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NGC 7380
NGC 7380 is a young open cluster of stars in the northern circumpolar constellation of Cepheus, discovered by Caroline Herschel in 1787. The surrounding emission nebulosity is known colloquially as the Wizard Nebula, which spans an angle of . German-born astronomer William Herschel included his sister's discovery in his catalog, and labelled it H VIII.77. The nebula is known as S 142 in the 1959 Sharpless catalog (Sh2-142). It is extremely difficult to observe visually, usually requiring very dark skies and an O-III filter. The NGC 7380 complex is located at a distance of approximately from the Sun, in the Perseus Arm of the Milky Way. The cluster spans ~ with an elongated shape and an extended tail. Age estimates range from 4 to 11.9 million years. At the center of the cluster lies DH Cephei, a close, double-lined spectroscopic binary system consisting of two massive O-type stars. This pair are the primary ionizing source for the surrounding H II region, and are dri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cepheus (constellation)
Cepheus is a constellation in the far northern sky, named after Cepheus, a king of Aethiopia in Greek mythology. It is one of the 48 constellations listed by the second century astronomer Ptolemy, and it remains one of the 88 constellations in the modern times. The constellation's brightest star is Alpha Cephei, with an apparent magnitude of 2.5. Delta Cephei is the prototype of an important class of star known as a Cepheid variable. RW Cephei, an orange hypergiant, together with the red supergiants Mu Cephei, MY Cephei, SW Cephei, VV Cephei, and V354 Cephei are among the largest stars known. In addition, Cepheus also has the hyperluminous quasar S5 0014+81, which hosts an ultramassive black hole in its core, reported at 40 billion solar masses, about 10,000 times more massive than the central black hole of the Milky Way, making this among the most massive black holes currently known. This paper does acknowledge the possibility of an optical illusion that would cause an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OB Association
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as the internal kinematics of more distant galaxies. Measurement of the kinematics of stars in different subcomponents of the Milky Way including the thin disk, the thick disk, the bulge, and the stellar halo provides important information about the formation and evolutionary history of our Galaxy. Kinematic measurements can also identify exotic phenomena such as hypervelocity stars escaping from the Milky Way, which are interpreted as the result of gravitational encounters of binary stars with the supermassive black hole at the Galactic Center. Stellar kinematics is related to but distinct from the subject of stellar dynamics, which involves the theoretical study or modeling of the motions of stars under the influence of gravity. Ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HR 8752
V509 Cassiopeiae (V509 Cas or HR 8752) is one of two yellow hypergiant stars found in the constellation Cassiopeia, which also contains Rho Cassiopeiae. HR 8752 is around 15,700 light-years from Earth. It has an apparent magnitude that has varied from below +6 in historical times to a peak of +4.6 and now around +5.3 and is classified as a semiregular variable star of type SRd. It is undergoing strong mass loss as part of its rapid evolution and has recently passed partway through the yellow evolutionary void by ejecting around a solar mass of material in 20 years. A hot main sequence companion (B1V) was described in 1978 on the basis of a colour excess in the ultraviolet. Observations Brightness HR 8752 is a naked eye star but it has no Bayer or Flamsteed designation, and is not recorded in other catalogues before the 19th century. When first recorded in the Radcliffe Observatory catalogue in 1840 it was 6th magnitude, and it is assumed it had been 6th magnitude o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RW Cephei
RW Cephei is a hypergiant variable star in the constellation Cepheus, at the edge of the Sharpless 132 HII region and close to the small open cluster Berkeley 94. One of the largest stars known, RW Cephei's radius is more than 1,000 times that of the Sun (), thus larger than the orbit of Jupiter. RW Cephei is also a semi-regular variable star of type SRd, meaning that it is a slowly varying yellow giant or supergiant. The visual magnitude range is from 6.0 to 7.6, while the photographic range is from 8.6 - 10.7. The General Catalogue of Variable Stars gives a period of approximately 346 days, but other studies suggest different periods and certainly no strong periodicity. The spectral has been classified as early as G8 and as late as M2, but it isn't clear that there has been actual variation. In the first MK spectral atlas, it was listed M0:Ia. RW Cephei was later listed as the standard star for spectral type G8 Ia, then as the standard for K0 0-Ia. Based on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Largest Stars
