astronomy

Noun
  1. The branch of physics that studies celestial bodies and the universe as a whole (synset 106104629)
    associated with:
    • phase - (astronomy) the particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun)
    • absolute magnitude - (astronomy) the magnitude that a star would have if it were viewed from a distance of 10 parsecs (32.62 light years) from the earth
    • hubble law, hubble's law - (astronomy) the generalization that the speed of recession of distant galaxies (the red shift) is proportional to their distance from the observer
    • kepler's law, kepler's law of planetary motion - (astronomy) one of three empirical laws of planetary motion stated by Johannes Kepler
    • copernican system - (astronomy) Copernicus' astronomical model in which the Earth rotates around the sun
    • ptolemaic system - (astronomy) Ptolemy's model of the universe with the Earth at the center
    • ascension - (astronomy) the rising of a star above the horizon
    • egress, emersion - (astronomy) the reappearance of a celestial body after an eclipse
    • immersion, ingress - (astronomy) the disappearance of a celestial body prior to an eclipse
    • alignment, conjunction - (astronomy) apparent meeting or passing of two or more celestial bodies in the same degree of the zodiac
    • inferior conjunction - (astronomy) the alignment of the Earth and a planet on the same side of the sun
    • superior conjunction - (astronomy) the alignment of the Earth and a planet on the opposite side of the sun
    • oort cloud - (astronomy) a hypothetical huge collection of comets orbiting the sun far beyond the orbit of Pluto; perturbations (as by other stars) can upset a comet's orbit and may send it tumbling toward the sun
    • extragalactic nebula, galaxy - (astronomy) a collection of star systems; any of the billions of systems each having many stars and nebulae and dust
    • apoapsis, point of apoapsis - (astronomy) the point in an orbit farthest from the body being orbited
    • node - (astronomy) a point where an orbit crosses a plane
    • equinoctial point, equinox - (astronomy) either of the two celestial points at which the celestial equator intersects the ecliptic
    • vernal equinox - (astronomy) the equinoctial point that lies in the constellation of Pisces
    • autumnal equinox - (astronomy) the equinoctial point that lies in the constellation of Virgo
    • barycenter - (astronomy) the common center of mass around which two or more bodies revolve
    • culmination - (astronomy) a heavenly body's highest celestial point above an observer's horizon
    • limb - (astronomy) the circumferential edge of the apparent disc of the sun or the moon or a planet
    • periapsis, point of periapsis - (astronomy) the point in an orbit closest to the body being orbited
    • anomaly - (astronomy) position of a planet as defined by its angular distance from its perihelion (as observed from the sun)
    • celestial latitude, dec, declination - (astronomy) the angular distance of a celestial body north or to the south of the celestial equator; expressed in degrees; used with right ascension to specify positions on the celestial sphere
    • celestial longitude, ra, right ascension - (astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky; usually expressed in hours and minutes and seconds; used with declination to specify positions on the celestial sphere
    • asterism - (astronomy) a cluster of stars (or a small constellation)
    • canal - (astronomy) an indistinct surface feature of Mars once thought to be a system of channels; they are now believed to be an optical illusion
    • coma - (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed
    • comet - (astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit
    • meteor, meteoroid - (astronomy) any of the small solid extraterrestrial bodies that hits the earth's atmosphere
    • nucleus - (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail
    • outer planet - (astronomy) a major planet whose orbit is outside the asteroid belt (Jupiter, Saturn, Uranus, Neptune, Pluto)
    • major planet, planet - (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction
    • primary - (astronomy) a celestial body (especially a star) relative to other objects in orbit around it
    • star - (astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior
    • astronomer, stargazer, uranologist - a physicist who studies astronomy
    • variation - (astronomy) any perturbation of the mean motion or orbit of a planet or satellite (especially a perturbation of the earth's moon)
    • red shift, redshift - (astronomy) a shift in the spectra of very distant galaxies toward longer wavelengths (toward the red end of the spectrum); generally interpreted as evidence that the universe is expanding
    • accretion - (astronomy) the formation of a celestial object by the effect of gravity pulling together surrounding objects and gases
    • libration - (astronomy) a real or apparent slow oscillation of a moon or satellite
    • nucleosynthesis - (astronomy) the cosmic synthesis of atoms more complex than the hydrogen atom
    • orbital plane - (astronomy) the plane on which a body is orbiting
    • ha, hour angle - (astronomy) the angular distance of a celestial point measured westward along the celestial equator from the zenith crossing; the right ascension for an observer at a particular location and time of day
    • inclination, inclination of an orbit - (astronomy) the angle between the plane of the orbit and the plane of the ecliptic stated in degrees
    • mean solar time, mean time - (astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)
    • ephemeris time, tdt, terrestrial dynamical time, terrestrial time, tt - (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
    • date of reference, epoch - (astronomy) an arbitrarily fixed date that is the point in time relative to which information (as coordinates of a celestial body) is recorded
    • ascend, come up, rise, uprise - come up, of celestial bodies
    • go down, go under, set - disappear beyond the horizon
    • stargaze - observe the stars
    • active - (of the sun) characterized by an increased occurrence of sunspots and flares and radio emissions
    • quiet - (of the sun) characterized by a low level of surface phenomena, such as sunspots
    • direct - moving from west to east on the celestial sphere; or--for planets--around the sun in the same direction as the Earth
    • retrograde - moving from east to west on the celestial sphere; or--for planets--around the sun in a direction opposite to that of the Earth
    • superior - having an orbit farther from the sun than the Earth's orbit
    • inferior - having an orbit between the sun and the Earth's orbit
    • nebular, nebulous - of or relating to or resembling a nebula
    is a type of: natural philosophy, physics - the science of matter and energy and their interactions
    subtypes:
    • astrodynamics - the branch of astronomy that studies the motion of natural and artificial bodies in space
    • astrometry - the branch of astronomy that deals with the measurement of the position and motion of celestial bodies
    • radio astronomy - the branch of astronomy that detects and studies the radio waves emitted by celestial bodies
    • celestial mechanics - the branch of astronomy concerned with the application of Newton's laws of motion to the motions of heavenly bodies
    • astrophysics - the branch of astronomy concerned with the physical and chemical properties of celestial bodies
    • selenology - the branch of astronomy that deals with the moon
    • solar physics - the branch of astronomy that deals with the sun
    same as: uranology

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