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

The science concerned with physical characteristics (stress, strain, strength, stiffness, stability) of various engineering components and structures when forces are applied on them.

→ strength; → material.

The force acting across a unit area in a solid body, tending to produce → strain in the body or part of it. When a stress is applied to a body, the ratio of stress to strain is a characteristic constant of the body. See also → shear.

Stress "hardship, adversity, force, pressure," in part a shortening of M.Fr. destresse (fr. détresse) in part from O.Fr. estrece "narrowness, oppression," from L. strictus "compressed," p.p. of stringere "draw tight."

Xošar variant of fešâr "pressure," cf. Lori xošâr, Aftari xešâr, Qazvini, Qomi xošâl, Tabari qošâr Khotanese ssarr- "to exhilarate;" loaned in Arm. ôšarak, in Ar. afšaraj "juice."

To make something longer or wider by pulling it.

M.E. strecchen, from O.E. streccan; cf. Dan. strække, Sw. sträcka, O.Fris. strekka, O.H.G. strecchan, M.L.G., M.Du., O.H.G., Ger. strecken "to stretch"), perhaps a variant of the root of stark, or from PIE root *strenk- "tight, narrow; pull tight, twist," → strain.

Dargidan, from darg "long" (Zâzâ, Ossetic), variants derâz, derež "long" (→ longitude); Mid.Pers. drâz "long;" O.Pers. darga- "long; " Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "long (in space and time);" PIE *dlonghos- "long."

The second term of the right-hand side in the → induction equation. This term is at the origin of the → dynamo effect and also of the → Alfven waves when in the presence of a mean field.

→ stretch; → term.

The area over which the → meteorite fragments from a particular → fall are dispersed.

Strewn, p.p. of strew, from M.E. strewen, O.E. strewian; cf. O.S. stroian, O.N. stra, Dan. strø, Swed. strö, M.Du. strowen, Du. strooien, O.H.G. strouwen, Ger. streuen, Goth. straujan "to sprinkle, strew;" PIE base *stere- "to spread, extend, stretch out;" from which Pers. gostar-, gostardan "to stretch, expand;" Av. star- "to spead out;" → field.

Meydân, → field; paxš "scattered," → diffuse.

A theoretical sphere of → ionized hydrogen created by energetic → ultraviolet→ photons of a hot, → massive star embedded in a uniform interstellar → molecular cloud and lying at the center of the sphere. → H II region.

Named after Bengt Strömgren (1908-1987), a Danish astrophysicist, who put forward the first and simplest version of the model in 1939; → sphere.

A → photometric system, also called the → uvby system.

→ Stromgren sphere; → system.

The arrangement of parts in an object or organism.

M.E., from L. structura "a fitting together, adjustment, building," from structus, p.p. of struere "to pile, build, assemble," related to strues "heap," from PIE *stere- "to spread, extend, stretch out;" cf. Pers. gostar-, gostardan "to spread;" Av. star- "to spread," starati "spreads;" Skt. star- "to spread out, extend, strew," strnati "spreads;" Gk. stornumi "I spread out," strotos "spread, laid out;" Ger. Strahlung "radiation," from strahlen "to radiate," from Strahl "ray;" from M.H.G. strāle; from O.H.G. strāla "arrow, stripe."

Sâxtâr, from sâxt "made; make, construction, structure; style," past stem of sâxtan, sâzidan "to build, make, fashion; to adapt, adjust, be fit" (Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach") + -âr verbal noun suffix.

The study of the processes that gave rise to the apparition of matter concentrations, such as → superclusters of galaxies, → galaxy clusters, and galaxies, in a homogeneous → expanding Universe. Cosmic structures are believed to result from → density fluctuations that existed in the → early Universe before radiation and matter decoupled (→ decoupling era or → recombination era). Initial → quantum fluctuations in the → inflaton field were expanded by → inflation. Inflation amplified them up to scales that correspond to those of galaxy clusters and beyond. Generally, a model of structure formation includes three main ingredients: 1) background cosmology, 2) model for fluctuation generation, and 3) types of → dark matter.
See also:
→ bottom-up structure formation, → hierarchical structure formation, → Silk damping, → top-down structure formation.

→ structure; → formation.

A → nuclear reactor in which the rate of production of → fission neutrons is lower than the rate of production in the previous generation, and therefore the number of fissions decreases over time.

→ subcritical; → reactor.

Describing a system or situation for which the → Lorentz factor, γ, is much smaller than 1. See also → ultrarelativistic.

→ ultra- + → relativistic

The point on the surface of a celestial body where the star is perceived to be directly overhead (in zenith). The sublunar point and subsolar point are the equivalent points for the Moon and Sun, respectively.

→ sub-; → terrestrial.

A condition in which there is an excess of the actual temperature gradient over the → adiabatic temperature gradient corresponding to the same pressure gradient. A region with superadiabatic temperature gradient is convectively unstable. → Hayashi forbidden zone.

→ super-; → adiabatic; → temperature; → gradient.

A radio receiver which uses the → superheterodyne technique.

→ super-; → heterodyne; → receiver.

The body of expanding gas ejected at a speed of about 10,000 km s^-1 by a → supernova explosion, observed as a diffuse → gaseous nebula, often with a → shell-like structure. Supernova remnants are generally powerful → radio sources. The evolution of the SNR can be divided into different phases according to the dominant physical processes. Simplified models are made for the first stages, to get an idea of typical time scales, expansion velocities, and sizes. The three main phases are: 1) the → free expansion phase, 2) the → Sedov-Taylor phase, and 3) the → snowplow phase.

→ supernova; → remnant.

1) To put down by authority or force.
2) To keep from public knowledge.
3) To restrain from a usual course or action. → suppression.

L. suppressus, p.p. of supprimere "to press down, stop, stifle," from → sub- "down, under" + premere "to press, push against," → express.

Nehâvidan, from ne-, → ni- "down, below," + hâvidan "to press," → express.

The act of suppressing; the state of being suppressed. → Compton suppression, → zero suppression.

→ suppress; → -tion.

1) Highest in rank or authority.
2) Of the highest quality, degree, character, importance, etc.

M.E., from M.Fr. suprême, and directly from L. supremus "highest," superlative of superus "situated above," from super "above," → super-.

Abartom "highest," from abar "high, upon," → super-, + -tom superlative suffix, → extreme.

Free from doubt as to the reliability, character, action, etc., of something (Dictionary.com).

M.E. sur(e), from M.Fr. sur, O.Fr. seur "safe, secure; trustworthy," from L. securus "free from care, untroubled, safe," from *se cura, from se "free from" + cura "care."

Tenz, from (Fine-e Bandar Abbâs) tenz "firm, fixed, solid," variant tereng; (Tabari) tereng, təreq "firm, fixed;" (Baxtiyâri) teng "firm;" cf. Baluci tranj-, dranjit, tranjit/drannj-, draht, dratk "to hang up;" ultimately from Proto-Ir. *dra(n)j- "to fix, fasten, hold;" Av. drənj- (draž-) "to fix, fasten, hold;" Parthian (*abi-) 'bdrynj- "to be sure, secure; make certain;" Khotanese drys- "to hold;" cognate with Gk. drassomai "I hold (with the hand), take;" O.Irish dringid "he climbs;" M.Welsh dringo "to climb;" PIE *dreg^h- "to hold, fasten."

Without doub; certainly; to be sure; for sure.

→ sure; → -ly.