|
DT Virginis C
DT Virginis, also known as Ross 458, is a binary star system in the constellation of Virgo. It has an apparent visual magnitude of 9.79 and is located at a distance of 37.6 light-years from the Sun. Both of the stars are low-mass red dwarfs with at least one of them being a flare star. This binary system has a circumbinary sub-stellar companion. This star was mentioned as a suspected variable by M. Petit in 1957. In 1960, O. J. Eggen classified it as a member of the Hyades moving group based on the system's space motion; it is now considered a likely member of the Carina Near Moving Group. Two flares were reported from this star in 1969 by N. I. Shakhovskaya, confirming it as a flare star. It was identified as an astrometric binary in 1994 by W. D. Heintz, who found a period of 14.5 years. The pair were resolved using adaptive optics in 1999. Early mass estimates placed the companion near the substellar limit, and it was initially proposed as a brown dwarf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wulff-Dieter Heintz
Wulff-Dieter Heintz (3 June 1930 – 10 June 2006) was a German astronomer who worked the latter part of his career in the United States. He was Professor Emeritus of Astronomy at Swarthmore College. He specialised in the characterisation of binary stars using astrometry. Life Wulff-Dieter Heintz was born in Würzburg, Germany on 3 June 1930. He earned his doctorate in astronomy from the University of Munich in 1953. He did research at thUniversity Observatory Munich'sSouthern Station on Mount Stromlo in Australia. Peter van de Kamp invited him to the Sproul Observatory to be a visiting professor in 1969. He subsequently joined the staff and became observatory director upon the retirement of van de Kamp in 1972. He remained a German citizen. He was an avid and expert chess player and authored a book on the game in German. The Barnard's Star affair Peter van de Kamp, Wulff's predecessor at Swarthmore, made claims since the 1960s of a planetary system around Barnard's Star. After ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GU Piscium B
GU Piscium b (GU Psc b) is a directly imaged planetary-mass companion orbiting the star GU Piscium, with an extremely large orbit of , and an apparent angular separation of 42 arc seconds. The planet is located at right ascension declination at a distance of . Properties An orbital revolution around its parent star (which is 1/3 the mass of the Sun) or "year", would take approximately 163,000 years to complete, considering a circular orbit with 2000 AU as the semi-major axis. It is a gas giant located in the constellation of Pisces, 155 light-years from the Solar System, and estimated to have a mass nine to thirteen times that of Jupiter, and a surface temperature of 1000 K. It is a relatively young stellar system, part of the AB Doradus moving group of ca. 30 main stars created from the same molecular cloud less than 100 million years ago, and the only one found among the 90 stars of the group examined. Discovery The discovery was made by an international team ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CM Draconis
CM Draconis (GJ 630.1A) is an eclipsing binary system approximately 47 light-years away in the constellation of Draco (the Dragon). The system consists of two nearly identical red dwarf stars located in the constellation Draco Draco is the Latin word for serpent or dragon. Draco or Drako may also refer to: People * Draco (lawgiver) (from Greek: Δράκων; 7th century BC), the first lawgiver of ancient Athens, Greece, from whom the term ''draconian'' is derived * .... The two stars orbit each other with a period of 1.27 days with a separation of 2.7 million kilometres (0.018 AU). Along with two stars in the triple system Kepler Object of Interest#Non-planet discoveries, KOI 126, the stars in CM Draconis are the lightest stars with precisely measured masses and radii. Consequently, the system plays an important role in testing stellar structure models for very low mass stars. These comparisons find that models underpredict the stellar radii by approximately 5%. T ... [...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] |
Photosphere
The photosphere is a star's outer shell from which light is radiated. The term itself 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. 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 deepest region of a luminous object, usually a star, that is transparent to photons of certain wavelengths. Temperature The surface of a star is defined to have a temperature given by the effective temperature in the Stefan–Boltzmann law. 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. Composition of the Sun The Sun is composed primarily of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Spot
Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in general much larger than those on the Sun: up to about 30% of the stellar surface may be covered, corresponding to starspots 100 times larger than those on the Sun. Detection and measurements To detect and measure the extent of starspots one uses several types of methods. *For rapidly rotating stars – Doppler imaging and Zeeman-Doppler imaging. With the Zeeman-Doppler imaging technique the direction of the magnetic field on stars can be determined since spectral lines are split according to the Zeeman effect, revealing the direction and magnitude of the field. *For slowly rotating stars – Line Depth Ratio (LDR). Here one measures two different spectral lines, one sensitive to temperature and one which is not. Since starspots have a low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emission Lines
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected ones of atoms and molecules, and are thus used to identify the atomic and molecular components of stars and planets, which would otherwise be impossible. Types of line spectra Spectral lines are the result of interaction between a quantum system (usually atoms, but sometimes molecules or atomic nuclei) and a single photon. When a photon has about the right amount of energy (which is connected to its frequency) to allow a change in the energy state of the system (in the case of an atom this is usually an electron changing orbitals), the photon is absorbed. Then the energy will be spontaneously re-emitted, either as one photon at the same frequenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H-alpha
H-alpha (Hα) is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm in air and 656.46 nm in vacuum; it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alpha light is the brightest hydrogen line in the visible spectral range. It is important to astronomers as it is emitted by many emission nebulae and can be used to observe features in the Sun's atmosphere, including solar prominences and the chromosphere. Balmer series According to the Bohr model of the atom, electrons exist in quantized energy levels surrounding the atom's nucleus. These energy levels are described by the principal quantum number ''n'' = 1, 2, 3, ... . Electrons may only exist in these states, and may only transit between these states. The set of transitions from ''n'' ≥ 3 to ''n'' = 2 is called the Balmer series and its members are named sequentially by Greek letters: *''n'' = 3 to ''n'' = 2 is called Balmer-alpha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Activity
A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magnetic field exerts a force on the plasma, effectively increasing the pressure without a comparable gain in density. As a result, the magnetized region rises relative to the remainder of the plasma, until it reaches the star's photosphere. This creates starspots on the surface, and the related phenomenon of coronal loops. Measurement The magnetic field of a star can be measured by means of the Zeeman effect. Normally the atoms in a star's atmosphere will absorb certain frequencies of energy in the electromagnetic spectrum, producing characteristic dark absorption lines in the spectrum. When the atoms are within a magnetic field, however, these lines become split into multiple, closely spaced lines. The energy also becomes polarized with a ... [...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] |
M-type Main-sequence Star
''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 pilo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
