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BAT99-98
BAT99-98 is a Wolf–Rayet star located in the Large Magellanic Cloud, in NGC 2070 near the R136 cluster in the Tarantula Nebula (30 Doradus). At estimates of and , it is one of the most massive known stars, and close to one of the most luminous stars currently known. Observations A 1978 survey carried out by Jorge Melnick covered the 30 Doradus region and found six new Wolf–Rayet (WR) stars, all belonging to the WN sequence. The survey observed stars that were above apparent magnitude 14 and within 2 arcminutes of the centre of the 30 Doradus nebula, and the star now known as BAT9998 was labelled as star J. It was found to have a magnitude of 13.5 and a spectral type of WN5. The following year, thirteen new WR stars in the Large Magellanic Cloud were reported, one of which was Mel J. It was numbered 12, and referred to as AB12, or LMC AB12 to distinguish it from the better-known AB stars in the Small Magellanic Cloud. Melnick conducted another study of stars in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wolf–Rayet Star
Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectroscopy, spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of Stellar nucleosynthesis, heavy elements, depletion of hydrogen, and strong stellar winds. The Effective temperature, surface temperatures of known Wolf–Rayet stars range from 20,000 Kelvin (unit), K to around 210,000 Kelvin (unit), K, hotter than almost all other kinds of stars. They were previously called W-type stars referring to their Stellar classification, spectral classification. Classic (or population I) Wolf–Rayet stars are Stellar evolution, evolved, massive stars that have completely lost their outer hydrogen and are nuclear fusion, fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Most Luminous Stars
This is a list of stars arranged by their absolute magnitude – their intrinsic stellar luminosity. This cannot be observed directly, so instead must be calculated from the apparent magnitude (the brightness as seen from Earth), the distance to each star, and a correction for interstellar extinction. The entries in the list below are further corrected to provide the bolometric magnitude, i.e. integrated over all wavelengths; this relies upon measurements in multiple photometric filters and extrapolation of the stellar spectrum based on the stellar spectral type and/or effective temperature. Entries give the bolometric luminosity in multiples of the luminosity of the Sun () and the bolometric absolute magnitude. As with all magnitude systems in astronomy, the latter scale is logarithmic and inverted i.e. more negative numbers are more luminous. Most stars on this list are not bright enough to be visible to the naked eye from Earth, because of their high distances, hig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Most Massive Stars
This is a list of the most massive stars that have been discovered, in solar mass units (). Uncertainties and caveats Most of the masses listed below are contested and, being the subject of current research, remain under review and subject to constant revision of their masses and other characteristics. Indeed, many of the masses listed in the table below are inferred from theory, using difficult measurements of the stars' effective temperature, temperatures, metallicity, composition, and absolute magnitude, absolute brightnesses. All the masses listed below are uncertain: Both the theory and the measurements are pushing the limits of current knowledge and technology. Both theories and measurements could be incorrect. Complications with distance and obscuring clouds Since massive stars are rare, astronomers must look very far from Earth to find them. All the listed stars are many thousands of light years away, which makes measurements difficult. In addition to being far away, many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dorado
Dorado (, ) is a constellation in the Southern Sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the mahi-mahi (''Coryphaena hippurus''), which is known as ''dorado'' ("golden") in Spanish, although it has also been depicted as a swordfish. Dorado contains most of the Large Magellanic Cloud, the remainder being in the constellation Mensa. The South Ecliptic pole also lies within this constellation. Even though the name Dorado is not Latin but Spanish, astronomers give it the Latin genitive form ''Doradus'' when naming its stars; it is treated (like the adjacent asterism Argo Navis) as a feminine proper name of Greek origin ending in -ō (like ''Io'' or ''Callisto'' or ''Argo''), which have a genitive ending ''-ūs''. History Dorado was one of twelve constellations named by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. It appeared: * On a celestial globe published in 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Wind
