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HD 181720
HD 181720 is star with an orbiting substellar companion in the southern constellation of Sagittarius. It is located at a distance of 196 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −45.4 km/s. The star has an absolute magnitude of 4.10, but at that distance it has an apparent visual magnitude of 7.84, which is too faint to be seen with the naked eye. It shows a high proper motion, traversing the celestial sphere at an angular rate of . The spectrum of HD 181720 presents as an ordinary G-type main-sequence star with a stellar classification of G1V. It is an older star with an estimated age of roughly 12 billion years and a minimal level of magnetic activity in its chromosphere. The star has 87% of the mass of the Sun but the radius is now 42% larger than the Sun's. Its metallicity content, as measured by the abundance of iron, is three-tenths as much as in the Sun. HD 181720 is radiating more th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagittarius (constellation)
Sagittarius is one of the constellations of the zodiac and is located in the Southern celestial hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its old astronomical symbol is (♐︎). Its name is Latin for " archer". Sagittarius is commonly represented as a centaur pulling back a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus and Microscopium to the east. The center of the Milky Way lies in the westernmost part of Sagittarius (see Sagittarius A). Visualizations As seen from the northern hemisphere, the constellation's brighter stars form an easily recognizable asterism known as "the Teapot". The stars δ Sgr (Kaus Media), ε Sgr (Kaus Australis), ζ Sgr (Ascella), and φ Sgr form the body of the pot; λ Sgr (Kaus Borealis) is the point of the lid; γ2 Sgr (Alnasl) is the tip of the spout; and σ Sgr (Nunki) and τ Sgr the handle. These s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a convenient short term for ''"all elements except hydrogen and helium"''. This word-use is distinct from the conventional chemical or physical definition of a metal as an electrically conducting solid. Stars and nebulae with relatively high abundances of heavier elements are called "metal-rich" in astrophysical terms, even though many of those elements are nonmetals in chemistry. The presence of heavier elements hails from stellar nucleosynthesis, where the majority of elements heavier than hydrogen and helium in the Universe (''metals'', hereafter) are formed in the cores of stars as they evolve. Over time, stellar winds and supernovae deposit the metals into the surrounding environment, enriching the interstellar medium and provid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 190984
HD 190984, also known as HIP 99496, is a star located in the southern circumpolar constellation Pavo, the peacock. It has an apparent magnitude of 8.76, making it readily visible in small telescopes, but not to the naked eye. Based on parallax measurements from the Gaia spacecraft, the object is estimated to be 486 light years away from the Solar System. It appears to be receding with a heliocentric radial velocity of . Characteristics This is an ordinary F-type main-sequence star with a stellar classification of F8 V, generating energy via hydrogen fusion at its core. It has 115% the mass of the Sun and an effective temperature of , giving it a yellowish-white hue. However, HD 190984 has an enlarged radius of and is 1.76 magnitudes brighter than the main sequence, indicating that it may instead be a subgiant evolving towards the red giant branch; it radiates 5.88 times the luminosity of the Sun from its photosphere. Unlike most planetary hosts, HD 190984 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 5388
HD 5388 is a single star in the southern constellation of Phoenix. It has the Gould designation 78 G. Phoenicis, while HD 5388 is the star's Henry Draper Catalogue identifier. This object has a yellow-white hue and is too faint to be readily visible to average human eyesight, having an apparent visual magnitude of 6.73. It is located at a separation of 173 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +39 km/s. This object is an ordinary F-type main-sequence star with a stellar classification of F6V, indicating that it is generating energy through core hydrogen fusion. It is not chromospherically active and its metal content is half as much as the Sun. The star is larger and more massive than the Sun, and radiates 4.8 times the Sun's luminosity from its photosphere at an effective temperature of 6297 K. In 2009, a substellar object (HD 5388 b) thought to be a gas giant planet was detected in orbit arou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 181720 B
HD 181720 b is an extrasolar planet which orbits the G-type main sequence star HD 181720, located approximately 190 light years away in the constellation Sagittarius. This planet has at least three-eighths the mass of Jupiter and takes over two and five-eighths years to orbit the star at a semimajor axis of 1.78 AU with an eccentricity of 0.26. This planet was detected by HARPS on October 19, 2009, together with 29 other planets. The planet HD 181720 b is named Toge. The name was selected in the NameExoWorlds campaign by Ghana, during the 100th anniversary of the IAU. Toge means earring in the Ewe language Ewe (''Eʋe'' or ''Eʋegbe'' ) is a language spoken by approximately 20 million people in West Africa, mainly in Ghana, Togo and Benin, and also in some other countries like Liberia and southwestern Nigeria. Ewe is part of a cluster of rela .... See also * HD 5388 b * HD 190984 b References Exoplanets discovered in 2009 Exoplanets detected by radial veloc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Dwarf
