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Disk Wind
In astronomy, a disk wind is a particle outflow observed around Accretion disk, accretion disks, mainly near Protoplanetary disk, protoplanetary disks and Active galactic nucleus, active galactic nulei (AGN). The disk wind is made up of a gaseous and a dusty component. Especially in edge-on protoplanetary disks this disk wind can be directly imaged. Young stellar objects The disk wind often appears as a nested structure, with high-velocity narrow collimated Astrophysical jet, jets surrounded by a slower and wider disk wind. This wider disk wind is often detected in molecular emission lines. The central star or protostar or the accretion process is emitting high-energy photons, from far-ultraviolet to x-rays. This ionizes and heats the gas and dust in the disk. This material is first ejected due to magnetorotational instability (MRI). Material is flung out by magneto-Centrifugal force, centrifugal processes and this model describes the wind as magnetohydrodynamic winds (MHD winds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, meteoroids, asteroids, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Egyptian astronomy, Egyptians, Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Chinese astronomy, Chinese, Maya civilization, M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoevaporation
Photoevaporation is the process where energetic radiation ionises gas and causes it to disperse away from the ionising source. The term is typically used in an astrophysical context where ultraviolet radiation from hot stars acts on clouds of material such as molecular clouds, protoplanetary disks, or planetary atmospheres. Molecular clouds One of the most obvious manifestations of astrophysical photoevaporation is seen in the eroding structures of molecular clouds that luminous stars are born within. Evaporating gaseous globules (EGGs) Evaporating gaseous globules or EGGs were first discovered in the Eagle Nebula. These small cometary globules are being photoevaporated by the stars in the nearby cluster. EGGs are places of ongoing star-formation. Planetary atmospheres A planet can be stripped of its atmosphere (or parts of the atmosphere) due to high energy photons and other electromagnetic radiation. If a photon interacts with an atmospheric molecule, the molecule is accel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Binary
X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the ''donor'' (usually a relatively common main sequence star), to the other component, called the ''accretor'', which can be a white dwarf, neutron star or black hole. The infalling matter releases gravitational potential energy, up to 30 percent of its rest mass, as X-rays. (Hydrogen fusion releases only about 0.7 percent of rest mass.) The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation. An estimated 1041 positrons escape per second from a typical low-mass X-ray binary. Classification X-ray binaries are further subdivided into several (sometimes overlapping) subclasses, that perhaps reflect the underlying physics better. Note that the classification by mass (high, intermediate, low) refers to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GRO J1655−40
GRO J1655−40 is a binary star consisting of an evolved F-type primary star and a massive, unseen companion, which orbit each other once every 2.6 days in the constellation of Scorpius. Gas from the surface of the visible star is accreted onto the dark companion, which appears to be a stellar black hole with several times the mass of the Sun. The optical companion of this low-mass X-ray binary is a subgiant F star. Along with GRS 1915+105, GRO J1655−40 is one of at least two galactic "microquasars" that may provide a link between the supermassive black holes generally believed to power extragalactic quasars and more local accreting black hole systems. In particular, both display the radio jets characteristic of many active galactic nuclei. The distance from the Solar System is probably about 11,000 light years, or approximately half-way from the Sun to the Galactic Center, but a closer distance of ~2800 ly is not ruled out. GRO J1655−40 and its companion are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Black Hole
A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. They are the remnants of supernova explosions, which may be observed as a type of gamma ray burst. These black holes are also referred to as collapsars. Properties By the no-hair theorem, a black hole can only have three fundamental properties: mass, electric charge, and angular momentum. The angular momentum of a stellar black hole is due to the conservation of angular momentum of the star or objects that produced it. The gravitational collapse of a star is a natural process that can produce a black hole. It is inevitable at the end of the life of a massive star when all stellar energy sources are exhausted. If the mass of the collapsing part of the star is below the TOV limit, Tolman–Oppenheimer–Volkoff (TOV) limit for Degenerate matter#Neutron degeneracy, neutron-degenerate matter, the end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IGR J17091-3624
