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Encyclopedia > Astronomy
A giant Hubble mosaic of the Crab Nebula, a supernova remnant
A giant Hubble mosaic of the Crab Nebula, a supernova remnant
Astronomy Portal

Astronomy (from the Greek words astro(αστέρι) = star and nomos(νόμος) = law) is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe. Astronomy is the scientific study of celestial objects. ... Image File history File linksMetadata Download high resolution version (2224x2212, 3149 KB) Summary Image: A Giant Hubble Mosaic of the Crab Nebula Source: http://hubblesite. ... Image File history File linksMetadata Download high resolution version (2224x2212, 3149 KB) Summary Image: A Giant Hubble Mosaic of the Crab Nebula Source: http://hubblesite. ... The Hubble Space Telescope (HST; also known colloquially as the Hubble or just Hubble) is a space telescope that was carried into Earth orbit by the Space Shuttle in April 1990. ... The Crab Nebula (catalogue designations M 1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus. ... Remnant of Keplers Supernova, SN 1604 Remnant of Tychos Nova, SN 1572 A supernova remnant (SNR) is the structure resulting from the gigantic explosion of a star in a supernova. ... Image File history File links Portal. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... Astronomical objects are significant physical entities, associations or structures which current science has confirmed to exist in space. ... This article is about the astronomical object. ... This article is about the astronomical term. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... For other uses, see Galaxy (disambiguation). ... For other uses, see Phenomena (disambiguation). ... Air redirects here. ... CMB redirects here. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... For other uses, see Chemistry (disambiguation). ... // Meteorology (from Greek: μετέωρον, meteoron, high in the sky; and λόγος, logos, knowledge) is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting. ... This article or section is in need of attention from an expert on the subject. ... This article is about the physics subject. ...


Astronomy is one of the oldest sciences. Astronomers of early civilizations performed methodical observations of the night sky, and astronomical artifacts have been found from much earlier periods. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and even astrology, but professional astronomy is nowadays often considered to be synonymous with astrophysics. Since the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring and analyzing data, mainly using basic principles of physics. Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results. This article does not cite any references or sources. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... For the episode of The West Wing, see Celestial Navigation (The West Wing). ... For other uses, see Calendar (disambiguation) A page from the Hindu calendar 1871–1872. ... Hand-coloured version of the anonymous Flammarion woodcut (1888). ... Spiral Galaxy ESO 269-57 Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature, and chemical composition) of celestial objects such as stars, galaxies, and the interstellar medium, as well as their interactions. ... Mayall telescope at Kitt Peak National Observatory Observational astronomy is a division of the astronomical science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measureable implications of physical models. ... Theoretical astrophysics is the discipline that seeks to explain the phenomena observed by astronomers in physical terms with a theoretic approach. ...


Amateur astronomers have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena. It has been suggested that this article or section be merged with Skygazing. ... A phenomenon (plural: phenomena) is an observable event, especially something special (literally something that can be seen from the Greek word phainomenon = observable). ...


Old or even ancient astronomy is not to be confused with astrology, the belief system that claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin and a part of their methods (namely, the use of ephemerides), they are distinct.[1] Hand-coloured version of the anonymous Flammarion woodcut (1888). ... This article needs additional references or sources for verification. ... An ephemeris (plural: ephemerides) (from the Greek word ephemeros = daily) is a device giving the positions of astronomical objects in the sky. ...

Contents

Lexicology

The word astronomy literally means "law of the stars" (or "culture of the stars" depending on the translation) and is derived from the Greek αστρονομία, astronomia, from the words άστρον (astron, "star") and νόμος (nomos, "laws or cultures").


Use of terms "astronomy" and "astrophysics"

Generally, either the term "astronomy" or "astrophysics" may be used to refer to this subject.[2][3][4] Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties"[5]and "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, and dynamic processes of celestial objects and phenomena".[6] In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject.[7] However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics.[2] Various departments that research this subject may use "astronomy" and "astrophysics", partly depending on whether the department is historically affiliated with a physics department,[3] and many professional astronomers actually have physics degrees.[4] Even the name of the scientific journal Astronomy & Astrophysics reveals the ambiguity of the use of the term. Frank Shu Frank Shu (born in Kunming, China), is an astrophysicist, author and professor of astronomy at the University of California, Berkeley and the university president of the National Tsing Hua University. ... Astronomy and Astrophysics (abbreviated as A&A in the astronomical literature, or else ) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ...


History

Main article: History of astronomy
Further information: Archaeoastronomy
A celestial map from the 17th century, by the Dutch cartographer Frederik De Wit.
A celestial map from the 17th century, by the Dutch cartographer Frederik De Wit.

In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye. In some locations, such as Stonehenge, early cultures assembled massive artifacts that likely had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops, as well as in understanding the length of the year.[8] Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, and astrological practices of pre-history: vestiges of these are still found in astrology, a discipline long interwoven with public and governmental astronomy, and not completely disentangled from it until a... The sun rising over Stonehenge at the 2005 Summer Solstice. ... Image File history File linksMetadata Size of this preview: 800 × 548 pixelsFull resolution (1804 × 1236 pixel, file size: 3. ... Image File history File linksMetadata Size of this preview: 800 × 548 pixelsFull resolution (1804 × 1236 pixel, file size: 3. ... For other uses, see Stonehenge (disambiguation). ...


Before tools such as the telescope were invented early study of the stars had to be conducted from the only vantage points available, namely tall buildings, trees and high ground using the bare eye.


As civilizations developed, most notably in Mesopotamia, Greece, Egypt, Persia, Maya, India, China, and the Islamic world, astronomical observatories were assembled, and ideas on the nature of the universe began to be explored. Most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon and the Earth in the universe were explored philosophically. The Earth was believed to be the center of the universe with the Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the universe. Babylonian astronomy refers to the astronomy that developed in Mesopotamia, the land between the rivers Tigris and Euphrates, where the ancient kingdoms of Sumer, Assyria, Babylonia and Chaldea were located. ... Persia redirects here. ... This article is about the pre-Columbian Maya civilization. ... This is a sub-article of Islamic science and astronomy. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ...


A few notable astronomical discoveries were made prior to the application of the telescope. For example, the obliquity of the ecliptic was estimated as early as 1000 BC by the Chinese. The Chaldeans discovered that lunar eclipses recurred in a repeating cycle known as a saros.[9] In the 2nd century BC, the size and distance of the Moon were estimated by Hipparchus.[10] In astronomy, axial tilt is the inclination angle of a planets rotational axis in relation to a perpendicular to its orbital plane. ... Babylonian astronomy refers to the astronomy that developed in Mesopotamia, the land between the rivers Tigris and Euphrates, where the ancient kingdoms of Sumer, Assyria, Babylonia and Chaldea were located. ... An eclipse occurs whenever the Sun, Earth and Moon line up exactly. ... A Saros cycle is a period of 6585 + 1/3 days (approximately 18 years 10 days and 8 hours) which can be used to predict eclipses of the sun and the moon. ... For the Athenian tyrant, see Hipparchus (son of Pisistratus). ...


During the Middle Ages, observational astronomy was mostly stagnant in medieval Europe, at least until the 13th century. However, observational astronomy flourished in the Islamic world and other parts of the world. Some of the prominent Arab astronomers, who made significant contributions to the science were Al-Battani and Thebit. Astronomers during that time introduced many Arabic names that are now used for individual stars.[11][12] The Middle Ages formed the middle period in a traditional schematic division of European history into three ages: the classical civilization of Antiquity, the Middle Ages, and modern times, beginning with the Renaissance. ... This is a sub-article of Islamic science and astronomy. ... Al Battani (c. ... Arabic redirects here. ...


