An Etymological Dictionary of Astronomy and Astrophysics

1a) A demand for something as due; an assertion of a right or an alleged right.

1b) An assertion of something as a fact.

2a) To demand by or as by virtue of a right; demand as a right or as due.

2b) To assert and demand the recognition of (Dictionary.com).

See also: → acclaim, → declaim, → proclaim.

Etymology (EN): M.E. claimen, from O.Fr. clamer “to call, name, describe; claim; complain,” from L. clamare “to cry out, shout, proclaim,” from PIE *kele- “to shout;” cf. Skt. usakala “cock,” literally “dawn-calling;” Middle Irish cailech “cock;” Gk. kalein “to call;” L. calare “to announce solemnly;” O.H.G. halan “to call;” O.E. hlowan “to make a noise like a cow;” Lith. kalba “language.”

Etymology (PE): Zuyidan, from zu- “to call;” cf. Av. zu- “to call;” O.Pers. (+ pati) zu- “to proclaim;” Sogd. ‘zw- “to call;” Pashtu zwag “noise, clamour;” Skt. havⁱ “to call upon, invoke;” O.C.S. zvati; Slov. zvati; Toch. B kwā- “to call out to, invite” (Cheung 2007).

1a) A demand for something as due; an assertion of a right or an alleged right.

1b) An assertion of something as a fact.

2a) To demand by or as by virtue of a right; demand as a right or as due.

2b) To assert and demand the recognition of (Dictionary.com).

See also: → acclaim, → declaim, → proclaim.

Etymology (EN): M.E. claimen, from O.Fr. clamer “to call, name, describe; claim; complain,” from L. clamare “to cry out, shout, proclaim,” from PIE *kele- “to shout;” cf. Skt. usakala “cock,” literally “dawn-calling;” Middle Irish cailech “cock;” Gk. kalein “to call;” L. calare “to announce solemnly;” O.H.G. halan “to call;” O.E. hlowan “to make a noise like a cow;” Lith. kalba “language.”

Etymology (PE): Zuyidan, from zu- “to call;” cf. Av. zu- “to call;” O.Pers. (+ pati) zu- “to proclaim;” Sogd. ‘zw- “to call;” Pashtu zwag “noise, clamour;” Skt. havⁱ “to call upon, invoke;” O.C.S. zvati; Slov. zvati; Toch. B kwā- “to call out to, invite” (Cheung 2007).

An equation that relates the temperature and pressure dependence of phases in equilibrium with the heat interaction and volume change associated with a phase change: dP/dT = L/T ΔV, where dP/dT is the slope of the coexistence curve, L is the → latent heat, T is the temperature, and ΔV is the volume change of the phase transition.

See also: Named after Émile Clapeyron (1799-1864), a French engineer and physicist, one of the founders of → thermodynamics; → equation.

An equation that relates the temperature and pressure dependence of phases in equilibrium with the heat interaction and volume change associated with a phase change: dP/dT = L/T ΔV, where dP/dT is the slope of the coexistence curve, L is the → latent heat, T is the temperature, and ΔV is the volume change of the phase transition.

See also: Named after Émile Clapeyron (1799-1864), a French engineer and physicist, one of the founders of → thermodynamics; → equation.

The action of making a statement or situation less confused and more comprehensible.

See also: Verbal noun of → clarify.

The action of making a statement or situation less confused and more comprehensible.

See also: Verbal noun of → clarify.

1. To make (an idea, statement, etc.) clear or intelligible; to free from ambiguity.
   

2. To remove solid matter from (a liquid); to make into a clear or pellucid liquid (Dictionary.com).

See also: → clear; → -fy.

1. To make (an idea, statement, etc.) clear or intelligible; to free from ambiguity.
   

2. To remove solid matter from (a liquid); to make into a clear or pellucid liquid (Dictionary.com).

See also: → clear; → -fy.

General: A set, collection or group formed of
members with certain attributes or traits in common.

Etymology (EN): From Fr. classe, from L. classis “summons, division of citizens for military draft, hence army, fleet, also class in general.”

Etymology (PE): Radé “a line, series, row,” from Mid.Pers. ratak “series, row,” O.Pers. râd-, Av. raz- “to direct, put in line, set,” Av. razan- “order.”

General: A set, collection or group formed of
members with certain attributes or traits in common.

Etymology (EN): From Fr. classe, from L. classis “summons, division of citizens for military draft, hence army, fleet, also class in general.”

Etymology (PE): Radé “a line, series, row,” from Mid.Pers. ratak “series, row,” O.Pers. râd-, Av. raz- “to direct, put in line, set,” Av. razan- “order.”

A low-mass → protostar deeply embedded in a → circumstellar dusty envelope and resulting from the → gravitational collapse of a dense → pre-stellar core. This stage in the process of star formation occurs typically a few
10⁴ years after the onset of the collapse. Class 0 protostars represent the earliest stage of → young stellar objects.
The → spectral energy distribution (SED) of a Class 0 object resembles a → blackbody spectrum at a temperature below ~ 15-30 K, peaking at → submillimeter wavelengths beyond 100 μm. The central protostar has not yet acquired its final mass, since → accretion is still going on, and the envelope (detected in submillimeter wavelengths) is more massive than the central protostellar mass. Moreover, these objects show powerful → bipolar ejections of material in the form of collimated → carbon monoxide (CO)→ outflows which distinguish them from the pre-stellar phase of star formation. The subsequent evolution of a Class 0 is a → Class I.

See also: → class; → zero.

A low-mass → protostar deeply embedded in a → circumstellar dusty envelope and resulting from the → gravitational collapse of a dense → pre-stellar core. This stage in the process of star formation occurs typically a few
10⁴ years after the onset of the collapse. Class 0 protostars represent the earliest stage of → young stellar objects.
The → spectral energy distribution (SED) of a Class 0 object resembles a → blackbody spectrum at a temperature below ~ 15-30 K, peaking at → submillimeter wavelengths beyond 100 μm. The central protostar has not yet acquired its final mass, since → accretion is still going on, and the envelope (detected in submillimeter wavelengths) is more massive than the central protostellar mass. Moreover, these objects show powerful → bipolar ejections of material in the form of collimated → carbon monoxide (CO)→ outflows which distinguish them from the pre-stellar phase of star formation. The subsequent evolution of a Class 0 is a → Class I.

See also: → class; → zero.

A protostellar phase resulting from the evolution of a → Class 0 object typically a few 10⁵ years after the beginning of the → gravitational collapse. The protostar grows in mass due to → accretion from the envelope, which becomes less massive than the protostar. An → accretion disk forms around the protostar through which mass is transferred to the central object. The
→ spectral energy distribution (SED) changes with respect to that of a Class 0. The peak of the SED shifts to → far infrared wavelengths (below 100 μm) as the temperature of the dust rises. Emission from both the envelope (about 100 K) and the thick disk (a few 100 K) are observed. The SED has a positive → spectral index (α_IR > 0), so that the bulk of the → luminosity (still due to accretion) emerges at the longer infrared wavelengths. Moreover, → bipolar outflows and → jets are observed which are generally less powerful than those in Class 0 objects. Class I objects evolve into → Class II.

See also: → class; → one.

