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Oort
Jan Hendrik Oort ( or ; 28 April 1900 – 5 November 1992) was a Dutch astronomer who made significant contributions to the understanding of the Milky Way and who was a pioneer in the field of radio astronomy. His ''New York Times'' obituary called him "one of the century's foremost explorers of the universe"; the European Space Agency website describes him as "one of the greatest astronomers of the 20th century" and states that he "revolutionised astronomy through his ground-breaking discoveries." In 1955, Oort's name appeared in ''Life (magazine), Life'' magazine's list of the 100 most famous living people. He has been described as "putting the Netherlands in the forefront of postwar astronomy." Oort determined that the Milky Way rotates and overturned the idea that the Sun was at its center. He also postulated the existence of the mysterious invisible dark matter in 1932, which is believed to make up roughly 84.5% of the total matter in the Universe and whose gravitational ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oort Cloud
The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years).The Oort cloud's outer limit is difficult to define as it varies over the millennia as different stars pass the Sun and thus is subject to variation. Estimates of its distance range from 50,000 to 200,000 au. It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and are in interstellar space. The Kuiper belt, the scattered disc and the detached objects, the other three reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort cloud. The outer limit of the Oort cloud defines the cosmographic boundary of the Solar System and the extent of the Sun's Hill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oort Constants
The Oort constants (discovered by Jan Oort) A and B are empirically derived parameters that characterize the local rotational properties of our galaxy, the Milky Way, in the following manner: : \begin & A=\frac\left(\frac-\frac\Bigg\vert_\right) \\ & B= - \frac\left(\frac+\frac\Bigg\vert_\right) \\ \end where V_0 and R_0 are the rotational velocity and distance to the Galactic Center, respectively, measured at the position of the Sun, and and are the velocities and distances at other positions in our part of the galaxy. As derived below, and depend only on the motions and positions of stars in the solar neighborhood. As of 2018, the most accurate values of these constants are A = 15.3 ± 0.4 km s−1 kpc−1, B = -11.9 ± 0.4 km s−1 kpc−1. From the Oort constants, it is possible to determine the orbital properties of the Sun, such as the orbital velocity and period, and infer local properties of the Galactic disk, such as the mass density and how the rotation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1691 Oort
1691 Oort, provisional designation , is a rare-type carbonaceous Themistian asteroid from the outer region of the asteroid belt, approximately 33 kilometers in diameter. It was discovered on 9 September 1956, by German astronomer Karl Reinmuth and Dutch astronomer Ingrid van Houten-Groeneveld at Heidelberg Observatory in south-west Germany. It was later named after Dutch astronomer Jan Oort. Orbit and classification is a member of the Themis family, a dynamical family of outer-belt asteroids with nearly coplanar ecliptical orbits. ''Oort'' orbits the Sun at a distance of 2.6–3.7 AU once every 5 years and 7 months (2,054 days). Its orbit has an eccentricity of 0.18 and an inclination of 1 ° with respect to the ecliptic. It was first identified as at Turku in 1945, extending body's observation arc by 14 years prior to its official discovery observation. Information about an earlier 1917-identification, , is not available. Physical characteristics The dark C-type ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect. Various astrophysical observationsincluding gravitational effects which cannot be explained by currently accepted theories of gravity unless more matter is present than can be seenimply dark matter's presence. For this reason, most experts think that dark matter is abundant in the universe and has had a strong influence on its structure and evolution. The primary evidence for dark matter comes from calculations showing that many galaxies would behave quite differently if they did not contain a large amount of unseen matter. Some galaxies would not have formed at all and others would not move as they currently do. Other lines of evidence include observa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect. Various astrophysical observationsincluding gravitational effects which cannot be explained by currently accepted theories of gravity unless more matter is present than can be seenimply dark matter's presence. For this reason, most experts think that dark matter is abundant in the universe and has had a strong influence on its structure and evolution. The primary evidence for dark matter comes from calculations showing that many galaxies would behave quite differently if they did not contain a large amount of unseen matter. Some galaxies would not have formed at all and others would not move as they currently do. Other lines of evidence include observa ... [...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] |
Franeker