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen (hydrogen-1, 1H) into helium in their cores, unlike a main sequence, main-sequence star. Instead, they have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 Jupiter mass, times that of Jupiter (). However, they can deuterium burning, fuse deuterium (deuterium, 2H), and the most massive ones (> ) can lithium burning, fuse lithium (lithium-7, 7Li). Astronomers classify self-luminous objects by spectral classification, spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. Despite their name, to the naked eye, brown dwarfs would appear in different colors depending on their temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 22781
HD 22781, is a single star about away. It is a K-type main-sequence star. The star’s age is poorly constrained at billion years, but is likely similar to that of the Sun. HD 22781 is heavily depleted in heavy elements, having just 45% of Sun's concentration of iron, yet is comparatively rich in carbon, having 90% of Sun`s abundance. An imaging survey in 2012 has failed to find any stellar companions, suggesting HD 22781 is a single star. Planetary system In 2011 a transiting superjovian planet or brown dwarf b was detected on an extremely eccentric orbit. It is located just outside of the conservative habitable zone of the parent star. Planets around such metal-poor stars are rare; the only three known similar cases are HD 111232 and HD 181720 HD 181720 is star with an orbiting substellar companion in the southern constellation of Sagittarius. It is located at a distance of 196 light years from the Sun based on parallax measurements, but is drift ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 111232
HD 111232 is a star in the southern constellation of Musca. It is too faint to be visible with the naked eye, having an apparent visual magnitude of 7.59. The distance to this star is 94.5 light years based on parallax. It is drifting away from the Sun with a radial velocity of +104 km/s, having come to within some 264,700 years ago. The absolute magnitude of this star is 5.25, indicating it would have been visible to the naked eye at that time. This is an ancient, thick disk population II star with an estimated age of twelve billion years. It is a G-type main-sequence star with a stellar classification of G8 V Fe-1.0, indicating an anomalous underabundance of iron in the stellar atmosphere. The star has 80% of the mass of the Sun and 88% of the Sun's radius. It is spinning slowly with a projected rotational velocity of 0.4 km/s. X-ray emission has not been detected, suggesting a low level of coronal activity. The star is radiating 70% of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Giant
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranus and Neptune are really a distinct class of giant planets, being composed mainly of heavier volatile substances (which are referred to as "ices"). For this reason, Uranus and Neptune are now often classified in the separate category of ice giants. Jupiter and Saturn consist mostly of hydrogen and helium, with heavier elements making up between 3 and 13 percent of their mass.The Interior of Jupiter, Guillot et al., in ''Jupiter: The Planet, Satellites and Magnetosphere'', Bagenal et al., editors, Cambridge University Press, 2004 They are thought to consist of an outer layer of compressed molecular hydrogen surrounding a layer of liquid metalli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ewe Language
Ewe (''Eʋe'' or ''Eʋegbe'' ) is a language spoken by approximately 20 million people in West Africa, mainly in Ghana, Togo and Benin, and also in some other countries like Liberia and southwestern Nigeria. Ewe is part of a cluster of related languages commonly called the Gbe languages. The other major Gbe language is Fon, which is mainly spoken in Benin. Like many African languages, Ewe is tonal as well as a possible member of the Niger-Congo family. The German Africanist Diedrich Hermann Westermann published many dictionaries and grammars of Ewe and several other Gbe languages. Other linguists who have worked on Ewe and closely related languages include Gilbert Ansre (tone, syntax), Herbert Stahlke (morphology, tone), Nick Clements (tone, syntax), Roberto Pazzi (anthropology, lexicography), Felix K. Ameka (semantics, cognitive linguistics), Alan Stewart Duthie (semantics, phonetics), Hounkpati B. Capo (phonology, phonetics), Enoch Aboh (syntax), and Chris Colli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile metal in a pure form. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions. Gold often occurs in free elemental (native state), as nuggets or grains, in rocks, veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium ( gold tellurides). Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid), forming a soluble tetrachloroau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ghana
Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in Ghana–Ivory Coast border, the west, Burkina Faso in Burkina Faso–Ghana border, the north, and Togo in Ghana–Togo border, the east.Jackson, John G. (2001) ''Introduction to African Civilizations'', Citadel Press, p. 201, . Ghana covers an area of , spanning diverse biomes that range from coastal savannas to tropical rainforests. With nearly 31 million inhabitants (according to 2021 census), Ghana is the List of African countries by population, second-most populous country in West Africa, after Nigeria. The capital and List of cities in Ghana, largest city is Accra; other major cities are Kumasi, Tamale, Ghana, Tamale, and Sekondi-Takoradi. The first permanent state in present-day Ghana was the Bono state of the 11th century. Numerous kingdoms and empires emerged over the centuri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
