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Adriaan Wesselink
Adriaan Jan Wesselink (1909–1995) was a Dutch astronomer who worked successively in the Netherlands, South Africa and the United States. He specialised in observing and understanding the characteristics of stars, particularly variable stars. Early life Adriaan Wesselink was born on 7 April 1909 in Hellevoetsluis in the Netherlands. His father was a medical doctor and his mother was a nurse. Inspired by his parents, Adriaan Wesselink developed an interest in science. Wesselink studied physics, mathematics and astronomy at Utrecht University, leading to the award of a bachelor of science degree. Astronomical research in the Netherlands Wesselink proceeded to Leiden University where he was appointed to an assistantship. He pursued research into variable stars. He was trained by prominent astronomers including Ejnar Hertzsprung, Willem de Sitter and Jan Woltjer. He made photographic observations of the brightness of the Sun during the total eclipse of 19 June 1936 outside of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hellevoetsluis
Hellevoetsluis () is a small city and municipality in the western Netherlands. It is located in Voorne-Putten, South Holland. The municipality covers an area of of which is water and it includes the population centres Nieuw-Helvoet, Nieuwenhoorn, and Oude en Nieuwe Struiten, all former municipalities. Hellevoetsluis is located on the Haringvliet with the sea, beach, and dunes close by, on the extreme southern edge of the Rijnmond and Europoort areas, close to the broad Zeeland landscape. The name translates as "lock at the foot of the Helle". The Helle was a small local river that disappeared over time. History The area has been settled since before Roman times and was concentrated around a body of water called the "Helle", which was later Latinized by the Romans to "''Helinium''" and "''Helius''". The name Hel(le) Voet, ''Helius' foot'' or "(land at) the lowest point of Helius", appears in documents from the 13th century and later, such as in 1395, when the Nieuw-Helvoet Polder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Star
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Félix Aguilar Observatory
Félix Aguilar Observatory ( es, Observatorio Astronómico Félix Aguilar ; OAFA) is an astronomical observatory. It was established in 1953, in San Juan Province, Argentina. In 1974, it was renamed to Carlos Ulrrico Cesco Astronomical Station ( es, Estación Astronómica Carlos Ulrrico Cesco, links=no ; EACUC). Its primary observing facility is located El Leoncito National Park in the west of San Juan Province. Also located in El Leoncito Park is the Leoncito Astronomical Complex. The observatory is operated by the School of Physical and Natural Sciences at National University of San Juan in San Juan, Argentina. The original OAFA observatory buildings are located at the west end of the city. OAFA is named after Félix Aguilar (1884–1943), an Argentine astronomer and engineer who was director of the La Plata Astronomical Observatory from 1919 to 1921, and again from 1934 until his death. EACUC was renamed after Carlos Ulrrico Cesco on the 25th anniversary of the beginning of ob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Columbia University
Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhattan, Columbia is the oldest institution of higher education in New York and the fifth-oldest institution of higher learning in the United States. It is one of nine colonial colleges founded prior to the Declaration of Independence. It is a member of the Ivy League. Columbia is ranked among the top universities in the world. Columbia was established by royal charter under George II of Great Britain. It was renamed Columbia College in 1784 following the American Revolution, and in 1787 was placed under a private board of trustees headed by former students Alexander Hamilton and John Jay. In 1896, the campus was moved to its current location in Morningside Heights and renamed Columbia University. Columbia scientists and scholars have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yale University
Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the world. It is a member of the Ivy League. Chartered by the Connecticut Colony, the Collegiate School was established in 1701 by clergy to educate Congregational ministers before moving to New Haven in 1716. Originally restricted to theology and sacred languages, the curriculum began to incorporate humanities and sciences by the time of the American Revolution. In the 19th century, the college expanded into graduate and professional instruction, awarding the first PhD in the United States in 1861 and organizing as a university in 1887. Yale's faculty and student populations grew after 1890 with rapid expansion of the physical campus and scientific research. Yale is organized into fourteen constituent schools: the original undergraduate col ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RR Lyrae
RR Lyrae is a variable star in the Lyra constellation, figuring in its west near to Cygnus. As the brightest star in its class, it became the eponym for the RR Lyrae variable class of stars and it has been extensively studied by astronomers. RR Lyrae variables serve as important standard candles that are used to measure astronomical distances. The period of pulsation of an RR Lyrae variable depends on its mass, luminosity and temperature, while the difference between the measured luminosity and the actual luminosity allows its distance to be determined via the inverse-square law. Hence, understanding the period-luminosity relation for a local set of such stars allows the distance of more distant stars of this type to be determined. History The variable nature of RR Lyrae was discovered by the Scottish astronomer Williamina Fleming at Harvard Observatory in 1901. The distance of RR Lyrae remained uncertain until 2002 when the Hubble Space Telescope's fine guidance sen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magellanic Clouds
