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

Endowed with sensation; having perception through the senses. Responding to a stimulus.

From M.Fr. sensitif, from M.L. sensitivus "capable of sensation," from L. sensus, p.p. of sentire "feel perceive," → sense.

hessmand, from hess, → sense + -mand possession suffix.

1) The required brightness for an object in order to be detected by an observing instrument. A highly sensitive telescope can detect dim objects, while a telescope with low sensitivity can detect only bright ones.
2) Of a radio receiver or similar device, the minimum input signal required to produce a specified output signal having a specified signal-to-noise ratio.

State noun from → sensitive.

A device that receives and responds to a signal or stimulus (light, temperature, radiation level, or the like) by transmitting to a control equipment with the required degree of accuracy. → wavefront sensor.

→ sense; → -or.

1) Grammar: A grammatical unit of one or more words that expresses an independent statement, question, request, command, exclamation, etc., and that typically has a subject as well as a predicate, as in John is here. or Is John here? (Dictionary.com).
2) Law: An authoritative decision; a judicial judgment or decree, especially the judicial determination of the punishment to be inflicted on a convicted criminal: Knowledgeable sources say that the judge will announce the sentence early next week (Dictionary.com).

M.E., from O.Fr. sentence "judgment, decision; statement of authority," from L. sententia "thought, opinion; judgment," also "a thought expressed," from sentientem, p.p. of sentire "be of opinion, feel, perceive."

Sahân, related to soxan, → speech and pâsox, → response; Mid.Pers saxwan "speech, word;" O.Pers. θaⁿh- "to declare, say;" Av. səngh- (sanh-) "to declare;" Proto-Ir. *sanh- "to declare, explain;" cf. Skt. śams- "to praise, recite;" L. censere "to estimate, think; decide;" PIE *kens- "to announce, proclaim" (Cheung 2007).

Pertaining to or of the nature of a → sentence.

From L. sententi(a), → sentence, + → -al.

Same as → propositional logic.

→ sentential; → logic.

1) Detached, disconnected, disjoined.
2) To set apart; disconnect; dissociate.

→ separation.

General: The act or process of separating. The place at which a division or parting occurs.
Astro.: The angular distance between the two components of a visual binary or optical double star.

M.E., from O.Fr. separation, from L. separationem, from separare "to pull apart," from se- "apart" + parare "make ready, prepare."

Jodâyi state noun of jodâ "separate," from Mid.Pers. yut "separate, different;" Av. yuta- "separate, apart."

The energy required to remove a particle (a proton or a neutron) from a particular atomic nucleus.

→ separation; → energy.

A person or thing that separates. → decimal point.

→ separate; → -or.

1) General: Something that divides or separates. Plural: separatrices.
2) Math.: Any mark that separates digits in groups, such as the decimal point placed at the left of a decimal fraction, to separate it from the whole number which it follows.
3) Physics: A bundle of magnetic field lines which creates separate plasma regions.

From L. separatrix "she that separates," → separation; -trix a suffix.

Jodâgar, from jodâ "separate," → separation, + -gar, → -or.

1) General: The following of one thing after another; succession; something that follows; connected line of events, ideas, etc.
2) Math.: A set of quantities that are ordered in some way, such as a₁, a₂, a₃, .... A sequence is said to be known if a formula can be given for any particular term using the preceding terms or using its position in the sequence. Special types of sequences are commonly called → progressions. The terms of a sequence, when written as an indicated sum, form a → series.

M.E., from O.Fr. sequence "answering verses," from M.L. sequentia "a following, a succession," from L. sequentem (nominative sequens), pr.p. of sequi "to follow;" PIE base *sek^w- "to follow;" cf. Pers. az from; Mid.Pers. hac "from;" Av. hac-, hax- "to follow," hacaiti "follows" (O.Pers. hacā "from;" Av. hacā "from, out of;" Skt. sácā "with"); Skt. sácate "accompanies, follows;" Gk. hepesthai "to follow;" Lith. seku "to follow."

