An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Optics: A strip or annulus of material, such as glass or film, whose density increases progressively from one end to the other. The function of the wedge is to weaken the light beam in an optical system.

Verbal adj. from → absorb; → wedge.

1) To admit to be real or true; recognize the existence, truth, or fact of.
2) To recognize the authority, validity, or claims of.
3) To show or express appreciation or gratitude for (Dictionary.com).

A blend of M.E aknow "admit or show one's knowledge" (from O.E. oncnawan "understand") and M.E. knowlechen "to admit."

Âdânidan, from âdân, from prefix â- + dân present stem of dânestan, → know; cf. Sogd. âzân, azân "to acknowledge, to confess," from prefixed zân, variant of dân.

In → graph theory, an edge where endpoints are distinguished; one is the head and the other is the tail. A directed edge is specified as an ordered pair of → vertices, u, v and is denoted by (u, v) or u→ v.

→ directed; → edge.

A process by which the nucleosynthesis products inside a star are drawn to upper layers of the star. → first dredge-up; → second dredge-up; → third dredge-up.

From M.E. (Scots) dreg-, O.E. draeg- (in drægnet "dragnet"), akin to dragan "to draw" + up.

Birunkašid, past stem of birun kašidan, from birun "out, the outside" (Mid.Pers. bêron, from bê "outside, out, away" + rôn "side, direction," Av. ravan- "(course of a) river") + kašidan "to draw," Mid.Pers. kašitan, Av. karš- "to draw," Skt. kars-, kársati "to pull, drag, plough," Gk. pelo, pelomai "to be busy, to bustle."

1) A line or border at which a surface terminates.
2) The thin, sharp side of the blade of a cutting instrument or weapon (Dictionary.com).
3) In → graph theory, any line in a → graph that joins two distinct → nodes. Any pair of → vertices.

M.E. egge; O.E. ecg "corner, edge;" cf. Ger. Eck "corner;" PIE base *ak- "sharp, pointed" (cf. L. acies; Gk. akis "point").

1) Labé "limb, edge," from lab "lip;" Mid.Pers. lap; cognate with L. labium; E. lip; Ger. Lefze.
2) Tiqé "blade of a knife or sword," from tiq "blade," tiz "sharp," variants tig, tež, tej, tij; Mid.Pers. tigr, têz, têž "sharp," O.Pers. tigra- "pointed," tigra.xauda- "pointed helmet (epithet of Scythians);" Av. tiγra- "pointed," tiγray- "arrow," tiži.arštay- "with the pointed spear," cf. Skt. tikta- "sharp, pungent, bitter," tejas- "sharpness, edge, point or top of a flame;" PIE base *st(e)ig- "to stick; pointed." Cognates in other IE languages: Gk. stizein "to prick, puncture," stigma "mark made by a pointed instrument," L. in-stigare "to goad," O.H.G. stehhan, Ger. stechen "to stab, prick," Du. stecken, O.E. sticca "rod, twig, spoon," E. stick.

A → spiral galaxy oriented edge-on to our view. → face-on galaxy.

→ edge; on, from O.E. on, variant of an "in, on, into" (cf. Du. aan; Ger. an; Goth. ana "on, upon"), from PIE base *ano "on" (cf. Av. ana "on;" Gk. ana "on, upon;" L. an-); → galaxy.

Kahkašân, → galaxy; pahlunemâ "showing the side," from pahlu, → side, + nemâ, from nemudan "to show, display," → display.

The → dredge-up occurring after core hydrogen burning as the core contracts before helium burning ignites (on the ascending giant branch). The hydrogen envelope becomes convective and this convective zone penetrates deep into the core dredging up material that has been processed by the central nuclear reactions. As a result the abundances of helium and nitrogen are boosted.

→ first; → dredge-up.

A method used to test the → image quality of → mirrors and → lenses. The test is performed by moving a knife edge laterally into the → image of a small → point source. The → eye, or a → camera, is placed immediately behind the knife edge, and the → exit pupil of the system is observed.

Named after the French physicist Léon Foucault (1819-1868), who invented the method; → knife; → edge; → test.

The same as → Foucault knife-edge test.

→ knife; → edge; → test.

1) Acquaintance with facts, truths, or principles, as from study or investigation.
2) All the information, facts, truths, and principles learned throughout time.

M.E. cnawlece, from O.E. cnawan, cf. O.H.G. bi-chnaan, ir-chnaan "to know;" cognate with Pers. šenâxt, as below.

1) Šenâxt, past stem of šenâxtan, šenâsidan "to know, discern, distinguish, be acquainted with;" Mid.Pers. šnâxtan, šnâs- "to know, recognize," dânestan "to know;" O.Pers./Av. xšnā- "to know, learn, come to know, recognize;" cf. Skt. jñā- "to recognize, know," jānāti "he knows;" Gk. gignoskein "to know, think, judge;" L. gnoscere, noscere "to come to know" (Fr. connaître; Sp. conocer); O.E. cnawan; E. know; Rus. znat "to know;" PIE base *gno- "to know."
2) Dânestgân, literally "body of (what is) known," from dânest, short for dâneste "known," p.p. of dânestan variant of šenâxtan, as above, + -gân suffix forming plural entities.

A rise in a planet's surface → reflectivity between red → absorbance and → near-infrared reflection due to → vegetation. The red-edge is one of the possible signs of life on distant → habitable  → exoplanets. Its presence is attributed to the chlorophyll molecule and leaf structure. The leaves of land plants reflect sunlight much more efficiently long-ward of this edge than they do in the visible. Although the red-edge position for Earth's vegetation is fixed at around 700-760 nm, that for exoplanets may not necessarily be the same (Takizawa et al., 2017, Nature Scientific Reports 7, Article number: 7561).

→ red; → edge.

A portion of the → space-time described by → Rindler coordinates.

→ Rindler coordinates; → wedge.

A → dredge-up process that occurs after core helium burning, in which the convective envelope penetrates much more deeply, pushing hydrogen burning shell into close proximity with the helium burning shell (→ first dredge-up). This arrangement is unstable and leads to burning pulses. The reason is that the hydrogen shell burns out until there is enough helium for the helium combustion to occur and all the helium is rapidly burnt. Afterward the hydrogen shell again burns outward and the process repeats.

→ second; → dredge-up.

A → dredge-up process that occurs in the stellar interior during He shell burning, as in → asymptotic giant branch (AGB) stars. These stars consist of a degenerate carbon-oxygen core, surrounded by a helium-rich region, above which lies a hydrogen-rich convective envelope. Following thermal pulses of the helium-burning shell, the convective envelope moves inward in mass, penetrating the hydrogen-exhausted regions. This is known as third dredge-up. As convection moves inward, nuclear processed materials are carried to the surface.

→ third; → dredge-up.

A glass prism of very small angle used as an optical element to divert the path of a beam of light for a particular purpose. → absorbing wedge.

M.E. wegge; O.E. wecg "a wedge," cf. M.Du. wegge, Du. wig, O.H.G. weggi "wedge," Ger. Weck "wedge-shaped bread roll."

Gové "wedge;" Av. vada- "wedge," ^xvaδa- "deadly weapon;" cf. Skt. vadhá- "killer, deadly weapon," vadh- "to slay, kill;" Gk. othein "to push" (root of → osmosis).

A photometer in which an → absorbing wedge is inserted in the brighter of two beams until the flux densities of the two light sources are equal.

→ wedge; → photometer.