Scientific revolution

Galileo's sketches and observations of the Moon revealed that the surface was mountainous
Galileo's sketches and observations of the Moon revealed that the surface was mountainous

During the Renaissance, Nicolaus Copernicus proposed a heliocentric model of the solar system. His work was defended, expanded upon, and corrected by Galileo Galilei and Johannes Kepler. Galileo innovated by using telescopes to enhance his observations. Image File history File linksMetadata Download high-resolution version (614x850, 591 KB) Subject : moon phases by Galileo Date : 1616 File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Astronomy Portal talk:History of science/Picture Portal:History of science... Image File history File linksMetadata Download high-resolution version (614x850, 591 KB) Subject : moon phases by Galileo Date : 1616 File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Astronomy Portal talk:History of science/Picture Portal:History of science... This article is about the European Renaissance of the 14th-17th centuries. ... Copernicus redirects here. ... In astronomy, heliocentrism is the theory that the Sun is at the center of the Universe and/or the Solar System. ... This article is about the Solar System. ... Galileo redirects here. ... Kepler redirects here. ...


Kepler was the first to devise a system that described correctly the details of the motion of the planets with the Sun at the center. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was left to Newton's invention of celestial dynamics and his law of gravitation to finally explain the motions of the planets. Newton also developed the reflecting telescope. Sir Isaac Newton in Knellers portrait of 1689. ... This article or section should include material from Celestial Mechanics This article or section should be merged with Astrodynamics Celestial mechanics is a term for the application of physics, historically Newtonian mechanics, to astronomical objects such as stars and planets. ... Gravity is a force of attraction that acts between bodies that have mass. ... 24 inch convertible Newtonian/Cassegrain reflecting telescope on display at the Franklin Institute. ...


Further discoveries paralleled the improvements in the size and quality of the telescope. More extensive star catalogues were produced by Lacaille. The astronomer William Herschel made a detailed catalog of nebulosity and clusters, and in 1781 discovered the planet Uranus, the first new planet found. The distance to a star was first announced in 1838 when the parallax of 61 Cygni was measured by Friedrich Bessel. Abbé Nicolas Louis de Lacaille (March 15, 1713 – March 21, 1762) was a French astronomer. ... For other persons named William Herschel, see William Herschel (disambiguation). ... For other uses, see Uranus (disambiguation). ... For other uses, see Parallax (disambiguation). ... 61 Cygni is a star in the constellation Cygnus. ... Friedrich Wilhelm Bessel (July 22, 1784 – March 17, 1846) was a German mathematician, astronomer, and systematizer of the Bessel functions (which, despite their name, were discovered by Daniel Bernoulli). ...


During the nineteenth century, attention to the three body problem by Euler, Clairaut, and D'Alembert led to more accurate predictions about the motions of the Moon and planets. This work was further refined by Lagrange and Laplace, allowing the masses of the planets and moons to be estimated from their perturbations. The n-body problem is the problem of finding, given the initial positions, masses, and velocities of n bodies, their subsequent motions as determined by classical mechanics, i. ... Euler redirects here. ... Alexis Claude Clairault (or Clairaut) (May 3, 1713 - May 17, 1765) was a French mathematician. ... Jean le Rond dAlembert, pastel by Maurice Quentin de La Tour Jean le Rond dAlembert (November 16, 1717 – October 29, 1783) was a French mathematician, mechanician, physicist and philosopher. ... Joseph-Louis, comte de Lagrange (January 25, 1736 Turin, Kingdom of Sardinia - April 10, 1813 Paris) was an Italian-French mathematician and astronomer who made important contributions to all fields of analysis and number theory and to classical and celestial mechanics as arguably the greatest mathematician of the 18th century. ... Pierre-Simon Laplace Pierre-Simon Laplace (March 23, 1749 – March 5, 1827) was a French mathematician and astronomer, the discoverer of the Laplace transform and Laplaces equation. ...


Significant advances in astronomy came about with the introduction of new technology, including the spectroscope and photography. Fraunhofer discovered about 600 bands in the spectrum of the Sun in 1814-15, which, in 1859, Kirchhoff ascribed to the presence of different elements. Stars were proven to be similar to the Earth's own Sun, but with a wide range of temperatures, masses, and sizes.[11] A spectroscope is a device which measures the spectrum of light. ... Photography [fәtɑgrәfi:],[foʊtɑgrәfi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor. ... Joseph von Fraunhofer Joseph von Fraunhofer (March 6, 1787 – June 7, 1826) was a German physicist. ... Gustav Robert Kirchhof (March 12, 1824 – October 17, 1887) was a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects. ... For other uses, see Temperature (disambiguation). ... For other uses, see Mass (disambiguation). ...


The existence of the Earth's galaxy, the Milky Way, as a separate group of stars, was only proved in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe, seen in the recession of most galaxies from us. Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars, and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as black holes and neutron stars. Physical cosmology made huge advances during the 20th century, with the model of the Big Bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's law, and cosmological abundances of elements. For other uses, see Milky Way (disambiguation). ... For other uses, see Universe (disambiguation). ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... It has been suggested that Radio pulsar be merged into this article or section. ... A blazar is a very compact and highly variable energy source associated with a supermassive black hole at the center of a host galaxy. ... An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... For other uses, see Black hole (disambiguation). ... For the story by Larry Niven, see Neutron Star (story). ... This article is about the physics subject. ... For other uses, see Big Bang (disambiguation). ... CMB redirects here. ... This box:      Hubbles law is a statement in physical cosmology which states that the redshift in light coming from distant galaxies is proportional to their distance. ... In cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. ...


Observational astronomy

In astronomy, information is mainly received from the detection and analysis of visible light or other regions of the electromagnetic radiation.[13] Observational astronomy may be divided according to the observed region of the electromagnetic spectrum. Some parts of the spectrum can be observed from the Earth's surface, while other parts are only observable from either high altitudes or space. Specific information on these subfields is given below. Very Large Array at Socorro, New Mexico, USA. Photo taken by Hajor, 08. ... Very Large Array at Socorro, New Mexico, USA. Photo taken by Hajor, 08. ... The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. U.S. Route 60 passes through the complex. ... Official language(s) None Spoken language(s) English 68. ... The 64 meter radio telescope at Parkes Observatory A radio telescope is a form of directional radio antenna used in radio astronomy and in tracking and collecting data from satellites and space probes. ... Mayall telescope at Kitt Peak National Observatory Observational astronomy is a division of the astronomical science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measureable implications of physical models. ... The ASCII codes for the word Wikipedia represented in binary, the numeral system most commonly used for encoding computer information. ... For other uses, see Light (disambiguation). ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ... Although some radiations are marked as N for no in the diagram, some waves do in fact penetrate the atmosphere, although extremely minimally compared to the other radiations The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. ... This article is about Earth as a planet. ...


Radio astronomy

Radio astronomy studies radiation with wavelengths greater than approximately one millimeter.[14] Radio astronomy is different from most other forms of observational astronomy in that the observed radio waves can be treated as waves rather than as discrete photons. Hence, it is relatively easier to measure both the amplitude and phase of radio waves, whereas this is not as easily done at shorter wavelengths.[14] The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... For other uses, see Wavelength (disambiguation). ... A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... Surface waves in water This article is about waves in the most general scientific sense. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... It has been suggested that pulse amplitude be merged into this article or section. ... This article is about a portion of a periodic process. ...


Though some radio waves are produced by astronomical objects in the form of thermal emission, most of the radio emission that is observed from Earth is seen in the form of synchrotron radiation, which is produced when electrons oscillate around magnetic fields.[14] Additionally, a number of spectral lines produced by interstellar gas, notably the hydrogen spectral line at 21 cm, are observable at radio wavelengths.[7][14] Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... General Electric synchrotron accelerator built in 1946, the origin of the discovery of synchrotron radiation. ... For other uses, see Electron (disambiguation). ... For the indie-pop band, see The Magnetic Fields. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate circumstellar environment) within a galaxy. ... This article is about the chemistry of hydrogen. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ...


A wide variety of objects are observable at radio wavelengths, including supernovae, interstellar gas, pulsars, and active galactic nuclei.[7][14] For other uses, see Supernova (disambiguation). ... It has been suggested that Radio pulsar be merged into this article or section. ... An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ...