The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular dwarf galaxies in the southern celestial hemisphere. Orbiting the Milky Way galaxy, these satellite galaxies are members of the Local Group. Because both show signs of a bar structure, they are often reclassified as Magellanic spiral galaxies. The two galaxies are: * Large Magellanic Cloud (LMC), approximately 163,000 light-years away * Small Magellanic Cloud (SMC), approximately 206,000 light years away Magellanic clouds are visible to the unaided eye in the Southern Hemisphere but they cannot be observed from the most northern latitudes. History The Magellanic Clouds have been known since ancient times to indigenous peoples across South America and Africa, and from the first millennium in Western Asia. The first preserved mention of the Large Magellanic Cloud is believed to be in petroglyphs and rock drawings found in Chile. They may be the objects mentioned by the polymath Ibn Qutay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term ''Milky Way'' is a translation of the Latin ', from the Greek ('), meaning "milky circle". From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy with an estimated D25 isophotal diameter of , but only about 1,000 light years thick at the spiral arms (more at the bulg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pretoria
Pretoria () is South Africa's administrative capital, serving as the seat of the Executive (government), executive branch of government, and as the host to all foreign embassies to South Africa. Pretoria straddles the Apies River and extends eastward into the foothills of the Magaliesberg mountains. It has a reputation as an academic city and center of research, being home to the Tshwane University of Technology (TUT), the University of Pretoria (UP), the University of South Africa (UNISA), the Council for Scientific and Industrial Research (CSIR), and the Human Sciences Research Council. It also hosts the National Research Foundation (South Africa), National Research Foundation and the South African Bureau of Standards. Pretoria was one of the host cities of the 2010 FIFA World Cup. Pretoria is the central part of the City of Tshwane Metropolitan Municipality which was formed by the amalgamation of several former local authorities, including Bronkhorstspruit, Centurion, Gaute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bulletin Of The Astronomical Institutes Of The Netherlands
''Astronomy & Astrophysics'' is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics. The journal is run by a Board of Directors representing 27 sponsoring countries plus a representative of the European Southern Observatory. The journal is published by EDP Sciences and the editor-in-chief is . History Origins ''Astronomy and Astrophysics'' (A&A) was created as an answer to the publishing scenario found in Europe in the 1960s. At that time, multiple journals were being published in several countries around the continent. These journals usually had a limited number of subscribers, and published articles in languages other than English, resulting in a small number of citations compared to American and British journals. Starting in 1963, conversations between astronomers from European countries assessed the need for a common astronomical journal. On 8 April 1968, leading astronomers from Belgium, Denmark, F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baade-Wesselink Method
The Baade-Wesselink method is a method for determining the distance of a Cepheid variable star suggested by Walter Baade in 1926 and further developed by Adriaan Wesselink in 1946. In the original method the color of the star at various points during its period of variation is used to determine its surface brightness. Then, knowing the apparent magnitude at these points in time the angular diameter can be calculated. Measurements are also taken of the radial velocity using Doppler spectroscopy. This allows one to determine the speed at which the front surface of the star moves toward or away from us at various points in the cycle. Since the difference between this and the average speed is the derivative of the radius, one obtains the variation in radius. Combining this with the change in angular diameter gives the distance. It is now possible to measure the angular diameter of the pulsating star directly using optical interferometers, allowing a more accurate measurement of the sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walter Baade
Wilhelm Heinrich Walter Baade (March 24, 1893 – June 25, 1960) was a German astronomer who worked in the United States from 1931 to 1959. Biography The son of a teacher, Baade finished school in 1912. He then studied maths, physics and astronomy at the universities of Münster and Göttingen. After receiving his PhD in 1919, Baade worked at Hamburg Observatory at Bergedorf from 1919 to 1931. There in 1920 he discovered 944 Hidalgo, the first of a class of minor planets now called Centaurs which cross the orbits of giant planets. He worked at Mount Wilson Observatory from 1931 to 1958. There, during World War II, he took advantage of wartime blackout conditions (which reduced light pollution), to resolve stars in the center of the Andromeda Galaxy for the first time. These observations led him to define distinct "populations" for stars (Population I and Population II). The same observations led him to discover that there are two types of Cepheid variable stars. Using this disc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
