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

A combining form used in the names of sciences or bodies of knowledge, such as → biology, → geology, → cosmology. See also → -ics.

M.E. -logie, from O.Fr. -logie, from L. -logia, from Gk. -logia, from legein "to speak, tell over; to choose, gather," logos "word, speech, thought, account."

-Šenâsi, from šenâs, present stem of šenâsidan, šenâxtan "to know, discern, distinguish, be acquainted with;" Mid.Pers. šnâxtan, šnâs- "to know, recognize," dânistan "to know;" O.Pers./Av. xšnā- "to know, learn, come to know, recognize;" cf. Skt. jñā- "to recognize, know," jānāti "he knows;" Gk. gignoskein "to know, think, judge;" L. gnoscere, noscere "to come to know" (Fr. connaître; Sp. conocer); P.Gmc. *knoeanan; O.E. cnawan; E. know; Rus. znat "to know;" PIE base *gno- "to know."

A catalog (Bennett, 1962) based on the original 3C survey (Edge et al., 1960) made at Cambridge at 159 MHz using a complex → interferometer system. This → survey was preceded by the 2C survey made with the same instrument at 81 MHz with a resolution two times poorer. The 2C catalog contained 1936 sources, but owing to the poor resolving power, it became clear at an early stage that many of these sources were not real, and were due to blends of two or more sources in the primary antenna beam. Moreover, except for the strongest sources, the determination of the flux density and angular coordinates was poor. The 3C survey contained only 471 sources and was considerably more reliable. Nevertheless, because of the relatively poor primary resolving power, there were still large errors in the positions and flux densities. In particular, it was frequently uncertain in which → lobe of the → interference pattern a particular source was located, and this introduced large positional uncertainties. In order to reduce these uncertainties an additional survey was made at 178 MHz using a large parabolic cylinder antenna. The narrow E-W beam of this antenna eliminated nearly all of the lobe ambiguities of the original 3C catalog. The data from the two surveys were combined to form the then most reliable radio source catalog - the Revised 3C or 3CR Catalogue. The same parabolic cylinder antenna was later used together with a smaller moveable antenna as an aperture synthesis instrument to make a complete high-resolution survey of the northern sky (the 4C survey), which contains about 2000 sources (NASA/IPAC Extragalactic Database, NED).

3, for the third "version;" C, for "catalog;" R, for "revised;" → catalog.

A catalog of 4073 rich → galaxy clusters grouped by constellation and by catalog number. Published first in 1958, it contained the clusters visible from the northern hemisphere. A supplement for the southern hemisphere survey was published in 1988.

George O. Abell (1927-1983), American astronomer; → catalog.

A subdivision of meteorology concerned with the total vertical extent of the atmosphere as opposed to the study of the atmosphere near Earth's surface.

Aerology from Gk. aero- "air" + Gk. logia "study of," from legein "to speak".

Javvšenâsi, from Ar. javv "air, atmosphere" + šenâsi "knowledge, knowing," from šenâxtan "to know," from Av./O.Pers. xšnâ "to learn, come to know, know," compare with Skt. jna "to know," Gk. gignoskein "to know, think, judge," L. gnoscere, noscere "to come to know," PIE *gno- "to know."

In electronics, a device that converts the analog signal to → analog-to-digital units or counts.

→ analogue; → digital; → converter.

A number that represents a → charge-coupled device (CCD)'s output and is proportional to the → electron charge created by the → photons, plus the constant → bias offset. The relationship between the ADUs generated and the number of electrons acquired on the CCD is defined by the → CCD gain. Intensities given in ADUs provide a convenient method for comparing images and data generated by different cameras. Also referred to as → count and digital number. In most cases, the analog signal is digitalized by an analog-to-digital (A/D) converter and fed into a computer where further manipulation and analysis are done on what the detector originally produced from the star's photons (Howell, S.B., Handbook of CCD Astronomy, Cambridge Univ. Press, 2000).

→ analogue; → digital; → unit.

Of, relating to, or based on analogy; expressing or implying analogy.

→ analogy + -i + → -al.

1) Similar or corresponding in some respect; having → analogy.
2) Biology: Similar in function but having different evolutionary origins, as the wings of birds and insects.
3) Chemistry: Similar in chemical properties and differing in chemical structure only with respect to one element or group.

L. analogus, from Gk. analogos "proportionate," → analogy.

1) (n.) Something that has → analogy to something else.
2) Chemistry: (n.) A chemical compound whose molecular structure is closely similar to that of another.
3) Relating to or using signals or information represented by a continuous variable physical quantity such as spatial position or voltage. Often contrasted with → digital.

