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κ Aquilae
Kappa Aquilae, Latinized from κ Aquilae, is the Bayer designation for a star in the equatorial constellation of Aquila. It is a faint star at apparent visual magnitude +4.957, but bright enough to be seen with the naked eye in dark suburban skies. The annual parallax is only 1.94 mas, which equates to a distance of approximately from Earth (with a 10% margin of error). The spectrum of Kappa Aquilae matches a stellar classification of B0.5 III, where the luminosity class of III is typically associated with evolved giant stars. This is a star with 15.50 times the Sun's mass and 12.5 times the radius of the Sun. Massive stars like this blaze brightly; it is radiating 52,630-fold the Sun's luminosity from its outer atmosphere with an effective temperature of 26,500 K, giving it the intense blue-white glow of a B-type star. It is only 11 million years of age and is spinning rapidly with a projected rotational velocity of 265 km/s. Etymology In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquila (constellation)
Aquila is a constellation on the celestial equator. Its name is Latin for 'eagle' and it represents the bird that carried Zeus/Jupiter's thunderbolts in Greek-Roman mythology. Its brightest star, Altair, is one vertex of the Summer Triangle asterism. The constellation is best seen in the northern summer, as it is located along the Milky Way. Because of this location, many clusters and nebulae are found within its borders, but they are dim and galaxies are few. History Aquila was one of the 48 constellations described by the second-century astronomer Ptolemy. It had been earlier mentioned by Eudoxus in the fourth century BC and Aratus in the third century BC. It is now one of the 88 constellations defined by the International Astronomical Union. The constellation was also known as ''Vultur volans'' (the flying vulture) to the Romans, not to be confused with ''Vultur cadens'' which was their name for Lyra. It is often held to represent the eagle which held Zeus's/Jupiter's t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Spectrum
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects. A stellar spectrum can reveal many properties of stars, such as their chemical composition, temperature, density, mass, distance and luminosity. Spectroscopy can show the velocity of motion towards or away from the observer by measuring the Doppler shift. Spectroscopy is also used to study the physical properties of many other types of celestial objects such as planets, nebulae, galaxies, and active galactic nuclei. Background Astronomical spectroscopy is used to measure three major bands of radiation in the electromagnetic spectrum: visible light, radio waves, and X-rays. While all spectroscopy looks at specific bands of the spectrum, different methods are required to acquire the signal depending on the frequency. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta Aquilae
Delta Aquilae, Latinized from δ Aquilae, is a binary star system in the equatorial constellation of Aquila. It has an apparent visual magnitude of 3.4 and, based upon parallax measurements, is located at a distance of about from Earth. It is drifting closer with a radial velocity of −30 km/s. The system is predicted to come to within of the Sun in around 335,000 years. Properties The binary nature of this system was first reported by H. L. Alden at Yale Observatory in 1936. It is an astrometric binary where the two components orbit each other with a period of 3.422 years and an eccentricity (ovalness) of about 0.36. This is a type of binary star system where the presence of the secondary component is revealed by its gravitational perturbation of the primary. The individual components have not been resolved with a telescope. The primary member, designated component Aa, is an aging subgiant star with a stellar classification of F0 IV, where the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sigma Aquilae
Sigma Aquilae, Latinized from σ Aquilae, is the Bayer designation for a binary star system in the equatorial constellation of Aquila. The baseline apparent magnitude of the pair is +5.17, which, according to the Bortle Dark-Sky Scale, is bright enough to be seen with the naked eye from suburban skies. Because of the Earth's orbit about the Sun, this system has an annual parallax shift of . This provides a distance estimate of approximately . Sigma Aquilae is a double-lined spectroscopic binary system consisting of two massive B-type main sequence stars; each has a stellar classification of B3 V. They are detached components, which means the two stars are sufficiently distant from each other that neither fills its Roche lobe. Because the orbital plane lies close to the line of sight with the Earth, they form an eclipsing binary system. The two components are each distorted by the gravity of the other star, and their shapes mean that the magnitude of the star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mu Aquilae
Mu Aquilae, Latinized from μ Aquilae, is the Bayer designation for a single star in the equatorial constellation of Aquila. With an apparent visual magnitude of 4.45, it is visible to the naked eye. The measured annual parallax shift of this star is , which gives a distance estimate of from Earth. It is drifting closer with a radial velocity of −25 km/s, and displays a relatively high proper motion, traversing the celestial sphere at the rate of per year. The stellar classification of Mu Aquilae is K3-IIIb Fe0.5, indicating that this is an evolved giant star with a mild overabundance of iron appearing in its spectrum. It belongs to a sub-category of giants called the red clump, which means it is generating energy through the fusion of helium at its core. Compared to the Sun, it has 116% of the mass and has expanded to 7.7 times the size. This inflated outer envelope has an effective temperature The effective temperature of a body such as a star or pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ox (Chinese Constellation)
