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Glossary of Astronomy Terms
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aberration Tweet Definition of aberration Like Definition of aberration on Facebook
  1. The act of wandering; deviation, especially from truth or moral rectitude, from the natural state, or from a type.
  • The of youth - Hall
  • Aberrations from theory - Burke
    1. A partial alienation of reason.
  • Occasional aberrations of intellect - Lingard
  • Whims, which at first are the aberrations of a single brain, pass with heat into epidemic form - I. Taylor
    1. (astronomy) A small periodical change of position in the stars and other heavenly bodies, due to the combined effect of the motion of light and the motion of the observer.
    2. (context, optics) The convergence to different focus, foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus.
    3. (physiology) The passage of blood or other fluid into parts not appropriate for it.
    4. The producing of an unintended effect by the glancing of an instrument, as when a shot intended for A glances and strikes B.
    5. (context, zoology, botany) atypical development or structure
    absolute magnitude Tweet Definition of absolute magnitude Like Definition of absolute magnitude on Facebook
    1. (star) the apparent magnitude that a star etc. would have if viewed from a distance of 10 parsecs. Opposed to apparent magnitude.
    accretion disk Tweet Definition of accretion disk Like Definition of accretion disk on Facebook
    1. (astronomy) A structure formed by matter falling into a gravitational source such as a galaxy, black hole, or protostar.
    aerolite Tweet Definition of aerolite Like Definition of aerolite on Facebook
    1. A meteorite consisting of silicate minerals
    air pump Tweet Definition of air pump Like Definition of air pump on Facebook
    1. A pump that moves air either into, or out of, something.
    albedo Tweet Definition of albedo Like Definition of albedo on Facebook
    1. (context, physics, meteorology, astronomy) The fraction of incident light or radiation reflected by a surface or body, commonly expressed as percentage.
    2. (context, biology) The white, whitish inner portion of the rind of citrus fruits that is a source of pectin.
    Alcyone Tweet Definition of Alcyone Like Definition of Alcyone on Facebook
    proper noun 
    1. (greekmyth) One of the Pleiades; daughter of Aeolus and wife of Ceyx. When her husband died in a shipwreck, Alcyone threw herself into the sea whereupon the gods transformed them both into halcyon birds (kingfishers). When Alcyone made her nest on the beach, waves threatened to destroy it. Aeolus restrained his winds and made the waves be calm during seven days in each year, so she could lay her eggs. These became known as the "halcyon days", when storms never occur.
    Aldebaran Tweet Definition of Aldebaran Like Definition of Aldebaran on Facebook
    proper noun 
    1. (star): A binary star in the constellation Taurus; alpha (α) Tauri. An orange giant, 68 light years from Earth, and one of the brightest stars in the sky.
    ALGOL Tweet Definition of ALGOL Like Definition of ALGOL on Facebook
    proper noun 
    1. (computing) A high-level programming language mostly used for solving mathematical and scientific problems.
    almucantar Tweet Definition of almucantar Like Definition of almucantar on Facebook
    1. (archaic) a small circle on the celestial sphere, parallel to the horizon, that is used in astronomy and navigation to show altitude of a star or any other heavenly body.
    alpha Tweet Definition of alpha Like Definition of alpha on Facebook
    1. The name of the first letter of the Greek alphabet (Î�,  Î±), followed by beta. In the Latin alphabet it is the predecessor to A.
    2. (context, science) The name of the symbol, symbols � and α used in science and mathematics, often interchangeable with the symbols when used as a prefix.
    : alpha particle ("α-particle")
    1. The highest scientific caste of people in the novel w:Brave New World, Brave New World by w:Aldous Huxley, Aldous Huxley.
    2. In finance, the amount by which a given asset or portfolio's return exceeds a "riskless" rate of return.
    1. Designates the first in an order of precedence.
    alpha male, male
    1. (star) Designates the brightest star in a constellation.
