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Kennicutt–Schmidt Law
In astronomy, the Kennicutt–Schmidt law is an empirical relation between the surface gas density and star formation rate (SFR) in a given region.The name "Schmidt law" is now commonly used for a general relation between volume gas density and star formation rate, and the Kennicutt-Schmidt law for the surface gas density and star formation rate. The relation was first examined by Maarten Schmidt in a 1959 paper where he proposed that the SFR surface density scales as some positive power n of the local gas surface density. i.e. :\Sigma_ \propto (\Sigma_)^n. In general, the SFR surface density (\Sigma_) is in units of solar masses per year per square parsec (M_\odot ~\textrm^ \textrm^) and the gas surface density in grams per square parsec (\textrm~\textrm^). Using an analysis of gaseous helium and young stars in the solar neighborhood, the local density of white dwarfs and their luminosity function, and the local helium density, Schmidt suggested a value of n \approx 2 (and v ... [...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] |
Maarten Schmidt
Maarten Schmidt (28 December 1929 – 17 September 2022) was a Dutch-born American astronomer who first measured the distances of quasars. He was the first astronomer to identify a quasar, and so was pictured on the March cover of ''Time'' magazine in 1966. Early life Schmidt was born in Groningen, The Netherlands, on 28 December 1929. His father, Wilhelm, worked as an accountant for the Dutch government; his mother, Annie Wilhelmina (Haringhuizen), was a housewife. Schmidt studied math and physics at the University of Groningen, graduating with a bachelor's degree in 1949 before obtaining a master's degree the following year. He then commenced doctoral studies at Leiden University under Jan Oort. Schmidt was awarded a Doctor of Philosophy from Leiden Observatory in 1956. Career After completing his doctorate, Schmidt resided in the United States for two years on a Carnegie Fellowship. He returned briefly to the Netherlands, but ultimately emigrated to the US on a permane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Neighborhood
The Local Interstellar Cloud (LIC), also known as the Local Fluff, is an interstellar cloud roughly across, through which the Solar System is moving. This feature overlaps a region around the Sun referred to as the solar neighborhood. It is unknown whether the Sun is embedded in the Local Interstellar Cloud, or is in the region where the Local Interstellar Cloud is interacting with the neighboring G-Cloud. Like the G-Cloud and others, the LIC is part of the Very Local Interstellar Medium which begins where the heliosphere and interplanetary medium end, the furthest that probes have traveled. Structure The Solar System is located within a structure called the Local Bubble, a low-density region of the galactic interstellar medium. Within this region is the Local Interstellar Cloud (LIC), an area of slightly higher hydrogen density. It is estimated that the Solar System entered the LIC within the past 10,000 years. It is uncertain whether the Sun is still inside of the LIC or h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarfs
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Luyten in 1922. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luminosity Function
A luminous efficiency function or luminosity function represents the average spectral sensitivity of human visual perception of light. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. It is not an absolute reference to any particular individual, but is a standard observer representation of visual sensitivity of theoretical human eye. It is valuable as a baseline for experimental purposes, and in colorimetry. Different luminous efficiency functions apply under different lighting conditions, varying from photopic in brightly lit conditions through mesopic to scotopic under low lighting conditions. When not specified, ''the luminous efficiency function'' generally refers to the photopic luminous efficiency function. The CIE photopic luminous efficiency function or is a standard function established by the Commission Internationale de l'Éclairage (CIE) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Kennicutt
Robert Charles Kennicutt, Jr. FRS is an American astronomer. He is currently a professor at Texas A&M University. He is a former Plumian Professor of Astronomy at the Institute of Astronomy in the University of Cambridge. He was formerly Editor-in-Chief of the ''Astrophysical Journal'' (1999–2006) and became a co-editor of the '' Annual Review of Astronomy and Astrophysics'' as of 2021. His research interests include the structure and evolution of galaxies and star formation in galaxies. Career He received his bachelor's degree in physics from Rensselaer Polytechnic Institute in 1973. He was a graduate student in astronomy at the University of Washington, where he received his master's degree in 1976 and his Ph.D. in 1978. Kennicutt formulated a version of the Kennicutt–Schmidt law, which is an empirical relation between the gas density and star formation rate (SFR) in a given region. Research Spitzer Infrared Nearby Galaxies Survey Kennicutt is the principal investiga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Astronomy
Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, 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 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 Babylonians, Greeks, Indians, Egyptians, Chinese, Maya, and many ancient indigenous peoples of the Americas. In the past, astronomy included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars. Nowadays, professional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galaxies
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than the Sun. As of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
