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Alar Toomre
Alar Toomre (born 5 February 1937, in Rakvere) is an American astronomer and mathematician. He is a professor of applied mathematics at the Massachusetts Institute of Technology. Toomre's research is focused on the dynamics of galaxies. He is a 1984 MacArthur Fellow. Career Following the Soviet occupation of Estonia in 1944, Toomre and his family fled to Germany; they emigrated to the United States in 1949. He received an undergraduate degree in Aeronautical Engineering and Physics from MIT in 1957 and then studied at the University of Manchester on a Marshall Scholarship where he obtained a Ph.D. in fluid mechanics. Toomre returned to MIT to teach after completing his Ph.D. and remained there for two years. After spending a year at the Institute for Advanced Study, he returned again to MIT as part of the faculty, where he stayed. Toomre was appointed an Associate Professor of Mathematics at MIT in 1965, and Professor in 1970. Scientific accomplishments In 1964, Toomre devis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rakvere, Estonia
Rakvere is a town in northern Estonia and the administrative centre of the Lääne-Viru County, Lääne-Viru ''maakond'' (county), 20 km south of the Gulf of Finland of the Baltic Sea. Rakvere is the 8th most populous urban area in Estonia. Rakvere has a total area of 10.75 square kilometres, and although about 15% of it is covered by forest, the city is still populated so densely as to make it the third most densely populated city in Estonia. From the 13th century until the early 20th century, Rakvere was more widely known by its historical German name, ''Wesenberg(h)''. History The earliest signs of human settlement dating back to the 3rd–5th centuries AD have been found on the present theatre hill. Probably to protect that settlement, a wooden stronghold was built on the present-day Vallimägi. Soon after the kingdom of Denmark had conquered northern Estonia, in 1220, the new rulers started to erect stone buildings. A settlement called ''Tarvanpea'' was first mentioned ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Wander
Polar wander is the motion of a pole in relation to some reference frame. It can be used, for example, to measure the degree to which Earth's magnetic poles have been observed to move relative to the Earth's rotation axis. It is also possible to use continents as reference and observe the relative motion of the magnetic pole relative to the different continents; by doing so, the relative motion of those two continents to each other can be observed over geologic time as paleomagnetism. Apparent polar wander The magnetic poles are relatively stationary in position over time and because of this, researchers often use magnetic minerals, like magnetite, in order to find at what latitude the continent was positioned relative to the magnetic poles of that time. Since the continents have been moving relative to the pole; it is as if they were immobile and the magnetic pole was moving instead. If enough data is collected, it is then possible to reconstruct the motion of the continents ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiral Galaxy
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''Alt URL pp. 124–151) and, as such, form part of the . Most spiral galaxies consist of a flat, rotating containing s, gas and dust, and a central concentration of stars known as the |
Major Merger
Major (commandant in certain jurisdictions) is a military rank of commissioned officer status, with corresponding ranks existing in many military forces throughout the world. When used unhyphenated and in conjunction with no other indicators, major is one rank above captain, and one rank below lieutenant colonel. It is considered the most junior of the field officer ranks. Background Majors are typically assigned as specialised executive or operations officers for battalion-sized units of 300 to 1,200 soldiers while in some nations, like Germany, majors are often in command of a company. When used in hyphenated or combined fashion, the term can also imply seniority at other levels of rank, including ''general-major'' or ''major general'', denoting a low-level general officer, and ''sergeant major'', denoting the most senior non-commissioned officer (NCO) of a military unit. The term ''major'' can also be used with a hyphen to denote the leader of a military band such as i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elliptical Galaxy
An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work ''The Realm of the Nebulae'', with their intermediate scale disks, a subset of the "early-type" galaxy population. Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity, and they tend to be surrounded by large numbers of globular clusters. Elliptical galaxies are believed to make up approximately 10–15% of galaxies in the Virgo Supercluster, and they are not the dominant type of galaxy in the universe overall. They are preferentially found close to the centers of galaxy clusters. Elliptical galaxies range in size from dwarf ellipticals with tens of millions of stars, to supergiants of over one hundred trillion stars that dominate their galaxy clusters. Original ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Astrophysical Journal
