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δ Ceti
Delta Ceti, Latinized from δ Ceti, is a single, blue-white hued star in the equatorial constellation of Cetus. The star's apparent visual magnitude of +4.06 means it is near to the cusp of the faintest third of the stars that are visible the ideally-placed naked eye. It is north of the celestial equator compared to the celestial north pole's . The star is positioned about WNW of the spiral galaxy M77, but which at apparent magnitude 9.6 needs magnification to be made out and has an apparent size of only by . Based upon an annual parallax shift of as seen from Earth, it is around from the Sun. Motion relative to our system's trajectory includes a highly parting vector: with a net radial velocity of about . It moves minutely across the celestial sphere – yet just over four times more in right ascension than in declination. This is a Beta Cephei variable with a stellar classification of B2 IV. It varies in brightness with a period of 0.16114 days ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cetus (constellation)
Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water-related constellations: Aquarius (constellation), Aquarius, Pisces (constellation), Pisces and Eridanus (constellation), Eridanus. Features Ecliptic Cetus is not among the 12 true zodiac constellations in the Epoch (astronomy), J2000 epoch, nor classical 12-part zodiac. The ecliptic passes less than 0.25° from one of its corners. Thus the Moon and planets will enter Cetus (occulting any stars as a foreground object) in 50% of their successive orbits briefly, and the southern part of the Sun appears in Cetus for about 14 hours each year on March 27 to 28. Many asteroids in belts have longer phases occulting the north-western part of Cetus, those with a slightly greater inclination to the ecliptic than the Moon and planets. Astronomy on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Classification
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grating into a spectrum exhibiting the Continuum (spectrum), rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The ''spectral class'' of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters ''O'', ''B'', ''A'', ''F'', ''G'', ''K'', and ''M'', a sequence from the hottest (''O'' type) to the cool ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xi2 Ceti
Xi2 Ceti, Latinized from ξ2 Ceti, is a star located in the equatorial constellation of Cetus. It is visible to the naked eye with an apparent visual magnitude of +4.3. This star is located at a distance of approximately 197 light years from the Sun based on parallax, and is drifting further away with a radial velocity of 12 km/s. It made its closest approach some 2.7 million years ago at a distance of around . Xi2 Ceti is a spectrophotometric standard star. It displays a stellar classification of B9.5III, which suggests it has exhausted its core hydrogen, evolved away from the main sequence, and expanded to become a giant star, although still only 127 million years old. It has 2.45 times the mass and 2.6 times the radius of the Sun. In Chinese, (), meaning '' Circular Celestial Granary'', refers to an asterism consisting of α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xi1 Ceti
Xi1 Ceti , Latinized from ξ1 Ceti, is a binary star system located in the equatorial constellation of Cetus. It is visible to the naked eye with a combined apparent visual magnitude of +4.36. The distance to this system is approximately 340 light years based on parallax measurements, and it is drifting closer to the Sun with a radial velocity of −4 km/s. The proximity of the star to the ecliptic means it is subject to lunar occultations. The spectroscopic binary nature of Xi1 Ceti was discovered in 1901 by William Wallace Campbell using the Mills spectrograph at the Lick Observatory. The pair have a circular orbit with a period of 4.5 years and a separation of . It is a suspected eclipsing binary with an amplitude of 0.03 in magnitude, which would suggest the orbital plane has a high inclination. The primary, designated component A, is a mild barium giant star with a stellar classification of . Morgan and Keenan in 1973 had classified it as a brigh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mu Ceti
Mu Ceti (μ Ceti) is a binary star in the constellation Cetus, the whale, close to Pisces. The combined apparent magnitude of the system is +4.27, making it visible as a faint star from skies with low or no luminous pollution. Based upon parallax measurements taken by the Gaia spacecraft, it is located 87 light-years away. The location of Mu Ceti next to the ecliptic make it succeptible to lunar occultations. Nomenclature Mu Ceti is the system's Bayer designation. It has no official proper name. In Chinese, (), meaning '' Circular Celestial Granary'', refers to an asterism consisting of α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for Mu Ceti itself is "the Fourth Star of Circular Celestial Granary". [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Ceti
