1) sayyârak (#); 2) axtarvâr
1) A small rocky object orbiting the Sun. There are millions of asteroids
moving in orbits in the main → asteroid belt,
between → Mars and → Jupiter
and in the → Kuiper belt.
The largest and the first discovered, → Ceres,
about 1,000 km in size, is now classified as → dwarf planet
(2006 IAU General Assembly).
The largest asteroid in the solar system (Ceres apart), is → Pallas,
with a size of 582 × 556 × 500 km.
On the other hand, the smallest asteroid ever studied is the 2 meters space rock 2015 TC25,
which was observed when it made a close flyby of Earth in October 2015.
See also → near-Earth asteroid;
→ binary asteroid.
Fr.: ceinture des astéroïdes
The region of the → solar system located between → Mars and → Jupiter where over a million objects bigger than 1 km across orbit the Sun. Another region populated by minor bodies lies beyond the orbit of → Neptune, the → Kuiper belt.
Fr.: désignation des astéroïdes
1) For an asteroid whose orbit is precisely known, a number and optionally
a proper name, e.g. (7) Iris, (24101) Cassini, (99942) Apophis.
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.