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

1) Physics, Chem.: A distinctive trace or sign that indicates the presence of a substance or the occurrence of a physical process or event.
2) Telecommunication: The complete set of electromagnetic and/or acoustic signals received, e.g., from an infrared source, a radio or radar transmitter, an aircraft, or a ship. Signatures may consist of analog or digital signals, or both, and may be analyzed to indicate the nature of their source and assist in its recognition.

M.Fr. signature, from M.L. signatura "sign," in classical L. "the matrix of a seal," from signatus, p.p. of signare "to mark, sign," → sign.

Nešânzad, literally "striking a mark, sign" (cf. angošt zadan "fingerprint"), from nešân, → sign, + zad past stem of zadan "to strike, beat; to do; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill").

In models of star formation, an isothermal sphere in which the density distribution in the static or nearly static outer envelope obeys an r^-2 power law. In the limit of infinite central concentration, the unstable equilibrium approaches the singular isothermal sphere which has the density and mass distributions ρ(r) = (a²/2πG)r^-2 and M(r) = (2a²/G)r, where a is the isothermal → sound speed inside the cloud, G is the → gravitational constant, and r the distance from the center (F. H. Shu, 1977, ApJ 214, 488).

→ singular; → isothermal; → sphere.

A member of a small class of objects which emit intense bursts of → gamma rays and → X-rays (> 100 keV) at irregular intervals. The bursts last for some 100 milli-seconds. It is conjectured that they are → magnetars. See also → starquake.

→ soft; → gamma rays; → repeater.

Same as → soft gamma repeater (SGR).

→ soft; → gamma ray; → repeater.

A general term used to describe a collection of computer programs, procedures, and documentation that perform some tasks on a computer system. → hardware.

→ soft + ware, from M.E., from O.E. waru, from P.Gmc. *waro (cf. Swed. vara, Dan. vare, M.Du. were, Du. waar, Ger. Ware "goods").

Narm, → soft + afzâr "instrument, means, tool," from Mid.Pers. afzâr, abzâr, awzâr "instrument, means," Proto-Iranian *abi-cāra- or *upa-cāra-, from cāra-, cf. Av. cārā- "instrument, device, means" (Mid.Pers. câr, cârag "means, remedy;" loaned into Arm. aucar, aucan "instrument, remedy;" Mod.Pers. câré "remedy, cure, help"), from kar- "to do, make, build;" kərənaoiti "he makes" (Pers. kardan, kard- "to do, to make"); cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base k^wer- "to do, to make").

The overall structure of a software system consisting of mutually dependent components that create a logical whole.

→ software; → architecture.

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

→ solar; → depression.

A bright eruption form the Sun's → chromosphere in the vicinity of a → sunspot. Solar flares are caused by tremendous explosions on the surface of the Sun. In a matter of just a few minutes they heat the material to many millions of degrees and release as much energy as a billion → megatons of → T.N.T..

→ solar; → flare.

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

→ solar; → radiation; → pressure.

Any of the various phenomena observable on the Earth that are caused by the influence of the Sun, such as aurora borealis.

→ solar; → terrestrial; → phenomenon.

The great circle of the celestial sphere which passes through the poles of the celestial equator and the solstice points. → equinoctial colure.

Solsticial, adj. of → solstice; → colure.

A → spiral galaxy in the constellation → Virgo. It was the first galaxy whose rotation was detected. Also named M104 and NGC 4594.

Sp. sombrero "broad-brimmed hat," originally "umbrella or parasol," from sombra "shade," from L.L. subumbrare, from → sub- "under" + umbra "shade, shadow;" → galaxy.

Kahkešân, → galaxy; sombrero, Sp., as above.

The periodic fluctuation above and below atmospheric pressure created by an oscillating body which provides the → sound power. Instantaneous sound pressure is the peak value of air pressure.

→ sound; → pressure.

A large area of the south polar region of → Mars which is covered with layers of → water ice and → dust. The SPLD, like the NPLD, has a maximum relief relative to the surrounding terrain of ~ 3.5 km and ~ 1,000 km across. Above the SPLD lies a very thin temporary (1-10 m) cap of → carbon dioxide ice/frost that snows out in the winter and sublimates over the spring and summer seasons. It is believed that the rhythmic nature of the deposits is related to oscillations in Mars' → orbital parameters (J. J. Plaut et al., 2007, Science 316, 92).

→ south; → polar; → layer; → deposit.

The half of the → Earth or another → north pole between the → south pole and the → equator.

→ southern; → hemisphere.

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.

→ curvature of space-time.

→ space; → time; → curvature.

In a wave train, a correlation between the phases of waves at points separated in space at a given time.

→ spatial; → coherence.

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

→ spatial; → resolution.

Of, relating to, or subject to the theory of → special relativity.

→ special; → relativistic.