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

A dark lane that appears behind the coma in some comets. It is not the shadow of the true nucleus but sometimes may be a region of the near-tail that lies behind the densest part of the inner coma and therefore receives less sunlight.

→ shadow; → nucleus.

Same as → Tarantula Nebula.

30 (→ thirty), the object number in the catalog of Johann Elert Bode (1747-1826) Allgemeine Beschreibung und Nachweisung der Gestirne nebst Verzeichniss, compiled in 1801; → Dorado.

A → thought experiment conceived by Einstein (1879-1955) at the age of sixteen in the Swiss town of Aarau where he attended the Argovian cantonal school. If an → observer moved at the → speed of light, pursuing a → beam of light, would he → observe such a beam of light as a spatially oscillatory → electromagnetic field at rest? The answer came some ten years later from Einstein himself by his theory of → special relativity. Accordingly, the speed of light is constant for all observers and no observer can move at the light velocity.

Aarau, the Swiss town, the capital of the northern Swiss canton of Aargau; → paradox.

A → quadruple system of stars consisting of two close pairs, AB Dor A / AB Dor C and AB Dor Ba / AB Dor Bb, separated by about 9 arcseconds. The brightest star of the system, AB Dor A, is a → pre-main sequence star of → spectral type K1, with strong emission at all wavelengths, from radio to X-rays. The companion of this star, i.e. component C, lying 0.185 arcseconds apart, is a very low-mass star of 0.090 → solar masses with a spectral type M 5.5 (Boccaletti et al. 2008, A&A 482, 939 and references therein).

A, a, B, b, and C designating letters of alphabet; → Dorado.

1) Of or relating to a college, academy, school, or other educational institution, especially one for higher education.
2) Pertaining to areas of study that are not primarily vocational or applied, as the humanities or pure mathematics.
3) Theoretical or hypothetical; not practical, realistic, or directly useful (Dictionary.com).

→ academy; → -ic.

A member of an association or institution for the advancement of arts, sciences, or letters.

From Fr. académicien, from académic-, → academic, + -ian a suffix forming adjectives and nouns.

Farhangestânvand, from farhangestân, → academy, + -vand a suffix forming adjectives and agent nouns, → actual.

1) A group of authorities and leaders in a field of scholarship, art, etc., who are often permitted to dictate standards, prescribe methods, and criticize new ideas.
2) An association or institution for the advancement of art, literature, or science (Dictionary.com).

From Fr. Académie, from L. Academia, from Gk. Akademeia "grove of Akademos," a legendary Athenian of the Trojan War tales, whose estate, six stadia from Athens, was the enclosure where Plato taught his school.

Farhangestân, literally "site of culture and education," from farhang, → culture, + -estân suffix of place and time, → summer.

For the specific purpose at hand, as opposed to a general solution; also, by extension, improvised or impromptu.

From L. ad "to, with, in," cf. Skt. adhi "near," PIE *ad- "to, near, at."

Pad im, from Mid.Pers. pad "to, at, for, in" (Mod.Pers. bé "to, for, in, on, with, by"); O.Pers. paity "agaist, back, opposite to, toward, face to face, in front of;" Av. paiti "to, toward, in, at;" cf. Skt. práti "toward, against, again, back, in return, opposite;" Pali pati-; Gk. proti, pros "face to face with, toward, in addition to, near;" PIE *proti) + Mid.Pers. im "this;" from Old.Pers./Av. ima "this;" Skt. imá; cf. Lori (Laki) im "this side." The Mid.Pers. im occurs in Mod.Pers. as em- in emruz "today," emšab "tonight," and emsâl "this year."

Addition of adjustments to a theory to save it from being falsified by compensating for anomalies not anticipated by the theory in its unmodified form. Theories that rely on continual, ad hoc adjustments are distrusted.

→ ad hoc; → hypothesis.

A fallacious objection to an argument or factual claim by appealing to a characteristic or belief of the person making the argument or claim, rather than by addressing the substance of the argument or producing evidence against the claim (wiktionary).

Literally "to a man," from → ad- "to," + hominem, accusative of homo "man," → human.

Pad mart, literally "to a man," from pad "to," → ad hoc, + mart, → man.

Prefix meaning "to, toward, addition to, near," from L. ad "to, toward." It is modified to ac- or af- or ag- or al- etc. according to the following consonant.

Cognate with E. at, from O.E. æt "near, by, at"; compare with O.N., Goth. at, O.Fris. et, O.H.G. az, Skt. adhi "near," PIE *ad- "to, near, at".

To make suitable to or fit for a specific use or situation.

From M.Fr. adapter, from L. adaptare "adjust," from ad- "to" + aptare "join," from aptus "fitted."

Niyâvidan from Mid. Pers. niyâw "apt, suitable, appropriate" + -idan verb making suffix.

Capable of adapting or of being adapted.

→ adapt + → -able.

1) The act or process of adapting.
2) The state of being adapted.

→ adapt.

Physiological process whereby the eye adjusts its sensitivity for different levels of illumination.

→ adaptation, → eye.

1) General: One that adapts.
An appliance for connecting objects of different sizes or designs in an apparatus.
2) Astro.: A device that allows an observing instrument (imaging camera, spectrograph) to be mounted on a focus (e.g. Cassegrain) of a telescope.

→ adapt + → -er.

Same as → adaptation.

→ adaptation.

1) Relating to or exhibiting adaptation.
2) Capable of adapting or of being adapted. → adaptive optics; → adaptive optics system; → extreme adaptive optics.

→ adapt; → -ive.

A type of → algorithm that dynamically achieves high → resolution in localized regions of multidimensional → numerical simulations. AMR provides a higher → accuracy solution at lower costs, through an automatically → optimal distribution of → grid points for the computation region. It relies on locally refined mesh or mesh patches to increase the resolution of an underlying coarse mesh only where needed. It can alleviate some of the complexities of the generation of high quality grid and reduce the number of → iterations of "trial-and-error" between the grid generation and solution required for tailoring the grid to the specification of a problem. Thus, it can offer orders of magnitude saving in computational and storage costs over an equivalent uniformly refined mesh. AMR was originally developed for → inviscid, → compressible flow (Berger et al., 1984, Adaptive Mesh Refinement for Hyperbolic Partial Differential Equations. J. Comp. Phy., 53, 484). It has been extended to solve → Navier-Stokes equations, time dependent problems and more. Several AMR techniques have been developed and applied to compressible flow fields to capture characteristics at the strong gradient or discontinuous regions requiring higher space resolution, such as regions involving → shock waves, vortices (→ vortex), and → wakes (see, e.g., Qingluan Xue, "Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations" (2009), Iowa State Univ., Graduate Theses and Dissertations, Paper 10678).
See also → Smoothed Particle Hydrodynamics.

→ adaptive; → mesh; → refinement.

A technique for improving the → image quality of a telescope against → atmospheric turbulence in which image distortions are compensated by high-speed changes in the shape of a small, thin mirror. → wavefront; → wavefront distortion; → wavefront correction; → Strehl ratio; → tip-tilt mirror, → Shack-Hartmann wavefront sensor, → active optics.

→ adaptive; → optics.