''The Astrophysical Journal'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work (peers). It functions as a form of self-regulation by qualified members of a profession within the relevant field. Peer review ... 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mice Galaxies
NGC 4676, or the Mice Galaxies, are two spiral galaxies in the constellation Coma Berenices. About 290 million light-years distant, they have begun the process of colliding and merging. Their name refers to the long tails produced by tidal action—the relative difference between gravitational pulls on the near and far parts of each galaxy—known here as a galactic tide. It is a possibility that both galaxies, which are members of the Coma Cluster, have experienced collision, and will continue colliding until they coalesce. The colors of the galaxies are peculiar. In NGC 4676A a core with some dark markings is surrounded by a bluish white remnant of spiral arms. The tail is unusual, starting out blue and terminating in a more yellowish color, despite the fact that the beginning of each arm in virtually every spiral galaxy starts yellow and terminates in a bluish color. NGC 4676B has a yellowish core and two arcs; arm remnants underneath are bluish as well. The galaxies were ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antennae Galaxies
The Antennae Galaxies (also known as NGC 4038/NGC 4039 or Caldwell 60/Caldwell 61) are a pair of interacting galaxy, interacting galaxies in the constellation Corvus (constellation), Corvus. They are currently going through a Starburst Galaxies, starburst phase, in which the collision of clouds of gas and dust, with entangled magnetic fields, causes rapid star formation. They were discovered by William Herschel in 1785. General information The Antennae Galaxies are undergoing a galactic collision. Located in the NGC 4038 group of galaxies, NGC 4038 group with five other galaxies, these two galaxies are known as the Antennae Galaxies because the two long tails of stars, interstellar medium, gas and dust ejected from the galaxies as a result of the collision resemble an insect, insect's antenna (biology), antennae. The galaxy nucleus, nuclei of the two galaxies are joining to become one giant galaxy. Most galaxies probably undergo at least one significant collision in their li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tidal Tail
A tidal tail is a thin, elongated region of stars and interstellar gas that extends into space from a galaxy. Tidal tails occur as a result of galactic tide forces between interacting galaxies. Examples of galaxies with tidal tails include the Tadpole Galaxy and the Mice Galaxies. Tidal forces can eject a significant amount of a galaxy's gas into the tail; within the Antennae Galaxies, for example, nearly half of the observed gaseous matter is found within the tail structures. Within those galaxies which have tidal tails, approximately 10% of the galaxy's stellar formation takes place in the tail. Overall, roughly 1% of all stellar formation in the known universe occurs within tidal tails. Some interacting galaxy pairs have two distinct tails, as is the case for the Antennae Galaxies, while other systems have only one tail. Most tidal tails are slightly curved due to the rotation of the host galaxies. Those that are straight may actually be curved but still appear to be stra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galaxy Merger
Galaxy mergers can occur when two (or more) galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution. The merger rate also provides astronomers with clues about how galaxies bulked up over time. Description During the merger, stars and dark matter in each galaxy become affected by the approaching galaxy. Toward the late stages of the merger, the gravitational potential (i.e. the shape of the galaxy) begins changing so quickly that star orbits are greatly altered, and lose any trace of their prior orbit. This process is called “violent r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactic Bridges And Tails (1971 Film)
Galactic Bridges and Tails is a computer animation film created in 1972 by astrophysicists Alar Toomre anJuri Toomre The brothers created the film as a teaching aid to accompany their 1972 landmark research paper of the same name, published in ''The Astrophysical Journal'', which described galaxy collisions and galaxy mergers. Technology of the original animated film The Toomre film contains both 2D and 3D computer graphics simulations of colliding galaxies. The animations are time-lapses that compress billions of years into just a few minutes. Written in the FORTRAN programming language, the simulations sent character and vector information to a CRT-based ASCII character film recorder. The film recorder exposed multiple frames of 16mm film to create the final animated film. Digital film restoration In 2007, filmmakeMichael Lauterworked with the Toomre brothers to digitally restore the 16mm original film and create a new HD video (1080p24) digital master. Derivative simul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
