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

A → molecular cloud that is physically or apparently related to a star formation region.

→ associate; → molecular; → cloud.

1) The act of associating, → associate; the state of being associated.
2) A group of → astronomical objects physically or apparently gathered in a particular area of sky, for example an → stellar association.
3) An organization of persons having a common interest. → dissociation.

Association, noun from → associate.

Âhazeš, verbal noun of → âhazidan→ associate. Anjoman, for the meaning 3, from Mid.Pers. anjaman, from Av. han-jamana, from han- "together" + jamana, from gam- "to come;" cf. Skt. samgamana "gathering together."

A celestial body making part of an astronomical association.

→ association; → member.

1) Of, characterized by, resulting from, or causing association.
2) In a mathematical operation, being independent of the sequence in which the elements are grouped. For ex., if a + (b + c) = (a + b) + c, the operation indicated by + (addition) is associative.

Adj. from associate.

An algebra whose multiplication is associative.

→ associative; → algebra.

A basic rule in → group theory stating that if a, b and c are members of a group then (a * b) * c and a * (b * c) are members of the group.

→ associative; → axiom.

In mathematics, the rule that states that the result of two identical operations is independent of the sequence of these operations. For ex., in the addition operation, a + (b + c) = (a + b) + c = a + b + c. Multiplication of numbers is also associative.

→ associative; → law.

Of or relating to association; state of being associative.

→ associative + → -ity.

To take as granted or true; suppose.

M.E., from L. assumere "to take up," from ad- "to, up" + sumere "to take," from sub "under" + emere "to take."

Âgarbidan, from âgarb, → assumption.

A fact or statement (as a proposition, axiom, postulate, or notion) taken for granted.

M.E., from L.L. assumption, assumptio "taking up," from L. assumere, → assume.

Âgarb, from â-, nuance prefix, + garb, from Av./O.Pers. grab-, Av. gərəb- "to take, to seize;" cf. Mod.Pers. gereftan "to take; to assume;" Skt. grah-, grabh- "to seize, to take," graha "seizing, holding, perceiving;" M.L.G. grabben "to grab;" E. grab "to take or grasp suddenly;" PIE *ghrebh- "to seize."
Ar. farz "assumption, hypothesis."

A positive declaration intended to give confidence; promise or pledge; guaranty; surety (Dictionary.com).

→ assure; → -ance.

1) To declare earnestly to; inform or tell positively; state with confidence to.
2) To give confidence to; encourage.

M.E. as(e)uren, assuren, from O.Fr. aseurer, from L.L. assecurare, from as-, variant of → ad-, + secur-, → secure, + -a- thematic vowel, + -re infinitive suffix.

Âtenzidan, from â- intensive prefix, + tenz, → sure, + -idan infinitive suffix, → -ize.

A small starlike symbol (*), used in printing or writing as a reference mark, as an indication of the omission of letters or words, to denote a hypothetical linguistic form, or for various arbitrary meanings.

M.E. astarisc, from L.L. asteriscus, from Gk. asteriskos "small star," from aster-, → astro- + -ikos "diminutive suffix."

Axtarak, from axtar "star" → astro- + -ak "diminutive suffix."

A group of stars in the sky which are traditionally imagined to present a pattern within a → constellation. Examples include the → Big Dipper, the → Northern Cross, the → Square of Pegasus, and → Orion's Belt.

Gk. asterismos "a marking with stars, constellation," from aster, → astro- + → -ism.

Axtargân, from axtar "star" → astro- + -gân suffix denoting collective nature.

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.
2) Math.: A → hypocycloid with four → cusps in which the → radius of the rolling → circle is a → quarter of the radius of the fixed circle. It has the → parametric equations x = a cos³θ, y = a sin³θ, where a is the radius of the fixed circle.

Gk. asteroeides "star-like," from aster, → astro- + → -oid "like, resembling."

Sayyârak "small planet," from sayyâré, → planet, + -ak "diminutive suffix."
Axtarvâr, from axtar, → astro-, + -vâr, → -oid.

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.

→ asteroid; → belt.

1) For an asteroid whose orbit is precisely known, a number and optionally a proper name, e.g. (7) Iris, (24101) Cassini, (99942) Apophis.
2) For an asteroid whose orbit is not known, a provisional designation composed of four elements: number.letter.letter.(optionally)number. The first number indicates the year of discovery. The first letter denotes the half-month of the discovery (A: first half of January, Y: second half of December; the letter "I" is excluded). The second letter and the following number indicate the order of discovery within the half-month. For example, the first asteroid discovered in the first half of May 1960 is: 1960 JA. Since more than 25 objects (without "I") might be detected within a half-month, the number following the second letter indicates the number of 25 discoveries. Hence, 2001 SD3 was discovered in the second half of September 2001 and was the (D =) 4 + (25 x 3) or the 79th object found during that period.

→ asteroid; → designation.

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.

→ asteroid; → family.

Systematic observation of the sky in particular searching for → asteroids that may have a close approach to the Earth. → near-Earth object.

→ asteroid; → survey.

Bardid, → survey; sayyârakhâ plural of sayyârak, → asteroid.

Of or relating to → asteroseismology.

→ spectropolarimetry; → -ic.