An Etymological Dictionary of Astronomy and Astrophysics
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General: (v.tr.) To reduce the volume of, to make more concise. (v.intr.) To become more compact, to undergo condensation.
Physics: To cause a gas or vapor to change to a liquid. To remove water from a substance.

L. condensare "to make dense," from → com- intensive prefix + densare "make thick," from densus, → dense.

Cagâlidan from cagâl "dense, thick," of unknown etymology, + -idan infinitive suffix.

Relating to or produced by → condensation.

Adj. from → condense.

Matter in the liquid or solid state.

→ condensed; → matter.

Having relatively high → density.
Math.: The quality of a subset A of a topological space X, indicating that any point in X can be well approximated by points in A.

From L. densus "thick, crowded," cognate with Gk. dasys "hairy, bushy, thick grown."

Cagâl "dense, thick," related to ceqer "stiff, hard, tough, firm" (dialectal Kermâni ceqel, Šândizi caqal), caqâlé "stiff, unripe fruit."

An opaque region of a → molecular cloud (A_V  10 mag) which is considered to be the progenitor of → star formation. Dense cores have temperatures of about 10 K and masses of roughly 1 to 10Msun each and in which the → molecular hydrogen density is roughly 10⁴-10⁵ cm^-3 and size 0.1 pc. The → self-gravity of a dense core plays a central part in star formation. See also → hot molecular core.

→ dense; → core.

→ core mass function.

→ dense; → core; → mass; → function.

A type of → interstellar medium cloud in which → carbon (C) becomes almost completely molecular due to relatively high → extinction. The chemistry is qualitatively different from that of → diffuse molecular clouds, as the → electron abundance is very low (→ cosmic-ray ionization being the dominant source) and the reactive C is replaced by the very stable → carbon monoxide (CO). This regime is found only in → sightlines with A_V > 5-10 mag; not all such sightlines will contain dense cloud material and if dense cloud material is present it is likely to be surrounded by → translucent material. These clouds are typically → self-gravitating, and are most often observed by → infrared absorption and → millimeter wave emission methods. Their densities are typically at least 10⁴ cm^-3, and their → kinetic temperatures are typically on the order of 10-50 K in the quiescent regions. Most of the more than 140 currently known → interstellar molecules were found through observations of → microwave→ rotational transitions in such clouds, starting with the discovery of OH, followed by a host of other new detections such as CO, NH₃, H₂O, and H₂CO (Snow & McCall, 2006, ARA&A 44, 367).

→ dense; → molecular; → cloud.

Matter whose density exceeds a reference level.

→ over-; → dense; → matter.