Infrared astronomy

Infrared astronomy deals with the detection and analysis of infrared radiation (wavelengths longer than red light). Except at wavelengths close to visible light, infrared radiation is heavily absorbed by the atmosphere, and the atmosphere produces significant infrared emission. Consequently, infrared observatories have to be located in high, dry places or in space. Infrared astronomy is particularly useful for observation of galactic regions cloaked by dust, and for studies of molecular gases. Infrared astronomy is the branch of astronomy and astrophysics which deals with objects visible in infrared (IR) radiation. ... For other uses, see Infrared (disambiguation). ...


Optical astronomy

The Subaru Telescope (left) and Keck Observatory (center) on Mauna Kea, both examples of an observatory that operates at near-infrared and visible wavelengths. The NASA Infrared Telescope Facility (right) is an example of a telescope that operates only at near-infrared wavelengths.
The Subaru Telescope (left) and Keck Observatory (center) on Mauna Kea, both examples of an observatory that operates at near-infrared and visible wavelengths. The NASA Infrared Telescope Facility (right) is an example of a telescope that operates only at near-infrared wavelengths.

Historically, optical astronomy, also called visible light astronomy, is the oldest form of astronomy.[15] Optical images were originally drawn by hand. In the late nineteenth century and most of the twentieth century, images were made using photographic equipment. Modern images are made using digital detectors, particularly detectors using charge-coupled devices (CCDs). Although visible light itself extends from approximately 4000 Å to 7000 Å (400 nm to 700 nm),[15] the same equipment used at these wavelengths is also used to observe some near-ultraviolet and near-infrared radiation. Image File history File linksMetadata Download high-resolution version (1280x960, 300 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Astronomy Mauna Kea Observatory Metadata This file contains additional information, probably added from the digital camera or scanner... Image File history File linksMetadata Download high-resolution version (1280x960, 300 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Astronomy Mauna Kea Observatory Metadata This file contains additional information, probably added from the digital camera or scanner... Subaru Telescope (In Japanese: すばる望遠鏡) is the 8. ... The Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ... Mauna Kea is a dormant volcano in the Hawaiian Islands, one of five volcanoes which together form the island of Hawaii. ... The NASA Infrared Telescope Facility (NASA IRTF) is a 3. ... Optical astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... An angstrom, angström, or Ã¥ngström (symbol Ã…) is a unit of length. ... A nanometre (American spelling: nanometer, symbol nm) (Greek: νάνος, nanos, dwarf; μετρώ, metrÏŒ, count) is a unit of length in the metric system, equal to one billionth of a metre (or one millionth of a millimetre), which is the current SI base unit of length. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...


Ultraviolet astronomy

Ultraviolet astronomy is generally used to refer to observations at ultraviolet wavelengths between approximately 100 and 3200 Å (10 to 320 nm).[14] Light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. Ultraviolet astronomy is best suited to the study of thermal radiation and spectral emission lines from hot blue stars (OB stars) that are very bright in this wave band. This includes the blue stars in other galaxies, which have been the targets of several ultraviolet surveys. Other objects commonly observed in ultraviolet light include planetary nebulae, supernova remnants, and active galactic nuclei.[14] However, ultraviolet light is easily absorbed by interstellar dust, and measurement of the ultraviolet light from objects need to be corrected for extinction.[14] UV astronomy is the branch of astronomy and astrophysics which deals with objects visible in ultraviolet (UV) radiation. ... For other uses, see Ultraviolet (disambiguation). ... This article is about the astronomical object. ... OB stars are hot, massive stars stars which form in loosely organized groups called OB associations. ... NGC 6543, The Cats Eye Nebula NGC 6853, The Dumbbell Nebula A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. ... Remnant of Keplers Supernova, SN 1604 Remnant of Tychos Nova, SN 1572 A supernova remnant (SNR) is the structure resulting from the gigantic explosion of a star in a supernova. ... Interstellar cloud is the generic name given to accumulations of gas and dust in our galaxy. ...


X-ray astronomy

X-ray astronomy is the study of astronomical objects at X-ray wavelengths. Typically, objects emit X-ray radiation as synchrotron emission (produced by electrons oscillating around magnetic field lines), thermal emission from thin gases (called bremsstrahlung radiation) that is above 107 (10 million) kelvins, and thermal emission from thick gases (called blackbody radiation) that are above 107 Kelvin.[14] Since X-rays are absorbed by the Earth's atmosphere, all X-ray observations must be done from high-altitude balloons, rockets, or spacecraft. Notable X-ray sources include X-ray binaries, pulsars, supernova remnants, elliptical galaxies, clusters of galaxies, and active galactic nuclei.[14] ROSAT image of X-ray fluorescence of, and occultation of the X-ray background by, the Moon. ... Synchrotron radiation is electromagnetic radiation, similar to cyclotron radiation, but generated by the acceleration of ultrarelativistic (i. ... Bremsstrahlung, German for braking radiation, is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. ... For other uses, see Kelvin (disambiguation). ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... US Smarties (by Ce De Candy) US Smarties (by Ce De Candy) In the United States, Smarties are a type of artificially fruit-flavored candy produced by Ce De Candy. ... X-ray binaries are a class of binary stars that are very luminous in X-rays. ... It has been suggested that Radio pulsar be merged into this article or section. ... An elliptical galaxy is a type of galaxy in the Hubble sequence characterized by the following physical properties: The giant elliptical galaxy NGC 4881 (the spherical glow at upper left) lies at the edge of the Coma Cluster of Galaxies. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ...


Gamma-ray astronomy

Gamma ray astronomy is the study of astronomical objects at the shortest wavelengths of the electromagnetic spectrum. Gamma rays may be observed directly by satellites such as the Compton Gamma Ray Observatory or by specialized telescopes called atmospheric Cherenkov telescopes.[14] The Cherenkov telescopes do not actually detect the gamma rays directly but instead detect the flashes of visible light produced when gamma rays are absorbed by the Earth's atmosphere.[16] Gamma-ray astronomy is the astronomical study of gamma rays. ... Illustration of CGRO The Compton Gamma Ray Observatory(CGRO) was the second of the NASA Great Observatories to be launched to space, following the Hubble Space Telescope. ... This article does not cite any references or sources. ...


Most gamma-ray emitting sources are actually gamma-ray bursts, objects which only produce gamma radiation for a few milliseconds to thousands of seconds before fading away. Only 10% of gamma-ray sources are non-transient sources. These steady gamma-ray emitters include pulsars, neutron stars, and black hole candidates such as active galactic nuclei.[14] This box:      For the music band, see Gamma Ray (band). ... In astronomy, gamma-ray bursts (GRBs) are flashes of gamma rays that last from seconds to hours, the longer ones being followed by several days of X-ray afterglow. ... For the story by Larry Niven, see Neutron Star (story). ... For other uses, see Black hole (disambiguation). ...


Fields of observational astronomy not based on the electromagnetic spectrum

Other than electromagnetic radiation, few things may be observed from the Earth that originate from great distances.


In neutrino astronomy, astronomers use special underground facilities such as SAGE, GALLEX, and Kamioka II/III for detecting neutrinos. These neutrinos originate primarily from the Sun but also from supernovae.[14] Neutrino astronomy is the science of observing astronomical phenomena by detecting neutrinos, a product of thermonuclear reactions going on inside every star. ... SAGE (Russian-American Gallium Experiment or Soviet-American Gallium Experiment) is a collaborative experiment devised by several prominent Physicists to measure the solar neutrino flux. ... GALLEX or Gallium Experiment was a radiochemical neutrino detection experiment ran between years 1991 and 1997 at Laboratori Nazionali del Gran Sasso (LNGS). ... For other uses, see Neutrino (disambiguation). ... Sol redirects here. ... For other uses, see Supernova (disambiguation). ...


Cosmic rays consisting of very high energy particles can be observed hitting the Earth's atmosphere.[citation needed] Additionally, some future neutrino detectors will also be sensitive to the neutrinos produced when cosmic rays hit the Earth's atmosphere.[14] Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...


