An Etymological Dictionary of Astronomy and Astrophysics
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A series of → nuclear reactions taking place in stars in which → carbon, → nitrogen, and → oxygen are used to transform → hydrogen into → helium. In → massive stars the carbon cycle is the dominant process of energy generation, whereas in → low-mass stars such as the Sun, the → proton-proton chain of reactions converts hydrogen into helium. The carbon cycle starts and ends with carbon-12, which acts as a catalyst in the sequential production of helium from hydrogen; neutrinos and gamma rays are also produced.

→ CNO; → cycle.

A late → O-type star or an early → B-type star in whose spectrum the lines of some of the elements → carbon (C), → nitrogen (N), and → oxygen (O) are present.

→ CNO; → star.

The chemical reaction that gives rise to → carbon monoxide in the → interstellar medium. According to models, several processes may lead to CO formation. For example, HCO⁺ + e → CO + H. The molecule HCO⁺ is itself produced through several paths, for example: H₃⁺ + C → CH₂⁺ + H, CH₂⁺ + H₂ → CH₃⁺ + H, CH₃⁺ + O → HCO⁺ + H. Alternatively: C⁺ + H₂O → HCO⁺ + H. Another possibility: C⁺ + OH → CO⁺ + H, CO⁺ + H₂→ HCO⁺ + H.

→ carbon monoxide; → formation.

A spectral line energy distribution which plots the intensity of each → carbon monoxide (CO) transition as a function of the upper J number. This type of → diagram is a powerful diagnostic tool, where models show that these CO ladders have very different shapes depending on the type of excitation (i.e. photon dominated region, PDR or X-ray dominated region, XDR) as well as density and radiation environment.

→ carbon monoxide (CO); → ladder.

→ com-.

An image made up of several individual images of relatively short exposure times which are added together in order to produce a final image of higher quality.

Co-added, from → co- "together" + added p.p. of → add; → image.

Tasvir, → image; hamafzudé from ham- "together", → com-, + afzudé p.p. of afzudan, → add.

A theory according to which the Earth and Moon formed from the → protoplanetary disk at the same time. See also → giant impact hypothesis, → capture theory, → fission theory.

→ co-; → formation; → theory.

Of or relating to two or more celestial bodies that share, or almost share, the same orbit.

→ co-; → orbital.

The motion of two or more bodies around the Sun on different orbits when it takes them the same amount of time to complete one revolution. There are three possible types of co-orbital motions of a small body associated with a planet: → tadpole orbits, → horseshoe orbits, and → quasi-satellite orbits.

→ co-orbital; → motion.

Any of satellites which either share the same orbit or which occupy immediately adjacent orbits that change periodically as the satellites approach one another (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ co-orbital; → satellite.

The action or quality of a → co-orbiting asteroid.

From co- "together," → com- + → orbit + → -ing.

From ham- "together," → com- + madâr→ orbit + -i noun suffix.

An asteroid having a → co-orbital motion.

→ co-orbiting; → asteroid.

For any rotating planetary body, a thermal limit beyond which the → rotational velocity at the equator intersects the → Keplerian orbital velocity. Beyond this corotation limit, a hot planetary body forms a structure, called a → synestia, with a corotating inner region connected to a disk-like outer region. Beyond this limit a body cannot have a single → angular velocity. It can instead exhibit a range of morphologies with disk-like outer regions. The (CoRoL is a function that depends upon the composition, thermal state, → angular momentum and mass of a body (Simon J. Lock nd Sarah T. Stewart, 2017, arXiv:1705.07858v1).

→ co-; → rotational; → limit.

1) (v.int.) Generally, of liquids, to change into a thickened mass, curdle; congeal.
2) Biology, Medicine: of blood, to form a clot.
3) Physical chemistry: of colloidal particles, to flocculate or cause to flocculate.
4) Astrophysics: of dust grains in the interstellar medium and protoplanetary disks, to grow into larger entities. → dust coagulation.

Mâsidan "to coagulate, clot," originally "of milk, to turn into yogurt," mâst "clotted milk, yogurt;" Gilaki mas, Lori mâs, Kurd. mâzd, mâst, Sangesari must, Baluchi madhagh, mastagh; Mid.Pers. mâs- "to coagulate, become hard;" cf. Skt. mástu- "milk cream," Arm. macum "soar milk," macanim "to clot, congeal."
Rocidan from Lori roc "congealed," rocesse "to congeal, clot."
Laxté bastin lit. "coagulate into (solid) piece," from laxté "piece, part, portion," + bastan "to coagulate, congeal; to bind, shut" (Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind).

Verbal noun from → coagulate.
Physical chemistry: A separation or precipitation of particles from a dispersed state in a colloid solution.
Astrophysics: The mechanism by which dust grains grow into larger entities in the interstellar medium and protoplanetary disks. → dust coagulation.

Verbal noun from → coagulate.

A black, hard mineral consisting of carbon and various carbon compounds. Coal is formed from the decomposition of ancient plants buried deep in the Earth's crust for millions of years. It is currently the most widely used substance to generate electricity and heat. Its combustion products are used as raw material for a variety of products including cement, asphalt, and plastics. Due to the harmful gases that it releases, the use of coal is constantly being reduced as alternative fuels are found.

M.E. cole, from O.E. col "charcoal, live coal;" (cf. O.Fr. kole, M.Du. cole, Du. kool, O.H.G. chol, Ger. Kohle, from PIE root *g(e)u-lo- "live coal" (cf. Irish gual "coal").

From zoqâl, → charcoal, + sang, → stone.

A prominent → dark nebula visible to the naked eye as a dark patch silhouetted against the starry band of → Milky Way in the Southern sky. It obscures an area of about 5 by 7 degrees on the sky and extends beyond the borders of → Crux into neighboring → constellations → Centaurus and → Musca. It lies at a distance of approximately 500 → light-years.

→ coal; sack, from M.E., from O.E. sacc, from L. saccus, from Gk. sakkos, of Semitic origin (cf. Heb. saq "sack").

Guni "sack;" zoqâl, → charcoal.

To grow together; to come together so as to form one whole, to fuse. → merge; → fusion.

From L. coalescere, from co- + al-, stem of alere "to nourish, make grow" + -esce, from -escere, a suffix conveying an inchoative meaning.

Âhamidan, from â- nuance prefix + ham "together" (Av. hama- "similar, the same;" Skt. samah "even, level, similar, identical;" Gk. hama "together with, at the same time," homos "one and the same," PIE *samos "same," from base *sem- "one, together") + -idan infinitive suffix.

1) General: The act or state of growing together, as similar parts; the act of uniting by natural affinity or attraction; the state of being united.
2) Merging of the stars composing a → binary system after having undergone → supernova explosion. General relativity predicts that binary systems of → compact objects will emit energy in the form of → gravitational radiation, and that this loss of energy eventually will lead to the coalescence of the system.

Verbal noun from → coalesce.

A scenario for building up → massive stars through merging of → intermediate-mass protostars. It occurs in the cores of dense stellar clusters that have undergone core contraction due to rapid → accretion of gas with low → specific angular momentum. The required densities are, however, very high, 10⁸ stars pc^-3, which are extremely rare (Bonnell et al. 1998, MNRAS 298, 93).

→ coalescence; → model.