Astronomy, COM-EAR
Human beings have long been fascinated by the celestial sphere above, whose twinkling lights have inspired not only scientific theories but also many artistic endeavors. Humankind's fascination with the world beyond Earth has led to many landmark moments in history, as when space exploration took a giant step forward with the advent of technology that allowed humans to successfully travel to the Moon and to build spacecraft capable of exploring the rest of the solar system and beyond.
Astronomy Encyclopedia Articles By Title
communications satellite, Earth-orbiting system capable of receiving a signal (e.g., data, voice, TV) and relaying......
The Hubble Space Telescope was launched in 1990 and has a primary mirror 2.4 metres (94 inches) in diameter. One......
Compton Gamma Ray Observatory (CGRO), U.S. satellite, one of the National Aeronautics and Space Administration......
conjunction, in astronomy, an apparent meeting or passing of two or more celestial bodies. The Moon is in conjunction......
Conon of Samos was a mathematician and astronomer whose work on conic sections (curves of the intersections of......
Pete Conrad was an American astronaut, copilot on the Gemini 5 spaceflight (1965), command pilot of Gemini 11,......
constellation, in astronomy, any of certain groupings of stars that were imagined—at least by those who named them—to......
Constellation program, canceled U.S. crewed spaceflight program that was scheduled as a successor to the space......
Gordon Cooper was one of the original team of seven U.S. astronauts. On May 15–16, 1963, he circled Earth 22 times......
Copernican Revolution, shift in the field of astronomy from a geocentric understanding of the universe, centred......
Copernican system, in astronomy, model of the solar system centred on the Sun, with Earth and other planets moving......
Copernicus, one of the most prominent craters on the Moon. It constitutes a classic example of a relatively young,......
Nicolaus Copernicus Polish astronomer who proposed that the planets have the Sun as the fixed point to which their......
Cor Caroli, binary star located 110 light-years from Earth in the constellation Canes Venatici and consisting of......
corona, outermost region of the Sun’s atmosphere, consisting of plasma (hot ionized gas). It has a temperature......
Corona Australis, constellation in the southern sky, at about 19 hours right ascension and 40° south in declination.......
Corona Borealis, constellation in the northern sky at about 16 hours right ascension and 30° north in declination.......
coronagraph, telescope that blocks the light of a star inside the instrument so that objects close to the star......
coronal mass ejection (CME), large eruption of magnetized plasma from the Sun’s outer atmosphere, or corona, that......
CoRoT, French satellite that studied the internal structure of stars and detected extrasolar planets. It was launched......
CoRoT-7b, the first extrasolar planet that was shown to be a rocky planet like Earth. CoRoT-7b orbits a main-sequence......
Corvus, constellation in the southern sky at about 12 hours right ascension and 20° south in declination. The brightest......
Cosmic Background Explorer (COBE), U.S. satellite placed in Earth orbit in 1989 to map the “smoothness” of the......
cosmic microwave background (CMB), electromagnetic radiation filling the universe that is a residual effect of......
cosmic neutrino background, low-energy neutrinos that pervade the universe. When the universe was one second old,......
cosmic ray, a high-speed particle—either an atomic nucleus or an electron—that travels through space. Most of these......
cosmic X-ray background, X-ray radiation pervading the universe. In 1962 the first X-ray detectors were flown above......
cosmogony, in astronomy, study of the evolutionary behaviour of the universe and the origin of its characteristic......
cosmological constant, term reluctantly added by Albert Einstein to his equations of general relativity in order......
cosmology, field of study that brings together the natural sciences, particularly astronomy and physics, in a joint......
Cosmos, in astronomy, the entire physical universe considered as a unified whole (from the Greek kosmos, meaning......
Crab Nebula, (catalog numbers NGC 1952 and M1), probably the most intensely studied bright nebula, in the constellation......
Crater, constellation in the southern sky at about 11 hours right ascension and 20° south in declination. The brightest......
Crimean Astrophysical Observatory, a major astronomical observatory, located at Nauchny and Simeiz in Crimea, Ukraine.......
Robert Crippen is a U.S. astronaut who served as pilot on the first space shuttle orbital flight. Crippen graduated......
Crux, constellation lying in the southern sky at about 12 hours 30 minutes right ascension and 60° south declination......
CryoSat, European Space Agency satellite designed to study the effect of climate change on ice in Earth’s polar......
Walter Cunningham was an American astronaut and civilian participant in the Apollo 7 mission (October 11–22, 1968),......
Curiosity, U.S. robotic vehicle, designed to explore the surface of Mars, which determined that Mars was once capable......
Cygnus, constellation in the northern sky at about 21 hours right ascension and 40° north in declination. The brightest......
Cygnus, uncrewed spacecraft developed by the American firm Orbital Sciences Corporation to carry supplies to the......
Cygnus A, most powerful cosmic source of radio waves known, lying in the northern constellation Cygnus about 500,000,000......
Cygnus Loop, group of bright nebulae (Lacework Nebula, Veil Nebula, and the nebulae NGC 6960, 6979, 6992, and 6995)......
Cygnus X-1, binary star system that is a strong source of X-rays and that provided the first major evidence for......
Córdoba Durchmusterung (CD), star catalog giving positions and apparent magnitudes of 613,959 stars more than 22°......
France A. Córdova is a French-born American astrophysicist who served in multiple prominent leadership positions......
D-lines, in spectroscopy, a pair of lines, characteristic of sodium, in the yellow region of the spectrum. Their......
