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

The Sun when the 11-year cycle of → solar activity is at a minimum.

Quiet, M.E., from from O.Fr. quiete, from L. quies (genitive quietis) "rest, quiet;" → Sun.

Xoršid, → Sun; ârâm "quiet, rest, tranquility," → rest.

In cosmology, a hypothetical new "element," distinct from any normalmatter (either → baryonic or not) or radiation, intended to explain the observed ever → accelerating expansion of the Universe. Quintessence can have several types and differs from the → cosmological constant in that it can vary in space and time. In modern physics, the four known "elements" are the → baryons (proton, neutron, etc.), the → leptons (neutrinos, electrons, etc.), the → photon, and the hypothetical → non-baryonic matter, which is thought to be 80% of the total matter in the Universe. The quintessence field is a possibility which can be confirmed or disproved by measurements of the → dark energy value at different → redshifts. In some models, the quintessence is fine-tuned to explain both the → cosmological constant problem and the → inflation in the very → early Universe.

Literally "fifth essence," from M.Fr. quinte essence, from M.L. quinta essentia, from L. quinta, fem. of quintus "fifth," from quinque "five," cognate with Pers. panj, → five + essentia "being, essence," from esse "being; → existence" + -entia "-ence." In Aristotelianism, the fifth element, distinguished from the four earthly elements, was the substance of celestial bodies. Subsequently, quintessence became the purest, most highly concentrated form of a nature or essence.

Panjomin gowhar "fifth essence," from panjomin "fifth," from panj, → five, cognate with L. quinque, + gowhar "essence, substance; jewel, pearl, gem," Mid.Pers. gohr "essence, substance; jewel; stock, lineage;" cf. Skt. gôtra- "family, race, lineage, origin."

Any group of five things or persons. → Stephan's Quintet.

From Fr. quintette, from It. quintetto, diminutive of quinto "fifth," from L. quintus, related to quinque "five" cognate with Pers. panj→ five.

Panjtâyé, from panj, → five, + tâ "fold, plait, ply, part;" Mid.Pers. tâg "piece, part" + -(y)é nuance suffix.

Math.: Of the fifth degree; a quantity of the fifth degree.

From L. quint(us) "fifth," → five, + → -ic;

Panjomik, from panjom "fifth," from panj "five" + -om "-th" + -ik, → -ic.

An equation containing unknowns of the fifth power.

→ quintic; → equation.

A polynomial of degree five.

→ quintic; → polynomial.

A bright → open cluster of stars located within 100 light-years of the center of the Milky Way Galaxy, and one of the three → Galactic center clusters. The Quintuplet cluster was originally noted for its five very bright stars, but it is now known to contain many luminous → massive stars that are not detected at visible wavelengths due to heavy extinction by dust along the line of sight. The cluster is about 4 million years old and had an initial mass over 10⁴ solar masses. The five brighter stars of the cluster are dusty → WC Wolf-Rayet stars. The Quintuplet cluster also contains two → Luminous Blue Variables, the Pistol star and FMM362. The Pistol star has a luminosity 10⁷ times solar making it one of the most luminous stars known. The Quintuplet cluster is more dispersed than the nearby → Arches cluster.

Quintuplet, from the five brightest stars originally observed; → cluster.

1) General: A proportional part or share of a fixed total amount or quantity.
2) Computers: The amount of a resource (disk, memory, CPU time, etc.) that is allocated to a user.

From L. quota pars "how big a share?," from quotus "of what number."

Bahrâl, from bahr "part, portion, share, lot," → quotient + -âl, → -al.

The number resulting from the division of one number by another. Also the fractional notation that indicates this number.

From L. quotiens "how many times," from quot "how many," related to quis "who."

Bahr "part, portion, share, lot," related to baxš "portion, part, division," baxšidan "to divide, distribute, grant" (Mid.Pers. baxt "fortune, fate," baxtan, baxšidan "to distribute, divide;" Av. base bag- "to attribute, allot, distribute," baxš- "to apportion, divide, give to," baxta- "what is allotted (luck, fortune)," baxədra- "part, portion," baγa- "master, god;" O.Pers. bâji- "tribute, tax;" cf. Skt. bhaj- "to share, divide, distribute, apportion," bhájati "divides," bhakta- "allotted; occupied with; a share; food or a meal, time of eating?" pitu-bháj- "enjoying food;" Gk. phagein "to eat (to have a share of food)"; PIE base *bhag- "to share out, apportion").