A protostellar phase resulting from the evolution of a → Class 0 object typically a few 10⁵ years after the beginning of the → gravitational collapse. The protostar grows in mass due to → accretion from the envelope, which becomes less massive than the protostar. An → accretion disk forms around the protostar through which mass is transferred to the central object. The
→ spectral energy distribution (SED) changes with respect to that of a Class 0. The peak of the SED shifts to → far infrared wavelengths (below 100 μm) as the temperature of the dust rises. Emission from both the envelope (about 100 K) and the thick disk (a few 100 K) are observed. The SED has a positive → spectral index (α_IR > 0), so that the bulk of the → luminosity (still due to accretion) emerges at the longer infrared wavelengths. Moreover, → bipolar outflows and → jets are observed which are generally less powerful than those in Class 0 objects. Class I objects evolve into → Class II.

See also: → class; → one.

A stage in the evolution of low-mass → protostars resulting from a → Class I object about 10⁶ years after the initial → gravitational collapse. Most of the envelope has been removed and the embedded object becomes visible at infrared and optical wavelengths. At this stage, the bulk of the material has → accreted onto the central object. A flattened → circumstellar disk or
→ protoplanetary disk is present in which material moves inward at a decreasing rate. The disk contributes only about 1% of the total mass of the system.
Material from a remaining envelope may still accrete onto the outer parts of the disk. The → spectral energy distribution (SED) at
→ near infrared wavelengths is dominated by the emission of the central protostar and typically peaks around 2 μm, corresponding to temperatures around 1000 to 2000 K. At longer wavelengths an → infrared excess is observed, originating from the disk.
The SED has a negative → spectral index (-1.5 < α_IR < 0). Estimated disk masses and → accretion rates are 10^-3 to 10^-1 → solar masses and 10^-8 solar masses per year, respectively. This stage initiates the → pre-main sequence stage of a star. The object is referred to as a → classical T Tauri star. The stellar → photosphere is revealed at optical wavelengths accompanied by strong → emission lines and photometric variability, but the infrared luminosity is far larger than can be explained by the photometric temperature and radius.

See also: → class; → two.

A stage in the evolution of low-mass → protostars resulting from a → Class I object about 10⁶ years after the initial → gravitational collapse. Most of the envelope has been removed and the embedded object becomes visible at infrared and optical wavelengths. At this stage, the bulk of the material has → accreted onto the central object. A flattened → circumstellar disk or
→ protoplanetary disk is present in which material moves inward at a decreasing rate. The disk contributes only about 1% of the total mass of the system.
Material from a remaining envelope may still accrete onto the outer parts of the disk. The → spectral energy distribution (SED) at
→ near infrared wavelengths is dominated by the emission of the central protostar and typically peaks around 2 μm, corresponding to temperatures around 1000 to 2000 K. At longer wavelengths an → infrared excess is observed, originating from the disk.
The SED has a negative → spectral index (-1.5 < α_IR < 0). Estimated disk masses and → accretion rates are 10^-3 to 10^-1 → solar masses and 10^-8 solar masses per year, respectively. This stage initiates the → pre-main sequence stage of a star. The object is referred to as a → classical T Tauri star. The stellar → photosphere is revealed at optical wavelengths accompanied by strong → emission lines and photometric variability, but the infrared luminosity is far larger than can be explained by the photometric temperature and radius.

See also: → class; → two.

An evolutionary stage in the formation of low-mass → protostars resulting from a → Class II object between 1 to 10 million years after the initial → gravitational collapse. At this stage → accretion has ceased completely and what remains
from the → circumstellar disk is a → debris disk. The temperature and density of the → pre-main sequence star keep increasing as the object slowly contracts to its final size. Most of the → luminosity derives from protostellar contraction. The → spectral energy distribution (SED) resembles a stellar → blackbody, peaking at optical and infrared wavelengths. Minor → infrared excess is still observed. The SED has a negative → spectral index (α_IR < -1.5). Class III objects are sometimes called → weak-line T Tauri stars.

See also: → class; → three.

An evolutionary stage in the formation of low-mass → protostars resulting from a → Class II object between 1 to 10 million years after the initial → gravitational collapse. At this stage → accretion has ceased completely and what remains
from the → circumstellar disk is a → debris disk. The temperature and density of the → pre-main sequence star keep increasing as the object slowly contracts to its final size. Most of the → luminosity derives from protostellar contraction. The → spectral energy distribution (SED) resembles a stellar → blackbody, peaking at optical and infrared wavelengths. Minor → infrared excess is still observed. The SED has a negative → spectral index (α_IR < -1.5). Class III objects are sometimes called → weak-line T Tauri stars.

See also: → class; → three.

1. Considered as the typical, traditional, or usual form of something. → classical T Tauri star.
   

2. → classical physics.

Etymology (EN): From classic (+ → -al), from Fr. classique, from L. classicus “belonging to a class, relating to the first or highest class of the Roman people,”
from classis perhaps akin to calare “to call.”

Etymology (PE): Loan from Fr. classique, as above.

1. Considered as the typical, traditional, or usual form of something. → classical T Tauri star.
   

2. → classical physics.

Etymology (EN): From classic (+ → -al), from Fr. classique, from L. classicus “belonging to a class, relating to the first or highest class of the Roman people,”
from classis perhaps akin to calare “to call.”

Etymology (PE): Loan from Fr. classique, as above.

A → galaxy bulge that appears protruding from the disk plane when seen at an appropriate → inclination. Classical bulges are somewhat → spheroidal, featureless (no → spiral arms, → bars, → rings, etc.), contain mostly → old stars (not much dust or star-forming regions), and are kinematically hot, i.e. dynamically supported by the → velocity dispersion of their stars. Their → surface brightness profile follows the → de Vaucouleurs law. Currently, they are thought to form through → gravitational collapse or → mergers
in violent events, inducing a fast → burst of star formation if gas is available. An example is the → Sombrero galaxy bulge (D. A. Gadotti, 2012, astro-ph/1208.2295).

See also: → classical; → bulge.

A → galaxy bulge that appears protruding from the disk plane when seen at an appropriate → inclination. Classical bulges are somewhat → spheroidal, featureless (no → spiral arms, → bars, → rings, etc.), contain mostly → old stars (not much dust or star-forming regions), and are kinematically hot, i.e. dynamically supported by the → velocity dispersion of their stars. Their → surface brightness profile follows the → de Vaucouleurs law. Currently, they are thought to form through → gravitational collapse or → mergers
in violent events, inducing a fast → burst of star formation if gas is available. An example is the → Sombrero galaxy bulge (D. A. Gadotti, 2012, astro-ph/1208.2295).

See also: → classical; → bulge.

The theory that studies distributions of → energy, → matter, and other physical quantities under circumstances where their discrete nature is unimportant. Classical field theory traditionally includes → Newtonian mechanics, Maxwell’s → electromagnetic theory, and Einstein’s theory of → general relativity.
The main scope of classical field theory is to construct the mathematical description of → dynamical systems with an infinite number of degrees of freedom. The word “classical” is used in contrast to those field theories that incorporate → quantum mechanics (→ quantum field theory). Classical field theories are usually categorized as → non-relativistic and → relativistic.

See also: → classical; → field; → theory.