Below are lists of the largest stars currently known, ordered by radius and separated into categories by galaxy. The unit of measurement used is the radius of the Sun (approximately ). The angular diameters of stars can be measured directly using stellar interferometry. Other methods can use lunar occultations or from eclipsing binaries, which can be used to test indirect methods of finding stellar radii. Only a few useful supergiant stars can be occulted by the Moon, including Antares A (Alpha Scorpii A). Examples of eclipsing binaries are Epsilon Aurigae (Almaaz), VV Cephei, and V766 Centauri (HR 5171). Angular diameter measurements can be inconsistent because the boundary of the very tenuous atmosphere (opacity) differs depending on the wavelength of light in which the star is observed. Uncertainties remain with the membership and order of the lists, especially when deriving various parameters used in calculations, such as stellar luminosity and effective temperature. Oft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
V354 Cephei
V354 Cephei is a red supergiant star located within the Milky Way. It is an irregular variable located over 8,900 light-years away from the Sun. It has an estimated radius of . If it were placed in the center of the Solar System, it would extend to between the orbits of Mars and Jupiter. Identification V354 Cephei is identified as a red supergiant variable star and included on surveys such as IRAS and 2MASS, but prior to its inclusion in the General Catalogue of Variable Stars in 1981, it was referred to only by its listings on relatively obscure catalogs. It is too faint to be included in catalogs such as the Henry Draper Catalogue or Bonner Durchmusterung. It was included on a 1947 Dearborn Observatory survey as star 41575, but that ID is hardly ever used. V354 Cephei has been referred to as Case 75. This is from one of several listings of cool stars made using the Burrell Schmidt telescope at the Warner and Swasey Observatory of Case Western Reserve University, altho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yellow Hypergiant
A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually luminous stars, with absolute magnitude (MV) around −9, but also one of the rarest, with just 20 known in the Milky Way and six of those in just a single cluster. They are sometimes referred to as cool hypergiants in comparison with O- and B-type stars, and sometimes as warm hypergiants in comparison with red supergiants. Classification The term "hypergiant" was used as early as 1929, but not for the stars currently known as hypergiants. Hypergiants are defined by their '0' luminosity class, and are higher in luminosity than the brightest supergiants of class Ia, although they were not referred to as hypergiants until the late 1970s. Another criterion for hypergiants was also suggested in 1979 for some other highly luminous mass-losing hot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
W Cephei
W Cephei is a spectroscopic binary and variable star located in the constellation Cepheus. It is thought to be a member of the Cep OB1 stellar association at about 8,000 light years. The supergiant primary star is one of largest known stars and as well as one of most luminous red supergiants. Discovery W Cephei was catalogued as BD+57°2568 in the Bonner Durchmusterung published in 1903, and HD 214369 in the Henry Draper Catalogue. It reported in 1896 as a red star varying from magnitude 7.3 to 8.3. In 1925, W Cep was included in a listing of Be stars. It was recognised as a cool star with spectral type Mep. It was classified as K0ep Ia from a 1949 spectrum, but also recognised to have a small hot companion, plus an unusual infrared excess. Ultraviolet spectra allowed absorption lines from the companion to be studied and it was given a spectral type of B0-1. System The W Cephei system contains a luminous red supergiant star with a non-supergiant early B c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Star
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
U Lacertae
U Lacertae is a spectroscopic binary star in the constellation Lacerta. Despite being in the constellation of Lacerta, U Lacertae is considered to be a member of the Cepheus OB1 association. It has been listed as a member of the open cluster ASCC 123. U Lacertae is a VV Cephei binary consisting of a red supergiant and a small hot companion. The companion has been identified from a high excitation component in the spectrum and from radial velocity variations, but the orbit is unknown. U Lacertae is a variable star classified as a semiregular variable. The periodicity is uncertain but a main period of 150 days and a long secondary period of 550 – 690 days have been suggested. A study of Hipparcos satellite photometry found an amplitude of 0.77 magnitudes and found no periodicity. The General Catalogue of Variable Stars lists an amplitude of 2.7 magnitudes. Water masers have been detected around U Lacertae, common in the extended atmospheres of very luminous cool star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
