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Phi Tauri
Phi Tauri (φ Tauri) is a solitary, orange-hued star in the zodiac constellation of Taurus. It has an apparent visual magnitude of +4.96, which indicates the star is faintly visible to the naked eye. Based upon an annual parallax shift of 10.16 mas as seen from Earth, it is located roughly 321 light years distant from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.27 due to interstellar dust. This is an evolved, K-type giant star with a stellar classification of K1 III, currently (97% probability) on the red giant branch. It has an estimated 1.36 times the mass of the Sun and has expanded to 19 times the Sun's radius. At the age of roughly five billion years, it is radiating 131 times the Sun's luminosity from its inflated photosphere at an effective temperature of 4,479 K. Phi Tauri has a magnitude 7.51 visual companion located at an angular separation of 48.80 arc seconds along a position ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Of The Sun
The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. More precisely, the mass of the Sun is The solar mass is about times the mass of Earth (), or times the mass of Jupiter (). History of measurement The value of the gravitational constant was first derived from measurements that were made by Henry Cavendish in 1798 with a torsion balance. The value he obtained differs by only 1% from the modern value, but was not as precise. The diurnal parallax of the Sun was accurately measured during the transits of Venus in 1761 and 1769, yielding a value of (9 arcseconds, compared to the present value of ). From the value of the diurnal parallax, one can determine the distance to the Sun from the geometry of Earth. The first known estimate of the solar mass was by Isaac N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hairy Head
The Hairy Head mansion (昴宿, pinyin: Mǎo Xiù) is one of the Twenty-eight mansions of the Chinese constellations. It is one of the western mansions of the White Tiger. This mansion corresponds to the Pleiades The Pleiades (), also known as Seven Sisters and Messier 45 (M45), is an Asterism (astronomy), asterism of an open cluster, open star cluster containing young Stellar classification#Class B, B-type stars in the northwest of the constellation Tau ... in English. Asterisms {{DEFAULTSORT:Hairy Head (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 China, 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). They flourished during the Han period (202 BCE – 220 CE) and subsequent dynasties with the publication of star catalogues. 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 framew ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chi Tauri
Chi Tauri, Latinised from χ Tauri, is a star system in the constellation of Taurus. Parallax measurements made by the ''Hipparcos'' spacecraft put it at a distance of about from Earth. The primary component has an apparent magnitude of about 5.4, meaning it is visible with the naked eye. The main component of the system is Chi Tauri A. It is a B-type main-sequence star. Its mass is 2.6 times that of the Sun and its surface glows with an effective temperature of . It may be a binary star itself, as suggested from astrometric data from ''Hipparcos'', although no orbit could be derived. The secondary component of the system is Chi Tauri B, separated about 19″ from Chi Tauri A. It was thought to be a post-T Tauri star from its unusual spectrum, but later studies ruled this out. It is a double-lined spectroscopic binary—the two stars are not resolved but their spectra have periodic Doppler shifts indicating orbital motion. The two stars are an F-type star and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upsilon Tauri
Upsilon Tauri (υ Tauri) is a solitary, white-hued star in the zodiac constellation of Taurus (constellation), Taurus, and is a member of the Hyades (star cluster), Hyades open cluster, star cluster. It is faintly visible to the naked eye with an apparent visual magnitude of +4.3. Based upon an annual stellar parallax, parallax shift of 21.21 milliarcsecond, mas seen from Earth, it is around 154 light years from the Sun. Properties This is an A-type main sequence star with a stellar classification of A8 Vn. It is classified as a Delta Scuti variable, Delta Scuti type variable star and its brightness varies from magnitude +4.28 to +4.31 with a period of 3.56 hours. At an estimated age of 827 million years, it is spinning rapidly with a rotation period of just 0.415 days. This is giving the star an Oblate spheroid, oblate shape with an equatorial bulge that is 9% larger than the polar radius. Occasionally this star system shares the Bayer designati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kappa Tauri
Kappa Tauri (κ Tau, κ Tauri) is a double star in the constellation Taurus, the two components κ1 Tauri and κ2 Tauri both members of the Hyades open cluster. The pair are approximately 150 light years from Earth and are separated from each other by about six light years. System The system is dominated by a visual double star, κ1 Tauri and κ2 Tauri. κ1 Tauri is a white A-type subgiant with an apparent magnitude of +4.22. It is emitting an excess of infrared radiation at a temperature indicating there is a circumstellar disk in orbit at a radius of 67 AU from the star. κ2 Tauri is a white A-type main sequence star with an apparent magnitude of +5.24. Between the two bright stars is a binary star made up of two 9th magnitude stars, Kappa Tauri C and Kappa Tauri D, which are 5.5 arcseconds from each other (as of 2013) and 175.1 arcseconds from κ1 Tau. Two more 12th magnitude companions fill out the visual group: Kappa Tauri E, which is 145 arcseconds from κ1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Position Angle
In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the Celestial pole, north celestial pole (NCP), turning positive into the direction of the right ascension. In the standard (non-flipped) images, this is a counterclockwise measure relative to the axis into the direction of positive declination. In the case of observed Visual binary, visual binary stars, it is defined as the angular offset of the secondary star from the primary relative to the Celestial pole, north celestial pole. As the example illustrates, if one were observing a hypothetical binary star with a PA of 30°, that means an imaginary line in the eyepiece drawn from the north celestial pole to the primary (P) would be offset from the secondary (S) such that the angle would be 30°. When graphing visual binaries, the NCP is, as in the illustration, normally drawn from the center po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arc Second
A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a turn. The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth's circumference is very near . A minute of arc is of a radian. A second of arc, arcsecond (abbreviated as arcsec), or arc second, denoted by the symbol , is a unit of angular measurement equal to of a minute of arc, of a degree, of a turn, and (about ) of a radian. These units originated in Babylonian astronomy as sexagesimal (base 60) subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying, and marksmanship. To express even smaller angles, standard SI prefixes can be employed; the milliar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angular Separation
Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When the rays are lines of sight from an observer to two points in space, it is known as the apparent distance or apparent separation. Angular distance appears in mathematics (in particular geometry and trigonometry) and all natural sciences (e.g., kinematics, astronomy, and geophysics). In the classical mechanics of rotating objects, it appears alongside angular velocity, angular acceleration, angular momentum, moment of inertia and torque. Use The term ''angular distance'' (or ''separation'') is technically synonymous with ''angle'' itself, but is meant to suggest the linear distance between objects (for instance, a pair of stars observed from Earth). Measurement Since the angular distance (or separation) is conceptually identical to an ang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Companion
In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a binary system of stars in mutual orbit, gravitationally bound to each other) or is an ''optical double'', a chance line-of-sight alignment of two stars at different distances from the observer. Binary stars are important to stellar astronomers as knowledge of their motions allows direct calculation of stellar mass and other stellar parameters. The only (possible) case of "binary star" whose two components are separately visible to the naked eye is the case of Mizar and Alcor (though actually a multiple-star system), but it is not known for certain whether Mizar and Alcor are gravitationally bound. Since the beginning of the 1780s, both professional and amateur double star observers have telescopically measured the distances and angles bet ... [...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, such as the 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
