'astronomy: terms used in astronomy'

achondritea rare stony meteorite that consists mainly of silicate minerals and has the texture of igneous rock but contains no chondrules aerolitea stony meteorite consisting of silicate minerals aerospacethe atmosphere and space beyond aerospherethe entire atmosphere surrounding the earth albedothe ratio of the intensity of light reflected from an object, such as a planet, to that of the light it receives from the sunalmucantar or almacantaran instrument for measuring altitudes altitudethe angular distance of a celestial body from the horizon measured along the vertical circle passing through the body analemmaa graduated scale shaped like a figure eight that indicates the daily declination of the sunannular eclipsean eclipse of the sun in which the moon does not cover the entire disc of the sun, so that a ring of sunlight surrounds the shadow of the moon antheliona faint halo sometimes seen in polar or high altitude regions around the shadow of an object cast onto a thick cloud bank or fog aphelionthe point in its orbit when a planet or comet is at its greatest distance from the sun apocynthionthe point at which a spacecraft in lunar orbit is farthest from the moon apolunethe point in a lunar orbit when a spacecraft is at its greatest distance from the moon appulsea very close approach of two celestial bodies so that they are in conjunction but no eclipse or occultation occurs apoapsisthe point in an elliptical orbit which is farthest from the object being orbitedapsis or apseeither of two points lying at the extremities of an eccentric orbit of a planet, satellite, etc, such as the aphelion and perihelion of a planet or the apogee and perigee of the moon. The line of apsides connects two such points and is the principal axis of the orbit asteroidany of numerous small celestial bodies that move around the sun mainly between the orbits of Mars and Jupiter. Their diameters range from 930 kilometres (Ceres) to less than one kilometre asteroid beltthe concentrations of asteroids that move around the sun mainly between the orbits of Mars and Jupiter astroblemea mark on the earth's surface, usually circular, formed by a large ancient meteorite impact atmospherethe gaseous envelope surrounding the earth or any other celestial bodyaureola or aureoleanother name for coronaauroraan atmospheric phenomenon consisting of bands, curtains, or streamers of light, usually green, red, or yellow, that move across the sky in polar regions. It is caused by collisions between air molecules and charged particles from the sun that are trapped in the earth's magnetic fieldaurora australisthe aurora seen around the South Pole aurora borealisthe aurora seen around the North Pole azimuththe angular distance usually measured clockwise from the north point of the horizon to the intersection with the horizon of the vertical circle passing through a celestial body barycentrea centre of mass, esp of the earth-moon system or the solar system basinbinary stara double star system comprising two stars orbiting around their common centre of mass. A visual binary can be seen through a telescope. A spectroscopic binary can only be observed by the spectroscopic Doppler shift as each star moves towards or away from the earth black dropblack holean object in space so dense that its escape velocity exceeds the speed of light blue stragglerbolidea large exceptionally bright meteor that often explodes brown dwarfa type of celestial body midway in mass between a large planet and a small star burstcataclysmic variableCepheid variableany of a class of variable stars with regular cycles of variations in luminosity (most ranging from three to fifty days). There is a relationship between the periods of variation and the absolute magnitudes, which is used for measuring the distance of such stars Chandrasekhar limitthe upper limit to the mass of a white dwarf, equal to 1.44 solar masses. A star having a mass above this limit will continue to collapse to form a neutron star chemospherea rare name for thermospherechondritea stony meteorite consisting mainly of silicate minerals in the form of chondrules chromospherea gaseous layer of the sun's atmosphere extending from the photosphere to the corona and visible during a total eclipse of the sun circumlunararound or revolving around the mooncircumpolar(of a star or constellation) visible above the horizon at all times at a specified locality on the earth's surfacecircumsolarsurrounding or rotating around the suncircumstellarsurrounding, or revolving around a starcislunarof or relating to the space between the earth and the moonclusteran aggregation of stars or galaxies moving together through space collapsara collapsed star, either a white dwarf, neutron star, or black hole colour indexthe difference between the apparent magnitude of a star measured in one standard waveband and in a longer standard waveband, indicating its colour and temperature colureeither of two great circles on the celestial sphere, one of which passes through the celestial poles and the equinoxes and the other through the poles