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Omega Draconis
Omega Draconis, Latinized from ω Draconis and also known as 28 Draconis, is a binary star in the constellation of Draco. The system is fairly close, and is located about 76 light-years (23 parsecs) away, based on its parallax. Omega Draconis is a spectroscopic binary, which means the two stellar components are too close to be resolved but periodic Doppler shifts in their spectra indicate orbital motion. In this case, light from both stars can be detected, and it is a double-lined spectroscopic binary. The orbital period of the system is 5.28 days, and the eccentricity of the system is 0.00220, implying a nearly circular orbit. The primary has a mass of , and is an F-type main-sequence star. The secondary is less massive, at . Naming With 27 Draconis, it composed the Arabs' الأظفار الذئب ''al-ʼaẓfār al-dhiʼb'', "the hyena's claws" in the asterism of the Mother Camels. The two stars have been distinguished as ''Adfar Aldib I'' (ω) and ''Adfar Aldib II ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Draco (constellation)
Draco is a constellation in the far northern sky. Its name is Latin for dragon. It was one of the 48 Lists of constellations, constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations today. The north pole of the ecliptic is in Draco. Draco is circumpolar star, circumpolar from northern latitudes. There it is never setting and therefore can be seen all year. Features Stars Thuban (α Draconis) was the northern pole star from 3942 BC, when it moved farther north than Theta Boötis, until 1793 BC. The Egyptian Pyramids were designed to have one side facing north, with an entrance passage geometrically aligned so that Thuban would be visible at night. Due to the effects of Axial precession (astronomy), precession, it would again be the pole star around the year AD 21000. It is a blue-white giant star of magnitude 3.7, 309 light-years from Earth. The traditional name of Alpha Draconis, Thuban, means "head of the serpent". T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angular Resolution
Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. It is used in optics applied to light waves, in antenna theory applied to radio waves, and in acoustics applied to sound waves. The colloquial use of the term "resolution" sometimes causes confusion; when an optical system is said to have a high resolution or high angular resolution, it means that the perceived distance, or actual angular distance, between resolved neighboring objects is small. The value that quantifies this property, ''θ,'' which is given by the Rayleigh criterion, is low for a system with a high resolution. The closely related term spatial resolution refers to the precision of a measurement with respect to space, which is directly connected to angular resolution in imaging instruments. The Rayleigh criterion shows th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
19 Draconis
19 Draconis, also known as h Draconis, is a star system in the constellation Draco. It is visible to the naked eye as a faint, yellow-white hued star with an apparent visual magnitude of 4.89. Based on its parallax, the system is located about 49.8 light-years (15.26 parsecs) away. It is moving closer to the Earth with a heliocentric radial velocity of −21 km/s. This is a binary star system with an orbital period of 52.1 days and an eccentricity of 0.22. Only the primary star can be directly detected, via Doppler shifts or perturbations around the system's barycenter. Using spectroscopy and astrometry, the nature of the secondary star can be inferred. The primary star is an F-type main-sequence star with a stellar classification of F8V, 4% more massive than the Sun. Its surface temperature is about 6,298 K, and it emits just over twice the amount of energy that the Sun does. The secondary is only 37% as massive as the Sun The Sun is the star a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
18 Draconis
18 Draconis is a likely binary star system in the northern circumpolar constellation of Draco. With an apparent visual magnitude of 4.84, it is just bright enough to be faintly visible to the naked eye. The distance to this system, as estimated from an annual parallax shift of , is roughly 720 light years. It is moving closer to the Sun with a heliocentric radial velocity of −1.4 km/s, and is a probable member of the Sirius stream of co-moving stars. The visible component has a stellar classification of , indicating it is an evolved K-type giant star with some abundance peculiarities in its atmosphere. At the age of around 280 million years, it is most likely (99% chance) on the horizontal branch. It is a barium star, which suggests it may have a degenerate white dwarf companion from which it accreted materials during an earlier stage of its evolution. 18 Dra has an estimated 3.8 times the mass of the Sun and has expanded to 47 times the Sun's radiu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