A few gravitational wave observatories have been constructed, but gravitational waves are extremely difficult to detect.[17] This box:      In physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from a moving object or system of objects. ...


Planetary astronomy has benefited from direct observation in the form of spacecraft and sample return missions. These include fly-by missions with remote sensors; landing vehicles that can perform experiments on the surface materials; impactors that allow remote sensing of buried material, and sample return missions that allow direct, laboratory examination.


Astrometry and celestial mechanics

Main articles: Astrometry and Celestial mechanics

One of the oldest fields in astronomy, and in all of science, is the measurement of the positions of celestial objects. Historically, accurate knowledge of the positions of the Sun, Moon, planets and stars has been essential in celestial navigation. Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... Celestial mechanics is a division of astronomy dealing with the motions and gravitational effects of celestial objects. ... For the episode of The West Wing, see Celestial Navigation (The West Wing). ...


Careful measurement of the positions of the planets has led to a solid understanding of gravitational perturbations, and an ability to determine past and future positions of the planets with great accuracy, a field known as celestial mechanics. More recently the tracking of near-Earth objects will allow for predictions of close encounters, and potential collisions, with the Earth.[18] Perturbation theory comprises mathematical methods that are used to find an approximate solution to a problem which cannot be solved exactly, by starting from the exact solution of a related problem. ... Celestial mechanics is a division of astronomy dealing with the motions and gravitational effects of celestial objects. ... Near-Earth objects (NEO) are asteroids, comets and large meteoroids whose orbit intersects Earths orbit and which may therefore pose a collision danger. ...


The measurement of stellar parallax of nearby stars provides a fundamental baseline in the cosmic distance ladder that is used to measure the scale of the universe. Parallax measurements of nearby stars provide an absolute baseline for the properties of more distant stars, because their properties can be compared. Measurements of radial velocity and proper motion show the kinematics of these systems through the Milky Way galaxy. Astrometric results are also used to measure the distribution of dark matter in the galaxy.[19] For other uses, see Parallax (disambiguation). ... The cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... For other uses, see Dark matter (disambiguation). ...


During the 1990s, the astrometric technique of measuring the stellar wobble was used to detect large extrasolar planets orbiting nearby stars.[20] Stellar wobble is the wobble of a star (this wobble is not visibile except via Doppler shifts) when a stars orbit is gravitationally affected by a nearby massive star. ... Any planet is an extremely faint light source compared to its parent star. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ...


Theoretical astronomy

Theoretical astronomers use a wide variety of tools which include analytical models(for example, polytropesto approximate the behaviors of a star) and computationalnumerical simulations. Each has some advantages. Analytical models of a process are generally better for giving insight into the heart of what is going on. Numerical models can reveal the existence of phenomena and effects that would otherwise not be seen.[21][22]Theorists in astronomy endeavor to create theoretical models and figure out the observational consequences of those models. This helps observers look for data that can refute a model or help in choosing between several alternate or conflicting models. Theorists also try to generate or modify models to take into account new data. In the case of an inconsistency, the general tendency is to try to make minimal modifications to the model to fit the data. In some cases, a large amount of inconsistent data over time may lead to total abandonment of a model. Topics studied by theoretical astronomers include: stellar dynamicsand evolution; galaxy formation; large-scale structureof matterin the Universe; origin of cosmic rays; general relativityand physical cosmology, including stringcosmology and astroparticle physics. Astrophysical relativity serves as a tool to gauge the properties of large scale structures for which gravitation plays a significant role in physical phenomena investigated and as the basis for black hole(astro)physicsand the study of gravitational waves. Some widely accepted and studied theories and models in astronomy, now included in the Lambda-CDM modelare the Big Bang, Cosmic inflation, dark matter, and fundamental theories of physics. A few examples of this process: A mathematical model is an abstract model that uses mathematical language to describe the behaviour of a system. ... A polytrope is a solution to the Lane-Emden equation. ... This article is about the astronomical object. ... Look up computation in Wiktionary, the free dictionary. ... Numerical analysis is the study of approximate methods for the problems of continuous mathematics (as distinguished from discrete mathematics). ... Stellar dynamics is the branch of astrophysics which describes in a statistical way the collective motions of stars subject to their mutual gravity. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ... In astrophysics, the questions of galaxy formation and evolution are: How, from a homogeneous universe, did we obtain the very heterogeneous one we live in? How did galaxies form? How do galaxies change over time? A spectacular head-on collision between two galaxies is seen in this NASA Hubble Space... To meet Wikipedias quality standards, this article or section may require cleanup. ... This article is about matter in physics and chemistry. ... For other uses, see Universe (disambiguation). ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... This article is about the physics subject. ... This box:      String theory is a still developing mathematical approach to theoretical physics, whose original building blocks are one-dimensional extended objects called strings. ... Astroparticle physics is a term used to indicate that branch of particle physics that studies elementary particles of astronomical origin, and their relation to astrophysics and cosmology. ... For other uses, see Black hole (disambiguation). ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... In physics, gravitational radiation is energy that is transmitted through waves in the gravitational field of space-time, according to Albert Einsteins theory of general relativity: The Einstein field equations imply that any accelerated mass radiates energy this way, in the same way as the Maxwell equations that any... A pie chart indicating the proportional composition of different energy-density components of the universe. ... For other uses, see Big Bang (disambiguation). ... In physical cosmology, cosmic inflation is the idea that the nascent universe passed through a phase of exponential expansion that was driven by a negative-pressure vacuum energy density. ... For other uses, see Dark matter (disambiguation). ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ...

Nucleosynthesis
Physical process Experimental tool Theoretical model Explains/predicts
Gravitation Radio telescopes Self-gravitating system Emergence of a star system
Nuclear fusion Spectroscopy Stellar evolution How the stars shine and how metals formed
The Big Bang Hubble Space Telescope, COBE Expanding universe Age of the Universe
Quantum fluctuations Cosmic inflation Flatness problem
Gravitational collapse X-ray astronomy General relativity Black holes at the center of Andromeda galaxy
CNO cycle in stars

Dark matter and dark energy are the current leading topics in astronomy, as their discovery and controversy originated during the study of the galaxies. Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... Gravity redirects here. ... The 64 meter radio telescope at Parkes Observatory A radio telescope is a form of directional radio antenna used in radio astronomy and in tracking and collecting data from satellites and space probes. ... In theoretical astrophysics, the Nordtvedt Effect refers to the relative motion between the Earth and the Moon which would be observed if the graviational self-energy of a body contributes to its gravitational mass but not its inertial mass. ... A star system or stellar system is a small number of stars that orbit each other,[1] bound by gravitational attraction. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... Animation of the dispersion of light as it travels through a triangular prism. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ... Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... According to the Big Bang theory, the universe originated in an infinitely dense and physically paradoxical singularity. ... The Hubble Space Telescope (HST; also known colloquially as the Hubble or just Hubble) is a space telescope that was carried into Earth orbit by the Space Shuttle in April 1990. ... The Cosmic Background Explorer (COBE), also referred to as Explorer 66, was the first satellite built dedicated to cosmology. ... Accelerating universe is a term for the idea that our universe is undergoing divergent rapid expansion. ... This box:      This article is about scientific estimates of the age of the universe. ... In quantum physics, a quantum fluctuation is the temporary change in the amount of energy in a point in space, arising from Werner Heisenbergs uncertainty principle. ... In physical cosmology, cosmic inflation is the idea that the nascent universe passed through a phase of exponential expansion that was driven by a negative-pressure vacuum energy density. ... The flatness problem is a cosmological problem with the Big Bang theory, which is solved by hypothesising an inflationary universe. ... This article or section does not cite its references or sources. ... ROSAT image of X-ray fluorescence of, and occultation of the X-ray background by, the Moon. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... For other uses, see Black hole (disambiguation). ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... This article does not cite its references or sources. ... This article is about the astronomical object. ... For other uses, see Dark matter (disambiguation). ... In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. ...


