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Subgiant
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of a star. Yerkes luminosity class IV The term subgiant was first used in 1930 for class G and early K stars with absolute magnitudes between +2.5 and +4. These were noted as being part of a continuum of stars between obvious main-sequence stars such as the Sun and obvious giant stars such as Aldebaran, although less numerous than either the main sequence or the giant stars. The Yerkes spectral classification system is a two-dimensional scheme that uses a letter and number combination to denote the temperature of a star (e.g. A5 or M1) and a Roman numeral to indicate the luminosity relative to other stars of the same temperature. Luminosity class IV stars are the subgiants, located between main-sequence stars (luminosity class&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Star
A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III. The terms ''giant'' and ''dwarf'' were coined for stars of quite different luminosity despite similar temperature or spectral type (namely K and M) by Ejnar Hertzsprung in 1905 or 1906. Giant stars have radii up to a few hundred times the Sun and luminosities over 10 times that of the Sun. Stars still more luminous than giants are referred to as supergiants and hypergiants. A hot, luminous main-sequence star may also be referred to as a giant, but any main-sequence star is properly called a dwarf, regardless of how large and luminous it is. Formation A star becomes a giant after all the hydrogen available for fusion at its core has been depleted and, as a r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sky, night; their immense distances from Earth make them appear as fixed stars, fixed points of light. The most prominent stars have been categorised into constellations and asterism (astronomy), asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy. A star's life star formation, begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements. Its stellar mass, total mass mainly determines it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Evolution
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the current age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from Gravitational collapse, collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main sequence star. Nuclear fusion powers a star for most of its existence. Initially the energy is generated by the fusion of hydrogen atoms at the stellar core, core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strontium
Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to air. Strontium has physical and chemical properties similar to those of its two vertical neighbors in the periodic table, calcium and barium. It occurs naturally mainly in the minerals celestine and strontianite, and is mostly mined from these. Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was discovered in 1790 by Adair Crawford and William Cruickshank; it was identified as a new element the next year from its crimson-red flame test color. Strontium was first isolated as a metal in 1808 by Humphry Davy using the then newly discovered process of electrolysis. During the 19th century, strontium was mostly used in the production of sugar from sugar beets (see strontian proces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theta Ophiuchi
Theta Ophiuchi, Latinized from θ Ophiuchi, is a multiple star system in the equatorial constellation of Ophiuchus. It lies on the "right foot" of the serpent-bearer, just southwest of Kepler's Star, the nova of 1604. This star has an apparent visual magnitude of +3.3, making it readily visible to the naked eye. Based upon parallax measurements from the Hipparcos mission, it is roughly from Earth. It is 1.8 degrees south of the ecliptic and therefore subject to lunar occultations and (very rarely) occulted by a planet. The next occultation by a planet will be by Mars on 3 October 2078. Theta Ophiuchi appears to be a triple star system. The brightest component is a spectroscopic binary with an orbital period of 56.71 days and an eccentricity of 0.17. The third component is 5.5 magnitude star with a stellar classification of B5. Its angular separation from the binary pair is 0.15 arcseconds. This system is a proper motion member of the Upper Scorpius sub-gro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi Scorpii
Pi Scorpii or π Scorpii, is a triple star system in the southern constellation of Scorpius. With a combined apparent magnitude of 2.9, it can be easily seen with the naked eye. Parallax measurements yield an estimated distance of around from the Sun. It consists of a binary pair, designated Pi Scorpii A, with a more distant third companion, B. A's two components are themselves designated Pi Scorpii Aa (formally named Fang) and Ab. Nomenclature ''π Scorpii'' ( Latinised to ''Pi Scorpii'') is the system's Bayer designation. The designations of the three constituents as ''Pi Scorpii A'' and ''B'' and those of ''A's'' components - ''Pi Scorpii 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). In Chinese, (), meaning ''Room'', refers to an asterism consisting of Pi Scorpii, Rho Scorpii, Delta Scorpii, Beta¹ Scorpii and Beta² Scorp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Orionis
