An Etymological Dictionary of Astronomy and Astrophysics
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A process in which a → close encounter between a → tightly bound binary star system and a → supermassive black hole causes one binary component to become bound to the black hole and the other to be ejected at very high velocities, up to 4,000 km s^-1. → hypervelocity star.

Hills, J. G, "Hyper-velocity and tidal stars from binaries disrupted by a massive Galactic black hole," Nature 331, 687; → mechanism.

A → mapping between two mathematical → objects that preserves the object structure. A general → morphism.

→ homo-; → morphism.

1) Any system or mode of thought or action in which human interests, values, and dignity predominate (dictionary.com).
2) Philo.: A variety of ethical theory and practice that emphasizes reason, scientific inquiry, and human fulfillment in the natural world and often rejects the importance of belief in God (dictionary.com).

→ human + → -ism.

Any one of a variety of systems of philosophical thought, which would make the ultimate reality of the Universe expressible or intangible only in terms of idea in mind, rather than in terms of matter in space.

From → ideal, see also → idea, + → -ism.

1) The extension of a nation's authority by territorial acquisition or by the establishment of economic and political dominance over other nations.
2) A political doctrine or system promoting such extension of authority (TheFreeDictionary.com).

→ imperial; → -ism.

1) A style of painting developed in the last third of the 19th century, characterized chiefly by short brush strokes of bright colors in immediate juxtaposition to represent the effect of light on objects.
2) A manner of painting in which the forms, colors, or tones of an object are lightly and rapidly indicated.
3) A manner of sculpture in which volumes are partially modeled and surfaces roughened to reflect light unevenly (Dictionary.com).

→ impression; → -ism.

Philosophy: The doctrine that there are events which do not correspond with determinism and therefore are uncaused in some sense.
Quantum physics: The claim that the most basic constituents of matter behave indeterministically, in accordance with such properties as the → uncertainty principle.

→ in-; → determinism.

Nâtarmbâvari, nâtarmvari, from nâ- negation prefix + (â)tarmbâvari, (â)tarmvari, → determinism.

1) A social theory advocating the liberty, rights, or independent action of the individual (Dictionary.com).
2) An individual peculiarity.

→ individual; → -ism.

In the philosophy of science, the pragmatic view that a scientific theory is no more than a useful instrument or tool for getting our experiences in some order.

→ instrumental; → -ism.

The environment containing the → interstellar matter, consisting of gas (mostly hydrogen) and dust. Even at its densest phase, the interstellar medium is emptier than the best vacuum man can create in the laboratory, but because space is so vast, the interstellar medium still adds up to a huge amount of mass.

→ interstellar; → medium.

A → philosophy of → mathematics that was introduced by the Dutch mathematician L.E.J. Brouwer (1881-1966). Intuitionism is based on the idea that mathematics is a creation of the mind. The truth of a mathematical statement can only be conceived via a mental construction that proves it to be true, and the communication between mathematicians only serves as a means to create the same mental process in different minds (Stanford Encyclopedia of Philosophy).

→ intuition; → -ism.

A one-to-one → mapping between two → sets, which preserves the relations existing between elements in its → domain. An isomorphism is a → bijective morphism.

→ iso-; → morphism.

In an imaging system, the unvarying of the → point spread function over an extended field of view.

From isoplanat(ic), → isoplanatic, + → -ism.

A process based on the effects of → opacity (κ) that drives the → pulsations of many types of variable stars. Consider a layer of material within a star and suppose that it undergoes inward contraction. This inward motion tends to compress the layer and increase the density. Therefore the layer becomes more opaque (See also → partial ionization zone). If a certain amount of flux comes from the deeper layers it gets stuck in the high κ region. The energy accumulates and heat builds up beneath it. The pressure rises below the layer, pushing it outward. The layer expands as it moves outward, cools and becomes more transparent to radiation. Energy can now escape from below the layer, and pressure beneath the layer diminishes. The layer falls inward and the cycle repeats. The κ mechanism is believed to account for the pulsations of several star families, including → Delta Scuti stars, → Beta Cephei variables, → Cepheids, and → RR Lyrae stars (See Baker & Kippenhahn, 1962, Zeitschrift für Astrophysik 54, 114). Same as κ effect and → valve mechanism. See also → gamma mechanism.

κ, the Gk. letter which denotes opacity; → mechanism.

The heating of a body that contracts under its own gravity. For a large body like a planet or star, gravity tries to compress the body. This compression heats the core of the body, which results in internal energy which in turn is radiated as → thermal energy. In this way a star could be heated by its own weight.

William Thomson (Lord Kelvin) and Hermann von Helmholtz proposed that the sun derived its energy from the conversion of gravitational potential energy; → mechanism.

In the → three-body problem, the → perturbation of the orbit of a → secondary body by the garvity of a third body located at a distance much larger than the separation between the → primary body and the secondary. The secondary's orbit oscillates about a constant value involving a periodic exchange between the extreme values of its → inclination and orbital → eccentricity. The Kozai-Lidov mechanism results from the conservation of the quantity (1 - e²)^1/2.cos i for each component, where e is eccentricity and i is inclination. The total → angular momentum of the system remains constant while the angular momentum is exchanged betwwen the components. It has been suggested that the Kozai mechanism is responsible for the high eccentricities observed in the orbits of → extrasolar planets. If the parent star has a massive yet unseen substellar companion, orbiting at a great distance, and in an orbit highly inclined to the plane of the planets' orbits, the mechanism should induce high eccentricities into the orbits of the planets. Similarly, this mechanism may be responsible for the high eccentricities observed in the orbits of many → Kuiper Belt Objects such as 2003 UB313.

Named for the japanese Yoshihide Kozai (1962, Astronomical J. 67, 591), and the Russian Michael Lidov (1962, Planetary & Space Science 9, 719).

A reformulation of classical mechanics that describes the evolution of a physical system using → variational principle The formalism does not require the concept of force, which is replaced by the → Lagrangian function. The formalism makes the description of systems more simpler. Moreover, the passage from classical description to quantum description becomes natural. Same as → Lagrangian dynamics.

→ Lagrangian; → formalism.

Suggested by Irving Langmuir (1881-1957) in 1921, who was awarded the Nobel Prize in Chemistry in 1932 for his work in surface chemistry. And further developed by Cyril Hinshelwood (1897-1967) in 1926, who received the Nobel Prize in Chemistry in 1956 for his researches into the mechanism of chemical reactions.

A prism having angles of 30, 60, and 90°, which uses the same face for input and dispersed radiation. The beam is reflected at the face opposite to the 60° angle because it is coated to be highly reflecting. A beam entering at the → Brewster angle undergoes minimum deviation and hence maximum dispersion. Littrow prisms are used in laser cavities to fine tune lasers by selection of wavelength.

Joseph Johann Littrow (1781-1840), Austrian astronomer; → prism.

The science of magnetic phenomena, including the fields and forces produced by magnets and, more generally, by moving electric charges.

N.L. magnetismus; → magnet + → -ism.