Peyâyé, literally "that follows; a subsequent event," from pey "after; step," related to pâ "foot" (Mid.Pers. pâd, pây, Av. pad-, Skt. pat, Gk. pos, gen. podos, L. pes, gen. pedis, P.Gmc. *fot, E. foot, Ger. Fuss, Fr. pied; PIE *pod-/*ped-) + ây- present stem of âmadan "to come, arrive, become" (Av. ay- "to go, to come," aēiti "goes;" O.Pers. aitiy "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go") +-é nuance suffix.
Rešté "thread, line, rope, row," p.p. of reštan, risidan "to spin;" Mid.Pers. rištag "rope, string, thread;" Av. uruuaēs- "to turn around," uruuaēsa- "vortex in water;" cf. Skt. vréśī- "an appellation of waters;" Gk. rhiknos "crooked;" Lith. rišti "tie, bind;" O.H.G. rīho "knee-bend."

Following in order of time or place.

Adj. from → sequence.

The formation of second-generation stars in a → molecular cloud, as triggered by the presence of → massive stars. The observation that some nearby → OB associations contain distinct, spatially separate subgroups of → OB stars in a sequence of monotonically changing age led Blaauw (1964, ARA&A 2, 213) to suggest that star formation in fact occurs in sequential bursts during the lifetimes of the corresponding molecular clouds. The first quantitative model of this mechanism was presented by Elmegreen and Lada (1977, ApJ 214, 725), who showed that the powerful ultraviolet photons of the massive star create an → ionization front which advances in the molecular cloud and is preceded by a → shock front. The compressed neutral gas lying between the ionization and shock fronts is gravitationally unstable and collapses in time-scales of a few million years to form a new generation of massive stars. The propagation of successive births of OB groups would produce a chain of associations presenting a gradient of age. Elmegreen and Lada estimated the propagation velocity to be 5 km s^-1. For a region with a length larger than 100 pc, this would imply an age difference of the order of 20 million years between the extremities. See also → stimulated star formation, → triggered star formation; → collect and collapse model.

→ sequential; → star formation.

1) Anything published, broadcast, etc., in short installments at regular intervals, as a novel appearing in successive issues of a magazine.
2) Pertaining to, arranged in, or consisting of a series (Dictionary.com).

→ series; → -al.

1) Math.: A sequence of numbers or mathematical expressions such as the n-th term may be written down in general form, and any particular term (say, the r-th) may be obtained by substituting r for n; e.g. xⁿ is the general term of the series 1, x, x², x³, ..., xⁿ.
2) Electricity: An arrangement of the components, as resistors, connected along a single path, so the same current flows through all of the components. Compare → parallel.
3) → spectral series; → Lyman-alpha series.

From L. series "row, chain, series," from serere "to join, link, bind together," from PIE base *ser- "to line up, join."

Seri, loan from Fr., as above.
Rise "string, thread, series," variant of rešte, → sequence.

1) Of or relating to a matter of importance.
2) Having important or dangerous possible consequences.

From M.E., from O.Fr. serios "grave, earnest" and directly from Late L. seriosus, from L. serius "weighty, important, grave," probably from a PIE root *swer- "slow, heavy;" cf. Lith. sveriu, sverti "to weigh, lift," svarus "heavy, weighty;" O.E. swaer "heavy," Ger. schwer "heavy," Gothic swers "honored, esteemed," literally "weighty").

Padel, from Balôci padel "serious," of unknown origin.

The Serpent. An inconspicuous, irregular constellation situated on both sides of → Ophiuchus. The constellation is divided into two unequal parts, originally called Serpens Caput "Serpent's Head" at 15h 30m right ascension, 15° north declination, and Serpens Cauda "Serpent's Body" at 18h 30m right ascension, 0° declination. The brightest star, Alpha Serpentis, is of second magnitude. Abbreviation: Ser; Genitive: Serpentis.

From L. serpens "snake," from pr.p. of serpere "to creep," from PIE *serp- "to crawl;" cf. Skt. sarp- "to creep, crawl," sárpati "creeps," sarpá- "serpent;" Gk. herpein "to creep," herpeton "serpent;" Alb. garper "serpent."

Mâr "snake, serpent;" Mid.Pers. mâr "snake;" Av. mairya- "snake, serpent."

A mathematical function that describes how the → intensity  I of a → galaxy varies with distance R from its center. It is given by: (dln I/dln R) = -(b/n)(R/R_e)^1/n. The constant b is chosen such that R_e is the → effective radius; n is the Sérsic index. The Sérsic profile is a generalization of → de Vaucouleurs law. Setting n = 4 gives the de Vaucouleurs profile.

J. L. Sérsic, 1963, Boletin de la Asociacion Argentina de Astronomia, Vol. 6, p.41; → profile.

To render assistance; be of use. To have definite use.

Verbal form of service, → server.