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

A solid angle whose cone is a tetrahedral pyramid with an angle between its edges equal to 1°. 1 square degree = 3.046 x 10^-4 sr = 2.424 x 10^-5 solid angle of a complete sphere.

→ square; → degree.

An international project to construct a highly sensitive radio interferometer array operating between 0.15 and 20 GHz with an effective collecting area of one square kilometer. The number of individual telescopes will be 2000 to 3000. SKA will have a sensitivity 100 times higher than that of today's best radio telescopes and an angular resolution < 0.1 arcsec at 1.4 GHz. The site will be selected in 2012 and early science with Phase 1 is scheduled for from 2016 on. See also the SKA homepage.

→ square; → kilometer; → array.

A → matrix with equal numbers of → rows and → columns (i.e., an n × n matrix).

→ square; → matrix.

A large → asterism of four stars, approximately square in shape, in the northern sky. Three of the stars, → → Markab, → Scheat, and → Algenib, belong to the constellation → Pegasus. The fourth, → Alpheratz, was lost to Pegasus when the constellation boundaries were formalised, and now lies just within the borders of → Andromeda.

→ square; → Pegasus.

Chahârguš, → tetragon; → Pegasus.

Quantity which when multiplied by itself produces another quantity.

→ square; → root.

An oscillation which alternatively assumes, for equal lengths of time, one or two fixed values.

→ square; → wave.

The mathematical problem of subdividing a square into a number of smaller squares, all of different sizes.

→ square; → square.

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

→ stagnation; → pressure.

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.

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.

A region in the → interstellar medium where processes of → star formation are going on or have occurred in the past.

→ star; → formation; → region.

A region in which → star formation is going on.

→ star; → formation; → region.

In → fluid mechanics, the → pressure felt by an object suspended in a → fluid and moving with it. This pressure is called static because the object is not moving relative to the fluid. See also → dynamic pressure.

→ static; → pressure.

The process of inferring certain facts about a → statistical population from results found in a → sample.

→ statistical; → inference.

1) The natural height of a human or animal in an upright position.
2) An achieved level; status (The FreeDictionary.com).

M.E., from from O.Fr. stature, estature "build, structure," from L. statura "height, size of body, size," from PIE root *sta- "to stand, make or be firm," cf. Pers. ist-, istâdan "to stand," → opposition.

Bašn "stature, height; the body;" Mid.Pers. bašn "the top;" O.Pers. baršan- "height," variant borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), related to boland "high," bâlâ "up, above, high, elevated, height," berg "mountain, hill;" Mid.Pers. buland "high;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. & E. force); O.E. burg, burh "castle, fortified place;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg); PIE base *bhergh- "high."

The → moment of inertia of a body about an arbitrary axis x' is equal to the sum of its moment of inertia about axis x, passing through the center of mass of the body and parallel to axis x', and the product of the mass M of the body by the square of the distance d between axes x and x': I_x' = I_x + Md². Same as → parallel axis theorem.

Named after Jakop Steiner (1796-1863), a Swiss mathematician who derived this statement; → theorem.

The outer envelope of gas and plasma that surrounds a star; characterized by pressure, temperature, density, chemical composition, and opacity at varying altitudes.

→ stellar; → atmosphere.

A model that computes the radiation field crossing the boundary layers of a star at all frequencies. The parameters used for the characterization of a stellar atmosphere model are: → effective temperature, → surface gravity, and → metallicity.

→ stellar; → atmosphere; → model.

The number of stars born per unit area in the mass range log M to log M + d log M during the time interval t to t + dt. The integration of the creation function over time gives the → present-day mass function (Miller & Scalo, 1797, ApJSS 41, 513).

→ stellar; → creation; → function.

A physical model that describes the internal arrangement of a star in detail and makes detailed predictions about the luminosity, the color, and the future evolution of the star.

→ stellar; → structure.