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

The act of disallocating or the state of being disallocated.

→ dis- + → allocate.

In models of magnetized → accretion disks, the process whereby the disk is disrupted at a radius where the → magnetic pressure overcomes the → ram pressure of the accreted material. This occurs at a distance typically 3-7 stellar radii, below the → corotation radius.

→ disk; → truncation.

An act or instance of disqualifying; the state of being disqualified.

→ disqualify; → -tion.

An act or instance of duplicating; the state of being duplicated.

Verbal noun of → duplicate.

The act or process of educating.
The knowledge or abilities gained through being educated.

Verbal noun of → educate.

The act or fact of evoking.

Verbal noun of → evoke.

A classification scheme for distinguishing a → radio galaxy from an → active galaxy based on their → radio frequency  and → luminosity and their kpc-scale appearance. Analyzing a sample of 57 radio galaxies from the → 3CR catalogue, which were clearly resolved at 1.4 GHz or 5 GHz, Fanaroff & Riley (1974) discovered that the relative positions of regions of high and low → surface brightness in the → lobes of extragalactic → radio sources are correlated with their radio luminosity. They divided the sample into two classes using the ratio R_FR of the distance between the regions of highest surface brightness on opposite sides of the central galaxy or quasar, to the total extent of the source up to the lowest brightness contour in the map. → Fanaroff-Riley Class I (FR-I) , → Fanaroff-Riley Class II (FR-II). The boundary between the two classes is not very sharp, and there is some overlap in the luminosities of sources classified as FR-I or FR-II on the basis of their structures. The physical cause of the FR-I/II dichotomy probably lies in the type of flow in the → radio jets.

Bernard L. Fanaroff and Julia M. Riley, 1974, MNRAS 167, 31P; → classification.

The first step carried out in a → fuzzy logic system during which a → crisp set of → input data are gathered and converted to a → fuzzy set using fuzzy → linguistic variables, fuzzy linguistic terms, and → membership functions.

Verbal noun of → fuzzify; → -tion.

A → geochemical classification scheme in which → chemical elements on the → periodic table are divided into groups based on their → affinity to form various types of compounds: → lithophile, → chalcophile, → siderophile, and → atmophile. The classification takes into account the positions of the elements in the periodic table, the types of electronic structures of atoms and ions, the specifics of the appearance of an affinity for a particular → anion, and the position of a particular element on the → atomic volume curve.

Developed by Victor Goldschmidt (1888-1947); → classification.

A classification of stellar spectra published in the Henry Draper catalogue, which was prepared in the early twentieth century by E. C. Pickering and Miss Annie Canon. It is based on the characteristic lines and bands of the chemical elements. The most important classes in order of decreasing temperatures are as follows: O, B, A, F, G, K, M.

Harvard, named for John Harvard (1607-1638), the English colonist, principal benefactor of Harvard College, now Harvard University. → classification

The classification of galaxies according to their visual appearance into four basic types suggested by E. Hubble: → ellipticals (E), → spirals (S), → barred spirals (SB), and → irregulars (Ir). Later on a separate class of → lenticulars (S0) was appended as an intermediate type between ellipticals and spirals. The sequence starts with round elliptical galaxies (E0). Flatter galaxies are arranged following a number which is calculated from the ratio (a - b)/a, where a and b are the major and minor axes as measured on the sky. Ellipticals are divided into eight categories (E0, E1, ..., E7). Beyond E7 a clear disk is apparent in the lenticular (S0) galaxies. The sequence then splits into two parallel branches of disk galaxies showing spiral structure: ordinary spirals, S, and barred spirals, SB. The spiral and barred types are subdivided into Sa, Sb, Sc, and SBa, SBb, SBc, respectively. Along the sequence from Sa to Sc, the central bulge becomes smaller, while the spiral arms become more and more paramount. The original, erroneous idea that such arrangement of the galaxies might represent an evolutionary sequence led to the ellipticals being referred to as early-type galaxies, and the spirals and Irr I irregulars as late-type galaxies. See also → dwarf galaxy, → dwarf elliptical galaxy, → dwarf spheroidal galaxy.

→ Hubble; → classification.

Same as the → Hubble classification.

→ Hubble; → Hubble-Sandage variable; → sequence.

1) An act or instance of identifying; the state of being identified.
2) Psychology: The process of associating the self closely with other persons and assuming their characteristics or views unconsciously or partially so.
3) In psychological theories, a phase of recognition, the way in which the child's personality is formed by modeling it on a chosen parent.

Verbal noun of → identify.

Idâneš, verbal noun of idânidan→ identify.

Recognizing the lines in the spectrum of a star, nebula, galaxy, etc. using a calibration template.

→ identification; → line.

1) General: Something implied; the act of implying.
2) A statement that follows from other given statements. For ex., an implication of x = -1 is that x² = 1.
3) A proposition found from two given propositions by connecting them in the form "If ..., then ...". The first statement is the antecedent (or hypothesis) and the second the consequent (or conclusion).

From L. implicationem "interweaving, entanglement," from implicatus, p.p. of implicare "involve, entangle, connect closely," from → in- "in" + plicare "to fold," → explain.

Dartâheš, verbal noun of dartâhidan "to imply," from dar-, → in- + tâhidan "to fold, ply," → explain.

The action of making or becoming stronger or more extreme.

verbal noun of → intensify.

The act of invoking.

Verbal noun of → invoke.

The spatial distribution of ionic species around an ionization source according to their → ionization potentials. The higher the ionization potential, the nearer to the source the corresponding ions will be.

→ ionization; → stratification.

1) A reason, fact, circumstance, or explanation that justifies or defends. What is offered as grounds for believing an assertion.
2) An act of justifying.

Verbal noun of → justify.

Râstâvard, from râst "right, true; just, upright, straight" (Mid.Pers. râst "true, straight, direct;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" 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;" Ger. recht; E. right; PIE base *reg- "move in a straight line," hence, "to direct, rule") + âvard past stem of âvardan "to bring; to adduce, bring forward in argument or as evidence" (Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring; to possess," from prefix ā- + Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother;" Mod.Pers. bordan "to carry;" Skt. bharati "he carries;" Gk. pherein; L. fero "to carry").

The process of recognizing the spectral lines in a spectrum.

→ line; → identification.