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

A metallic chemical element; symbol Sr. Atomic number 38; atomic weight 87.62; melting point 769°C; boiling point 1,384°C; specific gravity 2.6 at 20°C. Strontium is a soft, silver-yellow metal with three allotropic crystalline forms. It is found in nature only in the combined state, as in strontianite. It is used in fireworks, flares, and tracer bullets. The radioactive isotope Strontium-87, the daughter of Rubidium-87, has a half-life of 48.8 x 10⁹ years.

The name derives from Strontian "a town in Scotland." The mineral strontianite is found in mines in Strontian. The element was discovered by the Scottish chemist and physician Thomas Charles Hope in 1792 observing the brilliant red flame color of strontium. It was first isolated by the English chemist Humphry Davy in 1808.

The arrangement of parts in an object or organism.

M.E., from L. structura "a fitting together, adjustment, building," from structus, p.p. of struere "to pile, build, assemble," related to strues "heap," from PIE *stere- "to spread, extend, stretch out;" cf. Pers. gostar-, gostardan "to spread;" Av. star- "to spread," starati "spreads;" Skt. star- "to spread out, extend, strew," strnati "spreads;" Gk. stornumi "I spread out," strotos "spread, laid out;" Ger. Strahlung "radiation," from strahlen "to radiate," from Strahl "ray;" from M.H.G. strāle; from O.H.G. strāla "arrow, stripe."

Sâxtâr, from sâxt "made; make, construction, structure; style," past stem of sâxtan, sâzidan "to build, make, fashion; to adapt, adjust, be fit" (Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach") + -âr verbal noun suffix.

The study of the processes that gave rise to the apparition of matter concentrations, such as → superclusters of galaxies, → galaxy clusters, and galaxies, in a homogeneous → expanding Universe. Cosmic structures are believed to result from → density fluctuations that existed in the → early Universe before radiation and matter decoupled (→ decoupling era or → recombination era). Initial → quantum fluctuations in the → inflaton field were expanded by → inflation. Inflation amplified them up to scales that correspond to those of galaxy clusters and beyond. Generally, a model of structure formation includes three main ingredients: 1) background cosmology, 2) model for fluctuation generation, and 3) types of → dark matter.
See also:
→ bottom-up structure formation, → hierarchical structure formation, → Silk damping, → top-down structure formation.

→ structure; → formation.

1a) Application of the mind to the acquisition of knowledge, as by reading, investigation, or reflection.
1b) The cultivation of a particular branch of learning, science, or art.
1c) Something studied or to be studied.
1d) Research or a detailed examination and analysis of a subject, phenomenon, etc. A written account of such research, examination, or analysis.
2a) To apply oneself to the acquisition of knowledge, as by reading, investigation, or practice.
2b) To think deeply, reflect, or consider.
2c) To take a course of study, as at a college (Dictionary.com).

M.E. studie, from O.Fr. estudie "care, skill, thought; study, school," from L. studium "study, application;" originally "eagerness," from studere "to press forward, be eager for, pursue," from PIE *(s)teu- "to push, stick, beat;" cf. Gk. typtein "to strike," typos "a blow, mold;" Skt. tup- "harm," tundate "pushes, stabs;" Gothic stautan "push."

Parhâné, from Proto-Ir. *pari-huan- "to read thoroughly, to read through," from *pari- "through, throughout; thoroughly" (O.Pers. pariy "around, about;" Av. pairi "around, over") + *huanH- "to call;" cf. Pers. xândan, x^vandan "to read, to sing" (Av. x^van- "to sound;" Skt. svana- "sound," svan- "to sound," svanati "it sounds;" O.E. swinn "music, song"); cf. Kurd. xwendin "to study, read;" Lori hané "to read;" Karingâni hoyniyan, Baluci vonag, Awromâni wânây "to read;" Khotanese hâvn- "to speak."

The fifth confirmed → satellite of → Pluto discovered in 2012 using a set of the → Hubble Space Telescope. Also called Pluto V (P5). It orbits Pluto between → Charon and → Nix at a distance of about 42,000 km. Styx is estimated to have a diameter of between 10 and 30 km, and an → orbital period of 20.2 days.

Named for the Greek mythological river that separates the world of the living from the realm of the dead.

A prefix occurring originally in loanwords from L. but freely attached to elements of any origin and used with the meaning "under, below, beneath."

From L. preposition sub "under" (also "next to, up to, toward"), from PIE base *upo- "from below," hence "turning upward, upward, up, over, beyond;" cf. O.Pers. upā (prep.) "under, with;" Av. upā, upa (prep.; prevb) "toward, with, on, in" (upā.gam- "to arrive at," upāpa- "living in the water," upa.naxturušu "bordering on the night"); Mod.Pers. bâ "with," from abâ; Skt. úpa (adv., prevb., prep.) "toward, with, under, on;" Gk. hypo "under;" Goth. iup, O.N., O.E. upp "up, upward."