The theory that studies distributions of → energy, → matter, and other physical quantities under circumstances where their discrete nature is unimportant. Classical field theory traditionally includes → Newtonian mechanics, Maxwell’s → electromagnetic theory, and Einstein’s theory of → general relativity.
The main scope of classical field theory is to construct the mathematical description of → dynamical systems with an infinite number of degrees of freedom. The word “classical” is used in contrast to those field theories that incorporate → quantum mechanics (→ quantum field theory). Classical field theories are usually categorized as → non-relativistic and → relativistic.

See also: → classical; → field; → theory.

The traditional logic in which → sets are sharply defined (→ crisp set) for example, the number of students registered for a course, or the names beginning with P in a given telephone directory. Classical logic also defines relations between sets of → propositions. Consider for example two sets: elephants and mammals, a simple proposition would be the assertion that all elephants are mammals, that is E ⊂ M, where E is the elephant set and M is the mammal set. The classical logic proposition is either true or false. Compare with → fuzzy logic.

See also: → classical; → logic.

The traditional logic in which → sets are sharply defined (→ crisp set) for example, the number of students registered for a course, or the names beginning with P in a given telephone directory. Classical logic also defines relations between sets of → propositions. Consider for example two sets: elephants and mammals, a simple proposition would be the assertion that all elephants are mammals, that is E ⊂ M, where E is the elephant set and M is the mammal set. The classical logic proposition is either true or false. Compare with → fuzzy logic.

See also: → classical; → logic.

The branch of physical science which deals with the motions of bodies travelling at velocities that are very much less than that of light in a vacuum. Same as → Newtonian mechanics.

See also: → classical; → mechanics.

The branch of physical science which deals with the motions of bodies travelling at velocities that are very much less than that of light in a vacuum. Same as → Newtonian mechanics.

See also: → classical; → mechanics.

Physics not taking into account → quantum mechanics or Einstein’s → relativity theory. Classical physics includes the branches developed before the beginning of the 20th cantury: Mechanics, Acoustics, Optics, Thermodynamics, and Electricity and Magnetism. Most of classical physics is concerned with matter and energy on the normal scale of observation.

See also: → classical; → physics.

Physics not taking into account → quantum mechanics or Einstein’s → relativity theory. Classical physics includes the branches developed before the beginning of the 20th cantury: Mechanics, Acoustics, Optics, Thermodynamics, and Electricity and Magnetism. Most of classical physics is concerned with matter and energy on the normal scale of observation.

See also: → classical; → physics.

A → T Tauri star in which → accretion from a → circumstellar disk is responsible for ultraviolet and infrared excess emission and for a moderate to strong emission line spectrum superimposed on the photospheric spectrum. Classical T Tauri stars probably evolve into → weak-line T Tauri stars when their disks are fully accreted by the stars.

See also: → classical; → T Tauri star.

A → T Tauri star in which → accretion from a → circumstellar disk is responsible for ultraviolet and infrared excess emission and for a moderate to strong emission line spectrum superimposed on the photospheric spectrum. Classical T Tauri stars probably evolve into → weak-line T Tauri stars when their disks are fully accreted by the stars.

See also: → classical; → T Tauri star.

The systematic grouping of astronomical objects
into categories on the basis of physical, morphological, or evolutionary characteristics.

Etymology (EN): Classification, from O.Fr., from classifier, from → class + -fier, from L. -ficare, root of facere “to make, do;” PIE base *dhe- “to put, to do” (cf. Skt. dadhati “puts, places;” Av. dadaiti “he puts,” O.Pers. ada “he made,” Gk. tithenai “to put, set, place.”

Etymology (PE): Radebandi, from radé, → class,

• bandi, verbal noun of bastan “to bind, shut; to get, acquire, incur,” from Mid.Pers. bastan/vastan “to bind, shut;” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie;” cf.
  Skt. bandh- “to bind, tie, fasten;” Ger. binden, E. bind, → band; PIE base *bhendh- “to bind.”

The systematic grouping of astronomical objects
into categories on the basis of physical, morphological, or evolutionary characteristics.

Etymology (EN): Classification, from O.Fr., from classifier, from → class + -fier, from L. -ficare, root of facere “to make, do;” PIE base *dhe- “to put, to do” (cf. Skt. dadhati “puts, places;” Av. dadaiti “he puts,” O.Pers. ada “he made,” Gk. tithenai “to put, set, place.”

Etymology (PE): Radebandi, from radé, → class,

• bandi, verbal noun of bastan “to bind, shut; to get, acquire, incur,” from Mid.Pers. bastan/vastan “to bind, shut;” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie;” cf.
  Skt. bandh- “to bind, tie, fasten;” Ger. binden, E. bind, → band; PIE base *bhendh- “to bind.”

A chemical substance in which a molecule of one compound fills a cavity within the crystal lattice of another compound. An example is clathrate hydrate, a special type of gas hydrate in which small molecules (typically gases) are trapped inside “cages” of hydrogen bonded water molecules. Large amounts of methane have been discovered both in permafrost formations and under the ocean floor. Similarly oceans contain large quantities of trapped CO₂, which dissociate when the temperature rises sufficiently.

See also: From L. clathratus, p.p. of clathrarer “to fit with bars,” from clathra “bars, lattice,” from Gk. kleithron " bar," from kleiein “to close.”

A chemical substance in which a molecule of one compound fills a cavity within the crystal lattice of another compound. An example is clathrate hydrate, a special type of gas hydrate in which small molecules (typically gases) are trapped inside “cages” of hydrogen bonded water molecules. Large amounts of methane have been discovered both in permafrost formations and under the ocean floor. Similarly oceans contain large quantities of trapped CO₂, which dissociate when the temperature rises sufficiently.

See also: From L. clathratus, p.p. of clathrarer “to fit with bars,” from clathra “bars, lattice,” from Gk. kleithron " bar," from kleiein “to close.”

1. Grammar: A syntactic construction containing a subject and predicate and forming part of a sentence or constituting a whole simple sentence.
   

2. A distinct article or provision in a contract, treaty, will, or other formal or legal written document (Dictionary.com).

Etymology (EN): M.E., from O.Fr. clause, from M.L. clausa “conclusion,” used in the sense of classical L. clausula “the end, a closing, termination,” also “end of a sentence or a legal argument,” from clausa, from p.p. of claudere “to close, to shut, to conclude,” → closure.

Etymology (PE): Band present stem of bastan “to close, to fasten, to bind,” → closure.

1. Grammar: A syntactic construction containing a subject and predicate and forming part of a sentence or constituting a whole simple sentence.
   

2. A distinct article or provision in a contract, treaty, will, or other formal or legal written document (Dictionary.com).

Etymology (EN): M.E., from O.Fr. clause, from M.L. clausa “conclusion,” used in the sense of classical L. clausula “the end, a closing, termination,” also “end of a sentence or a legal argument,” from clausa, from p.p. of claudere “to close, to shut, to conclude,” → closure.

Etymology (PE): Band present stem of bastan “to close, to fasten, to bind,” → closure.

A first-order improvement on the → ideal gas law that corrects for the finite volume of molecules.

See also: After Rudolf Clausius (1822-1888), a German physicist and mathematician, → equation.

A first-order improvement on the → ideal gas law that corrects for the finite volume of molecules.