A stellar wind is a flow of gas ejected from the stellar atmosphere, upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric. Different stellar classification, types of stars have different types of stellar winds. Post-main sequence, main-sequence stars nearing the ends of their lives often eject large quantities of mass in massive ( \scriptstyle \dot > 10^ solar masses per year), slow (v = 10 km/s) winds. These include red giants and Red supergiant, supergiants, and asymptotic giant branch stars. These winds are understood to be driven by radiation pressure on Cosmic dust, dust condensing in the upper atmosphere of the stars. Young T Tauri stars often have very powerful stellar winds. Massive stars of stellar classification, types O star, O and B V star, B have stellar winds with lower mass loss rates (\scriptstyle \dot 1–2000 km ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radcliffe Observatory
Radcliffe Observatory was the astronomical observatory of the University of Oxford from 1773 until 1934, when the Radcliffe Trustees sold it and built a new observatory in Pretoria, South Africa. It is a Grade I listed building. Today, the building forms part of Green Templeton College of the University of Oxford. History The observatory was founded and named after the physician John Radcliffe (1650–1714) by the Radcliffe Trustees. It was built on the suggestion of the astronomer Thomas Hornsby, who was occupying the Savilian Chair of Astronomy, following his observation of the notable transit of Venus across the sun's disc in 1769 from a room in the nearby Radcliffe Infirmary. The observatory building, at a site on Woodstock Road, commenced to designs by Henry Keene in 1772 and was completed in 1794 to the designs of James Wyatt. It has a prominent octagonal tower based on the Tower of the Winds in Athens, topped with a statue by John Bacon of Atlas holding up the Wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass–luminosity Relation
In astrophysics, the mass–luminosity relation is an equation giving the relationship between a star's mass and its luminosity, first noted by Jakob Karl Ernst Halm. The relationship is represented by the equation: \frac = \left(\frac\right)^a where and are the luminosity and mass of the Sun and . The value is commonly used for main-sequence stars. This equation and the usual value of only applies to main-sequence stars with masses and does not apply to red giants or white dwarfs. As a star approaches the Eddington luminosity then . In summary, the relations for stars with different ranges of mass are, to a good approximation, as the following: \begin \frac &\approx 0.23\left(\frac\right)^ & (M < 0.43M_) \\ \frac &= \left(\frac\right)^4 & (0.43M_ < M < 2M_) \\ \frac &\approx 1.4\left(\frac\right)^ & (2M_ < M < 55M_) \\ \frac &\approx 32000 \frac & (M > 55M_) \end For stars with masses less than 0.43''M''⊙, |
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] |
Ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. The photons of ultraviolet have greater energy than those of visible light, from about 3.1 to 12 electron volts, around the minimum energy required to ionize atoms. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack sufficient energy, it can induce chemical reactions and cause many substances to glow or fluoresce. Many practical applications, including chemical and biological effects, are derived from the way that UV radiation can interact with organic molecules. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Astronomical Catalogues
An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. Astronomical catalogs are usually the result of an astronomical survey of some kind. 0–9 * 0ES — Einstein Slew Survey, version 0See p. 20, X-ray sources in SIMBAD, J. M. Hameury, C. Motch, and M. Pakull, ''Bull. Inf. Centre Données Stellaires'' 47, pp. 19–20, . * 1A, 2A, 3A — Lists of X-ray sources from the Ariel V satellite * 1C — First Cambridge Catalogue of Radio Sources * 1ES — Einstein Slew Survey * 1FGL, 2FGL — Lists of gamma-ray sources from the Fermi LAT, Large Area Telescope on board the Fermi Gamma-ray Space Telescope * 1RXH — ROSAT HRI Pointed Observations * 1RXS — ROSAT All-Sky Bright Source Catalogue, ROSAT All-Sky Survey Faint Source Catalog * 1SWASP — SuperWASP * 2A — see 1A * 2C — Second Cambridge Catalogue of Radio Sources * 2E — The Einste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human
Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing#Evolution of hairlessness, hairlessness, bipedality, bipedalism, and high Human intelligence, intelligence. Humans have large Human brain, brains, enabling more advanced cognitive skills that facilitate successful adaptation to varied environments, development of sophisticated tools, and formation of complex social structures and civilizations. Humans are Sociality, highly social, with individual humans tending to belong to a Level of analysis, multi-layered network of distinct social groups — from families and peer groups to corporations and State (polity), political states. As such, social interactions between humans have established a wide variety of Value theory, values, norm (sociology), social norms, languages, and traditions (co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