Subfield of astronomy for specific astronomical objects

Solar astronomy

Main article: Sun

The most frequently studied star is the Sun, a typical main-sequence dwarf star of stellar class G2 V, and about 4.6 Gyr in age. The Sun is not considered a variable star, but it does undergo periodic changes in activity known as the sunspot cycle. This is an 11-year fluctuation in sunspot numbers. Sunspots are regions of lower-than- average temperatures that are associated with intense magnetic activity.[23] Sol redirects here. ... Sol redirects here. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... This article or section contains a plot summary that is overly long or excessively detailed. ... 400 year sunspot history A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings, and intense magnetic activity. ... For other uses, see Sunspot (disambiguation). ...

An ultraviolet image of the Sun's active photosphere as viewed by the TRACE space telescope. NASA photo.
An ultraviolet image of the Sun's active photosphere as viewed by the TRACE space telescope. NASA photo.

The Sun has steadily increased in luminosity over the course of its life, increasing by 40% since it first became a main-sequence star. The Sun has also undergone periodic changes in luminosity that can have a significant impact on the Earth.[24] The Maunder minimum, for example, is believed to have caused the Little Ice Age phenomenon during the Middle Ages.[25] Image File history File links Download high-resolution version (1500x1500, 831 KB) Summary Transition Region and Coronal Explorer (TRACE), Stanford-Lockheed Institute for Space Research, NASA Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Astronomy ... Image File history File links Download high-resolution version (1500x1500, 831 KB) Summary Transition Region and Coronal Explorer (TRACE), Stanford-Lockheed Institute for Space Research, NASA Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Astronomy ... For other uses, see Ultraviolet (disambiguation). ... Solar disk redirects here. ... Look up Trace in Wiktionary, the free dictionary. ... For other uses, see NASA (disambiguation). ... The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ... The Little Ice Age (LIA) was a period of cooling occurring after a warmer era known as the Medieval climate optimum. ... The Middle Ages formed the middle period in a traditional schematic division of European history into three ages: the classical civilization of Antiquity, the Middle Ages, and modern times, beginning with the Renaissance. ...


The visible outer surface of the Sun is called the photosphere. Above this layer is a thin region known as the chromosphere. This is surrounded by a transition region of rapidly increasing temperatures, then by the super-heated corona. Solar disk redirects here. ... The chromosphere (literally, color sphere) is a thin layer of the Suns atmosphere just above the photosphere, roughly 10,000 kilometers deep (approximating to, if a little less than, the diameter of the Earth). ... This article is about the astronomical term. ...


At the center of the Sun is the core region, a volume of sufficient temperature and pressure for nuclear fusion to occur. Above the core is the radiation zone, where the plasma conveys the energy flux by means of radiation. The outer layers form a convection zone where the gas material transports energy primarily through physical displacement of the gas. It is believed that this convection zone creates the magnetic activity that generates sun spots.[23] The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... The radiation zone is the middle zone in the suns interior. ... The convection zone is a region of a stars interior where energy is transferred toward the surface by convection currents, rather than energetic photons. ...


A solar wind of plasma particles constantly streams outward from the Sun until it reaches the heliopause. This solar wind interacts with the magnetosphere of the Earth to create the Van Allen radiation belts, as well as the aurora where the lines of the Earth's magnetic field descend into the atmosphere.[26] The heliopause is the boundary between the heliosphere and the interstellar medium outside the solar system. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... Van Allen radiation belts The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field. ... The Aurora Borealis, or Northern Lights, shines above Bear Lake Aurora Borealis as seen over Canada at 11,000m (36,000 feet) Red and green Aurora in Fairbanks, Alaska Aurora Borealis redirects here. ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... Air redirects here. ...


Planetary science

This astronomical field examines the assemblage of planets, moons, dwarf planets, comets, asteroids, and other bodies orbiting the Sun, as well as extrasolar planets. The solar system has been relatively well-studied, initially through telescopes and then later by spacecraft. This has provided a good overall understanding of the formation and evolution of this planetary system, although many new discoveries are still being made.[27] Planetary science, also known as planetology or planetary astronomy, is the science of planets, or planetary systems, and the solar system. ... Astrogeology is the scientific discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. ... This article is about the astronomical term. ... A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. ... Artists impression of Pluto (background) and Charon (foreground). ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... For other uses, see Asteroid (disambiguation). ... This article is about the Solar System. ...

The black spot at the top is a dust devil climbing a crater wall on Mars. This moving, swirling column of Martian atmosphere (comparable to a terrestrial tornado) created the long, dark streak. NASA image.
The black spot at the top is a dust devil climbing a crater wall on Mars. This moving, swirling column of Martian atmosphere (comparable to a terrestrial tornado) created the long, dark streak. NASA image.

The solar system is subdivided into the inner planets, the asteroid belt, and the outer planets. The inner terrestrial planets consist of Mercury, Venus, Earth, and Mars. The outer gas giant planets are Jupiter, Saturn, Uranus and Neptune.[28] Beyond Neptune lie the Kuiper Belt, and finally the Oort Cloud, which may extend as far as a light-year. A dust devil on Mars Credit: Malin Space Science Systems, MGS, JPL, NASA For more copyright info, see also: [1] [2] Source http://antwrp. ... A dust devil on Mars Credit: Malin Space Science Systems, MGS, JPL, NASA For more copyright info, see also: [1] [2] Source http://antwrp. ... A dust devil in the Mojave Desert. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Mars, the fourth planet from the Sun, has a very different atmosphere from that of Earth. ... This article is about the weather phenomenon. ... For other uses, see NASA (disambiguation). ... For other uses, see Asteroid (disambiguation). ... The inner planets, Mercury, Venus, Earth, and Mars, their sizes to scale. ... This article is about the planet. ... For other uses, see Venus (disambiguation). ... This article is about Earth as a planet. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... This article does not cite any references or sources. ... For other uses, see Jupiter (disambiguation). ... This article is about the planet. ... For other uses, see Uranus (disambiguation). ... For other uses, see Neptune (disambiguation). ... The Kuiper belt, derived from data from the Minor Planet Center. ... Artists rendering of the Oort cloud and the Kuiper Belt. ...


The planets were formed by a protoplanetary disk that surrounded the early Sun. Through a process that included gravitational attraction, collision, and accretion, the disk formed clumps of matter that, with time, became protoplanets. The radiation pressure of the solar wind then expelled most of the unaccreted matter, and only those planets with sufficient mass retained their gaseous atmosphere. The planets continued to sweep up, or eject, the remaining matter during a period of intense bombardment, evidenced by the many impact craters on the Moon. During this period, some of the protoplanets may have collided, the leading hypothesis for how the Moon was formed.[29] A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Tycho crater on Earths moon. ... The Big Splash redirects here. ...


Once a planet reaches sufficient mass, the materials with different densities segregate within, during planetary differentiation. This process can form a stony or metallic core, surrounded by a mantle and an outer surface. The core may include solid and liquid regions, and some planetary cores generate their own magnetic field, which can protect their atmospheres from solar wind stripping.[30] In cosmogony, planetary differentiation is a process by which the denser portions of a planet will sink to the center; while less dense materials rise to the surface. ... For the indie-pop band, see The Magnetic Fields. ...


A planet or moon's interior heat is produced from the collisions that created the body, radioactive materials (e.g. uranium, thorium, and 26Al), or tidal heating. Some planets and moons accumulate enough heat to drive geologic processes such as volcanism and tectonics. Those that accumulate or retain an atmosphere can also undergo surface erosion from wind or water. Smaller bodies, without tidal heating, cool more quickly; and their geological activity ceases with the exception of impact cratering.[31] This article is about the chemical element. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight 232. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... It has been suggested that Tidal friction be merged into this article or section. ... This article is about volcanoes in geology. ... Atmospheres redirects here. ... For morphological image processing operations, see Erosion (morphology). ...