See also: After Rudolf Clausius (1822-1888), a German physicist and mathematician, → equation.

An approximation of the → Clapeyron equation for liquid-vapor equilibrium that incorporates the → ideal gas law and states that the logarithm of vapor pressure is inversely proportional to temperature.

See also: → Clausius equation; → Clapeyron equation.

An approximation of the → Clapeyron equation for liquid-vapor equilibrium that incorporates the → ideal gas law and states that the logarithm of vapor pressure is inversely proportional to temperature.

See also: → Clausius equation; → Clapeyron equation.

If heat flows by conduction from body A to another body B, then a transformation whose only final result is to transfer heat from B to A is impossible. Clausius’s postulate is a formulation of the → second law of thermodynamics. It is also equivalent to → Kelvin’s postulate.

See also: → Clausius equation; → postulate.

If heat flows by conduction from body A to another body B, then a transformation whose only final result is to transfer heat from B to A is impossible. Clausius’s postulate is a formulation of the → second law of thermodynamics. It is also equivalent to → Kelvin’s postulate.

See also: → Clausius equation; → postulate.

A broad class of hydrous → silicate minerals that has the tetrahedral silicate groups linked in sheets. Clay commonly forms as a product of rock weathering. Deposits of phyllosilicates, such as chamosite and nontronite, recently identified on Mars are attributed to the action of liquid water in the past history of this planet.

Etymology (EN): O.E. clæg “stiff, sticky earth; clay,” from PIE base *glei- “to stick together;” cf. Gk. gloios “sticky substance,” L. glus, gluten “glue,” O.Slav. glina “clay.” The Pers. gel “clay, mud,” Mid.Pers. gil “clay” may belong to this family.

Etymology (PE): Ros, variant rost “clay,” of unknown origin.

A broad class of hydrous → silicate minerals that has the tetrahedral silicate groups linked in sheets. Clay commonly forms as a product of rock weathering. Deposits of phyllosilicates, such as chamosite and nontronite, recently identified on Mars are attributed to the action of liquid water in the past history of this planet.

Etymology (EN): O.E. clæg “stiff, sticky earth; clay,” from PIE base *glei- “to stick together;” cf. Gk. gloios “sticky substance,” L. glus, gluten “glue,” O.Slav. glina “clay.” The Pers. gel “clay, mud,” Mid.Pers. gil “clay” may belong to this family.

Etymology (PE): Ros, variant rost “clay,” of unknown origin.

1. Free from darkness, obscurity, or cloudiness.
   

2. Transparent; pellucid.
   

3. Without discoloration, defect, or blemish (Dictionary.com). → clear night.

Etymology (EN): M.E. clere, from O.Fr. cler, from L. clarus “clear, bright, distinct.”

Etymology (PE): Runé, from Kurd. (Sorani) rûn “bright, clear,” rûn kirdin “to explain,” variant of rowšan, → bright.

1. Free from darkness, obscurity, or cloudiness.
   

2. Transparent; pellucid.
   

3. Without discoloration, defect, or blemish (Dictionary.com). → clear night.

Etymology (EN): M.E. clere, from O.Fr. cler, from L. clarus “clear, bright, distinct.”

Etymology (PE): Runé, from Kurd. (Sorani) rûn “bright, clear,” rûn kirdin “to explain,” variant of rowšan, → bright.

A night sky without clouds, mist, or haze, atmospheric dust particles, and without city lights in which a sixth magnitude star is visible by naked-eye.

See also: → clear; → night.

A night sky without clouds, mist, or haze, atmospheric dust particles, and without city lights in which a sixth magnitude star is visible by naked-eye.

See also: → clear; → night.

An ancient device for measuring time by marking the regulated flow of water through a small opening. A water clock.

Etymology (EN): L., from Gk. klepsudra, from kleptein “to steal” + hudor “water,” PIE *wed- “water.”

Etymology (PE): Pangân or pang was a clepsydra in Iran. It consisted
of “a copper bason with a small hole in the bottom, for water in which it is placed to flow through, used for measuring time;” etymology unknown.

An ancient device for measuring time by marking the regulated flow of water through a small opening. A water clock.

Etymology (EN): L., from Gk. klepsudra, from kleptein “to steal” + hudor “water,” PIE *wed- “water.”

Etymology (PE): Pangân or pang was a clepsydra in Iran. It consisted
of “a copper bason with a small hole in the bottom, for water in which it is placed to flow through, used for measuring time;” etymology unknown.

A very high steep rock or ice face, especially one that runs along a coastline. → scarp.

Etymology (EN): M.E., O.E. clif (cf. O.S. clif, O.N. klif, O.H.G. klep, M.Du. klippe, Ger. Klippe “cliff, steep rock”).

Etymology (PE): Tondân, from tond “swift, rapid, brisk,” → scarp + -ân a suffix of nuance/relation.

A very high steep rock or ice face, especially one that runs along a coastline. → scarp.

Etymology (EN): M.E., O.E. clif (cf. O.S. clif, O.N. klif, O.H.G. klep, M.Du. klippe, Ger. Klippe “cliff, steep rock”).

Etymology (PE): Tondân, from tond “swift, rapid, brisk,” → scarp + -ân a suffix of nuance/relation.

The characteristic meteorological conditions (temperature, precipitation, and wind) and their extremes, of any place or region. In other words, weather patterns averaged over a given period of time to obtain a consistent pattern of the expected atmospheric conditions.

Etymology (EN): M.E. climat, from M.Fr. climat, from L. clima, climat- “region, slope of the Earth,” from Gk. klima “region, zone,” from base of klinein “to slope,” thus “slope of the Earth from equator to pole,” from PIE base *klei- “to lean,” → inclination.

Etymology (PE): Kelimâ, loan from Fr., as above.
Âbohavâ, from âb, → water, + -o- “and” + havâ “weather” → air.

The characteristic meteorological conditions (temperature, precipitation, and wind) and their extremes, of any place or region. In other words, weather patterns averaged over a given period of time to obtain a consistent pattern of the expected atmospheric conditions.

Etymology (EN): M.E. climat, from M.Fr. climat, from L. clima, climat- “region, slope of the Earth,” from Gk. klima “region, zone,” from base of klinein “to slope,” thus “slope of the Earth from equator to pole,” from PIE base *klei- “to lean,” → inclination.

Etymology (PE): Kelimâ, loan from Fr., as above.
Âbohavâ, from âb, → water, + -o- “and” + havâ “weather” → air.

The scientific study of climates. More specifically, the analysis of weather condition trends over a relatively long period of time (past, present or future). Climatology is distinct from meteorology, which is associated with short-term weather system studies.

See also: → climate; → -logy.

The scientific study of climates. More specifically, the analysis of weather condition trends over a relatively long period of time (past, present or future). Climatology is distinct from meteorology, which is associated with short-term weather system studies.

See also: → climate; → -logy.

A device (not carried or worn) for measuring and showing the time. See also: → hour, → gnomon, → clepsydra.

Etymology (EN): M.E. clokke “clock with bells,” from O.Fr. cloque “bell” (Fr. cloche, Du. klok, Ger. Glocke), M.L. clocca “bell,” of Celtic origin.

Etymology (PE): Sâat from Ar.

