An Etymological Dictionary of Astronomy and Astrophysics

Geometry: The regular solid whose faces are six squares.
Algebra: The third power of a quantity; the product of three equal factors (a . a . a = a³).

Etymology (EN): From L. cubus, from Gk. kubos “a cube, a die; cavity before the hip,”
kubiton “elbow;” cf. Skt. kubra- “hole in the earth, pit;” Goth. hups “hip;” from PIE base *keu- “to bend.”

Etymology (PE): The currently used term in Pers. is moka’ab (مکعب), loan from Ar., from ka’b (کعب)
“talus, anklebone, heel; die.” There are several Pers. equivalents for the concepts “talus, anklebone; die,” one of which qâb, variants qâp and
in Tabari kâb “heel, talus.” This dictionary adopts kâb, which has already been introduced by other sources.

A number which taken three times as a factor produces another number, the cube of the given factor.

See also: → cube; → root.

1. Having the form of a cube; having three dimensions. → cubic crystal system.
   

2. Of or pertaining to the third degree of a quantity or variable. → cubic equation, → cubic function.

See also: → cube + → -ic.

A → crystal system whose three axes have equal lengths and all corners are 90°.

See also: → cubic; → crystal; → system.

An equation containing unknowns of the third power; the general form: ax³ + bx² + cx + d = 0.

See also: Cubic, of or pertaining to → cube; → equation.

A function defined by a → polynomial of → degree three. Its generalized form is:

f(x) = ax³ + bx² + cx + d, where a, b, c and d are constants, and a≠ 0.

See also: → cubic; → function.

To reach the highest point above an observer’s horizon; to attain → culmination.

Etymology (EN): From L.L. culminatus, p.p. of culminare “to exalt,” from L. culmen “top, summit,” cf. Gk. kolonos “hill,” Skt. kuta- “top,” Mod.Pers. kotal “hill,” Lith. kalmas “mountain,” P.Gmc. *khulnis Low Ger. hull “hill,” E. hill; PIE base *kel- “to be high; hill.”

Etymology (PE): Bâlestidan, verb from bâlest→ culmination.

The act of culminating or the instant at which a celestial object reaches its highest altitude above the horizon by crossing the observer’s meridian. → upper culmination;
→ lower culmination.

Etymology (EN): Verbal noun of → culminate.

Etymology (PE): Bâlest, from Mid.Pers. bâlist “culmination point of a star; highest, summit,” from bâlây “high” + -ist superlative suffix, Av. barəzišta- “highest,” from barəz- “high, mount” (Skt. bhrant- “high,” O.E. burg, burh “castle, fortified place,” from P.Gmc. *burgs “fortress,” Ger. Burg “castle,” Goth. baurgs “city,” E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- “high”)

• -išta- superlative suffix (Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost).

1a) Enlightenment and sophistication acquired by a person or society through education, arts, letters, manners, and scholarly pursuits.

1b) The beliefs, customs, practices, and social behavior of a certain nation, people, or period.

2a) The growing of biological material (such as plants, microorganisms, animal tissue) for scientific study, medicinal use, etc.

2b) The product or growth resulting from such cultivation.

Etymology (EN): M.E., from M.Fr. culture from L. cultura “cultivation, agriculture;
care; honoring,” from p.p. stem of colere “to till, cultivate; inhabit; maintain; cherish, honor;” PIE *k^wel- “to move around;” cf. Av. car- “to move, go, walk,” carāni “I would go,” carāt “he would go;” Mid.Pers. car- “to pasture, graze,” carag “pasture, grazing; flock;” Mod.Pers. caridan “to graze;” Skt. car- “to move, go, walk;” Gk. pelomai “to move.”

Etymology (PE): 1) Farhang “culture, education; dictionary,” related to farhixtan “to educate,” âhanjidan “to draw up;” Mid.Pers. frahang “education, instruction; knowledge,” frahixtan, frahanjidan “to educate;” Av. fraθang- “to drive forward, to drive to,” from frā-, fra- “forward, forth,” → pro-,

• θang-, θanj- “to draw, to pull.”
  