Stellar astronomy

The Ant planetary nebula. Ejecting gas from the dying central star shows symmetrical patterns unlike the chaotic patterns of ordinary explosions.
The Ant planetary nebula. Ejecting gas from the dying central star shows symmetrical patterns unlike the chaotic patterns of ordinary explosions.
Main article: Star

The study of stars and stellar evolution is fundamental to our understanding of the universe. The astrophysics of stars has been determined through observation and theoretical understanding; and from computer simulations of the interior. Planetary Nebula Mz3, the Ant Nebula. ... This article is about the astronomical object. ... This article is about the astronomical object. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ...


Star formation occurs in dense regions of dust and gas, known as giant molecular clouds. When destabilized, cloud fragments can collapse under the influence of gravity, to form a protostar. A sufficiently dense, and hot, core region will trigger nuclear fusion, thus creating a main-sequence star.[32] Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... Dark Nebula Dark Nebula (Dark Zero in the original Japanese version) is a fictional character in the Kirby series of video games for Nintendo. ... A Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve along which the majority of stars are located. ...


Almost all elements heavier than hydrogen and helium were created inside the cores of stars. This article is about the chemistry of hydrogen. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ...


The characteristics of the resulting star depend primarily upon its starting mass. The more massive the star, the greater its luminosity, and the more rapidly it expends the hydrogen fuel in its core. Over time, this hydrogen fuel is completely converted into helium, and the star begins to evolve. The fusion of helium requires a higher core temperature, so that the star both expands in size, and increases in core density. The resulting red giant enjoys a brief life span, before the helium fuel is in turn consumed. Very massive stars can also undergo a series of decreasing evolutionary phases, as they fuse increasingly heavier elements. Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ... According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ...


The final fate of the star depends on its mass, with stars of mass greater than about eight times the Sun becoming core collapse supernovae; while smaller stars form planetary nebulae, and evolve into white dwarfs. The remnant of a supernova is a dense neutron star, or, if the stellar mass was at least three times that of the Sun, a black hole.[33] Close binary stars can follow more complex evolutionary paths, such as mass transfer onto a white dwarf companion that can potentially cause a supernova. Planetary nebulae and supernovae are necessary for the distribution of metals to the interstellar medium; without them, all new stars (and their planetary systems) would be formed from hydrogen and helium alone. Sol redirects here. ... For other uses, see Supernova (disambiguation). ... NGC 6543, The Cats Eye Nebula NGC 6853, The Dumbbell Nebula A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. ... This article or section does not adequately cite its references or sources. ... For the story by Larry Niven, see Neutron Star (story). ... For other uses, see Black hole (disambiguation). ... The globular cluster M80. ...


Galactic astronomy

Main article: Galactic astronomy
Observed structure of the Milky Way's spiral arms
Observed structure of the Milky Way's spiral arms

Our solar system orbits within the Milky Way, a barred spiral galaxy that is a prominent member of the Local Group of galaxies. It is a rotating mass of gas, dust, stars and other objects, held together by mutual gravitational attraction. As the Earth is located within the dusty outer arms, there are large portions of the Milky Way that are obscured from view. Galactic astronomy is the study of galaxies, their formation, structure, components, dynamics, interactions, and the range of forms they take. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... This article is about the Solar System. ... For other uses, see Milky Way (disambiguation). ... NGC 1300, viewed nearly face-on. ... A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ...


In the center of the Milky Way is the core, a bar-shaped bulge with what is believed to be a supermassive black hole at the center. This is surrounded by four primary arms that spiral from the core. This is a region of active star formation that contains many younger, population II stars. The disk is surrounded by a spheroid halo of older, population I stars, as well as relatively dense concentrations of stars known as globular clusters.[34][35] Top: artists conception of a supermassive black hole tearing apart a star. ... Stars observed in our galaxy appear to group into two general types called Population I and Population II. (A hypothetical third group, Population III, does not occur in our galaxy. ... Spiral galaxies have a typical structure related to their history. ... Stars can be grouped into two general types called Population I and Population II. The criteria for classification include space velocity, location in the galaxy, age, chemical composition, and differences in distribution on the Hertzsprung-Russell diagram. ... The Globular Cluster M80 in the constellation Scorpius is located about 28,000 light years from the Sun and contains hundreds of thousands of stars. ...


Between the stars lies the interstellar medium, a region of sparse matter. In the densest regions, molecular clouds of molecular hydrogen and other elements create star-forming regions. These begin as irregular dark nebulae, which concentrate and collapse (in volumes determined by the Jeans length) to form compact protostars.[36] The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... A molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2). ... This article is about the chemistry of hydrogen. ... Dark Nebula Dark Nebula (Dark Zero in the original Japanese version) is a fictional character in the Kirby series of video games for Nintendo. ... The Jeans Length is the oscillation wavelength below which stable oscillations rather than gravitational collapse will occur. ...


As the more massive stars appear, they transform the cloud into an H II region of glowing gas and plasma. The stellar wind and supernova explosions from these stars eventually serve to disperse the cloud, often leaving behind one or more young open clusters of stars. These clusters gradually disperse, and the stars join the population of the Milky Way. NGC 604, a giant H II region in the Triangulum Galaxy. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Galactic cluster redirects here. ...


Kinematic studies of matter in the Milky Way and other galaxies have demonstrated that there is more mass than can be accounted for by visible matter. A dark matter halo appears to dominate the mass, although the nature of this dark matter remains undetermined.[37] Beyond the visible, inner portion of the galactic halo lies a much larger region, known as the dark matter halo which contains large amounts of dark matter. ...


Extragalactic astronomy

The study of objects outside of our galaxy is a branch of astronomy concerned with the formation and evolution of Galaxies; their morphology and classification; and the examination of active galaxies, and the groups and clusters of galaxies. The latter is important for the understanding of the large-scale structure of the cosmos. Extragalactic astronomy is the branch of astronomy concerned with objects outside our own Milky Way Galaxy (the study of all astronomical objects which are not covered by galactic astronomy). ... In astrophysics, the questions of galaxy formation and evolution are: How, from a homogeneous universe, did we obtain the very heterogeneous one we live in? How did galaxies form? How do galaxies change over time? A spectacular head-on collision between two galaxies is seen in this NASA Hubble Space... Astronomers classify galaxies based on their overall shape (elliptical, spiral or barred spiral) and further by the specific properties of the individual galaxy (for example degree of ellipse, number of spirals or definition of bar). ... An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... The galaxies of HCG 87, about four hundred million light-years distant. ... Astronomy and cosmology examine the universe to understand the large-scale structure of the cosmos. ...

This image shows several blue, loop-shaped objects that are multiple images of the same galaxy, duplicated by the gravitational lens effect of the cluster of yellow galaxies near the middle of the photograph. The lens is produced by the cluster's gravitational field that bends light to magnify and distort the image of a more distant object.
This image shows several blue, loop-shaped objects that are multiple images of the same galaxy, duplicated by the gravitational lens effect of the cluster of yellow galaxies near the middle of the photograph. The lens is produced by the cluster's gravitational field that bends light to magnify and distort the image of a more distant object.

Most galaxies are organized into distinct shapes that allow for classification schemes. They are commonly divided into spiral, elliptical and Irregular galaxies.[38] Download high resolution version (750x958, 92 KB)Gravitational lensing This Hubble Space Telescope image shows several blue, loop-shaped objects that actually are multiple images of the same galaxy. ... Download high resolution version (750x958, 92 KB)Gravitational lensing This Hubble Space Telescope image shows several blue, loop-shaped objects that actually are multiple images of the same galaxy. ... This article or section is in need of attention from an expert on the subject. ... An example of a spiral galaxy, the Pinwheel Galaxy (also known as Messier 101 or NGC 5457) A spiral galaxy is a galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae”[1] and, as... The giant elliptical galaxy ESO 325-G004. ... This article or section does not adequately cite its references or sources. ...


As the name suggests, an elliptical galaxy has the cross-sectional shape of an ellipse. The stars move along random orbits with no preferred direction. These galaxies contain little or no interstellar dust; few star-forming regions; and generally older stars. Elliptical galaxies are more commonly found at the core of galactic clusters, and may be formed through mergers of large galaxies. For other uses, see Ellipse (disambiguation). ... Random redirects here. ...