From Fr. analogue, from Gk. analogon, → analogy.

A computer in which data is stored and processed in the form of continually varying signals representing a physical quantity rather than in the form of individual numerical values. The simplest analogue computers are side rules, thermometers, voltmeters, and speedometers.

→ analogue; → computer.

1) A similarity or comparability between two things.
2) Math.: A general similarity between two problems or methods. Analogy is used to infer new theorems from existing ones. Hypotheses based on analogy must still be proved.
3) Logic: A form of reasoning which asserts that if two or more entities are similar in one or more respects, then they would be similar in other respects.
4) Biology: An analogous relationship.
5) Linguistics: The process by which a word or form is either created or changed according to existing patterns in the language.

M.E., from O.Fr. analogie or directly from L. analogia, from Gk. analogia "proportion," from → ana- "upon, according to" + logos "ratio; word, speech, reckoning," → -logy.

A solution to Einstein's theory of → general relativity that is spatially homogeneous but allows for rotation and/or shear. See also → Bianchi cosmological model.

→ anisotropic; → homogeneous; → cosmological; → model.

The study of the origin, history, and structure of Mars; the geology of Mars.

Areology, from Gk. Ares "Mars" + → -logy.

Bahrâm-šenâsi, from Bahrâm "Mars" + -šenâsi→ -logy.

Of or relating to → asteroseismology.

→ spectropolarimetry; → -ic.

The study of the → internal structure of stars through the interpretation of their pulsation periods (→ stellar pulsation). The radial pulsations are the result of → sound waves resonating in the stars interior. Different → pulsation modes penetrate to different depths inside a star. If a large number of pulsation modes occurs, then the stellar interior, which is not directly observable, can be probed from oscillation studies because the modes penetrate to various depths inside the star. Using a complex mathematical analysis, very detailed investigations of the structure of the star's interior can be carried out. Applied to the Sun, it is called → helioseismology.

From → astero- "star," from aster-, → astro-, + → seismology.

Axtarlarzešenâsi, from axtar "star," → astro-, + larzešenâsi, → seismology.

Same as → archaeoastronomy, megalithic astronomy.

The study of life throughout the Universe, also known as exobiology.

Astrobiology, from Gk. → astro- "star" + bio "life" + -logy "science, study."

Axtarzistšenâsi, from axtar, → star, → astro- + zistšenâsi, → biology.

A science concerned with the geology of solid bodies in the Solar system, such as planets, satellites, asteroids, and meteorites.

Astrogeology, from Gk. → astro- "star" + → geology.

Axtarzaminšenâsi, from axtar, → star, → + zaminšenâsi, → geology.

One who practices → astrology; one who professes to foretell events by the aspects and situation of the stars.

Agent noun from → astrology.

Axtargu, a classical term used by e.g. Jalâleddin Rumi (Mowlavi), 13th century poet, → astrology.

A → pseudoscience based on the belief that the apparent positions and → aspects of a small number of celestial bodies influence the course of human life and terrestrial events. Although the Sun and Moon have a gravitational influence on Earth, there is no known force that can cause celestial bodies to affect human affairs in the way claimed by → astrologers. Generally speaking, astrology is baseless and incoherent. In the astrological belief the influence of celestial bodies does not depend upon their distance from Earth, but on their positions and apparent angular separations. Outer planets can have a similar degree of influence as the inner planets. As a consequence, the billions of planets in our Galaxy and in billions of other galaxies should also influence us, and logically the effect of those planets must overwhelm any influence of the planets we see. Nevertheless astrologers do not care, and this fact makes astrological deductions absurd even in their scheme. Historically, the planets → Uranus, → Neptune, and → Pluto were not used in astrological predictions. They were added from the 18th century onward, after their discovery. Now that Pluto is disqualified as a planet, will astrologers remove it from their theories? If the answer is negative, they must logically include the numerous other similar → dwarf planets (such as → Charon, → Quaoar, → Sedna) residing in the → Kuiper belt. In brief, astrology is a superstition chiefly based on ignorance and man's need for mental contentment.

→ astro-; → -logy.

Axtarguyi, literally "star-telling," from axtar "star," → astro- + guyi verbal noun from goftan "to tell, speak, talk;" Mid.Pers. guftan "to say, tell, utter;" O.Pers. gaub- "to say."