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

A point where the → flow  → velocity is → zero. For example a point around an obstacle where a → flow tube splits into two portions.

→ stagnation; → point.

The sum of → static pressure and → dynamic pressure in the → Bernoulli equation.

→ stagnation; → pressure.

An uncastrated adult male horse, especially one used for breeding.

M.E. stalon, from O.Fr. estalon, "uncastrated male horse," cognate with O.H.G. stal "stable," cf. O.H.G. stall "stand, place, stable, stall," Ger. Stall "stable," Stelle "place"), from PIE root *stel- "to put, stand," with derivatives referring to a standing object or place; akin to Pers. istâdan "to stand," → station.

Nariyân, from nar "male," → masculine.

To have or maintain an upright position, supported by one's feet; rise to one's feet (OxfordDictionaries.com).

M.E. standen, from O.En. standan "occupy a place; stand firm; stay, be, exist; oppose, resist attack; stand up, be on one's feet;" cognate with O.Norse standa, O.Saxon and Gothic standan, O.H.G. stantan, Du. staan, Ger. stehen, cognate with Pers. istâdan, as below.

Istâdan "to stand," from 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."

Any set of conditions that describe the normal, desired, or ideal state of something, and that serves a basis for representing or evaluating actual examples of this thing.

M.E., from O.Fr. estandart "banner, standard," probably from Frankish *standord; cf. Ger. Standort "standing-point," from standan "to stand," cognate with Pers. istâdan, as below, with the second component conformed to -ard.

Estândé, literally "made stand, fixed," p.p. istândan transitive verb of istâdan, "to → stand."

A hypothetical vertical distribution of atmospheric temperature, pressure, and density that, by international agreement, is taken to be representative of the atmosphere for purposes of pressure altimeter calibrations, aircraft performance calculations, aircraft and missile design, ballistic tables, etc.

→ standard; → atmosphere.

An astronomical object, belonging to some class, that has a known luminosity. In principle, by comparing the known luminosity to the observed brightness, the distance to the object can be derived. The four major primary distance indicators are Cepheids, supernovae, novae, and RR Lyrae variables. The secondary distance indicators include H II regions, globular clusters, brightest red and blue stars. → primary calibrator; → secondary calibrator.

→ standard; → candle.

The conventional → Big Bang model, which is based on two assumptions: the → cosmological principle of homogeneity and isotropy leading to the → Robertson-Walker metric, and → Einstein's field equations of general relativity along with familiar properties of matter. This model is a remarkably successful operating hypothesis describing the evolution of the Universe from 1/100 second after the initial event through to the present day. It provides explanations for several basic problems such as: → Hubble's law of recession of galaxies, interpreted in terms of the expansion of the Universe; the abundances of the → light elements, in excellent agreement with the predictions of → primordial nucleosynthesis; and the thermal spectrum and angular isotropy of the → cosmic microwave background (CMB) radiation, as expected from a hot, dense early phase of expansion. For a non-standard model, see → ekpyrotic Universe.

→ standard; → cosmology.

The most widely used measure of dispersion of a frequency distribution. It is equal to the positive square root of the → variance. Same as → standard error. Not to be confused with the → root mean square error.

→ standard; → deviation.

A particular date and time that specifies the reference system to which celestial coordinates are referred. From 1984 the → Julian year is used, as denoted by the prefix J, e.g. J2000.0.

→ standard; → epoch.

Same as → standard deviation.

→ standard; → error.

The accepted but possibly incomplete theoretical framework which usually describes a set of phenomena. For example, the model that describes the origin of the Universe, or the model concerned with the processes in the interior of the Sun.

→ standard; → model.

The theory developed since the 1970s, which is based on the theories and discoveries since the 1930s, and aims at explaining the fundamental structure of matter. According to the standard model, everything in the universe is made from a few basic building blocks called fundamental particles, governed by four fundamental forces. The particles occur in two basic types, called quarks and leptons. Three of the four fundamental forces (except gravity) and their carrier particles are included in the Standard Model. The Standard Model has successfully explained almost all experimental results and precisely predicted a wide variety of phenomena. Over time and through many experiments, the Standard Model has become established as a well-tested physics theory.

→ standard; → model; → particle; → physics.

Stars for which accurate color indices and/or magnitudes exist, defining a standard system.

→ standard; → star.

Photometric system used as a reference.

→ standard; → system.

1) The most commonly used definition is temperature of 273.15 K (0 °C) and pressure of 1 → atmosphere.
2) Chemistry: Temperature of 273.15 K (0 °C) and pressure of 10⁵  → pascal (Pa)s (1 → bar). International Union of Pure and Applied Chemistry (IUPAC) recommends that the former use of the pressure of 1 atm as standard pressure (equivalent to 1.01325 × 10⁵ Pa) should be discontinued.

→ standard; → temperature; → pressure.

The time in any of the 24 internationally agreed time zones into which the Earth's surface is divided. The primary zone is centered on the Greenwich meridian (0° longitude).

→ standard; → time.

Photometric values of selected stars in a standard system.

→ standard; → value.

A wave produced by the simultaneous transmission of two similar wave motions in opposite directions. Same as stationary wave.

Standing verbal adjective from stand, cognate with Pers. istâdan, as below; → wave.

Istân pr.p. of 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;" O.N. standa, Goth. standan, O.H.G. stantan, Swed. stå, Du. staan, Ger. stehen; O.E. standan; PIE base *sta- "to stand;" mowj, → wave.

A huge mass of hot gas whose radiation is provided by its internal → thermonuclear reactions. A star represents a → hydrodynamic equilibrium between two opposing forces, the inward → gravitational force, which is attempting to make the mass collapse and the pressure caused by the generation of nuclear energy. Below a certain mass (0.08 → solar masses), the central pressures and temperatures are insufficient to trigger the → hydrogen fusion (→ brown dwarf). Stars have a variety of masses and sizes. → Massive stars are less common than → low-mass stars (→ initial mass function). → Star formation results from → gravitational collapse of → molecular clouds (→ fragmentation; → pre-stellar core; → protostar; → accretion). After leaving the → main sequence, they pass through several evolutionary stages (e.g., → red giant, → supergiant, → white dwarf, → supernova, → neutron star) depending on their initial masses. See also: → internal structure of stars; → spectral classification; → luminosity class; → variable star; → multiple star. The term star is sometimes loosely applied to objects that do not comply with the above specifications, but are evolutionary products of stars, such as neutron stars and white dwarfs. For ancient civilizations a star was anything appearing in the night sky, apart from perhaps the Moon.

M.E. sterre, O.E. steorra; cf. O.S. sterro, O.N. stjarna, O.Fris. stera, Du. ster, O.H.G. sterro, Ger. Stern, Goth. stairno; cognate with Gk. aster, astron, L. stella (Fr. étoile, Sp. esterella, It. stella), Bret. sterenn, Pers. setâré, as below.

Setâré, variants star, estâr, estâré, and probably axtar, → astro-, (Lori, Laki) âsâra, (Laki) hasâra, (Tabari) essâra, (Baluci) istâr, (Ossetic) st'aly, (i)sthalu, (Tâti) usdurâ; Mid.Pers. stârag, stâr; Av. star-; cf. Skt. stár-, tāra-, tārakā- "star;" akin to Gk. and L., as above; PIE base *ster- "star."