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Hertzsprung
Ejnar Hertzsprung (; 8 October 1873 – 21 October 1967) was a Danish chemist and astronomer. He is best remembered for his role in developing the Hertzsprung-Russell diagram of stars. Career Hertzsprung was born in Frederiksberg, Denmark, the son of Severin and Henriette. He studied chemical engineering at Copenhagen Polytechnic Institute, graduating in 1898. After spending two years working as a chemist in St. Petersburg, in 1901 he studied photochemistry at Leipzig University for a year. His father was an amateur astronomer, which led to Ejnar's interest in the subject. He began making astronomical observations in Frederiksberg in 1902, and within a few years had noticed that stars with similar spectral type could have widely different absolute magnitudes. In 1909, he took a position at the Göttingen Observatory under director Karl Schwarzschild. In 1911 Hertzsprung developed the Hertzsprung–Russell diagram, independently developed in 1913 by Henry Norris Russell. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertzsprung–Russell Diagram
The Hertzsprung–Russell diagram (abbreviated as H–R diagram, HR diagram or HRD) is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities and their stellar classifications or effective temperatures. The diagram was created independently in 1911 by Ejnar Hertzsprung and by Henry Norris Russell in 1913, and represented a major step towards an understanding of stellar evolution. Historical background In the nineteenth century large-scale photographic spectroscopic surveys of stars were performed at Harvard College Observatory, producing spectral classifications for tens of thousands of stars, culminating ultimately in the Henry Draper Catalogue. In one segment of this work Antonia Maury included divisions of the stars by the width of their spectral lines. Hertzsprung noted that stars described with narrow lines tended to have smaller proper motions than the others of the same spectral classification. He took this as an in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertzsprung Gap
The Hertzsprung gap is a feature of the Hertzsprung–Russell diagram for a star cluster. This diagram is a plot of effective temperature versus luminosity for a population of stars. The gap is named after Ejnar Hertzsprung, who first noticed the absence of stars in the region of the Hertzsprung–Russell diagram between A5 and G0 spectral type and between +1 and −3 absolute magnitudes. This gap lies between the top of the main sequence and the base of red giants for stars above roughly 1.5 solar mass. When a star during its evolution crosses the Hertzsprung gap, it means that it has finished core hydrogen burning. Stars do exist in the Hertzsprung gap region, but because they move through this section of the Hertzsprung–Russell diagram very quickly in comparison to the lifetime of the star (thousands of years, compared to millions or billions of years for the lifetime of the star Table 5.2, Figure 5.2.), that portion of the diagram is less densely populated. Full Her ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1627 Ivar
1627 Ivar (provisional designation ) is an elongated stony asteroid and near-Earth object of the Amor group, approximately 15×6×6 km. It was discovered on 25 September 1929, by Danish astronomer Ejnar Hertzsprung at Leiden Southern Station, annex to the Johannesburg Observatory in South Africa. It was named after Ivar Hertzsprung, brother of the discoverer. 1627 Ivar was the first asteroid to be imaged by radar, in July 1985 by the Arecibo Observatory.To See the Unseen, A History of Planetary Radar Astronomy - chapter 9 Andrew J. Butrica, The NASA History Series Classification and orbit Ivar orbits the Sun at a distance of 1.1–2.6 AU once every 2 y ...[...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 current age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from Gravitational collapse, 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 stellar core, 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 st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antonia Maury
Antonia Caetana de Paiva Pereira Maury (March 21, 1866 – January 8, 1952) was an American astronomer who was the first to detect and calculate the orbit of a spectroscopic binary. She published an important early catalog of stellar spectra using her own system of stellar classification, which was later adopted by the International Astronomical Union. She also spent many years studying the binary star Beta Lyrae. Maury was part of the Harvard Computers, a group of female astronomers and human computers at the Harvard College Observatory. Dorrit Hoffleit described Maury as an "independent Renegade", suffering at the Observation for her Independence not agreeing with the way Edward Charles Pickering had them working for minimal credit. Antonia Maury was awarded the Annie Jump Cannon Award in Astronomy in 1943. William Wilson Morgan, one of the developers of the MK system of stellar classification, which builds upon her work, has said that he considers Antonia Maury ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Type
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The ''spectral class'' of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters ''O'', ''B'', ''A'', ''F'', ''G'', ''K'', and ''M'', a sequence from the hottest (''O'' type) to the coolest (''M'' type). Each letter class is then subdivided ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leiden Observatory
