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Circumplanetary Disc
A circumplanetary disk (or circumplanetary disc, short CPD) is a torus, pancake or ring-shaped accumulation of matter composed of gas, Cosmic dust, dust, planetesimals, asteroids or collision fragments in orbit around a planet. They are reservoirs of material out of which Natural satellite, moons (or exomoons or subsatellites) may form. Such a disk can manifest itself in various ways. In August 2018, astronomers reported the probable detection of a circumplanetary disk around CS Chamaeleontis B, CS Cha B. The authors state that "The CS Cha system is the only system in which a circumplanetary disc is likely present as well as a resolved circumstellar disc." In 2020 though, the parameters of CS Chamaeleontis B, CS Cha B were revised, making it an accreting red dwarf star, and making the disk circumstellar disk, circumstellar. Theory A giant planet will mainly form via Core-accretion theory, core accretion. In this scenario a core forms via the accretion of small solids. Once the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PDS 70 Closeup - Eso2111a
PDS can refer to: Entertainment * Partially Deceased Syndrome, a fictional condition in BBC show ''In the Flesh (TV series), In the Flesh'' * ''Panzer Dragoon Saga'', a 1998 video game Computing * Data set (IBM mainframe), Partitioned data sets, IBM * Passive data structure, another term for ''record'' * Processor Direct Slot, in some old Macintosh computers * Personal data service, services to let individuals manage their own personal data by themselves * Program Development System, an early implementation of the DIGITAL Command Language for the IAS operating system. * Protective distribution system, a safeguarded telecommunication system * Microsoft BASIC Professional Development System (PDS), a superset of QuickBASIC * Paradox Development Studios, a game developer subsidiary of Paradox Interactive Medical * Paroxysmal depolarizing shift, a pre-seizure interictal neuronal EEG spike in epilepsy. * Pigment dispersion syndrome, an affliction of the eye * Polydioxanone, a type of ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core-accretion Theory
The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets. The theory was developed by Immanuel Kant and published in his ''Universal Natural History and Theory of the Heavens'' (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Astrophysical Journal
''The Astrophysical Journal'' (''ApJ'') is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler. The journal discontinued its print edition and became an electronic-only journal in 2015. Since 1953, ''The Astrophysical Journal Supplement Series'' (''ApJS'') has been published in conjunction with ''The Astrophysical Journal'', with generally longer articles to supplement the material in the journal. It publishes six volumes per year, with two 280-page issues per volume. ''The Astrophysical Journal Letters'' (''ApJL''), established in 1967 by Subrahmanyan Chandrasekhar as Part 2 of ''The Astrophysical Journal'', is now a separate journal focusing on the rapid publication of high-impact astronomical research. The three journals were published by the University of Chicago Press for the American Astronomical Society until, in January 2009, publication was transferred to IOP Publis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 100546 B
HD 100546, also known as KR Muscae, is a pre-main sequence star of spectral type B8 to A0 located from Earth in the southern constellation of Musca. The star is surrounded by a circumstellar disk from a distance of 0.2 to 4 AU, and again from 13 AU out to a few hundred AU, with evidence for a protoplanet forming at a distance of around 47 AU. Estimated to be less than 10 million years old, it belongs to Herbig Ae/Be stars, and also the nearest example to the Solar System. Planetary system The HD 100546 system as a whole has evidence for three protoplanets, thus it is considered an important evolutionary precursor to intermediate-mass stars with multiple super-jovian planets at moderate/wide separations like HR 8799. While other hypothetical planets have been claimed to exist around the star, none of the discoveries have been confirmed. Planet b In 2013, researchers reported that they had found what seems to be a planet in the process of being formed, embe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined and slightly less than one-thousandth the mass of the Sun. Its diameter is 11 times that of Earth and a tenth that of the Sun. Jupiter orbits the Sun at a distance of , with an orbital period of . It is the List of brightest natural objects in the sky, third-brightest natural object in the Earth's night sky, after the Moon and Venus, and has been observed since prehistoric times. Its name derives from that of Jupiter (god), Jupiter, the chief deity of ancient Roman religion. Jupiter was the first of the Sun's planets to form, and its inward migration during the primordial phase of the Solar System affected much of the formation history of the other planets. Jupiter's atmosphere consists of 76% hydrogen and 24% helium by mass, with a denser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Callisto (moon)