and the solstices comathe luminous cloud surrounding the frozen solid nucleus in the head of a comet, formed by vaporization of part of the nucleus when the comet is close to the sun cometa celestial body that travels around the sun, usually in a highly elliptical orbit: thought to consist of a solid frozen nucleus part of which vaporizes on approaching the sun to form a gaseous luminous coma and a long luminous tail companionthe fainter of the two components of a double star conjunctionthe position of a planet or the moon when it is in line with the sun as seen from the earth. The inner planets are in inferior conjunction when the planet is between the earth and the sun and in superior conjunction when the sun lies between the earth and the planet constellationany of the 88 groups of stars as seen from the earth and the solar system, many of which were named by the ancient Greeks after animals, objects, or mythological persons cooordinate systemCopernican systemthe theory published in 1543 by Copernicus which stated that the earth and the planets rotated around the sun and which opposed the Ptolemaic system coronathe outermost region of the sun's atmosphere, visible as a faint halo during a solar eclipse cosmicof or relating to the whole universe; occurring or originating in outer space, esp as opposed to the vicinity of the earth, the solar system, or the local galaxycosmogonythe study of the origin and development of the universe or of a particular system in the universe, such as the solar system cosmologythe branch of astronomy concerned with the evolution and structure of the universe cratera similarly shaped depression formed by the impact of a meteorite or exploding bomb crescentthe curved shape of the moon in its first or last quarters crust the solid outer shell of the earth, with an average thickness of 30–35 km in continental regions and 5 km beneath the oceans, forming the upper part of the lithosphere and lying immediately above the mantle, from which it is separated by the Mohorovičić discontinuityculminationthe highest or lowest altitude attained by a heavenly body as it crosses the meridian cuspeither of the points of a crescent moon or of a satellite or inferior planet in a similar phase dwarfshort for dwarf stardwarf starany luminosity class V star, such as the sun, lying in the main sequence of the Hertzsprung-Russell diagramdynamicsthe branch of mechanics concerned with the forces that change or produce the motions of bodieseccentric situated away from the centre or the axisecospherethe planetary ecosystem, consisting of all living organisms and their environment effective temperatureejectamatter thrown out of a crater by an erupting volcano or during a meteorite impact ellipseelongationthe difference between the celestial longitude of the sun and that of a planet or the moonemersionthe reappearance of a celestial body after an eclipse or occultation ephemerisa table giving the future positions of a planet, comet, or satellite epocha precise date to which information, such as coordinates, relating to a celestial body is referredequatorthe great circle of the earth with a latitude of 0°, lying equidistant from the poles; dividing the N and S hemispheres escape velocitythe minimum velocity that a body must have in order to escape from the gravitational field of the earth or other celestial bodyequinox either of the two occasions, six months apart, when day and night are of equal lengthevectionirregularity in the moon's motion caused by perturbations of the sun and planetsevolved starexospherethe outermost layer of the earth's atmosphere. It extends from about 400 km above the earth's surface extinctionthe dimming of light from a celestial body as it passes through an absorbing or scattering medium, such as the earth's atmosphere or interstellar dust faculaany of the bright areas on the sun's surface, usually appearing just before a sunspot and subject to the same 11-year cycle farsidethe farthest side, esp the side of the Moon which faces away from the Earthfilamenta long structure of relatively cool material in the solar corona fireballanother name for bolideflareshort for solar flare flocculusa marking on the sun's surface or in its atmosphere, as seen on a spectroheliogram. It consists of calcium when lighter than the surroundings and of hydrogen when darker galactic centregalactic equatorthe great circle on the celestial sphere containing the galactic planegalactic rotationgalaxyany of a vast number of star systems held together by gravitational attraction in an asymmetric shape (an irregular galaxy) or, more usually, in a symmetrical shape (a regular galaxy), which is either a spiral or an ellipse giantshort for giant stargiant starany of a class of stars, such as Capella and Arcturus, that have swelled and brightened considerably as they approach the end of their life, their energy supply having changedgravitationthe force of attraction that bodies exert on one another as a result of their mass heliocentrichaving the sun at its centreheliospherethe region around the sun outside of which the sun's influence is