A peculiar → Mira variable with a → pulsation period of 387 days surrounded by an extended → emission nebula. R Aqr is a → symbiotic  → binary star with a mass-losing, pulsating → red giant and an accreting hot companion with a jet → outflow which ionizes an emission nebula. The orbital period of the R Aqr binary is about 44 years as inferred from periodic phases of reduced brightness observed around 1890, 1933, and 1977. These phases are interpreted as partial obscurations of the mira by the companion with its → accretion disk and the associated gas and dust flows. The inferred orbital period is supported by → radial velocity measurements (Schmid et al., 2018, A&A 602, A53 and references therein).

R, → Beyer designation; → Aquarius.

A → stellar association containing a number of → reflection nebulae. The stars are of low or intermediate mass and young, less than a million years old. They are still surrounded by patches of dust that reflect and absorb light from the interstellar cloud in which they formed. This type of association was first suggested by Sidney van den Bergh (1966, AJ 71, 900).

R, from → reflection; → association.

A → nucleosynthesis process in which → chemical elements heavier than → zinc are created through the intense bombardment of other elements by → neutrons in rapid succession. The essential feature of the r-process is the release of great numbers of neutrons in a very short time (less than 100 seconds). The r-process is a "rapid" version of the → s-process, occurring in supernova → core collapse and possibly when a → neutron star merges with a → black hole in a → binary star.

r stands for rapid, since the process entails a succession of rapid neutron captures on iron seed nuclei; → process.

A spherical → ionization front of → H II regions that moves radially outward from the → exciting star at a velocity much higher than → sound speed in the surrounding cold neutral gas of uniform density (ahead of the front). R-type ionization fronts corresponds to early evolution of H II regions, and will eventually transform into → D-type ionization fronts. If the motion of the front is supersonic relative to the gas behind as well as ahead of the front, the front is referred to as weak R. The strong R front correspond to a large density increase across the front.

R referring to a rarefied gas; → type; → ionization; → front.

The central object of the → 30 Doradus nebula in the → Large Magellanic Cloud. Also known as HD 38268, it was thought to be a single star of several thousands → solar masses until → speckle interferometry techniques resolved it into a rich and compact star cluster. Recent high-resolution studies have shown that R136 contains 39 known O3 stars, which is more than known to be contained in the rest of the → Milky Way, → LMC, and → SMC combined. R136 is a prototype "super star cluster," with an estimated mass of 10⁵ solar masses. Its most massive stars are less than 1-2 million yeas old, while its lower-mass stars formed 4-5 millions years ago.

The Radcliffe serial number 136 (Feast et al. 1960, MNRAS 121, 25).

1a) A group of persons related by common descent or heredity.
1b) A population so related.
2) A contest of speed, as in running, riding, driving, or sailing (Dictionary.com).

1) From M.Fr. race "race, breed, lineage, family," from It. razza, (cf. Sp. and Port. raza), of unknown origin.
2) M.E. ras(e), from O.N. ras "running, race," cognate with O.E. ræs "a running, a rush, a leap, jump."

1) Nežâd, literally "born," ultimately from Proto-Ir. *nizat-, cf. Av. nizənta- "born," from → ni- + *zan- "to give birth, to be born," cognate with âzâd, → free; see also → generate.
2) Tâz, present stem of Tâxtan/tâz- "to run, rush upon, assault;" → surge.

1) A belief or doctrine that inherent differences among the various human races determine cultural or individual achievement, usually involving the idea that one's own race is superior and has the right to rule others.
2) A policy, system of government, etc., based upon or fostering such a doctrine; discrimination (Dictionary.com).

→ race; → -ism.

A unit of energy absorbed from ionizing radiation, equal to 100 → ergs per gram, or 0.01 → joules per kilogram, of irradiated material. Rad has been replaced by → gray (Gy).

Shortened form roentgen absorbed dose; → roentgen.

An emitting/receiving device in which the echo of a pulse of microwave radiation is used to detect and locate distant objects.

From ra(dio) d(etecting) a(nd) r(anging).

Graphic display of measurements by a → radar of mineral deposits on a planetary surface.

→ radar; → chart.

Emanating from a common central point; arranged like the radii of a circle.

From L. radialis, from → radius; → -al.