Callisto ( ) is the second-largest moon of Jupiter, after Ganymede. In the Solar System it is the third-largest moon after Ganymede and Saturn's largest moon Titan, and nearly as large as the smallest planet Mercury. Callisto is, with a diameter of , roughly a third larger than Earth's Moon and orbits Jupiter on average at a distance of , which is about five times further out than the Moon orbiting Earth. It is the outermost of the four large Galilean moons of Jupiter, which were discovered in 1610 with one of the first telescopes, and is today visible from Earth with common binoculars. The surface of Callisto is the oldest and most heavily cratered in the Solar System. Its surface is completely covered with impact craters. It does not show any signatures of subsurface processes such as plate tectonics or volcanism, with no signs that geological activity in general has ever occurred, and is thought to have evolved predominantly under the influence of impacts. Promine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galilean Moons
The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter. They are, in descending-size order, Ganymede (moon), Ganymede, Callisto (moon), Callisto, Io (moon), Io, and Europa (moon), Europa. They are the most apparent magnitude, readily visible Solar System objects after Saturn, the dimmest of the classical planets; though their closeness to bright Jupiter makes naked-eye observation very difficult, they are readily seen with common binoculars, even under night sky Bortle scale, conditions of high light pollution. The invention of the telescope allowed astronomers to discover the moons in 1610. Through this, they became the first Timeline of discovery of Solar System planets and their moons, Solar System objects discovered since humans have started tracking the classical planets, and the first objects to be found to orbit any planet beyond Earth. They are planetary-mass moons and among the List of Solar System objects by size, largest objects in the Sola ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 169142
HD 169142 is a single Herbig Ae/Be star. Its surface temperature is 7650 K. HD 169142 is depleted of heavy elements compared to the Sun, with a metallicity Fe/H index of , but is much younger at an age of 7.5 million years. The star is rotating slowly and has relatively low stellar activity for a Herbig Ae/Be star. Planetary system Disk The star is surrounded by a complex, rapidly evolving protoplanetary disk with two gaps. In the 1995-2005 period the disk inner edge has moved inward by 0.3 AU. The dust of the disk is rich in polycyclic aromatic hydrocarbons and carbon monoxide. A study using ALMA data found that the water (H2O) snow line is at around 20 astronomical units and the planet b is forming in beyond the water and carbon dioxide (CO2) snow lines, but within the carbon monoxide (CO) snow line. The CO snow line lies at around 150 AU. The study also detected a range of molecules in the disk: diazenylium (N2H+), methanol (CH3OH), I deuterated hydrogen c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon Monosulfide
Silicon monosulfide is a chemical compound of silicon and sulfur. The chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ... is SiS. Molecular SiS has been detected at high temperature in the gas phase. The gas phase molecule has an Si-S bondlength of 192.93 pm, this compares to the normal single bond length of 216 pm, and is shorter than the Si=S bond length of around 201 pm reported in an organosilanethione. Historically a pale yellow-red amorphous solid compound has been reported.E. G. Rochow, E. W. Abel ,1973, The Chemistry of Germanium Tin and Lead, Pergamon Press, The behavior of silicon can be contrasted with germanium which forms a stable solid monosulfide. Further reading * * * References Inorganic silicon compounds Monosulfides {{inorganic-co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoplanet
A protoplanet is a large planetary embryo that originated within a protoplanetary disk and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant planets. The planetesimal hypothesis A planetesimal is an object formed from dust, rock, and other materials, measuring from meters to hundreds of kilometers in size. According to the Chamberlin–Moulton planetesimal hypothesis and the theories of Viktor Safronov, a protoplanetary disk of materials such as gas and dust would orbit a star early in the formation of a planetary system. The action of gravity on such materials form larger and larger chunks until some reach the size of planetesimals. It is thought that the collisions of planetesimals created a few hundred larger planetary embryos. Over the course of hundreds of millions of years, they ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Young Stellar Object
Young stellar object (YSO) denotes a star in its early stage of evolution. This class consists of two groups of objects: protostars and pre-main-sequence stars. Classification by spectral energy distribution A star forms by accumulation of material that falls in to a protostar from a circumstellar disk or envelope. Material in the disk is cooler than the surface of the protostar, so it radiates at longer wavelengths of light producing excess infrared emission. As material in the disk is depleted, the infrared excess decreases. Thus, YSOs are usually classified into evolutionary stages based on the slope of their spectral energy distribution in the mid-infrared, using a scheme introduced by Lada (1987). He proposed three classes (I, II and III), based on the values of intervals of spectral index \alpha \,: \alpha=\frac. Here \lambda \, is wavelength, and F_\lambda is flux density. The \alpha \, is calculated in the wavelength interval of 2.2–20 m ( near- and mid-infrared r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
