Fr.: famille d'astéroïde
A group of asteroids that share the same or similar proper orbital elements (semi-major axis, eccentricity, inclination). In 1918, the Japanese astronomer K. Hirayama first recognized some non random concentrations of asteroid elements. He noticed that certain "groups" of asteroids had similar orbital elements, and hence he first introduced the concept of "asteroid families," and identified three of them: Koronos, Eos, and Themis. The names of these groups were chosen by the parent (brightest) asteroid that the smaller group asteroids follow. Some of the more common asteroid families include the Trojans, which are actually not an asteroid family, but a group of asteroids caught in the Sun-Jupiter gravitational equilibrium points known as L3 and L4 → Lagrangian points.
Fr.: recherche systématique d'astéroïdes
Of or relating to → asteroseismology.
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.
Asthenosphere, from Gk. asthenes "weak" + → sphere.
Sostsepehr, from sost "weak, tender" + sepehr, → sphere.
1) nâgerâvar, 2)nâgerâbin
The optical system which is affected by → astigmatism.
1) nâgerâvari, 2) nâgerâbini
1) An imperfection in an optical system whereby light from
a point source is formed into an image as a straight line,
ellipse, or circle. The rays of light in two perpendicular planes
appear as two lines at right angles.
From astigmatic, from Gk. → a- "without" + stigmatos, from stigma "a mark, spot, puncture."
1) Nâgerâvari, from nâ- "without, un" + gerâ,
stem of gerâyidan "to converge," + -var, agent forming
suffix, + -i, noun forming suffix.
Verbal form of → astration.
The cyclic process in which interstellar matter is incorporated into newly formed stars, where it undergoes nuclear processing, is thus enriched with heavier elements, and then returns into the interstellar medium through supernova explosion or stellar winds to be used in the formation of a newer generation of stars.
Astration, from astrate, from astr-, → astro-, + noun-forming suffix -ation.
Setâreš, from setâridan (from setâré "star" + verb-making suffix -idan) + noun-builder -eš.
A combining form with the meaning "pertaining to stars or celestial bodies" used in the formation of compound words. Variants aster-, and astr- before a vowel. → star.
Gk. astron "star," akin to L. stella (Fr. étoile, from O.Fr. esteile, from V.L. *stela), Skt. str-, tara-, Av. star-, Mid.Pers. star, stârag, Mod.Pers. setâré, axtar, see below; cf. O.E. steorra, E. star, Du. ster, O.H.G. sterro, Ger. Stern, PIE *ster- "star."
Mod.Pers. axtar, → star, from Mid.Pers. axtar.
The variants star-, estâr, estâré,
setâré are obvious. Note also the following
dialectal forms: (Lori, Laki) âsâra,
(Tabari) essâra, (Laki) hasâra, (Shughni)
xiterj, xtarag. The form axtar is less straightforward, leading
some philologists to suggest different origins for
setâré and axtar. According to
W. Eilers (Iranica), axtar is a back-fomation from
Mid.Pers. apâxtar "planet; north" produced by artificial dropping of the
first component. Apart from phonological difficulties inherent in this suggestion,
one must also explain how axtar meaning "planet"
became a general designation for star, as for example in
Mid.Pers. axtarmâr "astronomer," despite the relatively infinitesimal number
of planets known in ancient times.
W. Eilers' suggestion is pure theoretical construction; no factual evidence support it.
On the other hand, in Pahlavi texts, e.g. Bundahishn, axtar is extensively
used for "star, planet, and the signs of zodiac."
axtarbâstânšenâsi(#) , bâstânaxtaršenâsi (#)
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."
A geological structure on the Earth's surface from an ancient meteorite impact.
Astrobleme, from → astro- + Gk. blema "scar, wound, missile," from ballein "to throw;" PIE *gwele- "to throw".
Axtarxasts, from axtar "star," → astro- + xast "wounded; scratched," from xastan "to wound, wound by scratching," Mid.Pers. xst, xs "to injure," Av. vixad- "to crush," Proto-Iranian *xad- "to wound, hurt," Skt. khad- "to hurt."
The study of the chemical interactions between the gas and dust of the interstellar medium.
Astrochemistry, from → astro- "star" + → chemistry.
The science dealing with the motion of satellites, rockets, and spacecrafts. It uses the principles of celestial mechanics.
Astrodynamics, from → astro- "star" + → dynamics.
A science concerned with the geology of solid bodies in the Solar system, such as planets, satellites, asteroids, and meteorites.
A photographic instrument with great light gathering power which is used to photograph a large field in a single exposure.
An ancient instrument for solving problems relating to time and the position of the Sun and stars in the sky. It had many uses, including telling time during the day or night, finding the time of sunrise and sunset and, thus, the length of the day, and locating celestial objects in the sky. It was widely used until replaced by the → sextant. The → planispheric astrolabe, which is the most common type of the instrument, is typically made up of a graduated disk hanging vertically, which is rotated so that it can be directed to the star chosen. The local time can thus be read from the face of the astrolabe, and different tables, at various latitudes, can be used. More specifically, a planispheric astrolabe is made up of the following main components: → mater, → tympanum, → rete, → alidade, → throne, → limb, → pin, → horse, → front, and → back. The astrolabe was invented by Greeks, and some historians have attributed it to Hipparchus (c190-c120 BC). Modern, sophisticated versions (such as → prismatic astrolabe and → Danjon astrolabe), are used for high precision measurements of star positions. See also → particular astrolabe, → spherical astrolabe, and → universal astrolabe.
M.E., from O.Fr. astrelabe, from M.L. astrolabium, from Gk. astrolabos (organon) "star taking (instrument)," from astron "star," → astro- + lambanein "to take."
Ostorlâb, from Ar. usturlab, from Gk. astrolabos, as above.
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.
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."