John Henry Dallmeyer was a British inventor and manufacturer of lenses. Showing an aptitude for science, Dallmeyer......
Dalton minimum, period of reduced sunspot activity that occurred between roughly 1790 and 1830. It was named for......
André-Louis Danjon was a French astronomer noted for his important developments in astronomical instruments and......
dark energy, repulsive force that is the dominant component (69.4 percent) of the universe. The remaining portion......
dark matter, a component of the universe whose presence is discerned from its gravitational attraction rather than......
Sir George Darwin was an English astronomer who championed the theory that the Moon was once part of the Earth,......
Gabriel-Auguste Daubrée was a French geochemist and a pioneer in the application of experimental methods to the......
Paul Davies is a British theoretical physicist and astrobiologist who contributed to scholarly and popular debate......
William Rutter Dawes was an English astronomer known for his extensive measurements of double stars and for his......
Dawn, U.S. spacecraft that orbited the large asteroid Vesta and the dwarf planet Ceres. Dawn was launched September......
Warren De la Rue was an English pioneer in astronomical photography, the method by which nearly all modern astronomical......
declination, in astronomy, the angular distance of a body north or south of the celestial equator. Declination......
Deep Impact, a U.S. space probe that in 2005 studied cometary structure by shooting a 370-kg (810-pound) mass into......
Deep Space 1, U.S. satellite designed to test technologies—including an ion engine, autonomous navigation, and......
Deimos, the outer and smaller of Mars’s two moons. It was discovered telescopically with its companion moon, Phobos,......
Jean-Baptiste-Joseph Delambre was a French astronomer who prepared tables that plot the location of Uranus. In......
Charles-Eugène Delaunay was a French mathematician and astronomer whose theory of lunar motion advanced the development......
Joseph-Nicolas Delisle was a French astronomer who proposed that the series of coloured rings sometimes observed......
Delphinus, small constellation in the northern sky at about 21 hours right ascension and 10° north in declination.......
Delta, series of American launch vehicles, originally based on the Thor intermediate-range ballistic missile, that......
Delta Cephei, prototype star of the class of Cepheid variables, in the constellation Cepheus. Its apparent visual......
Democritus was an ancient Greek philosopher, a central figure in the development of philosophical atomism and of......
Deneb, one of the brightest stars, with an apparent magnitude of 1.25. This star, at about 1,500 light-years’ distance,......
Henri-Alexandre Deslandres was a French physicist and astrophysicist who in 1894 invented a spectroheliograph,......
Robert H. Dicke was an American physicist noted for his theoretical work in cosmology and investigations centring......
diffuse ionized gas, dilute interstellar material that makes up about 90 percent of the ionized gas in the Milky......
Dione, fourth nearest of the major regular moons of Saturn. It was discovered by the Italian-born French astronomer......
Discoverer, any of a series of 38 unmanned experimental satellites launched by the United States Air Force. Although......
diurnal motion, apparent daily motion of the heavens from east to west in which celestial objects seem to rise......
Eustachio Divini was an Italian scientist, one of the first to develop the technology necessary for producing scientific......
Technically speaking, no planets apart from Earth are known to have hurricanes. This is partly because of the definition......
Georgy Timofeyevich Dobrovolsky was a Soviet cosmonaut, mission commander on the Soyuz 11 mission in which he,......
Unlike Earth, where water falls as rain, other planets in our solar system experience vastly different precipitation.......
Audouin Dollfus was a French astronomer, successor to Bernard Lyot as the principal French authority on the solar......
George Dollond was a British optician who invented a number of precision instruments used in astronomy, geodesy,......
Giovanni Battista Donati was an Italian astronomer who, on Aug. 5, 1864, was first to observe the spectrum of a......
Dorado, constellation in the southern sky at about 5 hours right ascension and 60° south in declination. Its brightest......
Andrew Ellicott Douglass was an American astronomer and archaeologist who established the principles of dendrochronology......
Draco, constellation in the northern sky at about 18 hours right ascension and 70° north in declination. Its brightest......
Dragon, privately developed spacecraft built by the American corporation SpaceX and the first private spacecraft......
Drake equation, equation that purports to yield the number N of technically advanced civilizations in the Milky......
Henry Draper was an American physician and amateur astronomer who made the first photograph of the spectrum of......
Dresden Codex, one of the few collections of pre-Columbian Maya hieroglyphic texts known to have survived the book......
Johan Ludvig Emil Dreyer was a Danish astronomer who compiled the New General Catalogue of Nebulae and Clusters......
Nils Christofer Dunér was a Swedish astronomer who studied the rotational period of the Sun. Dunér was senior astronomer......
Pedro Duque is a Spanish aeronautical engineer and astronaut who became the first Spanish citizen to go into space.......
dwarf planet, body, other than a natural satellite (moon), that orbits the Sun and that is, for practical purposes,......
dwarf star, any star of average or low luminosity, mass, and size. Important subclasses of dwarf stars are white......
Ed Dwight is a sculptor and the first Black American to undergo astronaut training. In May 2024 he became the oldest......
Freeman Dyson was a British-born American physicist and educator best known for his speculative work on extraterrestrial......
Sir Frank Dyson was a British astronomer who in 1919 organized observations of stars seen near the Sun during a......
al-Dīnawarī was an astronomer, botanist, and historian, of Persian or Kurdish origin, whose interest in Hellenism......
Earth, third planet from the Sun and the fifth largest planet in the solar system in terms of size and mass. Its......