    Alpha Centauri, Alpha Centauri
    Alpha Centauri Tweet Definition of Alpha Centauri Like Definition of Alpha Centauri on Facebook
    proper noun 
    1. (star) The brightest star in the southern constellation of Centaurus. It is actually a binary star.
    Altair Tweet Definition of Altair Like Definition of Altair on Facebook
    proper noun 
    1. (star): The brightest star in the constellation Aquila; Alpha (α) Aquilae. It is the twelfth brightest star in the sky, and forms one corner of the Summer Triangle.
    altitude Tweet Definition of altitude Like Definition of altitude on Facebook
    1. the height measured from sea level up to any given point
    2. a distance measured upwards
    3. the distance measured perpendicularly from a figure's vertex to the opposite side of the vertex
    4. the distance measured angularly of a heavenly body above our Earth's horizon
    amplitude Tweet Definition of amplitude Like Definition of amplitude on Facebook
    1. the measure of something's size; magnitude
    2. (mathematics) the maximum absolute value of the vertical component of a periodic curve
    3. (physics) the maximum absolute value of some quantity that varies periodically
    analemma Tweet Definition of analemma Like Definition of analemma on Facebook
    noun (eng-noun)
    1. A scale on a terrestrial globe representing the sun's declination, usually drawn on or near the equator and in a roughly figure eight shape
    ananke Tweet Definition of ananke Like Definition of ananke on Facebook
    1. necessity, Necessity beyond all supplications or sway.
    Conceived as the ultimate dictator of all fate and circumstances" to which even the gods must ultimately pay homage and deference.      
    Andromeda Tweet Definition of Andromeda Like Definition of Andromeda on Facebook
    proper noun 
    1. (greekmyth): Daughter of Cepheus and Cassiopeia, king and queen of Eritrea, rescued from her sacrifice to a sea monster by Perseus who married her; mother of Perseus, ancient king of Persia.
    2. (constellation): An autumn constellation of the northern sky representing the "Chained Lady" Andromeda from Greek myth. The constellation lies between Pisces and Cassiopeia.
    3. (astronomy): The nearest spiral galaxy to the Milky Way; M31.
    annular eclipse Tweet Definition of annular eclipse Like Definition of annular eclipse on Facebook
    1. (astronomy) a solar eclipse in which the thin outer disk of the sun can be seen as a ring around the moon
    anomaly Tweet Definition of anomaly Like Definition of anomaly on Facebook
    noun (anomal, ies)
    1. An irregularity or misproportion.
    2. Something that is strange or unusual.
    3. (context, NASAspeak) Any event, big or small, out of the ordinary, like a shuttle explosion or a broken instrument.
    ansa Tweet Definition of ansa Like Definition of ansa on Facebook
    noun (ans, ae)
    1. (astronomy) the most protruding part of planetary rings as seen from distance
    Antares Tweet Definition of Antares Like Definition of Antares on Facebook
    proper noun 
    1. (star): A red giant binary with a blue companion star in the constellation Scorpius; alpha (α) Scorpii.
    antecedence Tweet Definition of antecedence Like Definition of antecedence on Facebook
    1. The act of preceding in time or order.
    aphelion Tweet Definition of aphelion Like Definition of aphelion on Facebook
    noun (aphelia)
    1. The point in the elliptical orbit of a planet, comet, etc., where it is farthest from the sun.
    apogee Tweet Definition of apogee Like Definition of apogee on Facebook
    1. (astronomy) In an orbit around the Earth, the point that is most distant from the Earth.
    2. (astronomy) (rfv-sense) More generally, the point in an orbit that is most distant from the center.
    3. The highest point.
      • 2004 March 22, w:The New Yorker, The New Yorker,
      • :The cult of the chief executive reached its in the nineteen-nineties, a period when C.E.O.s seemed not so much to serve their companies as to embody them.
    apparent magnitude Tweet Definition of apparent magnitude Like Definition of apparent magnitude on Facebook
    1. (star) a numerical measure of the brightness of a star, planet etc.; a decrease of 1 unit represents an increase in the light received by a factor of 2.512
    apparition Tweet Definition of apparition Like Definition of apparition on Facebook
    1. The act of becoming visible; appearance; visibility. --Milton.
    The sudden apparition of the Spaniards. --Prescott.