A device (not carried or worn) for measuring and showing the time. See also: → hour, → gnomon, → clepsydra.

Etymology (EN): M.E. clokke “clock with bells,” from O.Fr. cloque “bell” (Fr. cloche, Du. klok, Ger. Glocke), M.L. clocca “bell,” of Celtic origin.

Etymology (PE): Sâat from Ar.

Successive risings and lowerings of voltage on the electrodes of a CCD in order to move the electrons from one pixel to the next.

Successive risings and lowerings of voltage on the electrodes of a CCD in order to move the electrons from one pixel to the next.

In the same direction as the rotating hands of a clock when viewed from in front.

Etymology (EN): From → clock + wise “way, manner,” O.E. wise (adj.), from wis, from P.Gmc. *wisaz (cf. Du. wijs, Ger. weise “wise”), PIE base *weid-/*wid- “to see, to know;” cf. Av vaeda “I know,” Skt. veda “I know,” Gk. oida “I know”.

Etymology (PE): Sâ’atsu, from sâ’at, → clock, + su “direction,” Mid.Pers. sôg, sôk “side, direction”.

In the same direction as the rotating hands of a clock when viewed from in front.

Etymology (EN): From → clock + wise “way, manner,” O.E. wise (adj.), from wis, from P.Gmc. *wisaz (cf. Du. wijs, Ger. weise “wise”), PIE base *weid-/*wid- “to see, to know;” cf. Av vaeda “I know,” Skt. veda “I know,” Gk. oida “I know”.

Etymology (PE): Sâ’atsu, from sâ’at, → clock, + su “direction,” Mid.Pers. sôg, sôk “side, direction”.

A shoe made of wood.

Etymology (EN): M.E., of unknown origin.

Etymology (PE): Katelé, from (Tabari, Gilaki) katelé “wooden shoe,” from katel “tree log, tree stump.”

A shoe made of wood.

Etymology (EN): M.E., of unknown origin.

Etymology (PE): Katelé, from (Tabari, Gilaki) katelé “wooden shoe,” from katel “tree log, tree stump.”

Having little or no space between elements or parts, as in → close binary, → close approach; tight and compact.

Etymology (EN): M.E. clos, closed, from O.Fr., from L. clausus, p.p. of claudere “to close.”

Etymology (PE): Kip “close, tight” in spoken Pers.

Having little or no space between elements or parts, as in → close binary, → close approach; tight and compact.

Etymology (EN): M.E. clos, closed, from O.Fr., from L. clausus, p.p. of claudere “to close.”

Etymology (PE): Kip “close, tight” in spoken Pers.

In astronomy a general term to describe the positions of two or more objects that come unusually near one to another. In particular, regarding an asteroid’s position with respect to Earth, when it is within the Moon’s orbit.

See also: → close; → approach.

In astronomy a general term to describe the positions of two or more objects that come unusually near one to another. In particular, regarding an asteroid’s position with respect to Earth, when it is within the Moon’s orbit.

See also: → close; → approach.

A binary system in which the separation of the component stars is comparable to their diameters, so that they influence each other’s evolution most commonly by the tidal forces.

See also: → close; → binary;
→ star.

A binary system in which the separation of the component stars is comparable to their diameters, so that they influence each other’s evolution most commonly by the tidal forces.

See also: → close; → binary;
→ star.

A → binary system in which the distance separating the stars is comparable to their size. Most close binaries are spectroscopic binaries (→ spectroscopic binary) and/or eclipsing binaries (→ eclipsing binary). In most of them
→ mass transfer occurs at some stage,
an event which profoundly affects the → stellar evolution of the components. The evolution of close binaries depends on the → initial masses of the two stars and
their → separation. When the more massive star evolves into a → red giant first, material will spill through the inner point onto its companion, thereby affecting its companion’s evolution. Mass transfer can also alter the separation and → orbital period of the binary star.

See also: → close; → binary; → system.

A → binary system in which the distance separating the stars is comparable to their size. Most close binaries are spectroscopic binaries (→ spectroscopic binary) and/or eclipsing binaries (→ eclipsing binary). In most of them
→ mass transfer occurs at some stage,
an event which profoundly affects the → stellar evolution of the components. The evolution of close binaries depends on the → initial masses of the two stars and
their → separation. When the more massive star evolves into a → red giant first, material will spill through the inner point onto its companion, thereby affecting its companion’s evolution. Mass transfer can also alter the separation and → orbital period of the binary star.

See also: → close; → binary; → system.

1. In a → star cluster, coming across of two stars so closely that their → orbits alter by
   their mutual → gravitational attractions.
   

2. As regards an → asteroid or → comet, a situation when it crosses the Moon’s orbit and approaches the Earth with a risk of collision. See also → close approach, → encounter.

See also: → close; → encounter.

1. In a → star cluster, coming across of two stars so closely that their → orbits alter by
   their mutual → gravitational attractions.
   

2. As regards an → asteroid or → comet, a situation when it crosses the Moon’s orbit and approaches the Earth with a risk of collision. See also → close approach, → encounter.

See also: → close; → encounter.

Having boundaries; limited. → closed curve; → closed Universe.

Etymology (EN): Closed, p.p. of close, from M.E. clos, from O.Fr., from clore “to shut,” from L. clausus, p.p. of claudere “to close.”

Etymology (PE): Basté p.p.of bastan,
from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie,” Skt. bandh- “to bind, tie, fasten,” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind, → band.

Having boundaries; limited. → closed curve; → closed Universe.

Etymology (EN): Closed, p.p. of close, from M.E. clos, from O.Fr., from clore “to shut,” from L. clausus, p.p. of claudere “to close.”

Etymology (PE): Basté p.p.of bastan,
from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie,” Skt. bandh- “to bind, tie, fasten,” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind, → band.

A curve whose ends are joined.

See also: → closed; → curve.

A curve whose ends are joined.

See also: → closed; → curve.

A bounded space the surface of which has the property that if one travels in any direction upon it without changing direction, one will end up back to the departure point. An example is a sphere. Triangles which lie on the surface of a closed space will have a sum of angles which is greater than 180°. An closed space has a positive → curvature. See also → closed Universe, → open space.

See also: → closed; → space.

A bounded space the surface of which has the property that if one travels in any direction upon it without changing direction, one will end up back to the departure point. An example is a sphere. Triangles which lie on the surface of a closed space will have a sum of angles which is greater than 180°. An closed space has a positive → curvature. See also → closed Universe, → open space.

See also: → closed; → space.

Thermodynamics: A system which can exchange energy with the surroundings but not matter. → open system; → isolated system.

See also: → closed; → system.

Thermodynamics: A system which can exchange energy with the surroundings but not matter. → open system; → isolated system.

See also: → closed; → system.

A → cosmological model, first formulated by Friedmann and Lemaître, in which the Universe has a → finite size and lifetime and → space has a → positive → curvature,
e.g. a Universe with a density greater than the → critical density. See also → closed space.

See also: → closed; → Universe.

A → cosmological model, first formulated by Friedmann and Lemaître, in which the Universe has a → finite size and lifetime and → space has a → positive → curvature,
e.g. a Universe with a density greater than the → critical density. See also → closed space.

See also: → closed; → Universe.

In → predicate logic, a → wff with no → free occurrences of any → variable. Also called a → sentence.

