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

A coherent component of a larger system.

→ sub-; → system

A spherical → coordinate system in which the → equator is the → supergalactic plane. Supergalactic longitude, SGL, is measured → counterclockwise from direction l = 137.37 deg, b = 0 deg (between 0 and 360 deg). The zero point for supergalactic longitude is defined by the intersection of this plane with the → Galactic plane. In the → equatorial coordinate system (J2000) this is approximately 2.82 h, +59.5 deg. Supergalactic latitude, SGB, is measured from the supergalactic plane, positive northward and negative southward. The North Supergalactic Pole (SGB=90 deg) lies at galactic coordinates l = 47.37 deg, b = +6.32 degrees, corresponding to the equatorial coordinate system (J2000) 18.9 h, +15.7 deg.

→ supergalactic; → coordinate; → system.

1a) An assemblage or combination of things or parts forming a complex or unitary whole.
1b) An ordered and comprehensive assemblage of facts, principles, doctrines, or the like in a particular field of knowledge or thought (Dictionary.com).
2) Physics: An aggregate composed of physical bodies which we isolate, in our mind, from the region external to it in order to analyze physical situations. Everything outside the system which has a direct bearing on its behavior is called the → environment.
3) Astro.: An entity composed of a number of astronomical objects associated and acting together according to certain natural laws.
4) Computers: A system consisting of components (a combination of the hardware, software, and firmware) which are connected together in order to accomplish a specific function or set of functions.

From L.L. systema "an arrangement, a whole consisting of several parts," from Gk. systema "arrangement, organized whole," from sy-, variant of syn- "together" + ste- variant stem of histanai "to cause to stand" (from PIE base *sta- "to stand;" cf. Pers. ist, istâdan "to stand;" Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand") + -ma nominal suffix denoting result of action.

Râžmân, from raž, from Av. rāz- "to direct, put in line, set," rasman- "the lines or files of the army," razan "rule, order" (variants raj, râž, rak, râk, rezg (Lori), radé, râdé "line, rule, row," rasté, râsté "row, a market with regular ranges of shops;" ris, risé "straight"), related to râst "right, true; just, upright, straight;" Mid.Pers. râst "true, straight, direct," rây-, râyênitan "to arrange;" Sogdian rəšt "right;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" PIE base *reg- "move in a straight line," hence, "to direct, rule;" + -mân verbal noun suffix used with present and past stems, as in zâymân, câymân, sâxtemân, goftemân.

A person in charge of the configuration and administration of a multi-user computer system inside a network.

→ system; → manager.

The noise in a radio telescope, composed of the receiver noise and the sky noise.

→ system; → noise.

Having, showing, or involving a system, method, or plan.

L.L., from Gk. systematikos; → system; → -ic.

Râžmânvâr, râžmânmand, from râžmân, → system, + -mand suffix of possession.

The error that is constant in a series of repetitions of the same experiment or observation. Usually, systematic error is defined as the expected value of the overall error. opposite of → random error.

→ systematic; → error.

Biology: The science that deals with the systematic naming and classification of all kinds of organisms.

From → systematic + → -ics.

Relating to or affecting a system as a whole.

→ system; → -ic.

An interdisciplinary field of science which deals with the nature of complex systems in nature, society, and science, and studies complex parts of reality as systems.

→ system; → theory.

A quantity of substance or a working machine which in a well-defined way is set apart from its → environment. The boundary between the system and its surroundings can be real or an imaginary mathematical envelope. A thermodynamic system is not necessarily bound to a predefined geometry. Thermodynamic systems can be divided into three types: → open systems, → closed systems, and → isomated systems.

→ thermodynamic; → system.

→ close binary star.

→ tight; → bound system; → binary star.

An assembly of elements which are capable of functioning together to transmit power or signals.

→ transmission; → system.

A system of three stars which are physically associated among them.

→ triple; → system

A → dynamical system consisting of two masses that interact via → central forces.

→ two; → body; → system.

A → photometric system which consists of measuring an object's → apparent magnitude through three broad-band filters: the ultraviolet (U) at 3650 Å, the blue (B) at 4400 Å, and the visual (V) in the green-yellow spectral region at 5500 Å. The filter bandwidths are 680, 980, and 890 Å respectively. The system is defined so that for A0 stars B - V = U - B = 0. The system was devised by Harold Johnson (1921-1980) and William Morgan (1906-1994) at Yerkes Observatory. It was extended to the R and I bands centered at 7000 and 9000 Å respectively and later to other infrared bands.

U, B, and V referring to "ultraviolet," "blue," and "visible" respectively; → system.

An association of bodies which are not gravitationally tied together.

→ unbound; → system.

A class of gravitationally loose stellar conglomerate with a notable apparent shape making it different from typical → bound  → star clusters. The UYSS class includes a large range of objects, which extend at various size scales and at various degrees of self-binding; from small (semi-)compact → unbound systems named → stellar associations, to huge extended superstructures of → massive stars that make up whole parts of Galactic → spiral arms, known as → stellar complexes (Gouliermis, D. A., 2018, PASP 130:072001; arXiv:1806.11541).

→ unbound; → young; → stellar; → system.

A dwarf spheroidal galaxy of faint luminosity that is a member of the Local Group.

→ Ursa Minor; → system.

A four-color stellar → photometric system devised by B. Strömgren. It is based on measurements in the ultraviolet (3500 Å), violet (4100 Å), blue (4670 Å), and yellow (5470 Å) regions of the spectrum. The filters bandwidths are 340, 200, 160, and 240 Å respectively. Also known as Strömgren four-color photometry.

u, v, b, and y referring to ultraviolet, violet, blue, and yellow respectively; → system.