Leiden Observatory () is an astronomical institute of Leiden University, in the Netherlands. Established in 1633 to house the quadrant of Willebrord Snellius, it is the oldest operating university observatory in the world, with the only older still existing observatory being the Vatican Observatory. The observatory was initially located on the university building in the centre of Leiden before a new observatory building and dome were constructed in the university's botanical garden in 1860. It remained there until 1974 when the department moved to the science campus north-west of the city. Notable astronomers that have worked or directed the observatory include Willem de Sitter, Ejnar Hertzsprung and Jan Oort. History 1633–1860 Leiden University established the observatory in 1633; astronomy had been on the curriculum for a long time, and due to possession of a large quadrant built by Rudolph Snellius, Jacobus Golius requested an observatory in which to use it. The obse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Norris Russell
Henry Norris Russell ForMemRS HFRSE FRAS (October 25, 1877 – February 18, 1957) was an American astronomer who, along with Ejnar Hertzsprung, developed the Hertzsprung–Russell diagram (1910). In 1923, working with Frederick Saunders, he developed Russell–Saunders coupling, which is also known as LS coupling. Life Russell was born on 25 October 1877, at Oyster Bay, New York, the son of Rev Alexander Gatherer Russell (1845-1911) and his wife, Eliza Hoxie Norris. After graduating from Princeton Preparatory School in 1893, he studied astronomy at Princeton University, obtaining his B.A. in 1897 and his doctorate in 1900, studying under Charles Augustus Young. From 1903 to 1905, he worked at the Cambridge Observatory with Arthur Robert Hinks as a research assistant of the Carnegie Institution and came under the strong influence of George Darwin. He returned to Princeton to become an instructor in astronomy (1905–1908), assistant professor (1908–1911), professor (1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roskilde
Roskilde ( , ) is a city west of Copenhagen on the Danish island of Zealand. With a population of 53,354 (), the city is a business and educational centre for the region and the 10th largest city in Denmark. It is governed by the administrative council of Roskilde Municipality. Roskilde has a long history, dating from the pre-Christian Viking Age. Its UNESCO-listed Gothic architecture, Gothic Roskilde Cathedral, cathedral, now housing 39 tombs of the Danish monarchs, was completed in 1275, becoming a focus of religious influence until the Danish Reformation, Reformation. With the development of the rail network in the 19th century, Roskilde became an important hub for traffic with Copenhagen, and by the end of the century, there were tobacco factories, iron foundries and machine shops. Among the largest private sector employers today are the IT firm BEC (Bankernes EDB Central) and seed company DLF (seed company), DLF. The Risø DTU National Laboratory for Sustainable Energy, Ris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gerard Kuiper
Gerard Peter Kuiper ( ; born Gerrit Pieter Kuiper, ; 7 December 1905 – 23 December 1973) was a Dutch-American astronomer, planetary scientist, selenographer, author and professor. The Kuiper belt is named after him. Kuiper is considered by many to be the father of modern planetary science. Early life and education Kuiper, the son of a tailor in the village of Tuitjenhorn in North Holland, had an early interest in astronomy. He had extraordinarily sharp eyesight, allowing him to see with the naked eye Apparent magnitude, magnitude 7.5 stars, about four times fainter than those visible to normal eyes. He studied at Leiden University in 1924, where at the time a very large number of astronomers had congregated. He befriended fellow students Bart Bok and Pieter Oosterhoff, and was taught by Ejnar Hertzsprung, Antonie Pannekoek, Willem de Sitter, Jan Woltjer (astronomer), Jan Woltjer, Jan Oort, and the physicist Paul Ehrenfest. He received his Candidate (degree), c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cepheid
A Cepheid variable () is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period (typically 1–100 days) and amplitude. Cepheids are important cosmic benchmarks for scaling galactic and extragalactic distances; a strong direct relationship exists between a Cepheid variable's luminosity and its pulsation period. This characteristic of classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt after studying thousands of variable stars in the Magellanic Clouds. The discovery establishes the ''true luminosity'' of a Cepheid by observing its pulsation period. This in turn gives the distance to the star by comparing its known luminosity to its observed brightness, calibrated by directly observing the parallax distance to the closest Cepheids such as RS Puppis and Polaris. Cepheids change brightness due to the κ–mechanism, which occurs when opacity in a star increases with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karl Schwarzschild
Karl Schwarzschild (; 9 October 1873 – 11 May 1916) was a German physicist and astronomer. Schwarzschild provided the first exact solution to the Einstein field equations of general relativity, for the limited case of a single spherical non-rotating mass, which he accomplished in 1915, the same year that Einstein first introduced general relativity. The Schwarzschild solution, which makes use of Schwarzschild coordinates and the Schwarzschild metric, leads to a derivation of the Schwarzschild radius, which is the size of the event horizon of a non-rotating black hole. Schwarzschild accomplished this while serving in the German army during World War I. He died the following year, possibly from the autoimmune disease pemphigus, which he developed while at the Russian front. Asteroid 837 Schwarzschilda is named in his honour, as is the large crater ''Schwarzschild'', on the far side of the Moon. Life Karl Schwarzschild was born on 9 October 1873 in Frankfurt on Main, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