2. Kešt past stem of keštan, variants kâštan, kâridan “to cultivate, to plant;” Mid.Pers. kištan, kâridan “to sow, plant; to make furrows;” Av. kar- “to strew seed, cultivate,” kāraiieiti “cultivates;” cf. Skt. kar- “to scatter, strew, pour out.”

To heap up; → amass; → accumulate.

Etymology (EN): From L. cumulatus “heaped, increased, augmented,” p.p. of cumulare “to heap,” from cumulus “mound, heap,” from PIE *ku-m-olo-, from *keue- “to swell;” cf. Skt. śavi “to swell;” svayati “swells up, is strong;” Av. su-, sauu- “to bulge, swell up, increase;” Proto-Ir. *sauH- “to bulge, swell up, increase” (Cheung 2007, Pers. sud “gain, profit”); Gk. kuein “to swell;” Lith. saunas.

Etymology (PE): Kumidan, from kum, kumé “heap;” Hamedâni kumelé, kumelân “heap, pile, mound,” kumé kardan “to accumulate;” Kurd. kom “pile, group,” komel “society, organization,” related to Pers. kud “heap” (Mid.Pers. kôt), Gilaki kô-pâ “warehouse, barn,” kô-gâh “gathering site.” In the Gilan province there are several localities with protruding positions that bear names with an initial kom- (such as komâcâl, komâdol, kumélé, komsâr, etc.); probably related to L. cumul-, as above; if confirmed, interestingly it relates to the PIE form *keue- in contrast with Proto-Ir. *sauH-, as above.

1. Increasing or growing by accumulation or successive additions.
   

2. Formed by or resulting from accumulation or the addition of successive parts or elements (Dictionary.com). → cumulative distribution function.

See also: → cumulate; → -ive.

A function that gives the probability that a → random variable X is less than or equal to x, at each possible outcome: F(x) = P(X ≤ x), for -∞ < x < ∞. Same as → distribution function.

See also: → cumulative; → distribution; → function.

A natural satellite of Uranus discovered in 2003 (Uranus XXVII); mean diameter about 18 km, orbital semi-major axis about 74 km.

Etymology (EN): Discovered in 2003 using the Hubble Space Telescope. Named after a character in William Shakespeare’s play Timon of Athens.

Asteroid 763 Cupido, which belongs to the Main Belt.

See also: Cupido “desire,” the Roman god of love (also known as Amor), often equated with Eros,
one of the primordial gods in Greek mythology.

The traditional unit of → radioactivity defined as the quantity of any radioactive isotope in which the number of → disintegrations per second is 3.7 × 10¹⁰. Abbreviation: Ci. → becquerel.

See also: Named after the French physicists Pierre Curie (1859-1906) and his wife Marie Curie (1867-1934, née Maria Skłodowska), pioneers of research on radioactivity, who discovered → radium in 1898 and received the Nobel Prize in Physics, 1903, jointly with Henri Becquerel (1852-1908).

The highest temperature for a given → ferromagnetic substance above which the → magnetization is lost and the substance becomes merely → paramagnetic.
The Curie temperature of iron is about 1043 K and that of nickel 631 K.

See also: Named after the French physicist Pierre Curie (1859-1906), a pioneer in magnetism, crystallography, and radioactivity. In 1903 he received the Nobel Prize in Physics with his wife Marie Curie (1867-1934, née Maria Skłodowska), and Henri Becquerel (1852-1908); → temperature.

A → radioactive element not found in nature but discovered in 1944 among the products of → plutonium-239 after bombardment by high-energy → alpha particles in a cyclotron at the University of California at Berkeley; symbol Cm. Atomic number 96; mass number of most stable isotope 247; melting point about 1,340°C; boiling point 3,110°C.

See also: Named after French physicists Pierre Curie (1859-1906) and his wife Marie Curie (1867-1934, née Maria Skłodowska).

