An Etymological Dictionary of Astronomy and Astrophysics
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Of or pertaining to → astrophysics.

→ astrophysics + → -al

A very fast moving, → collimated beam of → ionized gas at high temperatures associated with most classes of compact objects that spin and/or accrete matter from their surroundings, such as → protostars, → X-ray binary systems, and, at a larger scale, with → active galactic nuclei, → gamma-ray bursts, and → quasars. In general, jet sources host → accretion disks and are associated with → magnetic fields. Astrophysical jets, despite their different physical scales and power, are morphologically very similar, suggesting a common physical origin. For example, in one extreme, → active galactic nuclei jets have typical sizes ≥ 10⁶ pc, velocities near that of light c, and parent sources (→ massive black holes) with masses 10^6-9  Msun and luminosities ~ 10^43-48Lsun; while in the other extreme, → young stellar objects jets have typical sizes ≤ 1 pc, velocities ≤ 10^-3 c, and emerge from low mass protostars with masses ~ 1 Msun and luminosities (0.1-2 × 10⁴) Lsun. Jets play an important → feedback role in the evolution of their host systems. See also: → jet launching.

→ astrophysical; → jet.

An extraterrestrial → object whose physical properties and formation are studied in → astrophysics.

→ astrophysical; → object.

Pertaining to the physical sciences, especially physics.

→ physics + → -al.

Same as → physisorption.

→ physical; → adsorption.

The branch of chemistry dealing with the relations between the physical properties of substances and their chemical composition and transformations.

→ physical; → chemistry.

The state of a → physical system regarding its temperature, density, pressure, etc. at a given time.

→ physical; → condition.

A fundamental → physical quantity that is generally believed to be both universal in nature and constant in time.

→ physical; → constant.

Any of basic physical quantities, such as mass, length, time, electric charge, and temperature in terms of which all other kinds of quantity can be expressed.

→ physical; → dimension.

A theoretical principle which is deduced from particular observational facts regarding the behavior of matter. Physical laws are expressed by a general statement that a particular → physical phenomenon always occurs if certain → conditions are present.

→ physical; → law.

A real periodic variation in the rotation rate of a celestial object, as distinct from a → geometrical libration. In particular, slight oscillations in the → Moon's rotation caused by the → gravitational attraction of the Earth on the → equatorial bulge of the Moon's near side. The Moon's physical libration is about 0.03° in longitude and about 0.04° in latitude.

→ physical; → libration.

The branch of optics concerned with the wave properties of light, → diffraction, → polarization, and other phenomena for which the ray approximation of → geometric optics is not valid. Also called → wave optics.

→ physical; → optics.

Any of a set of physical properties whose values determine the characteristics or behavior of a system; for example, → mass, → size, → temperature, → luminosity, etc.

→ physical; → parameter.

A natural → phenomenon that can be explained by → physical laws.

→ physical; → phenomenon.

A physical → property that can be measured and/or calculated.

→ physical; → quantity.

A set of physical components chosen to study their relations.

→ physical; → system.