD 37017 is a binary star system in the equatorial constellation of Orion. It has the variable star designation V1046 Orionis; ''HD 37017'' is the identifier from the ''Henry Draper Catalogue''. The system is a challenge to view with the naked eye, being close to the lower limit of visibility with a combined apparent visual magnitude of 6.55. It is located at a distance of approximately 1,230 light years based on parallax, and is drifting further away with a radial velocity of +32 km/s. The system is part of star cluster NGC 1981. The binary nature of this system was suggested by A. Blaauw and T. S. van Albada in 1963. It is a double-lined spectroscopic binary with an orbital period of 18.6556 days and an eccentricity of 0.31. The eccentricity is considered unusually large for such a close system. It forms a suspected eclipsing binary that ranges in brightness from 6.54 down to 6.58. The primary is a helium-strong, magnetic chemically peculiar star with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orion (constellation)
Orion is a prominent set of stars visible during winter in the northern celestial hemisphere. It is one of the IAU designated constellations, 88 modern constellations; it was among :Constellations listed by Ptolemy, the 48 constellations listed by the 2nd-century astronomer Ptolemy. It is named after Orion (mythology), a hunter in Greek mythology. Orion is most prominent during winter evenings in the Northern Hemisphere, as are five other constellations that have stars in the Winter Hexagon asterism (astronomy), asterism. Orion's two brightest stars, Rigel (β) and Betelgeuse (α), are both among the List of brightest stars, brightest stars in the night sky; both are supergiants and slightly variable star, variable. There are a further six stars brighter than magnitude 3.0, including three making the short straight line of the Orion's Belt asterism (astronomy), asterism. Orion also hosts the radiant (meteor shower), radiant of the annual Orionids, the strongest meteor shower as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 35456
HD may refer to: Business * H-D or Harley-Davidson, a motorcycle manufacturer * The Home Depot, NYSE stock symbol: HD Chemistry * Hydrogen deuteride, a diatomic compound of hydrogen and deuterium * Mustard gas Codes * Air Do, formerly Hokkaido International Airlines, IATA designator * HD postcode area, covering Huddersfield, Brighouse and Holmfirth in England, UK * Heidelberg's vehicle registration plate code * Hunedoara County (Romania)'s ISO 3166 code Medicine * Hansen's disease or leprosy * Hirschsprung's disease, a disorder of the abdomen * Huntington's disease, a genetic disorder affecting the central nervous system ** HD (gene) or huntingtin, the IT15 gene, which codes for the huntingtin protein People * H.D. or Hilda Doolittle (1886–1961), American poet and novelist Other uses * ''Helsingborgs Dagblad'', a Swedish newspaper * Henry Draper Catalogue, an astronomical catalogue often used to designate stars * Department of Highways (other) * ''H ... [...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 are a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 34797
HD may refer to: Business * H-D or Harley-Davidson, a motorcycle manufacturer * The Home Depot, NYSE stock symbol: HD Chemistry * Hydrogen deuteride, a diatomic compound of hydrogen and deuterium * Mustard gas Codes * Air Do, formerly Hokkaido International Airlines, IATA designator * HD postcode area, covering Huddersfield, Brighouse and Holmfirth in England, UK * Heidelberg's vehicle registration plate code * Hunedoara County (Romania)'s ISO 3166 code Medicine * Hansen's disease or leprosy * Hirschsprung's disease, a disorder of the abdomen * Huntington's disease, a genetic disorder affecting the central nervous system ** HD (gene) or huntingtin, the IT15 gene, which codes for the huntingtin protein People * H.D. or Hilda Doolittle (1886–1961), American poet and novelist Other uses * ''Helsingborgs Dagblad'', a Swedish newspaper * Henry Draper Catalogue, an astronomical catalogue often used to designate stars * Department of Highways (other) * ''H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