15 Draconis
15 Draconis is a single star in the northern circumpolar constellation of Draco, located 452 light years away from the Sun. ''15 Draconis'' is the Flamsteed designation; it also has the Bayer designation ''A Draconis''. This object is visible to the naked eye as a white-hued star with an apparent visual magnitude of 4.94. It is moving closer to the Earth with a heliocentric radial velocity of −7 km/s. This star has a stellar classification of A0 III, matching that of an A-type giant star. It has a relatively high rate of spin with a projected rotational velocity of 154 km/s. The star is radiating 286 times the Sun's luminosity The solar luminosity (), is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal ... from its photosphere at an effective temperature of 9,980 K. R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purple Forbidden Enclosure
The Purple Forbidden enclosure ( Zǐ wēi yuán) is one of the San Yuan ( Sān yuán) or Three Enclosures Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" ( Chinese ''xīng guān''). The Chinese asterisms are generally smaller than the constellations of Hellenistic .... Stars and constellations of this group lie near the north celestial pole and are visible all year from temperate latitudes in the Northern Hemisphere. Asterisms The asterisms are : See also * Twenty-eight mansions References Chinese constellations Chinese astrology {{china-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Language
Chinese (, especially when referring to written Chinese) is a group of languages spoken natively by the ethnic Han Chinese majority and many minority ethnic groups in Greater China. About 1.3 billion people (or approximately 16% of the world's population) speak a variety of Chinese as their first language. Chinese languages form the Sinitic branch of the Sino-Tibetan languages family. The spoken varieties of Chinese are usually considered by native speakers to be variants of a single language. However, their lack of mutual intelligibility means they are sometimes considered separate languages in a family. Investigation of the historical relationships among the varieties of Chinese is ongoing. Currently, most classifications posit 7 to 13 main regional groups based on phonetic developments from Middle Chinese, of which the most spoken by far is Mandarin (with about 800 million speakers, or 66%), followed by Min (75 million, e.g. Southern Min), Wu (74 million, e.g. Shangh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mother Camels
The protecting Mother Camels (Arabic العوائذ ''alʽawaʼid'') is an asterism in the constellation of Draco described by ancient Arabic nomadic tribes. The asterism was interpreted as a ring of mother camels – Beta Draconis (Rastaban), Gamma Draconis (Eltanin), Nu Draconis (Kuma) and Xi Draconis (Grumium) – surrounding a foal (the faint star Alruba), with another mother camel, Mu Draconis (Alrakis) running to join them. The Arabs did not see the constellation Draco as it is now. The Mother Camels were protecting the foal from the attack of two wolves or jackals – Zeta Draconis (Aldhibah) and Eta Draconis (Athebyne). The faint pair Omega Draconis Omega Draconis, Latinized from ω Draconis and also known as 28 Draconis, is a binary star in the constellation of Draco. The system is fairly close, and is located about 76 light-years (23 parsecs) away, based on its parallax. Omega Dra ... and 27 Draconis was known as the "wolf's claws" (الأظفار الذئب ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
27 Draconis
7 (seven) is the natural number following 6 and preceding 8. It is the only prime number preceding a cube. As an early prime number in the series of positive integers, the number seven has greatly symbolic associations in religion, mythology, superstition and philosophy. The seven Classical planets resulted in seven being the number of days in a week. It is often considered lucky in Western culture and is often seen as highly symbolic. Unlike Western culture, in Vietnamese culture, the number seven is sometimes considered unlucky. It is the first natural number whose pronunciation contains more than one syllable. Evolution of the Arabic digit In the beginning, Indians wrote 7 more or less in one stroke as a curve that looks like an uppercase vertically inverted. The western Ghubar Arabs' main contribution was to make the longer line diagonal rather than straight, though they showed some tendencies to making the digit more rectilinear. The eastern Arabs developed the digit fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