    The apparition of Lawyer Clippurse occasioned much speculation in that portion of the world. --Sir W. Scott.
    1. The thing appearing; a visible object; a form.
    Which apparition, it seems, was you. --Tatler.
    1. An unexpected, wonderful, or preternatural appearance; a ghost; a specter; a phantom. ``The heavenly bands . . . a glorious apparition.'' --Milton.
    I think it is the weakness of mine eyes That shapes this monstrous apparition. --Shak.
    1. (Astronomy) The first appearance of a star or other luminary after having been invisible or obscured;—opposed to occultation.
    2. Rock band, usually found in Dalgety Bay. "I saw Apparition last night, they rocked" -- Axl Rose.
    apse Tweet Definition of apse Like Definition of apse on Facebook
    1. A semicircular projection from a building, especially the rounded east-end of a church that contains the altar.
    2. (astronomy, obsolete) The nearest and furthest points to the centre of gravitational attraction for a body in orbit. More usually called an apsis.
    3. (obsolete, or, dialectal) In some local dialects and in archaic usage, an aspen tree.
    apsis Tweet Definition of apsis Like Definition of apsis on Facebook
    noun (aps, ides)
    1. A recess or projection, with a dome or vault, at the east end of a church; an apse.
    1. (astronomy) Either of the points in the elliptical orbit of a planet or comet where it is closest or furthest from the sun; perihelion or aphelion; an apside
    Apus Tweet Definition of Apus Like Definition of Apus on Facebook
    proper noun 
    1. (constellation): A constellation of the southern sky, said to resemble a bird of paradise.
    Aquarius Tweet Definition of Aquarius Like Definition of Aquarius on Facebook
    proper noun 
    1. (constellation): A constellation of the zodiac, supposedly shaped like a water carrier.
    2. (astrology): The Zodiac sign for the water carrier, covering January 21 through February 19.
    ARA Tweet Definition of ARA Like Definition of ARA on Facebook
    1. Aracruz Cellulose S.A.
    2. Applied Research Associates
    3. Awards and Recognition Association
    4. Australian Retailers Association
    5. Automotive Recyclers Association
    6. Australasian Railway Association
    Arcturus Tweet Definition of Arcturus Like Definition of Arcturus on Facebook
    proper noun 
    1. (star) A bright yellow-orange star in the constellation Boí¶tes; Alpha (α) Boí¶tis. It is the third brightest star in the night sky.
    areocentric Tweet Definition of areocentric Like Definition of areocentric on Facebook
    1. Of a coordinate system based on the planet Mars.
    areology Tweet Definition of areology Like Definition of areology on Facebook
    1. The observation and study of the planet Mars.
    Argo Tweet Definition of Argo Like Definition of Argo on Facebook
    proper noun (wikipedia, Argo)
    1. (greekmyth): The ship in which Jason and the Argonauts sailed on their quest for the Golden Fleece.
    Ariel Tweet Definition of Ariel Like Definition of Ariel on Facebook
    proper noun 
    1. Biblical Hebrew name meaning literally "lion of God", and used also in reference to the city of Jerusalem.
    2. Name of a spirit in the play The Tempest by Shakespeare.
    3. Name of the twelfth and brightest moon of the planet Uranus.
    4. (given name, male), often borrowed from Spanish usage.
    5. (given name, female), mostly of persons born after 1970.
    Aries Tweet Definition of Aries Like Definition of Aries on Facebook
    proper noun 
    1. (constellation): A constellation of the zodiac supposedly shaped like a ram.