Gamma Ceti (γ Ceti, abbreviated Gamma Cet, γ Cet) is a triple star system in the celestial equator, equatorial constellation of Cetus (constellation), Cetus. It has a combined apparent visual magnitude of 3.47. Based upon stellar parallax, parallax measurements, this star is located at a distance of about 80 light-years (24.4 parsecs) from the Sun. The three components are designated Gamma Ceti A (officially named Kaffaljidhma , the traditional name for the entire system), B and C. Nomenclature ''γ Ceti'' (Latinisation of names, Latinised to ''Gamma Ceti'') is the system's Bayer designation. The designations of the three components as ''Gamma Ceti A'', ''B'' and ''C'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). The close pair AB is also designated Hipparcos, HIP 12706, Henry Draper Catalogue, HD 16970, and Bright Star Catalogue, HR 804. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda Ceti
Lambda Ceti, Latinized from λ Ceti, is a B-type star of fifth-magnitude located in the constellation Cetus. Historically, the star bore the traditional name Menkar, although today that name is more commonly associated with α Ceti. This star, along with α Cet (Menkar), γ Cet (Kaffaljidhma), δ Cet, μ Cet, ξ1 Cet and ξ2 Cet were ''Al Kaff al Jidhmah'', "the Part of a Hand". In Chinese, (), meaning '' Circular Celestial Granary'', refers to an asterism consisting of λ Ceti, α Ceti, κ1 Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for λ Ceti itself is (, .) [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Ceti
Alpha Ceti (α Ceti, abbreviated Alpha Cet, α Cet), officially named Menkar , is the second-brightest star in the constellation of Cetus. It is a cool luminous red giant estimated to be about 250 light years away based on parallax. Nomenclature ''Alpha Ceti'' is the star's Bayer designation. It has the traditional name Menkar, deriving from the Arabic word منخر ''manħar'' "nostril" (of Cetus). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Menkar'' for this star. This star, along with γ Cet (Kaffaljidhma), δ Cet, λ Cet (also Menkar), μ Cet, ξ1 Cet and ξ2 Cet were ''Al Kaff al Jidhmah'', "the Part of a Hand". In Chinese, (), meaning '' Circular Celestial Granary'', refers to an asterism consisting of α Ceti, κ1 Ceti, λ C ... [...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] |
Photosphere
The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will escape without being scattered. A photosphere is the region of a luminous object, usually a star, that is transparent to photons of certain wavelengths. Stars, except neutron stars, have no solid or liquid surface. Therefore, the photosphere is typically used to describe the Sun's or another star's visual surface. Etymology The term ''photosphere'' is derived from Ancient Greek roots, φῶς, φωτός/''phos'', ''photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it being a spherical surface that is perceived to emit light. Temperature The surface of a star is defined to have a temperature given by the effective temperature in the Stefan–Boltzmann law. Various stars have photospheres of vari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 solar luminosity is defined by the International Astronomical Union to be . This corresponds almost exactly to a bolometric absolute magnitude of +4.74. The Sun is a weakly variable star, and its actual luminosity therefore fluctuates. The major fluctuation is the eleven-year solar cycle (sunspot cycle) that causes a quasi-periodic variation of about ±0.1%. Other variations over the last 200–300 years are thought to be much smaller than this. Determination Solar luminosity is related to solar irradiance (the solar constant). Slow changes in the axial tilt of the planet and the shape of its orbit cause cyclical changes to the solar irradiance. The result is orbital forcing that causes the Milankovitch cycles, which determine Eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sun's Radius
Solar radius is a unit of distance used to express the size of objects in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: 1\,R_ = 6.957\times 10^8 \hbox is approximately 10 times the average radius of Jupiter, 109 times the radius of the Earth, and 1/215 of an astronomical unit, the approximate distance between Earth and the Sun. The solar radius to either pole and that to the equator differ slightly due to the Sun's rotation, which induces an oblateness in the order of 10 parts per million. Measurements The uncrewed SOHO spacecraft was used to measure the radius of the Sun by timing transits of Mercury across the surface during 2003 and 2006. The result was a measured radius of . Haberreiter, Schmutz & Kosovichev (2008) determined the radius corresponding to the solar photosphere to be . This new value is consistent with helioseismic estimates; the same study showed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