The Ox mansion (牛宿, pinyin: Niú Xiù) is one of the Twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise. The primary asterism of this mansion is centered on the tail of the constellation known as Capricornus Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is half goat, half f ... in Western astronomy. Asterisms References {{DEFAULTSORT:Ox (Chinese Constellation) Chinese constellations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Astronomy
Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categorized in the twenty-eight mansions have been found on oracle bones unearthed at Anyang, dating back to the mid-Shang dynasty. The core of the "mansion" (宿 ''xiù'') system also took shape around this period, by the time of King Wu Ding (1250–1192 BCE). Detailed records of astronomical observations began during the Warring States period (fourth century BCE) and flourished from the Han period onward. Chinese astronomy was equatorial, centered on close observation of circumpolar stars, and was based on different principles from those in traditional Western astronomy, where heliacal risings and settings of zodiac constellations formed the basic ecliptic framework. Joseph Needham has described the ancient Chinese as the most persistent and accurate obser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Projected Rotational Velocity
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge due to centrifugal force. As stars are not solid bodies, they can also undergo differential rotation. Thus the equator of the star can rotate at a different angular velocity than the higher latitudes. These differences in the rate of rotation within a star may have a significant role in the generation of a stellar magnetic field. The magnetic field of a star interacts with the stellar wind. As the wind moves away from the star its rate of angular velocity slows. The magnetic field of the star interacts with the wind, which applies a drag to the stellar rotation. As a result, angular momentum is transferred from the star to the wind, and over time this gradually slows the star's rate of rotation. Measurement Unless a star is being obse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-type Star
A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars are extremely luminous and blue. Their spectra have neutral helium, which are most prominent at the B2 subclass, and moderate hydrogen lines. Examples include Regulus and Algol A. This class of stars was introduced with the Harvard sequence of stellar spectra and published in the ''Revised Harvard photometry'' catalogue. The definition of type B-type stars was the presence of non-ionized helium lines with the absence of singly ionized helium in the blue-violet portion of the spectrum. All of the spectral classes, including the B type, were subdivided with a numerical suffix that indicated the degree to which they approached the next classification. Thus B2 is 1/5 of the way from type B (or B0) to type A. Later, however, more refined s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve (as a function of wavelength) is not known. When the star's or planet's net emissivity in the relevant wavelength band is less than unity (less than that of a black body), the actual temperature of the body will be higher than the effective temperature. The net emissivity may be low due to surface or atmospheric properties, including greenhouse effect. Star The effective temperature of a star is the temperature of a black body with the same luminosity per ''surface area'' () as the star and is defined according to the Stefan–Boltzmann law . Notice that the total (bolometric) luminosity of a star is then , where is the stellar radius. The definition of the stellar radius is obviously not straightf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Atmosphere
The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone. Overview The stellar atmosphere is divided into several regions of distinct character: * The photosphere, which is the atmosphere's lowest and coolest layer, is normally its only visible part. Light escaping from the surface of the star stems from this region and passes through the higher layers. The Sun's photosphere has a temperature in the 5,770 K to 5,780 K range. Starspots, cool regions of disrupted magnetic field lie on the photosphere. * Above the photosphere lies the chromosphere. This part of the atmosphere first cools down and then starts to heat up to about 10 times the temperature of the photosphere. * Above the chromosphere lies the transition region, where the temperature increases rapidly on a distance of only around 100 km. * The outermost part of the stellar atmosphere is the corona, a tenuous plasma which has a tem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Star
A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press, 2002. . They lie above the main sequence (luminosity class V in the Spectral classification#Yerkes spectral classification, Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III.giant, entry in ''The Facts on File Dictionary of Astronomy'', ed. John Daintith and William Gould, New York: Facts On File, Inc., 5th ed., 2006. . The terms ''giant'' and ''dwarf'' were coined for stars of quite different luminosity despite similar temperature or spectral type by Ejnar Hertzsprung about 1905. Giant stars have radii up to a few hundred times the solar radii, Sun and luminosities between 10 and a few thousand times that of the Sun. Stars still mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