A spiral galaxy is organized into a flat, rotating disk, usually with a prominent bulge or bar at the center, and trailing bright arms that spiral outward. The arms are dusty regions of star formation where massive young stars produce a blue tint. Spiral galaxies are typically surrounded by a halo of older stars. Both the Milky Way and the Andromeda Galaxy are spiral galaxies. For other uses, see Milky Way (disambiguation). ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ...


Irregular galaxies are chaotic in appearance, and are neither spiral nor elliptical. About a quarter of all galaxies are irregular, and the peculiar shapes of such galaxies may be the result of gravitational interaction.


An active galaxy is a formation that is emitting a significant amount of its energy from a source other than stars, dust and gas; and is powered by a compact region at the core, usually thought to be a super-massive black hole that is emitting radiation from in-falling material.


A radio galaxy is an active galaxy that is very luminous in the radio portion of the spectrum, and is emitting immense plumes or lobes of gas. Active galaxies that emit high-energy radiation include Seyfert galaxies, Quasars, and Blazars. Quasars are believed to be the most consistently luminous objects in the known universe.[39] An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... Seyfert galaxies are spiral or irregular galaxies containing an extremely bright nucleus, most likely caused by a supermassive black hole, that can sometimes outshine the surrounding galaxy. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... A blazar is a very compact and highly variable energy source associated with a supermassive black hole at the center of a host galaxy. ...


The large-scale structure of the cosmos is represented by groups and clusters of galaxies. This structure is organized in a hierarchy of groupings, with the largest being the superclusters. The collective matter is formed into filaments and walls, leaving large voids in between.[40] Astronomy and cosmology examine the universe to understand the large-scale structure of the cosmos. ... Superclusters are large groupings of smaller galaxy groups and clusters, and are among the largest structures of the cosmos. ... In astronomy, filaments are one of the largest known structures in the Universe, thread-like structures with a typical length of 70 to 150 megaparsec that form the boundaries between large voids in the universe. ... In astronomy, voids are the empty spaces between filaments, the largest-scale structures in the Universe that contain very few, or no, galaxies. ...


Cosmology

Main article: Physical cosmology

Cosmology (from the Greek κοσμος "world, universe" and λογος "word, study") could be considered the study of the universe as a whole. This article is about the physics subject. ...


Observations of the large-scale structure of the universe, a branch known as physical cosmology, have provided a deep understanding of the formation and evolution of the cosmos. Fundamental to modern cosmology is the well-accepted theory of the big bang, wherein our universe began at a single point in time, and thereafter expanded over the course of 13.7 Gyr to its present condition. The concept of the big bang can be traced back to the discovery of the microwave background radiation in 1965. To meet Wikipedias quality standards, this article or section may require cleanup. ... For other uses, see Universe (disambiguation). ... This article is about the physics subject. ... For other uses, see Big Bang (disambiguation). ... This box:      The metric expansion of space is a key part of sciences current understanding of the universe, whereby spacetime itself is described by a metric which changes over time in such a way that the spatial dimensions grow or stretch as the universe gets older. ... CMB redirects here. ...


In the course of this expansion, the universe underwent several evolutionary stages. In the very early moments, it is theorized that the universe experienced a very rapid cosmic inflation, which homogenized the starting conditions. Thereafter, nucleosynthesis produced the elemental abundance of the early universe. (See also nucleocosmochronology.) In physical cosmology, cosmic inflation is the idea that the nascent universe passed through a phase of exponential expansion that was driven by a negative-pressure vacuum energy density. ... In cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. ... Nucleocosmochronology is the study of the evolution of the Universe with respect to the four fundamental processes of Nucleosynthesis. ...


When the first atoms formed, space became transparent to radiation, releasing the energy viewed today as the microwave background radiation. The expanding universe then underwent a Dark Age due to the lack of stellar energy sources.[41]


A hierarchical structure of matter began to form from minute variations in the mass density. Matter accumulated in the densest regions, forming clouds of gas and the earliest stars. These massive stars triggered the reionization process and are believed to have created many of the heavy elements in the early universe. Population III stars are a hypothetical population of extremely massive stars that are believed to have been formed in the early universe. ... Schematic timeline of the universe, depicting reionizations place in cosmic history. ...


Gravitational aggregations clustered into filaments, leaving voids in the gaps. Gradually, organizations of gas and dust merged to form the first primitive galaxies. Over time, these pulled in more matter, and were often organized into groups and clusters of galaxies, then into larger-scale superclusters.[42] The galaxies of HCG 87, about four hundred million light-years distant. ...


Fundamental to the structure of the universe is the existence of dark matter and dark energy. These are now thought to be the dominant components, forming 96% of the density of the universe. For this reason, much effort is expended in trying to understand the physics of these components.[43] For other uses, see Dark matter (disambiguation). ... In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. ...


Interdisciplinary studies

Astronomy and astrophysics have developed significant interdisciplinary links with other major scientific fields. These include:

The DNA structure might not be the only nucleic acid in the universe capable of supporting life[1] Astrobiology (from Greek: ἀστρο, astro, constellation; βίος, bios, life; and λόγος, logos, knowledge) is the interdisciplinary study of life in space, combining aspects of astronomy, biology and geology. ... The sun rising over Stonehenge at the 2005 Summer Solstice. ... For referencing in Wikipedia, see Wikipedia:Citing sources. ... This article is about the social science. ... Astrochemistry is the study of the chemicals found in outer space, usually in molecular gas clouds, and their formation, interaction and destruction. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... A molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2). ... Cosmochemistry is concerned with the origin and development of the elements and their isotopes in the universe. ... This article is about the Solar System. ... For other uses, see Isotope (disambiguation). ...

Amateur astronomy

Main article: Amateur astronomy
Amateur astronomers can build their own equipment, and can hold star parties and gatherings, such as Stellafane.
Amateur astronomers can build their own equipment, and can hold star parties and gatherings, such as Stellafane.

Collectively, amateur astronomers observe a variety of celestial objects and phenomena sometimes with equipment that they build themselves. Common targets of amateur astronomers include the Moon, planets, stars, comets, meteor showers, and a variety of deep-sky objects such as star clusters, galaxies, and nebulae. One branch of amateur astronomy, amateur astrophotography, involves the taking of photos of the night sky. Many amateurs like to specialize in the observation of particular objects, types of objects, or types of events which interest them.[44][45] It has been suggested that this article or section be merged with Skygazing. ... Image File history File linksMetadata Download high resolution version (540x700, 104 KB) Summary Description: A large trailer mounted Newtonian reflector on display at Stellafane in the early 1980s. ... Image File history File linksMetadata Download high resolution version (540x700, 104 KB) Summary Description: A large trailer mounted Newtonian reflector on display at Stellafane in the early 1980s. ... The Stellafane Convention is a gathering of amateur telescope makers and amateur astronomers (star party) every year in Springfield, Vermont, conducted by the Springfield Telescope Makers. ... A 22 Newtonian reflector sits in front of the clubhouse at Stellafane, home of the Springfield Telescope Makers The field of amateur telescope making is considered an offshoot of the amateur astronomy community. ... Deep sky object (DSO) is a term used often in amateur astronomy to denote objects in the night sky other than solar system objects (such as planets, comets and asteroids), single stars and multiple star systems. ... Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies. ...


Most amateurs work at visible wavelengths, but a small minority experiment with wavelengths outside the visible spectrum. This includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes. The pioneer of amateur radio astronomy was Karl Jansky who started observing the sky at radio wavelengths in the 1930s. A number of amateur astronomers use either homemade telescopes or use radio telescopes which were originally built for astronomy research but which are now available to amateurs (e.g. the One-Mile Telescope).[46][47] Karl Guthe Jansky (October 22, 1905 – February 14, 1950), was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way. ... One antenna from the One-Mile Telescope The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO) was completed by the Radio Astronomy Group of Cambridge University in 1964. ...


