An Etymological Dictionary of Astronomy and Astrophysics
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One of two light beams derived from the same source in → interference experiments. It is impossible to obtain interference from two separate sources because their → wavefronts do not have a constant → phase difference. In → Young's experiment, → Fresnel's biprism, → Fresnel's mirrors, and → Lloyd's mirror the two sources always have a point-to-point correspondence of phase, since they are both derived from the same source.

→ coherent; → source.

Holding together.
Physics: The attraction between the molecules of a solid or liquid that holds the parts of the substance together.

From L. cohæsus, p.p. of cohærere "to stick together," → coherence.

Hamduseš, verbal noun from hamdusidan "to cohere," → coherence.

1) Of or pertaining to the molecular force → cohesion.
2) Characterized by or causing → cohesion.

Adjective from → cohere.

The energy associated with the chemical bonding of atoms in a solid.

→ cohesive; → energy.

The force of → attraction between the molecules of the same substance.

→ cohesive; → force.

A device consisting of a length of electrical wire wound in a spiral to provide magnetic field by → electromagnetic induction.

Maybe from M.E. cull, from M.Fr. culier, coillir "to gather," from L. colligere "to bind together," → collect.

Picé "a curled, a twisted figure or object," from picidan "to twist, invove, enttwine, coil."

1) (Of two more objects) to correspond in area and outline; to occupy the same place.
2) To happen at the same time.

Coincide, from Fr. coincider, from M.L. coincidere, from L. → co- "together" + incidere "to fall upon," from in- "upon" + cadere "to fall," PIE base *kad- "to fall".

Barhamoftâdan, from bar- "to, upon, together" + oftâdan "to fall," Mid.Pers. patet "falls," opastan "to fall," Av. pat- " to fly, fall, rush," cf. Skt. patati "he flies, falls," L. petere "to fall, rush out," Gk. piptein "to fall," petomai "I fly," PIE base *pet- "to fly, to rush."

1) Fact, event, or condition of coinciding.
2) The occurrence of events simultaneously in a striking manner but without any causal connexion between them.

→ coincide.

Occupying the same area in space or happening at the same time. Of two geometric figures, matching point for point.

From Fr. coincident, from M.L. coincident-, coincidens, pr.p. of coincidere, → coincide.

→ coincide.

The polar angle on a sphere measured from the north pole instead of the equator; equal to "90° - latitude".

→ co- + → latitude.

Having a relatively low temperature.

M.E., from O.E. cald, ceald "cold, cool" (cf. O.Fr. and O.Sax. kald, O.H.G. and Ger. kalt, Goth. kalds "cold"), from PIE root *gel-/*gol- "cold;" cf. L. gelare "to freeze," gelu "frost," glacies "ice;" Kurd. girsân, girsiân "to coagulate" (Cheung 2007).

Sard "cold, cool," afsordan, afsârdan "to congeal;" Mid.Pers. sard/sart "cold;" Av. sarəta- "cold;" cf. Skt. śiśira- "cold;" L. calidus "warm;" Lith. šaltas "cold;" Welsh clyd "warm;" PIE *keltos- "cool."

A broad → absorption feature observed in → X-ray spectra of → active galactic nuclei (AGN). It is caused by material associated with the → interstellar medium in our → Galaxy and/or the host galaxy of the AGN or cold material near the AGN. → Quasars commonly have their X-ray spectrum absorbed by cold gas between us and the quasar X-ray source (along our → line of sight). This is particularly common in less luminous quasars. See also → warm absorber.

→ cold; → absorber.

1) A type of → accretion flow by a → compact object such as a → black hole that consists of cool → optically thick gas and has a relatively high mass → accretion rate, in contrast to → hot accretion flows.
2) Gas accreting from the → intergalactic medium (IGM) onto → galactic haloes with sufficiently low velocities so that it will not be shocked to the → virial temperature of the halo, but will instead flow at a relatively low temperature (T ~ 10⁴ K). Galaxies grow by accreting gas from → cosmic filaments. Feedback from star formation and → active galactic nuclei returns a significant fraction of the → interstellar medium (ISM) to the halo and may even blow it out of the halo into the IGM. This "cold accretion" will happen if the cooling time of → virialized gas is too short to maintain a hot, → hydrostatic halo. The existence of such a cold accretion mode has been confirmed by simulations, which have furthermore demonstrated that cold mode accretion can also be important for halos sufficiently massive to contain hot, hydrostatic gas. Because gas accretes preferentially along the filaments of the cosmic web, the streams of infalling gas have relatively high gas densities and correspondingly low cooling times. This allows the cold streams to penetrate the hot, hydrostatic halos surrounding massive galaxies, particularly at → high redshifts (F. van de Voort et al., 2012, MNRAS 421, 2809).

→ cold; → accretion; → flow.

Any → hypothetical → non-baryonic  → dark matter that is → non-relativistic at the point of → decoupling in the → early Universe. CDM plays a key role in → cosmic structure formation. See also → CDM model, → lambda cold dark matter, → Meszaros effect, → missing satellites problem.

→ cold; → dark; → matter.

An accretion process whereby material coming from an → accretion disk settles onto the → protostellar surface through a geometrically thin layer or thin accretion columns. Heat brought into the protostar in the accretion flow radiates freely into space until the temperature attains the photospheric value. Most of the stellar surface is unaffected by the accretion flow (see, e.g., Hosokawa et al. 2010, ApJ 721, 478).

→ cold; → disk; → accretion.

The act or process of working with another or others on a joint project.

From Fr. collaboration, noun of action from L. collaborare from → com- "with" + labore "to work."

Hamkâri, from ham-, → com-, + kâr, → work, + -i verbal noun suffix.

The collapse of the core of a very massive star which results in a black hole accompanied by a very energetic → gamma-ray burst.

From collaps(e) + (st)ar.

1) (v.) To fall inward abruptly under its own → gravity.
2) (n.) The act of falling inward abruptly under its own gravity. → gravitational collapse; → core collapse.

From L. collapsus, p.p. of collabi "fall together," from → com- "together" + labi "to fall, slip."

1) Mod.Pers. rombidan "to fall apart, to crumble," Hamadâni, Malâyeri: rommidan, Lori remese "get destroyed," remane "to destroy a building," possibly cognate with E. crumble "to break into small fragments," from O.E. cruma, akin to D. kruim, Ger. Krume "crumb," L. grumus "heap of earth," root of Fr. grumeau "lump."
2) Rombeš from present stem romb "collapse" + noun suffix -eš.

The idea, central to the → Copenhagen Interpretation of quantum theory, whereby at the moment of observation the → wave function changes irreversibly from a description of all of the possibilities that could be observed to a description of only the event that is observed. More specifically, quantum entities such as electrons exist as waves until they are observed, then "collapse" into point-like particles. According to the Copenhagen Interpretation, observation causes the wave function to collapse. However it is not known what causes the wave function to collapse. Same as → wave collapse.

→ collapse; → wave function.

A star that has undergone → collapse.

Collapsed p.p. of → collapse; → star.

Setâré, → star; rombidé p.p. of rombidan, → collapse.