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Gamma Arietis
Gamma Arietis (γ Arietis, abbreviated Gamma Ari, γ Ari) is a binary star (possibly trinary) in the northern constellation of Aries. The two components are designated γ1 Arietis or Gamma Arietis B and γ2 Arietis or Gamma Arietis A (formally named Mesarthim , the traditional name for the Gamma Arietis system). γ1 Arietis may itself be a spectroscopic binary with a low mass companion. The combined apparent visual magnitude of the stars is 3.86, which is readily visible to the naked eye and makes this the fourth-brightest member of Aries. Based upon parallax measurements obtained during the Hipparcos mission, the distance to Gamma Arietis from the Sun is approximately . Properties The double star nature of this system was discovered by Robert Hooke in 1664. The two components have an angular separation of 7.606 arcseconds, which can be resolved with a small telescope. The orbital period of the pair is greater than 5000 years. The brighter component, γ2 Ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aries (constellation)
Aries is one of the constellations of the zodiac. It is located in the Northern celestial hemisphere between Pisces to the west and Taurus to the east. The name Aries is Latin for ram. Its old astronomical symbol is (♈︎). It is one of the 48 constellations described by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is a mid-sized constellation ranking 39th in overall size, with an area of 441 square degrees (1.1% of the celestial sphere). Aries has represented a ram since late Babylonian times. Before that, the stars of Aries formed a farmhand. Different cultures have incorporated the stars of Aries into different constellations including twin inspectors in China and a porpoise in the Marshall Islands. Aries is a relatively dim constellation, possessing only four bright stars: Hamal (Alpha Arietis, second magnitude), Sheratan (Beta Arietis, third magnitude), Mesarthim (Gamma Arietis, fourth magnitude), and 41 Arietis (also fourt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angular Separation
Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in particular geometry and trigonometry) and all natural sciences (e.g. 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 couple of stars observed from Earth). Measurement Since the angular distance (or separation) is conceptually identical to an angle, it is measured in the same units, such as degrees or radians, using instruments such as goniometers or optical instruments specially designed to point in well-defined directions and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron Peak
The iron peak is a local maximum in the vicinity of Fe ( Cr, Mn, Fe, Co and Ni) on the graph of the abundances of the chemical elements. For elements lighter than iron on the periodic table, nuclear fusion releases energy. For iron, and for all of the heavier elements, nuclear fusion consumes energy. Chemical elements up to the iron peak are produced in ordinary stellar nucleosynthesis, with the alpha elements being particularly abundant. Some heavier elements are produced by less efficient processes such as the r-process and s-process. Elements with atomic numbers close to iron are produced in large quantities in supernova due to explosive oxygen and silicon fusion, followed by radioactive decay of nuclei such as Nickel-56. On average, heavier elements are less abundant in the universe, but some of those near iron are comparatively more abundant than would be expected from this trend. Binding energy A graph of the nuclear binding energy per nucleon for all the eleme ... [...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 coo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemically Peculiar Star
In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual Metallicity, metal abundances, at least in their surface layers. Classification Chemically peculiar stars are common among hot main-sequence (hydrogen-burning) stars. These hot peculiar stars have been divided into 4 main classes on the basis of their spectra, although two classification systems are sometimes used: * non-magnetic metallic-lined star, metallic-lined (Am, CP1) * Ap and Bp stars, magnetic (Ap, CP2) * non-magnetic mercury-manganese star, mercury-manganese (HgMn, CP3) * Helium-weak star, helium-weak (He-weak, CP4). The class names provide a good idea of the peculiarities that set them apart from other stars on or near the main sequence. The Am stars (CP1 stars) show weak lines of singly ionized Calcium, Ca and/or Scandium, Sc, but show enhanced abundances of heavy metals. They also tend to be slow rotators and have an effective temperature between 7000 and . The Ap stars (CP2 sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda Boötis Star
A Lambda Boötis star is a type of chemically peculiar star which has an unusually low abundance of iron peak elements in its surface layers. One possible explanation for this is that it is the result of accretion of metal-poor gas from a circumstellar disc, and a second possibility is the accretion of material from a hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temp ... suffering from mass loss. The prototype is Lambda Boötis. References Further reading * * Star types {{star-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Dwarf
''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. The series follows low-ranking technician Dave Lister, who awakens after being in suspended animation for three million years to find that he is the last living human, and that he is alone on the mining spacecraft ''Red Dwarf''—save for a hologram his deceased bunkmate Arnold Rimmer and "Cat", a life form which evolved from Lister's pregnant cat. As of 2020, the cast includes Chris Barrie as Rimmer, Craig Charles as Lister, Danny John-Jules as Cat, Robert Llewellyn as the sanitation droid Kryten, and Norman Lovett as the ship's computer, Holly. To date, twelve series of the show have aired, (including one miniseries), in addition to a feature-length special ''The Promised Land''. Four novels were published from 1989 to 1996. Two pilot ep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subgiant
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of a star. Yerkes luminosity class IV The term subgiant was first used in 1930 for class G and early K stars with absolute magnitudes between +2.5 and +4. These were noted as being part of a continuum of stars between obvious main-sequence stars such as the Sun and obvious giant stars such as Aldebaran, although less numerous than either the main sequence or the giant stars. The Yerkes spectral classification system is a two-dimensional scheme that uses a letter and number combination to denote that temperature of a star (e.g. A5 or M1) and a Roman numeral to indicate the luminosity relative to other stars of the same temperature. Luminosity class IV stars are the subgiants, located between main-sequence stars (luminosity class V) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ap Star
Ap and Bp stars are chemically peculiar stars (hence the "p") of spectral types A and B which show overabundances of some metals, such as strontium, chromium and europium. In addition, larger overabundances are often seen in praseodymium and neodymium. These stars have a much slower rotation than normal for A and B-type stars, although some exhibit rotation velocities up to about 100 kilometers per second. Magnetic fields Ap and Bp stars have stronger magnetic fields than classical A- or B-type stars; in the case of HD 215441, reaching 33.5 k G (3.35 T). Typically the magnetic field of these stars lies in the range of a few kG to tens of kG. In most cases a field which is modelled as a simple dipole is a good approximation and provides an explanation as to why there is an apparent periodic variation in the magnetic field, as if such a field is not aligned with the rotation axis—the field strength will change as the star rotates. In support of this theory it has been no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromospheric
A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the Sun's atmosphere, the chromosphere is roughly in height, or slightly more than 1% of the Sun's radius at maximum thickness. It possesses a homogeneous layer at the boundary with the photosphere. Hair-like jets of plasma, called spicules, rise from this homogeneous region and through the chromosphere, extending up to into the corona above. The chromosphere has a characteristic red color due to electromagnetic emissions in the ''H''α spectral line. Information about the chromosphere is primarily obtained by analysis of its emitted electromagnetic radiation. Chromospheres have also been observed on stars other than the Sun. On large stars, chromospheres sometimes make up a significant proportion of the entire star. For example, the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: * Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. * Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of the Sun, for example, varies by about 0.1% over an 11-year solar cycle. Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. Of the modern astronomers, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
