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Pavel Kroupa
Pavel Kroupa (born 24 September 1963 in Jindřichův Hradec, Czechoslovakia) is a Czech-Australian astrophysicist and professor at the University of Bonn. Biography and career After the 1968 failure of Prague spring, Kroupa's family fled from Czechoslovakia losing all possessions; as a consequence Kroupa grew up in Germany and South Africa. He acquired in 1983 his Abitur final exams in Göttingen and afterwards studied physics at The University of Western Australia in Perth. In 1988 he won the Isaac Newton scholarship at the University of Cambridge and in 1992 the senior Rouse Ball research scholarship at Trinity College, Cambridge and attained a doctorate in England in 1992 with a dissertation on the distribution of low mass stars in the Milky Way. Afterwards Kroupa worked until 2000 in astronomical research groups at Heidelberg University and at the Max Planck Institute for Astronomy, before he went to the University of Kiel and earned his Habilitation there. He was awarded a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jindřichův Hradec
Jindřichův Hradec (; german: Neuhaus) is a town in the South Bohemian Region of the Czech Republic. It has about 21,000 inhabitants. The town centre is well preserved and is protected by law as an urban monument reservation. Administrative parts Town parts of Jindřichův Hradec I–V and villages of Buk, Děbolín, Dolní Radouň, Dolní Skrýchov, Horní Žďár, Matná, Otín, Políkno and Radouňka are administrative parts of Jindřichův Hradec. Geography Jindřichův Hradec is located about northeast of České Budějovice. It lies in the Křemešník Highlands, which is part of Bohemian-Moravian Highlands. The highest point is the hill Rýdův kopec at above sea level. The town is situated on the Nežárka river, on the shore of Vajgar pond, which is one of the symbols of the town. It is a large fish pond established in 1399. There is a significant amount of other fish ponds in the municipal territory. History The predecessor of today's town was a Slavic gord. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Sheffield
, mottoeng = To discover the causes of things , established = – University of SheffieldPredecessor institutions: – Sheffield Medical School – Firth College – Sheffield Technical School – University College of Sheffield , type = Public research university , academic_staff = 5,670 (2020) - including academic atypical staff , administrative_staff = , chancellor = Lady Justice Rafferty , vice_chancellor = Koen Lamberts , students = () , undergrad = () , postgrad = () , endowment = £46.7 million (2021) , budget = £741.0 million (2020–21) , city = Sheffield , state = South Yorkshire , country = England , coor = , campus = Urban , colours = Black & gold , affiliations = Russell Group WUN ACUN8 Group White Rose Sutton 30EQUISAMBAUniversities UK , website = , logo = The University of Sheffield (informally Sheffield University or TUOS) is a public research university in Sheffield, South Yorkshire, England. Its history traces back to the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a convenient short term for ''"all elements except hydrogen and helium"''. This word-use is distinct from the conventional chemical or physical definition of a metal as an electrically conducting solid. Stars and nebulae with relatively high abundances of heavier elements are called "metal-rich" in astrophysical terms, even though many of those elements are nonmetals in chemistry. The presence of heavier elements hails from stellar nucleosynthesis, where the majority of elements heavier than hydrogen and helium in the Universe (''metals'', hereafter) are formed in the cores of stars as they evolve. Over time, stellar winds and supernovae deposit the metals into the surrounding environment, enriching the interstellar medium and providing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dwarf Galaxies
A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy. Dwarf galaxies' formation and activity are thought to be heavily influenced by interactions with larger galaxies. Astronomers identify numerous types of dwarf galaxies, based on their shape and composition. Formation One theory states that most galaxies, including dwarf galaxies, form in association with dark matter, or from gas that contains metals. However, NASA's Galaxy Evolution Explorer space probe identified new dwarf galaxies forming out of gases with low metallicity. These galaxies were located in the Leo Ring, a cloud of hydrogen and helium around two massive galaxies in the constellation Leo. Because of their small size, dwarf galaxies have bee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar System" and "solar system" structures in theinaming guidelines document. The name is commonly rendered in lower case ('solar system'), as, for example, in the ''Oxford English Dictionary'' an''Merriam-Webster's 11th Collegiate Dictionary''. is the gravity, gravitationally bound system of the Sun and the objects that orbit it. It Formation and evolution of the Solar System, formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The solar mass, vast majority (99.86%) of the system's mass is in the Sun, with most of the Jupiter mass, remaining mass contained in the planet Jupiter. The four inner Solar System, inner system planets—Mercury (planet), Mercury, Venus, Earth and Mars—are terrest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circumstellar Disk