See also: → closed; → wff.

In → predicate logic, a → wff with no → free occurrences of any → variable. Also called a → sentence.

See also: → closed; → wff.

Math.: The property of a set in which the application of a given mathematical operation to any member of the set always has another member of the set as its result.
The intersection of all closed sets that contain a given set.

Etymology (EN): M.E., from M.Fr., from O.Fr. closure “that which encloses,” from L. clausura “lock, fortress, a closing,” from p.p. stem of claudere “to close.”

Etymology (PE): Bandeš, verbal noun of bastan “to shut, bind; to clot; to form seed buds,” from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie;”
Skt. bandh- “to bind, tie, fasten;” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind.

Math.: The property of a set in which the application of a given mathematical operation to any member of the set always has another member of the set as its result.
The intersection of all closed sets that contain a given set.

Etymology (EN): M.E., from M.Fr., from O.Fr. closure “that which encloses,” from L. clausura “lock, fortress, a closing,” from p.p. stem of claudere “to close.”

Etymology (PE): Bandeš, verbal noun of bastan “to shut, bind; to clot; to form seed buds,” from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie;”
Skt. bandh- “to bind, tie, fasten;” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind.

A basic rule in → group theory stating that if a and b are a group element then a * b is also a group element.

See also: → closure; → axiom.

A basic rule in → group theory stating that if a and b are a group element then a * b is also a group element.

See also: → closure; → axiom.

In astronomical interferometry, a method using triplets of telescopes in an array to calculate the phase information and get over the effects of atmospheric turbulence. The method, used in high-resolution astronomical observations, both at radio and at optical wavelengths, allows imaging of complex objects in the presence of severe aberrations.

See also: → closure; → phase.

In astronomical interferometry, a method using triplets of telescopes in an array to calculate the phase information and get over the effects of atmospheric turbulence. The method, used in high-resolution astronomical observations, both at radio and at optical wavelengths, allows imaging of complex objects in the presence of severe aberrations.

See also: → closure; → phase.

A plane curve of spiral form, → Cornu’s spiral.

See also: From Gk. kloth, from klothein “to spin” + epenthetic vowel -o- + eides “form,” → -oid; because the curve is reminiscent of the thread that winds around a weaving loom.
→ Klotho.

A plane curve of spiral form, → Cornu’s spiral.

See also: From Gk. kloth, from klothein “to spin” + epenthetic vowel -o- + eides “form,” → -oid; because the curve is reminiscent of the thread that winds around a weaving loom.
→ Klotho.

1. A visible mass of water droplets and/or ice particles in the atmosphere above the Earth’s surface.
   

2. → interstellar cloud.

Etymology (EN): Cloud, from O.E. clud “mass of rock,” from P.Gmc. *kludas.

Etymology (PE): Abr, from Mid.Pers. awr, abr (Laki owr, Baluchi haur, Kordi Soriani hewr),
Av. awra- “rain cloud, rain,” cf. Skt. abhra-“thunder cloud,” Gk. afros “scum, foam,” L. imber “rain;” also Sk. ambha- “water,” Gk. ombros “rain,” PIE *mbhros “rain cloud, rain,” from *mbh-.

1. A visible mass of water droplets and/or ice particles in the atmosphere above the Earth’s surface.
   

2. → interstellar cloud.

Etymology (EN): Cloud, from O.E. clud “mass of rock,” from P.Gmc. *kludas.

Etymology (PE): Abr, from Mid.Pers. awr, abr (Laki owr, Baluchi haur, Kordi Soriani hewr),
Av. awra- “rain cloud, rain,” cf. Skt. abhra-“thunder cloud,” Gk. afros “scum, foam,” L. imber “rain;” also Sk. ambha- “water,” Gk. ombros “rain,” PIE *mbhros “rain cloud, rain,” from *mbh-.

An early type of → bubble chamber used for detecting particles of ionizing radiation. It was
invented in 1900 by Charles Thomson Rees Wilson (1869-1959), a Scottish physicist, who along with Arthur Compton (1892-1962 ) received the Nobel Prize for physics in 1927.

See also: → cloud; → chamber.

An early type of → bubble chamber used for detecting particles of ionizing radiation. It was
invented in 1900 by Charles Thomson Rees Wilson (1869-1959), a Scottish physicist, who along with Arthur Compton (1892-1962 ) received the Nobel Prize for physics in 1927.

See also: → cloud; → chamber.

The fraction of the sky covered by clouds. It is expressed in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky.

See also: → cloud; → cover.

The fraction of the sky covered by clouds. It is expressed in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky.

See also: → cloud; → cover.

Process by which a → collapsing → giant molecular cloud breaks into dense → clumps, eventually bringing about
→ pre-stellar cores.

See also: → cloud; → fragmentation.

Process by which a → collapsing → giant molecular cloud breaks into dense → clumps, eventually bringing about
→ pre-stellar cores.

See also: → cloud; → fragmentation.

A large, faintly colored arc formed usually by sunlight falling on a cloud. Also called white rainbow, fogbow, and mistbow. Cloudbow appears white because the water droplets in the cloud or fog are very small compared with those of ordinary rainbows.

See also: → cloud; → bow.

A large, faintly colored arc formed usually by sunlight falling on a cloud. Also called white rainbow, fogbow, and mistbow. Cloudbow appears white because the water droplets in the cloud or fog are very small compared with those of ordinary rainbows.

See also: → cloud; → bow.

Any sudden and heavy fall of → rain, always of the → shower type.

Etymology (EN): → cloud; → burst.

Etymology (PE): Ragbâr, from rag + bâr. The second component bâr, variant bârân “rain,” from bâridan “to rain.” The origin of the first component is not clear. Rag in Persian means “blood vein, vessel,” but this sense seems irrelevant here. In Gilaki the bare
râk (without bâr) means cloudburst. Râk/rag
may be related (via an extinct Iranian parent) to the Skt. stem ri- “to flow, to drop, to become liquid.”

Any sudden and heavy fall of → rain, always of the → shower type.

Etymology (EN): → cloud; → burst.

Etymology (PE): Ragbâr, from rag + bâr. The second component bâr, variant bârân “rain,” from bâridan “to rain.” The origin of the first component is not clear. Rag in Persian means “blood vein, vessel,” but this sense seems irrelevant here. In Gilaki the bare
râk (without bâr) means cloudburst. Râk/rag
may be related (via an extinct Iranian parent) to the Skt. stem ri- “to flow, to drop, to become liquid.”

Same as → cloud cover.

See also: From cloudy, from cloudy, from → cloud

• → -ness.

Same as → cloud cover.

See also: From cloudy, from cloudy, from → cloud

• → -ness.

Light from nearby stars scattered by → dust grains in low-density outer regions of → molecular clouds.
It is seen not only in the → near infrared bands JHK, but also continuously from the visible to 5 μm. Cloudshine could be considered as an intermediate between → scattering in the visible and the → coreshine effect
(Foster & Goodman, 2006, ApJ 636, L105). See also

See also: → cloud; → shine.

Light from nearby stars scattered by → dust grains in low-density outer regions of → molecular clouds.
It is seen not only in the → near infrared bands JHK, but also continuously from the visible to 5 μm. Cloudshine could be considered as an intermediate between → scattering in the visible and the → coreshine effect
(Foster & Goodman, 2006, ApJ 636, L105). See also

See also: → cloud; → shine.

