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

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.

General: Something that serves or is used in serving.
Computers: A computer software application that carries out some task on behalf of users. When users connect to a server, they can access programs, files, and other information from the server. Common servers are Web, mail, and database servers. A single computer can have several different server programs running on it.

Server, agent noun from serve, from M.E. serven, from O.Fr. servir "to serve," from L. servire "to serve," originally "be a slave," related to servus "slave;" cognate with Av. har- "to guard, watch," harətar- "guardian," hāra- "caring for;" Mid./Mod.Pers. zinhâr "protection, security; beware! mind!"

Zâvar "attendant, servant" (Dehxodâ), zâvari "attendance, service" (Dehxodâ), maybe related to Skt. sev- "to attend upon, serve," sevā- "service, attendance, worship," sevati "serves, attends," sevaka- "attendant, servant, follower."

1) A helpful act by somebody for somebody else as a job, duty, or favor.
2) A system or organization supplying some public demand, e.g. transportation, telephone, health.
3) A facility providing maintenance and repair.

M.E., from O.Fr. servise, from L. servitium "slavery, servitude," from servus "slave," servire "to serve," originally "be a slave;" cognate with Av. har- "to guard, watch," → server.

Zâvari "service" (Dehxodâ) → server.

Observation approved by the selection committee of an observatory which is carried out by the staff astronomers of the observatory.

→ service; → observation.

1) Math.: A finite or infinite collection of objects in which order has no significance. Members of a set are often referred to as elements and the notation a ∈ A is used to denote that a is an element of a set A. The study of sets and their properties is the object of set theory.
2) To pass below the horizon. → moonset; → sunset.
3a) (tr.v.) To put (something or someone) in a particular place.
3b) To adjust a device to a desired position.

1) M.E. sette, from O.Fr. sette "sequence," variant of secte, from M.L. secta "religious group, sect," from L. secta "manner, following, school of thought," literally "something to follow, pathway, course of conduct, school of thought," from sectari "to pursue, accompany," "a way, road," from sequi "to follow," → sequence.
2) M.E. setten, O.E. settan "cause to sit, put in some place, fix firmly;" cf. O.N. setja, O.Fris. setta, Du. zetten, Ger. setzen.

1) Hangard, from Mid.Pers. hangart "whole, complete," hangartik "complete," hangartênitan "to collect, assemble," from *hamkard- literally "created, cut together," from han- variant of ham- "together," cognate with L.L. insimul "at the same time," from in- intensive prefix + simul "together, at the same time" (cf. Gk. homos "same," Mod./Mid.Pers. ham- "together, with," O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- "one and the same," Skt. sama-; originally identical with PIE numeral *sam- "one," from *som-). (→ com-), + gard, variant of kard "created, cut," Mid.Pers. kirrēnītan, kirrēn- "to cut, create," cf. fragard "section, chapter," Av. karət- "to cut," kərəntaiti "cuts, breaks," with fraca- "to create, bring forth," karəta- "knife, dagger" (Mid.Pers. kârt "knife;" Mod.Pers. kârd "knife"), Skt. kart- "to cut, split, break," krti- "sword, knife;" PIE base *(s)kert- "to cut;" Hitt. kartae- "to cut;" Arm. kherthem "to skin;" L. cortex "bark of a tree," corium "skin, leather;" O.H.G. scrinden "to split;" Lith. kertu "to fell, cut down."
2) Forušodan, literally "to descend, go down," from foru- "down, downward; below; beneath" (Mid.Pers. frôt "down, downward;" O.Pers. fravata "forward, downward;" cf. Skt. pravát- "a sloping path, the slope of a mountain") + šodan "to go, to pass; to become, to be, to be doing" (Mid.Pers. šudan, šaw- "to go;" Av. š(ii)auu-, šiyav- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro").
3) Beštidan, from bešt past stem of Tabari/Mâzandarâni beštan "to place, put, set," from intensive prefix be- + eštan, from heštan "to place, put," → intercalate.

A collection of → nonempty subsets of a set A such that every element of A is in exactly one of the subsets. In other words, A is the → disjoint  → union of these subsets.

→ partition; → set.

The branch of mathematics that studies sets. Set theory is closely associated with the branch of mathematics known as logic. It was initiated by the German mathematician Georg Cantor (1845-1918).

→ set; → theory.

To install and configure hardware and software on a computer.

Verb of → setup.

1) The act of setting; the appearance of a → celestial body below the → horizon. Opposite of → rising.
2) A change in a software program or hardware device that adjusts it to the user's preference. For example, date and time setting, language setting, display setting, font setting, etc.

→ set; → -ing.

Two graduated disks attached to the right ascension and declination axis of an equatorial mount used in amateur astronomy that help an observer find astronomical objects in the sky by their equatorial coordinates.

M.E.; O.E. settan "cause to sit, put in some place, fix firmly" (cf. O.N. setja, O.Fris. setta, Du. zetten, Ger. setzen); → circle.

Dâyeré, → circle; âmâj-giri "taking aim," from âmâj "aim, target," → point + giri "taking" (vebal noun of gereftan "to take, seize, hold;" Mid.Pers. griftan, gir- "to take, hold, restrain;" O.Pers./Av. grab- "to take, seize," cf. Skt. grah-, grabh- "to seize, take," graha- "seizing, holding, perceiving," M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE *ghrebh- "to seize").

1) (tr.) To put in order; arrange in a desired state or condition.
2) (intr.) To come to rest or a halt. To become fixed in a particular place, direction, etc. (Dictionary.com).

M.E. set(t)len, O.E. setlan "to place," derivative of setl "a seat; stall; position, abode;" related to sittan "to sit," from Proto-Germanic *setla- (cognates: Middle Low German, Middle Dutch setel, Dutch zetel, German Sessel, Gothic sitls), from PIE *sedla- (cognates: L. sella "seat, chair," O.C.S. sedlo "saddle," O.E. sadol "saddle"), from root *sed-.

Niyâšidan, from Yidghda niâst- , Munji niôst- "to sit down;" Nâini âš-/âšis- "to become seated;" Baluci ništ, related to nešastan "to sit down," → sit (see also → reside); ultimately from Proto-Ir. *had- "to sit, be setaed."

A → galactic disk that has undergone → disk settling.

→ settle; → disk.

The act of a person or thing that settles. → disk settling, → dust settling.

→ settle; → -ing.