negligible and interstellar space begins immersion or ingressthe disappearance of a celestial body prior to an eclipse or occultation inclinationthe angle between a line on a graph and the positive limb of the x-axis inequalitya departure from uniform orbital motioninertiathe tendency of a body to preserve its state of rest or uniform motion unless acted upon by an external forceinferior planeteither of the planets Mercury and Venus, whose orbits lie inside that of the earth inner planetany of the planets Mercury, Venus, earth, and Mars, whose orbits lie inside the asteroid belt insolationthe quantity of solar radiation falling upon a body or planet, esp per unit area interplanetaryof, relating to, or existing between planetsinterstellarconducted, or existing between two or more starsionospherea region of the earth's atmosphere, extending from about 60 kilometres to 1000 km above the earth's surface, in which there is a high concentration of free electrons formed as a result of ionizing radiation entering the atmosphere from space jeta long thin feature extending from an active galaxy and usually observed at radio wavelengths light yeara unit of distance used in astronomy, equal to the distance travelled by light in one year, i.e. 9.4607 × 1012 kilometres or 0.3066 parsecs limbthe edge of the apparent disc of the sun, a moon, or a planetlodestar or loadstara star, esp the North Star, used in navigation or astronomy as a point of reference luminositya measure of the radiant power emitted by a star lunarof or relating to the moonlunar eclipsethe total or partial obscuring of reflected light from a celestial body as a result of its passage through the shadow of another. A lunar eclipse occurs when the moon passes through the shadow of the earthmagnetospherethe region surrounding a planet, such as the earth, in which the behaviour of charged particles is controlled by the planet's magnetic fieldmagnitudethe apparent brightness of a celestial body expressed on a numerical scale on which bright stars have a low value. Values are measured by eye (visual magnitude) or more accurately by photometric or photographic methods, and range from –26.7 (the sun), through 1.5 (Sirius), down to about +30. Each integral value represents a brightness 2.512 times greater than the next highest integral value major planeta planet of the solar system, as opposed to an asteroid (minor planet) mareany of a large number of huge dry plains on the surface of the moon, visible as dark markings and once thought to be seas: Mare Imbrium (Sea of Showers); a similar area on the surface of Mars, such as Mare Sirenummassa physical quantity expressing the amount of matter in a body. It is a measure of a body's resistance to changes in velocity (inertial mass) and also of the force experienced in a gravitational field (gravitational mass): according to the theory of relativity, inertial and gravitational masses are equalmass lossmass transfermergermeridianone of the imaginary lines joining the north and south poles at right angles to the equator, designated by degrees of longitude from 0° at Greenwich to 180° meridian passagemesospherethe atmospheric layer lying between the stratosphere and the thermosphere, characterized by a rapid decrease in temperature with height metallicitymetal ratiometeora very small meteoroid that has entered the earth's atmosphere. Such objects have speeds approaching 70 kilometres per second meteoritea rocklike object consisting of the remains of a meteoroid that has fallen on earth. It may be stony (chondrite), iron, or stony iron (pallasite) meteoroidany of the small celestial bodies that are thought to orbit the sun, possibly as the remains of comets. When they enter the earth's atmosphere, they become visible as meteors meteoroid streammeteor showera transient rain of meteors, such as the Perseids, occurring at regular intervals and coming from a particular region in the sky. It is caused by the earth passing through a large number of meteoroids (a meteor swarm) missing massthe difference in mass in the universe between that observed to exist and that necessary for the closed universe modelmolecular clouda cool dense interstellar region composed of a wide variety of molecules, mainly hydrogen, plus some dust, in which stars are forming moonquakea light tremor of the moon, detected on the moon's surfacemoving clustermultiple stara system of three or more stars associated by gravitation nadirthe point on the celestial sphere directly below an observer and diametrically opposite the zenith naked singularityan infinitely dense point mass without a surrounding black hole nearsidenebulaany substance for use in an atomizer spray neutron stara star that has collapsed under its own gravity to a diameter of about 10 to 15 km. It is composed mostly of neutrons, has a mass of between 1.4 and about 3 times that of the sun, and a density in excess of 1017 kilograms per cubic metre new moonthe moon when it appears as a narrow waxing crescent nodeeither of the two points at which the orbit of a body intersects the plane of the ecliptic. When the body