Any of various plants of the genus Trifolium with three round, green leaves that are joined together. Clovers occasionally have leaves with four leaflets, instead of the usual three.

Etymology (EN): M.E. clovere; O.E. clafre; cf. M.L.G. klever, M.Du. claver, Du. klaver, O.S. kle, O.H.G. kleo, Ger. Klee “clover,” of uncertain origin.

Etymology (PE): Šabdar, of unknown origin.

Any of various plants of the genus Trifolium with three round, green leaves that are joined together. Clovers occasionally have leaves with four leaflets, instead of the usual three.

Etymology (EN): M.E. clovere; O.E. clafre; cf. M.L.G. klever, M.Du. claver, Du. klaver, O.S. kle, O.H.G. kleo, Ger. Klee “clover,” of uncertain origin.

Etymology (PE): Šabdar, of unknown origin.

A bright → quasar whose image is split into four spots due to → gravitational lensing (Magain et al. 1988, Nature 334, 325). The four images of comparable brightness all lie within 0.7 arc seconds of the image center. The quasar has a → redshift of 2.56, corresponding to a distance of about 11 billion → light-years. Observations indicate that the lensing galaxy is located approximately at the geometrical center of the four images. A firm spectroscopic redshift of the lens has yet to be obtained; however, a → cluster of galaxies at a redshift of z = 1.7 has been suggested to account for the lensing of this system. H1413+117 was the first quasar to be detected in the → submillimeter wave → continuum and in → carbon monoxide emission.

See also: So named because of the optical image; → clover; → leaf; → quasar.

A bright → quasar whose image is split into four spots due to → gravitational lensing (Magain et al. 1988, Nature 334, 325). The four images of comparable brightness all lie within 0.7 arc seconds of the image center. The quasar has a → redshift of 2.56, corresponding to a distance of about 11 billion → light-years. Observations indicate that the lensing galaxy is located approximately at the geometrical center of the four images. A firm spectroscopic redshift of the lens has yet to be obtained; however, a → cluster of galaxies at a redshift of z = 1.7 has been suggested to account for the lensing of this system. H1413+117 was the first quasar to be detected in the → submillimeter wave → continuum and in → carbon monoxide emission.

See also: So named because of the optical image; → clover; → leaf; → quasar.

1. A compact mass, in particular that contained in a less dense environment.
   

2. → molecular clump.
   

3. Inhomogeneities on small scales present in → stellar winds. See also → clumped wind.

Etymology (EN): Clump, from Du. klomp “lump, mass,” or Low Ger. klump.

Etymology (PE): Gudé “ball, bowl, tumour” in Gilaki, cf. Skt. guda- “ball, mouthful, lump, tumour,”
Gk. gloutos “rump,” L. glomus “ball,” globus “globe,” Ger. Kugel, E. clot, PIE *gel- “to make into a ball.”

1. A compact mass, in particular that contained in a less dense environment.
   

2. → molecular clump.
   

3. Inhomogeneities on small scales present in → stellar winds. See also → clumped wind.

Etymology (EN): Clump, from Du. klomp “lump, mass,” or Low Ger. klump.

Etymology (PE): Gudé “ball, bowl, tumour” in Gilaki, cf. Skt. guda- “ball, mouthful, lump, tumour,”
Gk. gloutos “rump,” L. glomus “ball,” globus “globe,” Ger. Kugel, E. clot, PIE *gel- “to make into a ball.”

A → radiation-driven wind of → Wolf-Rayet and → O stars, which is not homogeneous, and contains compressions and rarefactions in the form of density clumps. Observationally, wind clumping appears as moving, small-scale structures in spectral line profiles. Indirect indicators of wind clumping include: electron scattering wings of emission lines, too-weak observed UV line profiles, and shapes of X-ray lines. The most likely physical explanation for the presence of these clumps is an instability in radiatively-driven winds. The inclusion of a clumping factor in the models of W-R winds reduces the → mass loss rates by a factor ~ 2-4 relative to homogeneous models. See also → clumping factor.

See also: → clumpy; → wind.

A → radiation-driven wind of → Wolf-Rayet and → O stars, which is not homogeneous, and contains compressions and rarefactions in the form of density clumps. Observationally, wind clumping appears as moving, small-scale structures in spectral line profiles. Indirect indicators of wind clumping include: electron scattering wings of emission lines, too-weak observed UV line profiles, and shapes of X-ray lines. The most likely physical explanation for the presence of these clumps is an instability in radiatively-driven winds. The inclusion of a clumping factor in the models of W-R winds reduces the → mass loss rates by a factor ~ 2-4 relative to homogeneous models. See also → clumping factor.

See also: → clumpy; → wind.

Of a → molecular cloud, the property of being made up of → clumps.
The extent with which a molecular cloud is → clumpy.

Etymology (EN): Clumpiness, from → clumpy + → -ness.

Etymology (PE): Gudegi from gudé, → clump, + -gi suffix forming noun from adjectives ending in -é.

Of a → molecular cloud, the property of being made up of → clumps.
The extent with which a molecular cloud is → clumpy.

Etymology (EN): Clumpiness, from → clumpy + → -ness.

Etymology (PE): Gudegi from gudé, → clump, + -gi suffix forming noun from adjectives ending in -é.

The massing together of material to form clumps. → wind clumping.

See also: → clump; → -ing.

The massing together of material to form clumps. → wind clumping.

See also: → clump; → -ing.

The ratio f_cl = <ρ²> / <ρ >², where ρ represents the → stellar wind density and the brackets mean values. Unclumped wind has f_cl = 1 and → clumping becomes significant for f_cl≅ 4.

See also: → clumping; → factor.

The ratio f_cl = <ρ²> / <ρ >², where ρ represents the → stellar wind density and the brackets mean values. Unclumped wind has f_cl = 1 and → clumping becomes significant for f_cl≅ 4.

See also: → clumping; → factor.

Of a → molecular cloud, being composed of → clumps.

Etymology (EN): Clumpy, from → clump + -y suffix meaning “full of or characterized by,” from O.E. -ig, from P.Gmc. *-iga, akin to Gk. -ikos, L. -icus,
→ -ics.

Etymology (PE): Gudedâr, from gudé, → clump, + dâr “having, possessor,” from dâštan “to have, to possess,” O.Pers./Av. root dar- “to hold, keep back, maitain, keep in mind,” Skt. dhr-, dharma- “law,”
Gk. thronos “elevated seat, throne,” L. firmus “firm, stable,” Lith. daryti “to make,” PIE *dher- “to hold, support.”

Of a → molecular cloud, being composed of → clumps.

Etymology (EN): Clumpy, from → clump + -y suffix meaning “full of or characterized by,” from O.E. -ig, from P.Gmc. *-iga, akin to Gk. -ikos, L. -icus,
→ -ics.

Etymology (PE): Gudedâr, from gudé, → clump, + dâr “having, possessor,” from dâštan “to have, to possess,” O.Pers./Av. root dar- “to hold, keep back, maitain, keep in mind,” Skt. dhr-, dharma- “law,”
Gk. thronos “elevated seat, throne,” L. firmus “firm, stable,” Lith. daryti “to make,” PIE *dher- “to hold, support.”

