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

A continuing process whereby an individual acquires a personal identity and learns the norms, values, behavior, and social skills appropriate to his or her social position (Dictionary.com).

→ socialize; → -tion.

The → angle between the → sea horizon, the → center of → Earth, and the center of the → solar disk.

→ solar; → depression.

In ancient astronomy, the difference between the Sun's mean and actual position. The ancients observed that, although the motion of the Sun in the ecliptic is almost uniform, it is subject to a small annual variation.

→ solar; → equation.

All the constituents making up the Sun's emission: photons, electrons, protons, neutrinos, and atomic nuclei.

→ solar; → radiation.

The → radiation pressure of solar photons, which pushes a comet's dust outward to form a → dust tail.

→ solar; → radiation; → pressure.

The motion of the Sun around an axis which is roughly perpendicular to the plane of the → ecliptic; the Sun's rotational axis is tilted by 7.25° from perpendicular to the ecliptic. It rotates in the → counterclockwise direction (when viewed from the north), the same direction that the planets rotate (and orbit around the Sun). The Sun's rotation is differential, i.e. the period varies with latitude on the Sun (→ differential rotation). Equatorial regions rotate in about 25.6 days. The regions at 60 degrees latitude rotate more slowly, in about 30.9 days.

→ solar; → rotation.

A criterion for → convective stability in → massive stars. The Solberg-Høiland stability criterion corresponds to the inclusion of the effect of → rotation (variation of → centrifugal force) in the convective stability criterion. It is a combination of → Ledoux's criterion (or possibly → Schwarzschild's criterion) and → Rayleigh's criterion. Both the dynamical shear and Solberg-Høiland instabilities occur in the case of a very large → angular velocity decrease outwards. Therefore, in a → rotating star the Ledoux or Schwarzschild criteria for convective instability should be replaced by the Solberg-Høiland criterion. More specifically, this criterion accounts for the difference of the centrifugal force for an adiabatically displaced fluid element. It is also known as the axisymmetric baroclinic instability. It arises when the net force (gravity + buoyancy + centrifugal force) applied to a fluid parcel in an adiabatical displacement has components only in the direction of the displacement (A. Maeder, Physics, Formation and Evolution of Rotating Stars, 2009, Springer).

E. Høiland, 1939, On the Interpretation and Application of the Circulation Theorems of V. Bjerknes. Archiv for mathematik og naturvidenskab. B. XLII. Nr. 5. Oslo.
H. Solberg, 1936 (reprint), Le mouvement d'inertie de l'atmosphere stable et son rôle dans la théorie des cyclones.
H. Solberg, 1941, On the Stability of the Circular Vortex. Avhandl. utg. av Det Norske Videnskaps-Akademi i Oslo. I. Mat-Naturv. Klasse. No. 11.
Wasiutynski, J. 1946, Astrophysica Norvegica, 4, 1.

1) To become or make solid, hard, or firm.

→ solid; → -fy.

1) The act of solving a problem, question. The state of being solved.
2a) Math.: The process of determining the answer to a problem. The answer itself.
2b) Math.: Of a differential equation, any function which, when put into the equation, converts it into an identity.
3) Chem.: The process by which a gas, liquid, or solid is dispersed homogeneously in a gas, liquid, or solid without chemical change. a homogeneous, molecular mixture of two or more substances.

Verbal noun of → solve.

Any of a class of chemical reactions in which solute and solvent molecules combine.

From solv(ent), → solvent + -ation.

Luyé, from luy- the stem of luyidé→ solute and luyandé→ solvent + -é nuance suffix.

The process of sorbing. The state of being sorbed. → absorption; → adsorption.

Verbal noun of → sorb

For a radiating material, the ratio of emissivity to opacity.

→ source; → function.

A manned or unmanned space flight outside the Earth's atmosphere.

→ space; mission, from L. missionem (nominative missio) "act of sending," from mittere "to send," of unknown origin.

Gosilân, from gosil, variant gosi "sending away, dismission;" Mid.Pers. wisé "to despatch" (Parthian Mid.Pers. wsys- "to despatch;" Buddhist Mid.Pers. wsydy "to despatch;" Sogdian 'ns'yd- "to exhort"), from Proto-Iranian *vi-sid- "to despatch, send off," from prefix vi- "apart, away, out," + *sid- "to call" + -ân nuance suffix; fazâyi adj. of fazâ, → space.

The velocity and direction of motion of a star or celestial object with respect to the Local Standard of Rest. Same as → peculiar velocity.

→ space; → motion.

A program aimed at monitoring the near-Earth environment for recognizing and preventing space hazards by means of radar and optical observations from either space or the ground. The objective of the → European Space Agency initiative is to support the European independent utilization of, and access to, space for research or services, through the provision of timely and quality data, information, services and knowledge regarding the space environment, the threats and the sustainable exploitation of the outer space surrounding our planet Earth. The SSA Program was authorized at the November 2008 Ministerial Council and formally launched on 1 January 2009. The mandate was extended at the 2012 and 2016 Ministerial Councils, and the program is funded through to 2020. The program comprises three segments: 1) Space Surveillance and Tracking (SST), which is the monitoring and tracking of every object orbiting the Earth, such as satellites, space stations and debris. The objective is the prediction and warning of collisions and re-entry events. 2) → Space Weather (SWE), which aims at detection and forecasting of space weather and its effects through monitoring of the Sun, solar wind, magnetosphere, radiation belts, ionosphere and disturbances in the geomagnetic field. 3) → Near-Earth Objects (NEOs), which provides warning services against potential asteroid impact risks, including discovery, identification, orbit prediction and civil alert capabilities.

→ space; → situation; → -al; → awareness.

A large satellite equipped to support a human crew and designed to remain in orbit around Earth for an extended period and be used for a variety of purposes (conducting research, repairing satellites, performing other space-related activities).

→ space; → station.

A nuclear reaction in which a high energy particle that collides with a nucleus causes the target to eject several particles, thus changing both its mass number and its atomic number.

From → spall + -ation.

Verbal noun from terišidan, → spall.

The smallest detail that can be seen in an image. Same as → angular resolution.

→ spatial; → resolution.

Star formation rate per unit → mass. More specifically, the → star formation rate in a galaxy divided by the → stellar mass of the galaxy. Observations of galaxies over a wide range of → redshifts suggest that the slope of the SFR-M_* relation is about unity, which implies that their sSFR does not depend strongly on stellar mass. Specific star formation rates increase out to z ~ 2 and are constant, or perhaps slowly increasing, from z = 2 out to z = 6, though with a large scatter, sSFR ~ 2-10 Gyr^-1 (Lehnert et al., 2015, A&A 577, A112, and references therein).

→ specific; → star; → formation; → rate.

1) The act of specifying.
2) A particular item, aspect, calculation, etc., in such a description.
3) Something specified, as in a bill of particulars; a specified particular, item, or article (Dictionary.com).

Verbal noun of → specify.