    Aristoteles Tweet Definition of Aristoteles Like Definition of Aristoteles on Facebook
    proper noun (wikipedia, Aristoteles (crater))
    1. a lunar impact crater
    artificial horizon Tweet Definition of artificial horizon Like Definition of artificial horizon on Facebook
    1. (aviation) An instrument that displays the pitch and roll of an aircraft in flight by comparing its attitude to a gyroscopically-maintained indication of the flat horizon line.
    association Tweet Definition of association Like Definition of association on Facebook
    1. The act of associating.
    2. The state of being associated.
    3. A group of persons associated for a common purpose; an organization; society.
    4. A connection to or an affiliation with something.
    asteroid Tweet Definition of asteroid Like Definition of asteroid on Facebook
    noun (plural asteroids)
    1. (astronomy) A naturally occurring solid object, smaller than a planet, orbiting the Sun.
    astral Tweet Definition of astral Like Definition of astral on Facebook
    1. Relating to or resembling the stars.
    2. (theosophy) Relating to a supposed supersensible substance taking the form of an aura discernible to certain gifted individuals.
    astrolabe Tweet Definition of astrolabe Like Definition of astrolabe on Facebook
    1. An astronomical and navigational instrument for gauging the altitude of the Sun and stars.
    astrometry Tweet Definition of astrometry Like Definition of astrometry on Facebook
    1. that branch of astronomy that deals with the measurement of the position, positions and motion, motions of celestial bodies, particularly star, stars
    astronomical Tweet Definition of astronomical Like Definition of astronomical on Facebook
    1. Of or relating to astronomy.
      • 1839, w:Edgar Allan Poe, Edgar Allan Poe, s:The Conversation of Eiros and Charmion, The Conversation of Eiros and Charmion,
      • : Finally, all men saw that knowledge lied not, and they awaited the comet.
        1. Very large; of vast measure.
      • 1959, w:Andre Norton, Andre Norton, s:Voodoo Planet/Chapter IV, Voodoo Planet - Chapter IV,
      • : At the moment he wondered why anyone would want to visit Khatka, let alone pay some sum for the privilege.
    astronomical unit Tweet Definition of astronomical unit Like Definition of astronomical unit on Facebook
    1. (astronomy) The mean distance from the Earth to the Sun (semi-major axis of Earth's orbit). Approximately 149,600,000 kilometres (symbol AU), used to measure distances in the solar system. By definition, when used to describe the motion of bodies within solar system, solar systems, the heliocentric gravitational constant is equal to (0.017 202 098 95)² AU³/d² (IERS Conventions (1996), D. D. McCarthy? ed., IERS Technical Note 21, Observatoire de Paris, July 1996); hence 1 AU = 149,597,870,691±30 km.
    astronomy Tweet Definition of astronomy Like Definition of astronomy on Facebook
    noun (astronomies)
    1. The study of the physical universe beyond the Earth's atmosphere, including the process of mapping locations and properties of the matter and radiation in the universe. The study of the physical processes which control matter and energy in the universe is commonly called astrophysics. The investigation of the origin, evolution, and fate of the universe itself is called cosmology.
    astrophysics Tweet Definition of astrophysics Like Definition of astrophysics on Facebook
    1. The branch of astronomy or physics that deals with the physical properties of celestial bodies and with the interaction between matter and radiation in celestial bodies and in the space between them.
    atmosphere Tweet Definition of atmosphere Like Definition of atmosphere on Facebook
    noun (wikipedia, atmosphere, Atmosphere (layer of gases))
    1. The gases surrounding the Earth or any astronomical body.
    2. The air in a particular place.
    3. The mood or feeling in a situation.
    AU Tweet Definition of AU Like Definition of AU on Facebook
    1. astronomical unit
    2. Australia
    3. African Union
    aureole Tweet Definition of aureole Like Definition of aureole on Facebook
    1. (astronomy) Corona.
    2. A circle of light or halo around the head of a deity.
    3. (context, by extension) Any luminous or colored ring that encircles something.
    Auriga Tweet Definition of Auriga Like Definition of Auriga on Facebook
    proper noun 
    1. (constellation): A winter constellation of the northern sky, said to resemble a charioteer. It includes the star Capella.

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