Franeker (; fry, Frjentsjer) is one of the eleven historical cities of Friesland and capital of the municipality of Waadhoeke. It is located north of the Van Harinxmakanaal and about 20 km west of Leeuwarden. As of 1 January 2014, it had 12,781 inhabitants. The Eise Eisinga Planetarium, established in 1781, is located in the city. History Franeker was founded around 800 as a Carolingian stronghold. The name probably derives from ''Froon-acker'', meaning "land of the lord/king"; the oldest street in the city is still called Froonacker. Beginning around the 11th century, Franeker developed into the administrative center Westergoa. Franeker received city rights in 1374. In the 15th century, Albert, Duke of Saxony established himself in Franeker. The city appeared for a time to be growing into the primary city of Friesland, but was eventually overshadowed in this role by Leeuwarden. During the period of the Dutch Revolt, the town sided early on with William I. From 1585 to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jacobus Cornelius Kapteyn
Prof Jacobus Cornelius Kapteyn FRS FRSE LLD (19 January 1851 – 18 June 1922) was a Dutch astronomer. He carried out extensive studies of the Milky Way and was the discoverer of evidence for galactic rotation. Kapteyn was also among the first to suggest the existence of dark matter using stellar velocities as early as 1922. Kapteyn's family and early life Kapteyn was born in Barneveld in the Netherlands to Gerrit J. and Elisabeth C. (née Koomans) Kapteyn, and was one of 15 children. Many of the Kapteyns were gifted in mathematics and physics. He passed his entrance exams for university at the age of 16 but Kapteyn's parents wouldn't allow him to go until the following year. He went to the University of Utrecht to study mathematics and physics in 1868. He did very well in his studies and when he graduated he was magna cum laude. This laid the foundation for his later career. Jacobus Kapteyn was a very doting father during the earlier years in his career and took an int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Egyptian astronomy, Egyptians, Chinese astronomy, Chinese, Maya civilization, Maya, and many anc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vetlesen Prize
The Vetlesen Prize is a prize in geology awarded jointly by Columbia University's Lamont–Doherty Earth Observatory and the G. Unger Vetlesen Foundation. The prize is generally regarded as the highest distinction in geologic studies, and the " Nobel Prize for geology". Background The Vetlesen Prize has been described as an attempt to establish an equivalent of a Nobel Prize for geophysics or geology. The prize is awarded for scientific achievement resulting in a clearer understanding of the Earth, its history, or its relations to the universe. The prize was established in 1959 and is awarded on average once every two years, if the jury selects at least one worthy candidate during this period. History G. Unger Vetlesen established the foundation which bears his name shortly before his death in 1955. In addition to the Vetlesen Prize, the foundation provides support in the Earth sciences for institutions of excellence. The prize is awarded for scientific achievement resulting in a c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leiden
Leiden (; in English and archaic Dutch also Leyden) is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 119,713, but the city forms one densely connected agglomeration with its suburbs Oegstgeest, Leiderdorp, Voorschoten and Zoeterwoude with 206,647 inhabitants. The Netherlands Central Bureau of Statistics (CBS) further includes Katwijk in the agglomeration which makes the total population of the Leiden urban agglomeration 270,879, and in the larger Leiden urban area also Teylingen, Noordwijk, and Noordwijkerhout are included with in total 348,868 inhabitants. Leiden is located on the Oude Rijn, at a distance of some from The Hague to its south and some from Amsterdam to its north. The recreational area of the Kaag Lakes (Kagerplassen) lies just to the northeast of Leiden. A university city since 1575, Leiden has been one of Europe's most prominent scientific centres for more than four centuries. Leide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotterdam
Rotterdam ( , , , lit. ''The Dam on the River Rotte'') is the second largest city and municipality in the Netherlands. It is in the province of South Holland, part of the North Sea mouth of the Rhine–Meuse–Scheldt delta, via the ''"New Meuse"'' inland shipping channel, dug to connect to the Meuse first, but now to the Rhine instead. Rotterdam's history goes back to 1270, when a dam was constructed in the Rotte. In 1340, Rotterdam was granted city rights by William IV, Count of Holland. The Rotterdam–The Hague metropolitan area, with a population of approximately 2.7 million, is the 10th-largest in the European Union and the most populous in the country. A major logistic and economic centre, Rotterdam is Europe's largest seaport. In 2020, it had a population of 651,446 and is home to over 180 nationalities. Rotterdam is known for its university, riverside setting, lively cultural life, maritime heritage and modern architecture. The near-complete destruction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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