A vector → operator which is the vector product of the → del operator with a vector function. For a three-dimensional function, it is equal to the sum of the vector products of the unit vectors and → partial derivatives in each of the component directions:
∇ x F(x,y,z) = (∂F_z/∂y - ∂F_y/∂z)i + (∂F_x/∂z - ∂F_z/∂x)j + (∂F_y/∂x - ∂F_x/∂y)k.
The curl of a vector field is a vector field. ∇ x F is sometimes called the rotation of F and written rot F.

Etymology (EN): Metathesis of crulle “curly,” probably from an unrecorded O.E. word or from M.Du. krul “curly.”

Etymology (PE): Tâv, variants tow, tâb “twist, swing,” from tâbidan “to spin, to twist.”

Any steady movement of material in space. In particular, any movement of electric charge. → stream; → flow;
→ flux.

Etymology (EN): From O.Fr. corant “running,” pr.p. of courre “to run,” from L. currere “to run,” from PIE *kers- “to run” (cf. Gk. -khouros “running,” Lith. karsiu “go quickly,” O.N. horskr “swift,” Welsh carrog “torrent”).

Etymology (PE): Jarayân from Ar.

The → Universe at the → redshift z = 0.

See also: → current; → cosmological; → epoch.

The electric current per unit of cross-sectional area perpendicular to the direction of current flow. It is a vector quantity and represented by symbol J. Electric current density is usually expressed in amperes per square meter.

See also: → current; → density

A movable, sometime blinking, indicator on a computer screen identifying the point that will be affected by input from the user (OxfordDictionaries.com).

Etymology (EN): From L. cursor “runner,” also “errand-boy,” from curs-, p.p. stem of currere “to run,” → current.

Etymology (PE): Jâbân, literally “position/place keeper,” or “position/place maker,” from jâ, → place, + -bân a suffix denoting “keeper, guard,” sometimes forming agent nouns or indicating relation, → host.

A hypothetical → scalar field that is used to explain the → primordial curvature perturbation in the Universe. It is generally supposed that the primordial perturbation originates during → inflation, from the → quantum fluctuation of the inflation field. The curvaton model is an attempt to account for the primordial perturbation by a completely different origin, namely the quantum fluctuation during inflation of a light scalar field which is not the assumed slowly-rolling inflation.
In this model, the curvaton field is an energetically sub-dominant component during inflation. As the energy density of the Universe drops after inflation, the fraction of this component becomes significant. At this time the curvaton perturbation is converted into an adiabatic curvature perturbation of the Universe. The amplitude of the final perturbation, which should match observations, depends on both how long the curvaton oscillates before it decays, and on the shape of the potential. The first curvaton model was proposed by D. H. Lyth & D.Wands and in 2002 (Physics Letters B524).

See also: From curvat-, from → curvature, + → -on. Although not related, the term curvaton exists in Fr. meaning “small curve” with variants curvatone, courbaton, and corbatone (A. Jal, 1848, Glossaire nautique).

A measure of the amount by which a curve, a surface, or any other manifold deviates from a straight line, a plane, or a hyperplane. In particular,
The reciprocal of the radius of the circle which most nearly approximates a
curve at a given point.

See also:
→ curvature constant, → curvature of space-time, → field curvature, → primordial curvature perturbation.

Etymology (EN): From L. curvatura, from curvatus, p.p. of curvare “to bend,” from curvus “curved,” → curve.

Etymology (PE): Xamidegi, from xamidé “curved,” from xamidag “curved”

• noun suffix -i.

A parameter occurring in the → Friedmann equations of
→ general relativity describing the geometry of → space-time. A spatially → open Universe is defined by k = -1, a → closed Universe by k = + 1 and a → flat Universe by k = 0. See also the → Robertson-Walker metric. See also → curvature of space-time.

See also: → curvature; → parameter.

