An Etymological Dictionary of Astronomy and Astrophysics
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A prefix meaning "resembling, almost, having some, but not all of the features of."

From L. quasi "as if, as though," from qua(m)" as" + si "if."

Cunân "so, like that; just as if," from cun "how?," (Mid.Pers. cigôn "how?," cigônêh "nature, character," O.Pers/Av. ci- "what, any," collateral stem to ka- "who?, what?;" cf. Skt. ka-; Gk. po-; L. quo-; E. what, who; PIE *qwos/*qwes) + suffix ân. -vaš a suffix of similitude.

A system in which the nuclei of two colliding atoms approach each other closely for a brief lapse of time so that their electrons are arranged in atomic orbitals characteristic of a single atom with combined atomic number.

→ quasi-; → atom.

A subsystem if its intrinsic energy is large, on the average, with respect to the energy of its interaction with other portions of the → closed system.

→ quasi-; → closed; → subsystem.

In plasma physics, the theory that considers the interactions between waves and particles are of first order only. It ignores all terms of second order in the fluctuating quantities.

→ quasi-; → linear; → theory.

An asteroid moving around the Sun having the same mean motion and mean → longitude as a planet, but a different → eccentricity. The asteroid remains near the planet much like a satellite even when its distance is large enough so that it is well outside the planet's → Hill sphere. The quasi-satellite motion is one class of possible → co-orbital motions of small bodies in 1:1 mean-motion → resonance with a planet. If the quasi-satellite orbit is coplanar with the planet, then the motion is stable in the → secular approximation. When the orbits are inclined enough, an asteroid can be trapped into such a motion for a finite period of time. Earth has several quasi-satellites (mainly 3753 Cruithne, 2002 AA₂₉, 2003 YN₁₀₇), also does Venus (the only one so far discovered, 2002 VE₆₈). The possibility of such orbits was first suggested by J. Jackson (1913, MNRAS 74, 62).

The term quasi-satellite was first used by S. Mikkola & K. Innanen 1997, The Dynamical Behaviour of our Planetary System; Proceedings, p. 345); → quasi-; → satellite.

A region of the solar atmosphere where the gradient of the field line → linkage from one boundary to another is large so that the field lines can slip-run rapidly through the → plasma. The QSL results from → magnetic reconnection without → null point.

→ quasi-; → separatrix; → layer.

A model of radiative transfer that ignores forward scattering of photons; assuming forward-scattered light as un-scattered.

→ quasi-; → single; → scattering; → approximation.

Initial name of → quasars.

→ quasi-; → stellar; → object.

A quasar with detectable radio emission.

→ quasi-; → stellar; → radio; → source.