A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form. Around mature stars, they indicate that planetesimal formation has taken place, and around white dwarfs, they indicate that planetary material survived the whole of stellar evolution. Such a disc can manifest itself in various ways. Young star According to the widely accepted model of star formation, sometimes referred to as the nebular hypothesis, a young star (protostar) is formed by the gravitational collapse of a pocket of matter within a giant molecular cloud. The infalling material possesses some amount of angular momentum, which results in the formation of a gaseous protoplanetary disc around the young, rotating star. The former is a rotating circumstellar disc of dense gas and du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary System
A planetary system is a set of gravitationally In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ... bound non-Star, stellar objects in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consist of bodies such as dwarf planets, asteroids, natural satellites, meteoroids, comets, planetesimals and circumstellar disks. The Sun together with the planetary system revolving around it, including Earth, forms the Solar System. The term exoplanetary system is sometimes used in reference to other planetary systems. Debris disks are also known to be common, though other objects are more difficult to observe. Of particular interest to astrobiology is the habitable zone of planetary sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Dwarves
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] |
Star Cluster
Star clusters are large groups of stars. Two main types of star clusters can be distinguished: globular clusters are tight groups of ten thousand to millions of old stars which are gravitationally bound, while open clusters are more loosely clustered groups of stars, generally containing fewer than a few hundred members, and are often very young. Open clusters become disrupted over time by the gravitational influence of giant molecular clouds as they move through the galaxy, but cluster members will continue to move in broadly the same direction through space even though they are no longer gravitationally bound; they are then known as a stellar association, sometimes also referred to as a ''moving group''. Star clusters visible to the naked eye include the Pleiades, Hyades, and 47 Tucanae. Open cluster Open clusters are very different from globular clusters. Unlike the spherically distributed globulars, they are confined to the galactic plane, and are almost always found wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Evolution
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star. Nuclear fusion powers a star for most of its existence. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing throug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initial Mass Function
In astronomy, the initial mass function (IMF) is an empirical function that describes the initial Frequency distribution, distribution of masses for a population of stars. The IMF is an output of the process of star formation. The IMF is often given as a Probability distribution, probability distribution function (PDF) for the mass at which a star enters the main sequence (begins nuclear fusion, hydrogen fusion). The distribution function can then be used to construct the mass distribution (the histogram of stellar masses) of a population of stars. It differs from the ''present day mass function'' (PDMF), the current distribution of masses of stars, due to the evolution and death of stars which occurs at different rates for different masses as well as dynamical mixing in some populations. The properties and evolution of a star are closely related to its mass, so the IMF is an important diagnostic tool for astronomers studying large quantities of stars. For example, the initial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gerard F
Gerard is a masculine forename of Proto-Germanic origin, variations of which exist in many Germanic and Romance languages. Like many other early Germanic names, it is dithematic, consisting of two meaningful constituents put together. In this case, those constituents are ''gari'' > ''ger-'' (meaning 'spear') and -''hard'' (meaning 'hard/strong/brave'). Common forms of the name are Gerard (English, Scottish, Irish, Dutch, Polish and Catalan); Gerrard (English, Scottish, Irish); Gerardo (Italian, and Spanish); Geraldo (Portuguese); Gherardo (Italian); Gherardi (Northern Italian, now only a surname); Gérard (variant forms ''Girard'' and ''Guérard'', now only surnames, French); Gearóid (Irish); Gerhardt and Gerhart/Gerhard/Gerhardus (German, Dutch, and Afrikaans); Gellért ( Hungarian); Gerardas ( Lithuanian) and Gerards/Ģirts ( Latvian); Γεράρδης (Greece). A few abbreviated forms are Gerry and Jerry (English); Gerd (German) and Gert (Afrikaans and Dutch); Gerrit (Af ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