According to → general relativity, → space-time is curved by the presence of → matter. The curvature is described in terms of → Riemann’s geometry. In → cosmological models three types of curvature are considered: positive (spherical, → closed Universe), zero (Euclidean, → flat Universe), and negative (hyperbolic, → open Universe). See also → curvature constant.

See also: → curvature; → space-time.

A line that deviates from straightness in a smooth, continuous fashion. A line representing a variable on a graph.

Etymology (EN): From L. curvus “crooked, curved, bent;” cf. Av. skarəna- “round,”
Gk. kirkos, krikos “a ring;” PIE base *sker- “to turn, bend.”

Etymology (PE): Xam, variant kamân “arc,” Mid.Pers. kamân, probably from PIE *kamb- “to bend, crook,” cf. Breton kamm “curved, bent.”

Construction of mathematical functions whose graphs are curves that “best” approximate a given collection of data points.

See also: → curve; → fitting.

A plot showing how the → equivalent width of an → absorption line, or the radiance of an → emission line, increases as a → function of the → number of → atoms that produce the line.

See also: → curve; → growth.

Not straight.

See also: Adj. from → curve.

Consisting of, represented by, or bound by curved lines. → rectilinear.

See also: From → curve + → linear.

1. General: Pointed end. A point of transition. → polar cusp.
   

2. Either point of a → crescent moon.
   

3. A steep power-law representing the number density of stars in the central region of a galaxy. Cusps are characteristic of low-mass ellipticals. They are thought to result from the gravitational attraction of a central → supermassive black hole.
   

4. A peaked concentration of dark matter in the center of galaxies, as predicted by the → cold dark matter (CDM) model of galaxy formation. See also → cusp problem.
   

5. Math: A tooth-like meeting of two branches of a curve, with sudden change of direction.

Etymology (EN): L. cuspis “point, spear, pointed end.”

Etymology (PE): Tizé, noun from tiz “sharp, pointed,” from Mid.Pers. tēz, tēž, tigr “sharp,” O.Pers. tigra- “pointed,” Av. taēža-, tighra- “pointed,” Skt. taējas- “the sharp edge (of a knife), piercing (flame)”, from tij- “to be sharp, to pierce,” Gk. stizein “to prick, puncture,” stigma “mark made by a pointed instrument,” L. instigare “to goad,” P.Gmc. *stik- “to pierce, prick, be sharp,” O.H.G. stehhan, Ger. stechen “to prick,” O.E. stician “to pierce, stab,” E. stick “to pierce;” PIE *st(e)ig- “to stick; pointed”.

A problem encountered by the → cold dark matter (CDM) model of galaxy formation. The numerical simulations with CDM predict a large concentration of dark matter in the center of galaxies, with a peaked density distribution, in contrast to the real, observed galaxies. See also: → angular momentum catastrophe; → missing dwarfs.

See also: → cusp; → problem.

To penetrate or divide something, as with a sharp-edged instrument.

Etymology (EN): M.E. cutten, kytten, kitten; O.E. *cyttan, cognate with O.Swed. kotta “to cut;” O.N. kuti “little knife,” or from
O.Fr. couteau “knife.”

Etymology (PE): Boridan “to cut off;” Mid.Pers. brin-, britan, brinitan “to cut off,” brin “cut, delimitation, determined;” Av. (pairi-) brī- “to shave, shear;”
cf. Skt. bhrī- “to hurt, injure,” bhrinanti “they hurt.”

1. A designated limit beyond which the passage of something must be stopped.
   

2. A device that cuts off a transmission of photons.

Etymology (EN): → cut; → off.

Etymology (PE): Boré, from bor- present stem of boridan “to → cut” + noun suffix -é.

Filter rejecting all light with wavelengths on one side of the cutoff wavelength.

See also: → cutoff; → filter.

The electrode voltage which reduces the value of a dependent variable, e.g. anode current, to a specified low value.

See also: → cutoff; → voltage.

Wavelength at which the transmittance of a filter, or the detectivity of a detector, has fallen to one-half its peak value.

See also: → cutoff; → wavelength.