|
FUors
In stellar evolution, an FU Orionis star (also FU Orionis object, or ''FUor'') is a pre–main-sequence star which displays an extreme change in magnitude and spectral type. One example is the star V1057 Cyg, which became six magnitudes brighter and went from spectral type dKe to F-type supergiant during 1969–1970. These stars are named after their type-star, FU Orionis. The current model developed primarily by Lee Hartmann and Scott Jay Kenyon associates the FU Orionis flare with abrupt mass transfer from an accretion disc onto a young, low mass T Tauri star. Mass accretion rates for these objects are estimated to be around 10−4 solar masses per year. The rise time of these eruptions is typically on the order of 1 year, but can be much longer. The lifetime of this high-accretion, high-luminosity phase is on the order of decades. However, even with such a relatively short timespan, no FU Orionis object had been observed shutting off. By comparing the number of FUor o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scott Jay Kenyon
Scott Jay Kenyon (born 1956) is an American astrophysicist. His work has included advances in symbiotic and other types of interacting binary stars, the formation and evolution of stars, and the formation of planetary systems. Career Kenyon received a B.S. in physics from Arizona State University in 1978 and a Ph.D. in astronomy from the University of Illinois Urbana-Champaign in 1983. His doctoral dissertation is titled ''The Physical Structure of the Symbiotic Stars'' and was expanded into a book, ''The Symbiotic Stars''. After postdoctoral work at the Center for Astrophysics Harvard & Smithsonian, including a CfA Fellowship, he joined the scientific staff at the Smithsonian Astrophysical Observatory. Kenyon is a Fellow of the AAAS, a Fellow of the American Physical Society, and is included in the Web of Knowledge index of highly cited researchers. Scientific work Kenyon has worked extensively on symbiotic binary stars. His book ''The Symbiotic Stars'' was the first to summ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FU Orionis
FU Orionis is a variable star, variable and binary star system in the constellation of Orion (constellation), Orion, that in 1937 rose in apparent visual magnitude from 16.5 to 9.6, and has since been around magnitude 9. The name ''FU Orionis'' is a variable star designation in the Friedrich Wilhelm Argelander, Argelander system, which are assigned sequentially as new variables are discovered. FU Orionis is about 1,360 light years distant and is associated with the molecular cloud Barnard 35. For a long time this variable was considered unique, but in 1970 a similar star, V1057 Cygni, was discovered, and a number of additional examples have been discovered since then. These stars constitute the FU Orionis star, FU Orionis class of variable stars, GCVS type ''FU'', often nicknamed ''FUors''. These stars are pre–main sequence stars which display an extreme change in magnitude and spectral type. Stellar system FU Orionis consists of two components, both surrounded by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
V1057 Cyg
V1057 Cygni is a suspected binary star system in the northern constellation of Cygnus. It is a variable star of the FU Orionis-type, and was the second FU Orionis-type variable to be discovered. The system is located at a distance of approximately 3,000 light years from the Sun, in the North America Nebula. It has an apparent visual magnitude of around 12.4. The initial classification of the primary was as a young T Tauri star. During 1969–1970 it underwent a nova-like outburst, increasing in brightness by five magnitudes and emitting a strong mass outflow. For the next ten years the brightness stayed at a plateau before decreasing rapidly in the mid–1990s, accompanied by a change in its spectrum. As of 2013, it is 1.5 magnitudes brighter than it was before the nova-like event. The mass of FU Ori objects is estimated to be in the range of 0.3–. A faint binary companion was discovered in 2016, and designated component B. It is located at a projected separa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Young Star Flaunts Its X-ray Spots
A, or a, is the first Letter (alphabet), letter and the first vowel letter of the Latin alphabet, used in the modern English alphabet, and others worldwide. Its name in English is ''English alphabet#Letter names, a'' (pronounced ), plural ''aes''. It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version is often written in one of two forms: the double-storey and single-storey . The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children, and is also found in italic type. In English, ''English articles, a'' is the indefinite article, with the alternative form ''an''. Name In English, the name of the letter is the ''long A'' sound, pronounced . Its name in most other languages matches the letter's pronunciation in open syllables. History The earliest know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Near-infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of red light (the longest waves in the visible spectrum), so IR is invisible to the human eye. IR is generally (according to ISO, CIE) understood to include wavelengths from around to . IR is commonly divided between longer-wavelength thermal IR, emitted from terrestrial sources, and shorter-wavelength IR or near-IR, part of the solar spectrum. Longer IR wavelengths (30–100 μm) are sometimes included as part of the terahertz radiation band. Almost all black-body radiation from objects near room temperature is in the IR band. As a form of EMR, IR carries energy and momentum, exerts radiation pressure, and has properties corresponding to wave–particle duality, both those of a wave and of a subatomic particle, particle, the photon. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Types