Zir- "below, down;" Mid.Pers. azêr "below, under," êr "below, down; low, under," adar "low;" Av. aδara- (adj.), aδairi- (prep.) "below;" cf. Skt. ádhara- "lower;" L. infra (adv., prep.) "below, underneath, beneath," inferus "lower;" O.E. under "under, among"); PIE base *ndher.

A measure of angle smaller than 1 arcsecond, usually until 0.1 arcsecond.

→ sub-; → arc second.

Imaging in excellent seeing conditions using an adequate detector to obtain stellar images whose profile lies in the sub-arcsecond range.

→ sub-arcsecond; → imaging.

A part of a larger image.

→ sub-; → image.

Of, relating to, or being smaller than the atom; of or relating to the inside of the atom.

→ sub-; → atomic.

Any particle that is small compared to the size of the atom, e.g. an electron, proton, neutron, neutrino, quark, meson, all of which are either bosons or fermions.

→ subatomic; → particle.

A smaller group among several into which a main class is divided, e.g. subclasses a and b among supergiants. → subtype.

→ sub-; → class.

Of or pertaining to a state, value, or quantity that is less than critical, especially the condition of a → subcritical reactor.

→ sub-; → critical.

An amount of → fissile material that by its mass or geometry is incapable of sustaining a → fission → chain reaction.

→ subcritical; → mass.

A → nuclear reactor in which the rate of production of → fission neutrons is lower than the rate of production in the previous generation, and therefore the number of fissions decreases over time.

→ subcritical; → reactor.

Geology: The process by which one tectonic plate slides down and below another tectonic plate as the two converge. The subduction zone is the zone of convergence of two tectonic plates, one of which usually overrides the other.

From L. subductionem (nominative subductio), from subductus, p.p. of subducere "to draw away, withdraw, remove," from → sub- + ducere "to lead."

Zir-hâzeš, verbal noun of zir-hâzidan, from zir-→ sub- + hâzidan, hâxtan, from Mid.Pers. "to lead, guide, persuade;" Av. hak-, hacaiti "to attach oneself to, to join;" cf. Skt. sacate "accompanies, follows;" Gk. hepesthai "to follow,"; L. sequi "to follow;" PIE *sekw-.

A metal-poor main-sequence star with spectral type later than M7 and luminosity class VI. They are population II dwarfs which appear less luminous than their solar metallicity counterparts due to the dearth of metals in their atmospheres. Subdwarfs are halo members with high proper motions and large heliocentric velocities. They are important tracers of the chemical enrichment history of the Galaxy and belong to the first generation of stars formed in the Galaxy (at least 10 billion years old).

→ sub-; → dwarf.

A star with a lower absolute magnitude than a normal giant star of its → spectral type. It is a star that has exhausted the hydrogen at its center and is evolving into a → red giant. Subgiants are luminosity class IV.

→ sub-; → giant.

1) Something that is being discussed, examined, or otherwise dealt with.
2) A branch of learning that forms a course of study.
3) Philosophy: That which thinks, feels, perceives, intends, as contrasted with the objects of thought, feeling, etc.
4) Grammar: The part of a sentence or clause referring to the person or thing that does or causes the action of a verb. In English, the subject is typically a noun ("The cat ..."), a noun phrase ("His father's first trip ..."), or a pronoun ("It ...").

M.E. suget, from O.Fr. suget, subget "a subject person or thing," from L. subjectus "placed beneath, inferior, open to inspection," noun use of p.p. of subicere "to place under," from → sub-"under" + combining form of jacere "to throw,"from PIE base *ye- "to do" (cf. Gk. iemi, ienai "to send, throw," Hitt. ijami "I make").

Darâxt "thing drawn in, under" from dar- + âxt. The prefix dar-, from preposition dar "in, into, within; on, upon, above; of, about, concerning;" from Mid.Pers. andar "in, into, within," → inter-.
The second component âxt, contraction of âxté, p.p. of âxtan, variants âhixtan, âhiz- "to draw (a sword)," âhanjidan "to draw up, pull, extract," Mid.Pers. âhixtan, âhanjitan "to draw out, pull up, extract," Av. θanj- "to draw, pull, drive;" Proto-Iranian *θanj-.
Karin, from Sogd. karênê (variant kunênê) "doer, maker," from kar-, kardan "to do, to make," → -or.

1) That which depends upon the personal or individual, especially where it is supposed to be an arbitrary expression of private taste, in contrast with the objective.
2) Grammar: Pertaining to or constituting the subject of a sentence.

Adjective of → subject.