IGR J17091-3624 (also IGR J17091) is a stellar mass black hole 28,000 light-years away. It lies in the constellation Scorpius in the Milky Way galaxy. Discovery IGR J17091 was discovered by ESA's INTEGRAL satellite in April 2003. Description IGR J17091 is a stellar mass black hole with a mass between 3 and 10 . It is a binary system in which a star orbits the black hole. Its small size may make it a candidate for the smallest black hole discovered. However, as of 2017 its mass was described as "unknown". Observations by the Chandra X-ray Observatory in 2011 discovered that it produces the fastest winds ever coming from an accretion disk at 3,218,688 km/h (20 million mph) making it about 3% of the speed of light. This is 10 times faster than the next-highest-measured wind speed. According to Ashley King from the University of Michigan "Contrary to the popular perception of black holes pulling in all of the material that gets close, we estimate up to 95 percent of the ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonance
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximum amplitude response in the system. When this happens, the object or system absorbs energy from the external force and starts vibrating with a larger amplitude. Resonance can occur in various systems, such as mechanical, electrical, or acoustic systems, and it is often desirable in certain applications, such as musical instruments or radio receivers. However, resonance can also be detrimental, leading to excessive vibrations or even structural failure in some cases. All systems, including molecular systems and particles, tend to vibrate at a natural frequency depending upon their structure; when there is very little damping this frequency is approximately equal to, but slightly above, the resonant frequency. When an Oscillation, oscillat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Broad Absorption Line Quasar
Broad(s) or The Broad(s) may refer to: People * A slang term for a woman. * Broad (surname), a surname Places * Broad Peak, on the border between Pakistan and China, the 12th highest mountain on Earth * The Broads, a network of mostly navigable rivers and lakes in the English counties of Norfolk and Suffolk, United Kingdom **The Broads include several areas of navigable water known as Broads; the largest is Hickling Broad (see :Norfolk Broads) * The Broads (New Hampshire), a wide portion of Lake Winnipesaukee in Belknap County, New Hampshire, United States * Broad Bay (other) * Broad Canal, East Cambridge, Massachusetts, United States * Broad Channel, a neighborhood in Queens, United States * Broad Crag, a fell in the English Lake District, United Kingdom * Broad Creek (other) * Broad River (other) * Broad Run (other) * Broad Sound (other) * Broad Valley, Graham Land, Antarctica * Broad Water, a salt water lagoon near Tyw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speed Of Light
The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time interval of second. The speed of light is invariant (physics), the same for all observers, no matter their relative velocity. It is the upper limit for the speed at which Information#Physics_and_determinacy, information, matter, or energy can travel through Space#Relativity, space. All forms of electromagnetic radiation, including visible light, travel at the speed of light. For many practical purposes, light and other electromagnetic waves will appear to propagate instantaneously, but for long distances and sensitive measurements, their finite speed has noticeable effects. Much starlight viewed on Earth is from the distant past, allowing humans to study the history of the universe by viewing distant objects. When Data communication, comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supermassive Black Holes
A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, including light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars. Two supermassive black holes have been directly imaged by the Event Horizon Telescope: the black hole in the giant elliptical galaxy Messier 87 and the black hole at the Milky Way's center (Sagittarius A*). Description ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Transit
In astronomy, a transit (or astronomical transit) is the passage of a astronomical object, celestial body directly between a larger body and the observer. As viewed from a particular vantage point, the transiting body appears to move across the face of the larger body, eclipse, covering a small portion of it. The word "transit" refers to cases where the nearer object apparent size, appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as occultation, ''occultations''. However, the probability of seeing a transiting planet is low because it is dependent on the alignment of the three objects in a nearly perfectly straight line. Many parameters of a planet and its parent star can be determined based on the transit. In the Solar System One type of transit involves the motion of a planet between a Earth, terrestrial observer and the Sun. This can happen only with inferior and superior pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 163296
HD 163296 is a young Herbig Ae/Be star, Herbig Ae star surrounded by a protoplanetary disk. The disk is a popular target to study disk composition, and several works suggested the presence of Protoplanet, protoplanets inside the gaps of the disk. The star HD 163296 was first identified in the Henry Draper Catalogue. The star was first identified to have peculiar hydrogen emission lines in 1925, based on observations with the Mount Wilson Observatory by Paul W. Merrill, Milton L. Humason and Cora G. Burwell. The star was classified as having a spectral type of A2e. In 1984, it was first considered that HD 163296 is a Herbig Ae star due to the H-alpha and NaD lines having a P Cygni profile. The status as a Herbig Ae star was questioned at the time. It was, however concluded that it is surrounded by a dust shell from near-infrared excess. Later in 1989, it was found that magnesium and calcium lines have short-term variability from observations with the International Ultravi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
