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HD 95086 B
HD 95086 b is a confirmed, directly imaged exoplanet orbiting the young, 17 Myr A-class pre-main-sequence star HD 95086. It is roughly 5 times as massive as Jupiter and orbits about 70 AU away from the parent star. It was detected at thermal infrared wavelengths (3.8 μm) through direct imaging, using the NACO instrument on the VLT. A debris disk has been detected in this system at submillimeter wavelengths and has been resolved in the far-infrared from data obtained with the Herschel Space Observatory. The planet was initially detected in data taken in 2012 at a separation from the parent star of (~56 AU) and position angle of . The planet was recovered at a high signal-to-noise ratio in June 2013. Astrometry for the planet in January 2012 and June 2013, and from a marginal detection in March 2013 confirm that it is bound to the parent star, not a background star. HD 95086 b's brightness at 3.8 μm when combined with sensitive upper limits on its brigh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Very Large Telescope
The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, which are generally used separately but can be used together to achieve very high angular resolution. The four separate optical telescopes are known as ''Antu'', ''Kueyen'', ''Melipal'', and ''Yepun'', which are all words for astronomical objects in the Mapuche language. The telescopes form an array complemented by four movable Auxiliary Telescopes (ATs) of 1.8 m aperture. The VLT operates at visible light, visible and infrared wavelengths. Each individual telescope can detect objects roughly four billion times fainter than can be detected with the naked eye, and when all the telescopes are combined, the facility can achieve an angular resolution of about 0.002 arcsecond. In single telescope mode of operation angular resolution is ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Dwarfs
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter (). However, they can fuse deuterium ( 2H), and the most massive ones (> ) can fuse lithium ( 7Li). Astronomers classify self-luminous objects by spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. Despite their name, to the naked eye, brown dwarfs would appear in different colors depending on their temperature. The warmest ones are possibly orange or red, while cooler brown dwarfs would likely appear magenta or black to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exoplanets Discovered In 2013
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, initially detected in 1988, was confirmed in 2003. There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. In several cases, multiple planets have been observed around a star. About 1 in 5 Sun-like starsFor the purpose of this 1 in 5 statistic, "Sun-like" means G-type star. Data for Sun-like stars was not available so this statistic is an extrapolation from data about K-type stars. have an "Earth-sized"For the purpose of this 1 in 5 statistic, Earth-sized means 1–2 Earth radii. planet in the habitable zone.F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forsterite
Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite. Forsterite crystallizes in the orthorhombic system (space group ''Pbnm'') with cell parameters ''a'' 4.75 Å (0.475 nm), ''b'' 10.20 Å (1.020 nm) and ''c'' 5.98 Å (0.598 nm). Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites. In 2005 it was also found in cometary dust returned by the Stardust probe. In 2011 it was observed as tiny crystals in the dusty clouds of gas around a forming star. Two polymorphs of forsterite are known: wadsleyite (also orthorhombic) and ringwoodite ( isometric, Cubic crystal system). Both are mainly known from meteorites. Peridot is the gemstone variety of forsterite olivine. Composition Pure forsterite is composed of magnesium, oxygen and silicon. The chemical formula is Mg2SiO4. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Astronomical Union
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and development through global cooperation. It was founded in 1919 and is based in Paris, France. The IAU is composed of individual members, who include both professional astronomers and junior scientists, and national members, such as professional associations, national societies, or academic institutions. Individual members are organised into divisions, committees, and working groups centered on particular subdisciplines, subjects, or initiatives. As of 2018, the Union had over 13,700 individual members, spanning 90 countries, and 82 national members. Among the key activities of the IAU is serving as a forum for scientific conferences. It sponsors nine annual symposia and holds a triannual General Assembly that sets policy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NameExoWorlds
NameExoWorlds (also known as IAU NameExoWorlds) is the name of various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, which would later be considered for official adoption by the organization. History The first such project (NameExoWorlds I), in 2015, regarded the naming of stars and exoplanets. 573,242 votes were submitted by members by the time the contest closed on October 31, 2015, and the names of 31 exoplanets and 14 stars were selected from these. Many of the names chosen were based on world history, mythology and literature. In June 2019, another such project (NameExoWorlds II), in celebration of the organization's hundredth anniversary, in a project officially called IAU100 NameExoWorlds, welcomed countries of the world to submit names for exoplanets and their host stars. A star with an exoplanet was assigned to each country, and members of the public submitted names for them. In August 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoplanetary Disk