Bellatrix is the third-brightest star and a candidate binary star in the constellation of Orion, positioned 5° west of the red supergiant Betelgeuse (Alpha Orionis). It has the Bayer designation γ Orionis, which is Latinized to Gamma Orionis. With a slightly variable magnitude of around 1.6, it is typically the 25th-brightest star in the night sky. According to parallax measurements by the Hipparcos spacecraft, Bellatrix is located at a distance of 250 light-years. Nomenclature The traditional name ''Bellatrix'' is from the Latin ''bellātrix'' "female warrior". It first appeared in the works of Abu Ma'shar al-Balkhi and Johannes Hispalensis, where it originally referred to Capella, but was transferred to Gamma Orionis by the Vienna school of astronomers in the 15th century, and appeared in contemporary reprints of the '' Alfonsine tables''. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Cephei
Beta Cephei (β Cephei, abbreviated Beta Cep, β Cep) is a triple star system of the third magnitude in the constellation of Cepheus. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 690 light-years distant from the Sun. It is the prototype of the Beta Cephei variable stars. It consists of a binary pair (designated Beta Cephei A) together with a third companion (B). The binary's two components are themselves designated Beta Cephei Aa (officially named Alfirk , the traditional name for the system) and Ab. Nomenclature ''β Cephei'' ( Latinised to ''Beta Cephei'') is the system's Bayer designation. The designations of the two constituents as ''Beta Cephei A'' and ''B'', and those of ''A's'' components - ''Beta 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). Beta Cephei bore the traditional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Omicron Persei
Omicron Persei (ο Persei, abbreviated Omicron Per, ο Per) is a triple star system in the constellation of Perseus. From parallax measurements taken during the Hipparcos mission it is approximately 1,100 light-years (330 parsecs) from the Sun. The system consists of a spectroscopic binary pair designated Omicron Persei A and a third companion Omicron Persei B. A's two components are themselves designated Omicron Persei Aa (officially named Atik , the traditional name of the system) and Ab. Etymology ''ο Persei'' ( Latinised to ''Omicron Persei'') is the system's Bayer designation. The designations of the two constituents as ''Omicron Persei A'' and ''B'', and those of ''A's'' components - ''Omicron Persei 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). It bore the traditional name ''Atik'' (also ''Ati'', ''Al Atik''), Arabic for "th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Scorpii
Beta Scorpii is a Star system, multiple star system in the southern zodiac constellation of Scorpius. It bore the traditional proper name of Acrab , though the International Astronomical Union now regards that name as applying only to the β Scorpii Aa component. Components Observed through a small telescope, Beta Scorpii appears as a binary star with a separation between the two components of 13.5 arcseconds and a combined apparent magnitude of 2.50. This pair, designated β¹ Scorpii and β² Scorpii, form the top branches of a hierarchy of six orbiting components. Hierarchy of orbits in the β Scorpii system β¹ Scorpii, the brighter of the pair, consists of two sub-components, designated β Scorpii A and β Scorpii B, orbiting at an angular separation of 0.3 arcseconds with an orbital period of 610 years. β Scorpii A is itself a spectroscopic binary, with the two components designated β Scorpii Aa (also named Acrab) and β Scorpi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta Scorpii
Delta Scorpii (Latinisation of names, Latinised from δ Scorpii, abbreviated Delta Sco, δ Sco) is a binary star (the presence of a third star in the system is being debated) in the constellation of Scorpius. The primary star is named Dschubba . Observation Delta Scorpii is 2.0 degrees south of the ecliptic. It is a binary star with two components of magnitudes 2.4 and 4.6 separated by . In 1981 it was occultation, occulted by Rings of Saturn, Saturn's rings as seen by Voyager 2, with starlight unexpectedly blocked even by the apparently empty gaps, indicating that "there is very little empty space anywhere in the main ring system." Variability Delta Scorpii A is a Gamma Cassiopeiae variable star. This type of star shows irregular slow brightness variations of a few hundredths of a magnitude due to material surrounding the star. In June 2000 Delta Scorpii was observed by Sebastian Otero to be 0.1 magnitudes brighter than normal; its brightness has varied since then a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Cassiopeiae
Gamma Cassiopeiae, Latinized from γ Cassiopeiae, is a bright star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ... at the center of the distinctive "W" asterism in the northern circumpolar constellation of Cassiopeia (constellation), Cassiopeia. Although it is a fairly bright star with an apparent visual magnitude of 2.47, it has no traditional Arabic or Latin name. It sometimes goes by the informal name Navi. It was observed in 1866 by Angelo Secchi, the first star ever observed with emission lines. It is now considered a Be star. Gamma Cassiopeiae is also a variable star and a multiple star system. Based upon parallax measurements made by the Hipparcos satellite, it is located at a distance of roughly 550 light-years from Earth. Together with its common-proper-moti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