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the 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 coolest (''M'' type). Each letter class is then subdivided ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FU Orionis Stars
In stellar evolution, an FU Orionis star (also FU Orionis object, or ''FUor'') is a pre–main-sequence star which displays an extreme change in magnitude and spectral type. One example is the star V1057 Cyg, which became six magnitudes brighter and went from spectral type dKe to F-type supergiant during 1969–1970. These stars are named after their type-star, FU Orionis. The current model developed primarily by Lee Hartmann and Scott Jay Kenyon associates the FU Orionis flare with abrupt mass transfer from an accretion disc onto a young, low mass T Tauri star. Mass accretion rates for these objects are estimated to be around 10−4 solar masses per year. The rise time of these eruptions is typically on the order of 1 year, but can be much longer. The lifetime of this high-accretion, high-luminosity phase is on the order of decades. However, even with such a relatively short timespan, no FU Orionis object had been observed shutting off. By comparing the number of FUor outbu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EX Lup Variable Star
EX Lupi is a young, single T-Tauri star in the southern constellation of Lupus. An irregular variable, it is the prototype of young, low-mass eruptive stars named EXors, with ''EX Lupi'' being this object's variable star designation. At its minimal activity level, EX Lupi resembles a classical T-Tauri star of the M0 dwarf type. The low latitude of this star, at a declination of −40°, makes it difficult for northern observers to view. Based on parallax measurements, it is located at a distance of about 505 light years from the Sun. The star lies next to a gap in the Lupus cloud complex, a star forming region. During 1944, Edith M. Janssen at Harvard Observatory noticed a stellar spectrum that displayed bright lines on a photographic plate taken April 11, 1929, but these lines were missing on a spectrum from July 13, 1928. This star was found to be only two magnitudes fainter than at maximum, so a nova was ruled out. D. B. McLaughlin then undertook a study of this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orion Variable
An Orion variable is a variable star which exhibits irregular and eruptive variations in its luminosity and is typically associated with diffuse nebulae. It is thought that these are young stars which will later become regular, non-variable stars on the zero-age main sequence. Brightness fluctuations can be as much as several magnitudes. T Tauri star T Tauri stars are Orion variables exhibiting characteristic fluorescent violet emission lines from singly ionized iron (Fe II) in their star spectra, and also emission from lithium, a metal that usually is destroyed by the nuclear fusion in the stars. FU Orionis FU Orionis stars or simply "Fuors", are Orion variables that rise 5–6 magnitudes, then sink up to one magnitude and stay there for many decades. The prototype is FU Orionis, and other specimens are V1057 Cygni and V1515 Cygni. Variability Of this diverse class of stars, some Orion variables may exhibit a small amplitude (up to 1 magnitude Magnitude may refer to: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
V1647 Orionis
V1647 Orionis ( V1647 Ori) is a young stellar object visible in the constellation Orion, located about 1470 light-years from the Solar System. It is situated in the reflection nebula M78 and is associated with McNeil's Nebula. The object is known to have experienced intense eruptive phenomena on several occasions (the last of which occurred in 2008), the characteristics of which have led to the object being considered a middle ground between two classes of pre-main-sequence star, FU Orionis (FUor) and EX Lupi (EXor). Characteristics Studies have revealed that V1647 Orionis is a young stellar object, presumably a pre-main sequence star; the age of the object, based on evolutionary models and data obtained, is between 100,000 and half a million years. Like all forming stars, V1647 Orionis has a disk of gas and silicate dust in its orbit, which mediates the accretion of the star, surrounded by a gas envelope that replenishes the disk with material. The accretion pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protostar
A protostar is a very young star that is still gathering mass from its parent molecular cloud. It is the earliest phase in the process of stellar evolution. For a low-mass star (i.e. that of the Sun or lower), it lasts about 500,000 years. The phase begins when a molecular cloud fragment first collapses under the force of Self-gravitation, self-gravity and an opaque, pressure-supported core forms inside the collapsing fragment. It ends when the infalling gas is depleted, leaving a pre-main-sequence star, which contracts to later become a main-sequence star at the onset of hydrogen Nuclear fusion, fusion producing helium. History The modern picture of protostars, summarized above, was first suggested by Chushiro Hayashi in 1966. In the first models, the size of protostars was greatly overestimated. Subsequent numerical calculations clarified the issue, and showed that protostars are only modestly larger than main-sequence stars of the same mass. This basic theoretical result has b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