A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, because gases or other material may be falling from the inner edge of the disk onto the surface of the star. This process should not be confused with the accretion process thought to build up the planets themselves. Externally illuminated photo-evaporating protoplanetary disks are called proplyds. Formation Protostars form from molecular clouds consisting primarily of molecular hydrogen. When a portion of a molecular cloud reaches a critical size, mass, or density, it begins to collapse under its own gravity. As this collapsing cloud, called a solar nebula, becomes denser, random gas motions originally present in the cloud average out in favor of the direction of the nebula's net angular momentum. Conservation of angular momentum causes t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetesimals
Planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. Per the Chamberlin–Moulton planetesimal hypothesis, they are believed to form out of cosmic dust grains. Believed to have formed in the Solar System about 4.6 billion years ago, they aid study of its formation. Formation A widely accepted theory of planet formation, the so-called planetesimal hypotheses, the Chamberlin–Moulton planetesimal hypothesis and that of Viktor Safronov, states that planets form from cosmic dust grains that collide and stick to form ever-larger bodies. Once a body reaches around a kilometer in size, its constituent grains can attract each other directly through mutual gravity, enormously aiding further growth into moon-sized protoplanets. Smaller bodies must instead rely on Brownian motion or turbulence to cause the collisions leading to sticking. The mechanics of collisions and mechanisms of sticking are intricate. Alternatively, planetesimals may for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parsecs
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and is defined as the distance at which 1 au subtends an angle of one arcsecond ( of a degree). This corresponds to astronomical units, i.e. 1\, \mathrm = 1/\tan \left( \ \mathrm \right)\, \mathrm. The nearest star, Proxima Centauri, is about from the Sun. Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand. The word ''parsec'' is a portmanteau of "parallax of one second" and was coined by the British astronomer Herbert Hall Turner in 1913 to make calculations of astronomical distances from only raw observational data easy for astronomers. Partly for this reason, it is the unit preferred in astronomy and astrophysics, though the light-year remains prominent in pop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Masses
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of the Sun. This equates to about two nonillion (short scale), two quintillion (long scale) kilograms or 2000 quettagrams: The solar mass is about times the mass of Earth (), or times the mass of Jupiter (). History of measurement The value of the gravitational constant was first derived from measurements that were made by Henry Cavendish in 1798 with a torsion balance. The value he obtained differs by only 1% from the modern value, but was not as precise. The diurnal parallax of the Sun was accurately measured during the transits of Venus in 1761 and 1769, yielding a value of (9 arcseconds, compared to the present value of ). From the value of the diurnal parallax, one can determine the distance to the Sun from the geometry of E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HR 8799
HR 8799 is a roughly 30 million-year-old main-sequence star located away from Earth in the constellation of Pegasus. It has roughly 1.5 times the Sun's mass and 4.9 times its luminosity. It is part of a system that also contains a debris disk and at least four massive planets. Those planets, along with , were the first exoplanets whose orbital motion was confirmed by direct imaging. The star is a Gamma Doradus variable: its luminosity changes because of non-radial pulsations of its surface. The star is also classified as a Lambda Boötis star, which means its surface layers are depleted in iron peak elements. It is the only known star which is simultaneously a Gamma Doradus variable, a Lambda Boötis type, and a Vega-like star (a star with excess infrared emission caused by a circumstellar disk). Location HR 8799 is a star that is visible to the naked eye. It has a magnitude 5.96 and it is located inside the western edge of the great square of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Unit
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once each year. The astronomical unit was originally conceived as the average of Earth's aphelion and perihelion; however, since 2012 it has been defined as exactly (see below for several conversions). The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec. History of symbol usage A variety of unit symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union (IAU) had used the symbol ''A'' to denote a length equal to the astronomical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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