moves from the south to the north side of the ecliptic, it passes the ascending node; moving from the north to the south side, it passes the descending node north celestial polethe point of intersection of the earth's extended axis and the northern half of the celestial sphere, lying about 1° from Polarisnorthern hemispherethat half of the globe lying north of the equator northern lightsanother name for aurora borealisnorthinga north or positive declinationnorth polar distancenovaa variable star that undergoes a cataclysmic eruption, observed as a sudden large increase in brightness with a subsequent decline over months or years; it is a close binary system with one component a white dwarf nucleosynthesisthe formation of heavier elements from lighter elements by nuclear fusion in stars nucleusthe central portion in the head of a comet, consisting of small solid particles of ice and frozen gases, which vaporize on approaching the sun to form the coma and tail nutationa periodic variation in the precession of the earth's axis causing the earth's poles to oscillate about their mean position oblatenessthe state of having an oblate shapeobliquitythe angle between the plane of the earth's orbit and that of the celestial equator, equal to approximately 23° 27′ at present observatoryan institution or building specially designed and equipped for observing meteorological and astronomical phenomenaoccultationthe temporary disappearance of one celestial body as it moves out of sight behind another bodyoctantany of the eight parts into which the three planes containing the Cartesian coordinate axes divide space open clustera comparatively young, irregularly shaped group of stars, often numbering up to several hundred, and held together by mutual gravitation; usually found along the central plane of the Milky Way and other galaxiesoppositionthe position of an outer planet or the moon when it is in line or nearly in line with the earth as seen from the sun and is approximately at its nearest to the earth orbitthe curved path, usually elliptical, followed by a planet, satellite, comet, etc, in its motion around another celestial body under the influence of gravitation orbital elementsorbital velocitythe velocity required by a spacecraft, satellite, etc, to enter and maintain a given orbit oscillating universe theorythe theory that the universe is oscillating between periods of expansion and collapseouter planetany of the planets Jupiter, Saturn, Uranus, Neptune, and (formerly) Pluto, whose orbit lies outside the asteroid belt parallaxthe angle subtended at a celestial body, esp a star, by the radius of the earth's orbit. Annual or heliocentric parallax is the apparent displacement of a nearby star resulting from its observation from the earth. Diurnal or geocentric parallax results from the observation of a planet, the sun, or the moon from the surface of the earth partial eclipsean eclipse, esp of the sun, in which the body is only partially hiddenpenumbral eclipseperiapsisthe closest point to a central body reached by a body in orbit periastronthe point in the orbit of a body around a star when it is nearest to the star, esp applied to double-star systems percentreperigeethe point in its orbit around the earth when the moon or an artificial satellite is nearest the earth perihelionthe point in its orbit when a planet or comet is nearest the sun photospherethe visible surface of the sun, several hundred kilometres thickphysical librationplagesa bright patch in the sun's chromosphereplanetarya train of planetary gears planetary alignmentplanetary systemplanetesimalany of a number of small bodies formerly thought to have been drawn from the sun by the close passage of a star to the sun, eventually coalescing to form the planets planetoidanother name for asteroidplasmaspherepleriona filled-centre supernova remnant in which radiation is emitted by the centre as well as the shell polar axisthe fixed line in a system of polar coordinates from which the polar angle, θ, is measured anticlockwisepoleeither of the two antipodal points where the earth's axis of rotation meets the earth's surface precessionthe motion of a spinning body, such as a top, gyroscope, or planet, in which it wobbles so that the axis of rotation sweeps out a cone precession of the equinoxesthe slightly earlier occurrence of the equinoxes each year due to the slow continuous westward shift of the equinoctial points along the ecliptic by 50 seconds of arc per year. It is caused by the precession of the earth's axis around the ecliptic pole, with a period of 25 800 years primarya celestial body around which one or more specified secondary bodies orbit prominencean eruption of incandescent gas from the sun's surface that can reach an altitude of several hundred thousand kilometres. Prominences are visible during a total eclipse. When viewed in front of the brighter solar disc, they are called filaments proper motionthe very small continuous change in the direction of motion of a star relative to the sun. It is determined from its radial and tangential motion protogalaxya cloud of gas in