An irregularly shaped, clumpy → star-forming galaxy that does not fall anywhere on the → Hubble sequence and appears frequently at → redshifts z ~ 1-4. Galaxies at z ≤ 1 with similar morphologies and enhanced → star formation have been identified, but become less common with decreasing redshift. Clumpy galaxies are prominent in the → early Universe.

See also: → clumpy; → galaxy.

An irregularly shaped, clumpy → star-forming galaxy that does not fall anywhere on the → Hubble sequence and appears frequently at → redshifts z ~ 1-4. Galaxies at z ≤ 1 with similar morphologies and enhanced → star formation have been identified, but become less common with decreasing redshift. Clumpy galaxies are prominent in the → early Universe.

See also: → clumpy; → galaxy.

1. A group of the same astronomical objects gathered or occurring closely together, such as → cluster of galaxies, → globular cluster, → open cluster, and so on.
   

2. To gather or grow into clusters.

→ Arches cluster, → Beehive Cluster, → bound cluster, → Brocchi’s Cluster, → Bullet cluster, → Central cluster, → cluster core, → cluster mass function, → cluster of galaxies, → clustering, → clustering law, → Coma cluste, → Galactic center cluster, → galactic cluster, → galaxy cluster, → globular cluster, → Hercules cluster, → hierarchical clustering, → intercluster medium, → Local Supercluster, → moving cluster, → open cluster, → Perseus Cluster, → pre-cluster core, → protocluster, → rich cluster, → S cluster, → Sgr A* cluster, → star cluster, → super star cluster, → supercluster, → superclustering, → tight star cluster, → Trapezium cluster, → unbound cluster, → Ursa Major cluster.

Etymology (EN): O.E. clyster “cluster,” probably akin to O.E. clott “clot”.

Etymology (PE): Xušé “cluster, a bunch of grapes, an ear of corn,” (Laki huša), from Mid.Pers. hošag or xušak; cf. Skt. guccha- “bundle, bunch of flowers, cluster of blossom, clump;” xušé bastan, with
bastan “to bind, shut; to clot; to form seed buds”, from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie,” Skt. bandh- “to bind, tie, fasten,” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind.

1. A group of the same astronomical objects gathered or occurring closely together, such as → cluster of galaxies, → globular cluster, → open cluster, and so on.
   

2. To gather or grow into clusters.

→ Arches cluster, → Beehive Cluster, → bound cluster, → Brocchi’s Cluster, → Bullet cluster, → Central cluster, → cluster core, → cluster mass function, → cluster of galaxies, → clustering, → clustering law, → Coma cluste, → Galactic center cluster, → galactic cluster, → galaxy cluster, → globular cluster, → Hercules cluster, → hierarchical clustering, → intercluster medium, → Local Supercluster, → moving cluster, → open cluster, → Perseus Cluster, → pre-cluster core, → protocluster, → rich cluster, → S cluster, → Sgr A* cluster, → star cluster, → super star cluster, → supercluster, → superclustering, → tight star cluster, → Trapezium cluster, → unbound cluster, → Ursa Major cluster.

Etymology (EN): O.E. clyster “cluster,” probably akin to O.E. clott “clot”.

Etymology (PE): Xušé “cluster, a bunch of grapes, an ear of corn,” (Laki huša), from Mid.Pers. hošag or xušak; cf. Skt. guccha- “bundle, bunch of flowers, cluster of blossom, clump;” xušé bastan, with
bastan “to bind, shut; to clot; to form seed buds”, from Mid.Pers. bastan/vastan “to bind, shut,” Av./O.Pers. band- “to bind, fetter,” banda- “band, tie,” Skt. bandh- “to bind, tie, fasten,” PIE *bhendh- “to bind,” cf. Ger. binden, E. bind.

The central part of a cluster (globular, galaxies, etc.) where the spatial density of the objects making up the cluster is much higher than the average value.

See also: → cluster; → core.

The central part of a cluster (globular, galaxies, etc.) where the spatial density of the objects making up the cluster is much higher than the average value.

See also: → cluster; → core.

The fraction of → star formation which happens in → bound clusters. It is defined as the ratio between the → cluster formation rate and → star formation rate
(Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

See also: → cluster; → formation; → efficiency.

The fraction of → star formation which happens in → bound clusters. It is defined as the ratio between the → cluster formation rate and → star formation rate
(Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

See also: → cluster; → formation; → efficiency.

A parameter used in star formation models representing the ratio of the total mass in → star clusters to the corresponding age range (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

See also: → cluster; → formation; → rate.

A parameter used in star formation models representing the ratio of the total mass in → star clusters to the corresponding age range (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

See also: → cluster; → formation; → rate.

An empirical power-law relation representing the number of clusters as a function of their mass. It is defined as: N(M)dM ∝ M ^-αdM, where the exponent α has an estimated value of about 2 and dM is the mass interval. It is believed that this is a universal law applying to a variety of objects including globular clusters, massive young clusters, and H II regions.

See also: → cluster; → mass; → function.

An empirical power-law relation representing the number of clusters as a function of their mass. It is defined as: N(M)dM ∝ M ^-αdM, where the exponent α has an estimated value of about 2 and dM is the mass interval. It is believed that this is a universal law applying to a variety of objects including globular clusters, massive young clusters, and H II regions.

See also: → cluster; → mass; → function.

Same as → galaxy cluster.

See also: → cluster; → galaxy.

Same as → galaxy cluster.

See also: → cluster; → galaxy.

Grouping of a number of similar astronomical objects.

See also: Noun from verb → cluster.

Grouping of a number of similar astronomical objects.

See also: Noun from verb → cluster.

An empirical power-law representing the number of stellar clusters as a function of the number of stars per cluster within an interval. It is expressed as: N(N) dN∝ N^-α dN, where N(N) is the number of clusters containing N stars and dN_* is the interval in star number. It is believed that this relationship applies to a variety of systems, including stellar clusters, globular clusters, H II regions (Oey et al. 2004, AJ 127, 1632).

See also: → clustering; → law.

An empirical power-law representing the number of stellar clusters as a function of the number of stars per cluster within an interval. It is expressed as: N(N) dN∝ N^-α dN, where N(N) is the number of clusters containing N stars and dN_* is the interval in star number. It is believed that this relationship applies to a variety of systems, including stellar clusters, globular clusters, H II regions (Oey et al. 2004, AJ 127, 1632).

See also: → clustering; → law.

A disorderly heap or assemblage; a state or condition of confusion.

Etymology (EN): Variant of clotter (now obsolete), from to clot + -er.

Etymology (PE): Âluzé, from Kurd. âluz, Tabari âluz, âliz “messy, disorderly, untidy,” Dehxodâ âlofté “astonished; mad; broken,” âloftan “to rage, grow mad.”

A disorderly heap or assemblage; a state or condition of confusion.

Etymology (EN): Variant of clotter (now obsolete), from to clot + -er.

Etymology (PE): Âluzé, from Kurd. âluz, Tabari âluz, âliz “messy, disorderly, untidy,” Dehxodâ âlofté “astonished; mad; broken,” âloftan “to rage, grow mad.”