Amateur astronomers continue to make scientific contributions to the field of astronomy. Indeed, it is one of the few scientific disciplines where amateurs can still make significant contributions. Amateurs can make occultation measurements that are used to refine the orbits of minor planets. They can also discover comets, and perform regular observations of variable stars. Improvements in digital technology have allowed amateurs to make impressive advances in the field of astrophotography.[48][49][50]


Major questions in astronomy

See also: Unsolved problems in physics

Although the scientific discipline of astronomy has made tremendous strides in understanding the nature of the universe and its contents, there remain some important unanswered questions. Answers to these may require the construction of new ground- and space-based instruments, and possibly new developments in theoretical and experimental physics. This is a list of some of the unsolved problems in physics. ...

  • What is the origin of the stellar mass spectrum? That is, why do astronomers observe the same distribution of stellar masses—the initial mass function—apparently regardless of the initial conditions?[51] A deeper understanding of the formation of stars and planets is needed.
  • Is there other life in the Universe? Especially, is there other intelligent life? If so, what is the explanation for the Fermi paradox? The existence of life elsewhere has important scientific and philosophical implications.[52][53]
  • What is the nature of dark matter and dark energy? These dominate the evolution and fate of the cosmos, yet we are still uncertain about their true natures.[54]
  • Why did the universe come to be? Why, for example, are the physical constants so finely tuned that they permit the existence of life? Could they be the result of cosmological natural selection? What caused the cosmic inflation that produced our homogeneous universe?[55]
  • What will be the ultimate fate of the universe?[56]

The initial mass function (IMF) is a relationship that specifies the mass distribution of a newly formed stellar population, by giving the number of stars of mass per pc3 and per unit mass. ... Green people redirects here. ... A graphical representation of the Arecibo message - Humanitys first attempt to use radio waves to communicate its existence to alien civilizations The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for or contact with... The deepest visible-light image of the cosmos. ... The fecund universes theory of cosmology advanced by Lee Smolin suggests that the rules of biology apply on the grandest scales, and is often referred to as cosmological natural selection. Smolin summarized the idea in a book aimed at a lay audience called The Life of the Cosmos (ISBN 0... In physical cosmology, cosmic inflation is the idea that the nascent universe passed through a phase of exponential expansion that was driven by a negative-pressure vacuum energy density. ... This box:      The ultimate fate of the universe is a topic in physical cosmology. ...

See also

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Astronomy

Image File history File links This is a lossless scalable vector image. ... Wikiversity logo Wikiversity is a Wikimedia Foundation beta project[1], devoted to learning materials and activities, located at www. ... Image File history File links This is a lossless scalable vector image. ... Wikiquote is one of a family of wiki-based projects run by the Wikimedia Foundation, running on MediaWiki software. ...

Lists

Astronomy is the science of celestial objects (, stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere. ... This article needs cleanup. ...

Related articles

This article needs additional references or sources for verification. ... Galileo is often referred to as the Father of Modern Astronomy. ... The NASA Astrophyiscs Data System (also known as ADS, adswww, or adsabs) is an online database of all peer reviewed and some submitted astronomy articles. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... There are very few or no other articles that link to this one. ... This article is about the Solar System. ... Space exploration is the physical exploration of outer space, both by human spaceflights and by robotic spacecraft. ... Space science is an all-encompassing term that describes most all of the various science fields that are concerned with the study of the Universe, generally also meaning excluding the Earth and outside of the Earths atmosphere. Originally, all of these fields were considered part of astronomy. ...

References

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Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... Project Gutenberg, abbreviated as PG, is a volunteer effort to digitize, archive and distribute cultural works. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Also see: 2002 (number). ... is the 226th day of the year (227th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 229th day of the year (230th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 234th day of the year (235th in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... is the 87th day of the year (88th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 233rd day of the year (234th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 222nd day of the year (223rd in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... is the 208th day of the year (209th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 223rd day of the year (224th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 254th day of the year (255th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 341st day of the year (342nd in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 271st day of the year (272nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 234th day of the year (235th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... {| style=float:right; |- | |- | |} is the 235th day of the year (236th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 131st day of the year (132nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 233rd day of the year (234th in leap years) in the Gregorian calendar. ... For the band, see 1997 (band). ... is the 125th day of the year (126th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 223rd day of the year (224th in leap years) in the Gregorian calendar. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... is the 111th day of the year (112th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... {| style=float:right; |- | |- | |} is the 235th day of the year (236th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 159th day of the year (160th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 213th day of the year (214th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 194th day of the year (195th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 222nd day of the year (223rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 251st day of the year (252nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 38th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 236th day of the year (237th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 148th day of the year (149th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 224th day of the year (225th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 224th day of the year (225th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 224th day of the year (225th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 224th day of the year (225th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 148th day of the year (149th in leap years) in the Gregorian calendar. ...

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  • Celestia Motherlode Educational site for Astronomical journeys through space
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  • Astronomy - A History - G. Forbes - 1909 (eLibrary Project - eLib Text)
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  • Prof. Sir Harry Kroto, NL, Astrophysical Chemistry Lecture Series. 8 Freeview Lectures provided by the Vega Science Trust.
  • Core books and core journals in Astronomy, from the Smithsonian/NASA Astrophysics Data System
Wikipedia does not have an article with this exact name. ... Image File history File links Wikibooks-logo. ... Image File history File links Wikiquote-logo. ... Image File history File links Wikisource-logo. ... Image File history File links Commons-logo. ... Image File history File links WikiNews-Logo. ... Image File history File links Wikiversity-logo-Snorky. ... The NASA Astrophyiscs Data System (also known as ADS, adswww, or adsabs) is an online database of all peer reviewed and some submitted astronomy articles. ... Spiral Galaxy ESO 269-57 Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature, and chemical composition) of celestial objects such as stars, galaxies, and the interstellar medium, as well as their interactions. ... This article is about the physics subject. ... Extragalactic astronomy is the branch of astronomy concerned with objects outside our own Milky Way Galaxy (the study of all astronomical objects which are not covered by galactic astronomy). ... Galactic astronomy is the study of galaxies, their formation, structure, components, dynamics, interactions, and the range of forms they take. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... For other uses, see Astronomy (disambiguation). ... Planetary science, also known as planetology or planetary astronomy, is the science of planets, or planetary systems, and the solar system. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... Astrochemistry is the study of the chemicals found in outer space, usually in molecular gas clouds, and their formation, interaction and destruction. ... The DNA structure might not be the only nucleic acid in the universe capable of supporting life[1] Astrobiology (from Greek: ἀστρο, astro, constellation; βίος, bios, life; and λόγος, logos, knowledge) is the interdisciplinary study of life in space, combining aspects of astronomy, biology and geology. ...

  Results from FactBites:
 
astronomy: Definition and Much More From Answers.com (7865 words)
Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, "law of the stars") is the science of celestial objects (e.g., stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (e.g., auroras and cosmic background radiation).
Although classical astronomy was one of the seven key subjects taught at medieval universities in Europe, observational astronomy was mostly stagnant in medieval Europe until the XIII century, with astronomers and astrologers such as Johannes de Sacrobosco, in England, and Guido Bonatti from Forlì, in Italy.
One of the oldest fields in astronomy, and in all of science, is the measurement of the positions of celestial objects in the sky.
CATHOLIC ENCYCLOPEDIA: Astronomy (4523 words)
Descriptive astronomy, meanwhile took its rise from the invention of the telescope, and the facilities thus afforded for the close scrutiny of the denizens of the sky; while practical astronomy gained continually in refinement with the improvement of optical and mechanical arts.
But mathematical astronomy, grounded on the law of gravitation keeps its place apart, though depending for the perfecting of its theories and the widening of its scope upon advances along the old, and explorations in new, directions.
Greek astronomy was embodied in Ptolerny's "Almagest" (the name is of mixed Greek and Arabic derivation), composed at Alexandria about the middle of the second century A. It was based upon the geocentric principle.
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