the early stages of its evolution into a galaxy protoplaneta planet in its early stages of evolution by the process of accretionprotostara cloud of interstellar gas and dust that gradually collapses, forming a hot dense core, and evolves into a star once nuclear fusion can occur in the core Ptolemaic systemthe theory of planetary motion developed by Ptolemy from the hypotheses of earlier philosophers, stating that the earth lay at the centre of the universe with the sun, the moon, and the known planets revolving around it in complicated orbits. Beyond the largest of these orbits lay a sphere of fixed stars pulsating universepulsating variablequadraturea configuration in which two celestial bodies, usually the sun and the moon or a planet, form an angle of 90° with a third body, usually the earthquarterone fourth of the moon's period of revolution around the earth quasarany of a class of extragalactic objects that emit an immense amount of energy in the form of light, infrared radiation, etc, from a compact source. They are extremely distant and their energy generation is thought to involve a supermassive black hole located in the centre of a galaxy quasi-stellar objecta member of any of several classes of astronomical bodies, including quasars (strong radio sources) and quasi-stellar galaxies (no traceable radio emission), both of which have exceptionally large red shifts quiet(of the sun) exhibiting a very low number of sunspots, solar flares, and other surface phenomena; inactiveradiantthe point in space from which a meteor shower appears to emanate radio sourcea celestial object, such as a supernova remnant or quasar, that is a source of radio waves rayany of a number of bright streaks that radiate from the youngest lunar craters, such as Tycho; they are composed of crater ejecta not yet darkened, and extend considerable distances reciprocal massred gianta giant star towards the end of its life, with a relatively low temperature of 2000–4000 K, that emits red light red supergiantregoliththe layer of loose material covering the bedrock of the earth and moon, etc, comprising soil, sand, rock fragments, volcanic ash, glacial drift, etcretardationthe rate of decelerationrevolutionthe orbital motion of one body, such as a planet or satellite, around another ringan enclosed space, usually circular in shape, where circus acts are performed ring plainrisingdesignating or of the ascendantrotationthe spinning motion of a body, such as a planet, about an internal axisrupessarosa cycle of about 18 years 11 days (6585.32 days) in which eclipses of the sun and moon occur in the same sequence and at the same intervals as in the previous such cyclesatellitea celestial body orbiting around a planet or star Schwarzschild radiusthe radius of a sphere (Schwarzschild sphere) surrounding a non-rotating uncharged black hole, from within which no information can escape because of gravitational forces scintillationthe twinkling of stars or radio sources, caused by rapid changes in the density of the earth's atmosphere, the interplanetary medium, or the interstellar medium, producing uneven refraction of starlight secondarya celestial body that orbits around a specified primary body sextilean aspect or position of 60° between two planets or other celestial bodiesSeyfert galaxyany of a class of spiral galaxies having a very bright nucleus, possibly corresponding to an active period in the lives of all spiral galaxies shell stara type of star, usually of spectral type B to F, surrounded by a gaseous shell shepherd satellitesidereal timetime based upon the rotation of the earth with respect to the distant stars, the sidereal day being the unit of measurement singularitya hypothetical point in space-time at which matter is infinitely compressed to infinitesimal volume solarof or relating to the sunsolar constantthe rate at which the sun's energy is received per unit area at the top of the earth's atmosphere when the sun is at its mean distance from the earth and atmospheric absorption has been corrected for. Its value is 1367 watts per square metre solar eclipsethe total or partial obscuring of the sun by the moonsolar spectrumsolar systemthe system containing the sun and the bodies held in its gravitational field, including the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), the dwarf planets (Eris, Pluto, and Ceres), the asteroids, and comets solar yearthe period of time, the solar year, during which the earth makes one revolution around the sun, measured between two successive vernal equinoxes: equal to 365.242 19 days solsticeeither the shortest day of the year (winter solstice) or the longest day of the year (summer solstice)south celestial polesouthern hemispherethat half of the earth lying south of the equator southern lightsanother name for aurora australissouthinga south or negative declinationsouth polar distancespacethe region beyond the earth's atmosphere containing the other planets of the solar system, stars, galaxies, etc; universe space-timethe four-dimensional continuum having three spatial coordinates and one time coordinate that together