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

Describing two → compound propositions → if and only if they have the same → truth table.

→ logical; → equivalent.

1) The act of logging in to a database, mobile device, or computer, especially a multi-user computer or a remote or networked computer system.
2) A user name and password that allows a person to log in to a computer system, network, mobile device, or user account (Dictionary.com).

→ log; → in.

A → probability distribution in which the natural logarithm (logX) of the → random variable (X) has a → Gaussian distribution.

→ logarithm; → normal distribution.

The process by which a computer user logs out.

→ log; → out.

The study of the → Moon's → crust, → rocks, strata (→ stratum), etc.

→ lunar; → geology.

Combined study of the large-scale → magnetic field (→ magnetometry) and → stellar pulsations (→ asteroseismology). Magneto-asteroseismology provides strong complementary diagnostics suitable for detailed stellar modeling and permits the determination of the → internal structure and conditions within → magnetic massive  → pulsators, for example the effect of magnetism on → mixing processes. More specifically, asteroseismology yields information on the → density, → composition, and → chemical mixing in multiple internal layers (depending on the number of studied frequencies). Additionally, when rotationally split pulsation modes are observed, the internal rotation profile can be retrieved. From magnetometry surface properties are determined, related to the → chemical composition, including → starspots, and the magnetic field, such as its geometry, obliquity, and strength. Magnetic studies also provide constraints about the → stellar wind geometry and the → circumstellar environment. Moreover, the stellar → rotation period period and the → angle of inclination toward the observer are also retrieved (Buysschaert et al., 2017, astro-ph/1709.02619).

→ magneto-; → asteroseismology.

That point on the → celestial sphere at which an object would be seen from the solar system → barycenter affected by the → e-terms → aberration.

→ catalog; → mean; → place.

A catalog of more than 100 nebulous-appearing astronomical objects, initially established to avoid confusion with comets. These objects are now well known to be among the brightest and most striking gaseous nebulae, star clusters, and galaxies. The designations of the catalog are still used in identification; e.g. M1 is the Crab Nebula (in Taurus).

In honor of the French astronomer Charles Messier (1730-1817), who compiled the list between 1760 and 1784 in order to avoid confusion with comets; → catalog.

Evaluation or measurement of one or more meteorological elements.

Meteorological, of or pertaining to → meteorology; → observation.

A scientific establishment dedicated to making precise and detailed meteorological observations and to studying and forecasting atmospheric phenomena by means of special equipments.

Meteorological, of or pertaining to → meteorology; → observatory.

The study of the physics, chemistry, and dynamics of the Earth's atmosphere, including the related effects at the air-earth boundary over both land and the oceans.

From Gk. meteorologia "discussion of celestial phenomena," from meteoron→ meteor + -logia, &rarr-logy.

Havâšenâsi, from havâ "weather, air," → air.

The science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty in any field of science and technology.

From metro-, a combining form meaning "measure," → meter, + → -logy.

Andâze-šenâsi, from andâzé, → measure, + -šenâsi, → -logy.

Same as → Milne Universe.

→ Milne Universe; → cosmological; → model.

Of or relating to → morphology. Same as morphological

→ morphology; → -ic.

Of or relating to → morphology. Same as morphological

→ morphologic; → -al.

A classification scheme of galaxies based on their apparent shape. → Hubble classification.

→ morphological; → classification.

1) The study of the form or → structure of anything.
2) The → form and structure of a whole entity under study.
3) Linguistics: The structure of → words in a → language, including patterns of → inflections and → derivation. The study and description of such structures.

From Gk. morphe "form, shape, outward appearance" + → -logy.

Rixt "shape, the way something is cast, as in founding," past stem of rixtan "to cast; to pour; to flow" (Mid.Pers. rēxtan and rēcitan "to flow;" Av. raēk- "to leave, set free; to yield, transfer," infinitive *ricyā; Mod.Pers; rig in morderig "heritage" (literally, "left by the dead"); cf. Skt. rinakti "he leaves," riti- "stream; motion, course;" L. rivus "stream, brook;" Old Church Slavic rēka "river;" Rus. reka "river;" Goth. rinnan "run, flow," rinno "brook;" O.E. ridh "stream." šenâsi, → -logy.

An observationally determined relationship between the → morphological classification of galaxies and the → environments in which they are located. Specifically, the morphology-density relation indicates that early-type galaxies (→ ETG) are preferentially located in high density environments, whereas late-type galaxies (→ LTG) are preferentially found in low density environments. Hence, spiral galaxies are rare in the high densities of clusters and are common in the lower density group environments. Early-type galaxies, on the other hand, are common in clusters and are rarely found in isolation.

→ morphology; → density; → relation.

The science and technology of producing and exploiting structures and systems at dimensions of roughly 1 to 100 → nanometers, that is those of single atoms and molecules. Materials with such minute structures possess mechanical, optical, chemical, magnetic or electronic properties not found in ordinary materials.

→ nano-; → technology.

Same as the → natural logarithm.

After John Laird Napier (1550-1617), the Scottish mathematician who invented logarithm; → logarithm.