completely specify the location of a particle or an eventspectral type or spectral classany of various groups into which stars are classified according to characteristic spectral lines and bands. The most important classification (Harvard classification) has a series of classes O, B, A, F, G, K, M, the series also being a scale of diminishing surface temperature spherulea very small sphere or globulespiculea spiked ejection of hot gas occurring over 5000 kilometres above the sun's surface (in its atmosphere) and having a diameter of about 1000 kilometres spinara fast-spinning star or celestial mass spraystara hot gaseous mass, such as the sun, that radiates energy, esp as light and infrared radiation, usually derived from thermonuclear reactions in the interior, and in some cases as ultraviolet, radio waves, and X-rays. The surface temperature can range from about 2100 to 40 000°C star cloudstellarof, relating to, involving, or resembling a star or starsstellar evolutionthe sequence of changes that occurs in a star as it ages stellar structurestellar windstreams of ionized gas particles constantly emitted in all directions by a star Strömgren spheresublunar pointsubsolar pointsubstellar pointsunspotany of the dark cool patches, with a diameter of up to several thousand kilometres, that appear on the surface of the sun and last about a week. They occur in approximately 11-year cycles and possess a strong magnetic fieldsunspot cyclethe cycle, averaging in duration slightly more than 11 years, in which the frequency of sunspots varies from a maximum to a minimum and back to a maximum againsuperclustera giant cluster of galaxies, a cluster consisting of a number of smaller clusters supergiantany of a class of extremely large and luminous stars, such as Betelgeuse, which have expanded to a large diameter and are eventually likely to explode as supernovae superior planetany of the planets (Mars, Jupiter, Saturn, Uranus, Neptune, and (formerly) Pluto) whose orbit lies outside that of the earth supernovaa star that explodes catastrophically owing to either instabilities following the exhaustion of its nuclear fuel or gravitational collapse following the accretion of matter from an orbiting companion star, becoming for a few days up to one hundred million times brighter than the sun. The expanding shell of debris (the supernova remnant) creates a nebula that radiates radio waves, X-rays, and light, for hundreds or thousands of years symbiotic starsynodic periodsyzygyeither of the two positions (conjunction or opposition) of a celestial body when sun, earth, and the body lie in a straight line telluric lineterminatorthe line dividing the illuminated and dark part of the moon or a planetterrestrial planetany of the planets Mercury, Venus, earth, and Mars, whose orbits lie inside the asteroid belttidal capturetidal forcetidal frictiontidethe cyclic rise and fall of sea level caused by the gravitational pull of the sun and moon. There are usually two high tides and two low tides in each lunar day total eclipsean eclipse as seen from a particular area of the earth's surface where the eclipsed body is completely hiddentotal magnitudethermospherean atmospheric layer lying between the mesosphere and the exosphere, reaching an altitude of about 400 kilometres where the temperature is over 1000°C traintransient lunar phenomenatriple startropical yearanother name for solar yeartropospherethe lowest atmospheric layer, about 18 kilometres (11 miles) thick at the equator to about 6 km (4 miles) at the Poles, in which air temperature decreases normally with height at about 6.5°C per km universal time(from 1928) name adopted internationally for Greenwich Mean Time (measured from Greenwich midnight), now split into several slightly different scales, one of which (UT1) is used by astronomersuniversethe aggregate of all existing matter, energy, and space variable starany star that varies considerably in brightness, either irregularly or in regular periods. Intrinsic variables, in which the variation is a result of internal changes, include novae, supernovae, and pulsating stars variationany change in or deviation from the mean motion or orbit of a planet, satellite, etc, esp a perturbation of the moon velocity dispersionvertical circlea great circle on the celestial sphere passing through the zenith and perpendicular to the horizon visual magnitudethe magnitude of a star as determined by visual observation white dwarfone of a large class of small faint stars of enormous density (on average 108 kg/m3) with diameters only about 1 per cent that of the sun, and masses less than the Chandrasekhar limit (about 1.4 solar masses). It is thought to mark the final stage in the evolution of a sun-like star white holea hypothetical portal in space through which matter and energy emerge: thought to be an outlet for black holes and a possible explanation for quasars zeniththe point on the celestial sphere vertically above an observerzenith distance ▷ See astronomy


astronomy: terms used in astronomy 的词汇表—— 柯林斯 英语词汇表
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