An Etymological Dictionary of Astronomy and Astrophysics
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Situated around a → nucleus, as of a → circumnuclear disk.

→ circum- + → nuclear.

A thick disk of gas and dust clouds surrounding the → Galactic Center up to about 20 → light-years. The disk is very clumpy; the → clumps have densities of several 10⁵ particles/cm³, radii of about 0.3 light-years, and gas temperatures above 100 K. The hydrogen mass of the disk is a few 10⁴ → solar masses. Such circumnuclear disks are present also in other galaxies.

→ circumnuclear; → disk.

1) Free from darkness, obscurity, or cloudiness.
2) Transparent; pellucid.
3) Without discoloration, defect, or blemish (Dictionary.com). → clear night.

M.E. clere, from O.Fr. cler, from L. clarus "clear, bright, distinct."

Runé, from Kurd. (Sorani) rûn "bright, clear," rûn kirdin "to explain," variant of rowšan, → bright.

A night sky without clouds, mist, or haze, atmospheric dust particles, and without city lights in which a sixth magnitude star is visible by naked-eye.

→ clear; → night.

A molecule that is composed of only one type of → chemical element, e.g. the → molecular hydrogen and → ozone.

→ homo-; → nuclear; → molecule.

Same as → LINER.

→ low; → ionization; → nuclear; → emission; → line; → region.

Of or pertaining to a → nucleus.

From nucle(us), → nucleus, + -ar variant of the adjective-forming suffix → -al.

Haste-yi, from hasté, → nucleus, + -i adjective-forming suffix.

The region of high potential energy through which a charged particle must pass on entering or leaving an atomic nucleus. → Gamow barrier.

→ nuclear; → barrier.

A → nuclear reaction inside a star that produces the energy to make the star shine and also transform chemical elements into others.

→ nuclear; → burning.

The positive electric charge on the nucleus of an atom.

→ nuclear; → charge.

→ nuclear burning.

→ nuclear; → combustion.

Apparent cross-section possessed by an atomic nucleus when it undergoes a particular type of collision process.

→ nuclear; → cross section.

The density of an atomic nucleus (about 10¹⁴ g/cm³).

→ nuclear; → density.

Energy released during a nuclear reaction as the result of the conversion of mass into energy. → mass-energy equivalence.

→ nuclear; → energy.

A → nuclear reaction in which a heavy atomic nucleus splits into two or more approximately equal parts, usually as the result of the capture of a slow, or → thermal neutron by the nucleus. It is normally accompanied by the emission of further neutrons or → gamma rays and very large amounts of energy. The neutrons can continue the process as a → chain reaction, so that it becomes the source of energy in a → nuclear reactor or an atomic bomb. It may also be a trigger for → nuclear fusion in a hydrogen bomb. Fission occurs spontaneously in nuclei of uranium-235, the main fuel used in nuclear reactors.

→ nuclear; → fission.

The attractive force which acts between nucleons when they are extremely close together (closer than 10^-13 cm).

→ nuclear; → force.

A substance, such as uranium-238 or plutonium-239, which undergoes nuclear fission in a nuclear reactor.

→ nuclear; → fuel.

A → nuclear reaction between atomic nuclei as a result of which a heavier → atomic nucleus is formed, a small fraction of mass is lost, and a large quantity of energy is released. Nuclear fusion is the source of the energy of stars.

→ nuclear; → fusion.

An analysis technique applied to some atomic nuclei that have the property to behave as small magnets and respond to the application of a magnetic field by absorbing or emitting electromagnetic radiation. When nuclei which have a magnetic moment (such as ¹H, ¹³C, ²⁹Si, or ³¹P) are submitted to a constant magnetic field and at the same time to a radio-frequency alternating magnetic field, the nuclear magnetic moment is excited to higher energy states if the alternating field has the specific resonance frequency. This technique is especially used in spectroscopic studies of molecular structure and in particular provides valuable information in medicine that can be used to deduce the structure of organic compounds.

→ nuclear; → magnetic; → resonance.

The magnetism associated with the magnetic field generated by atomic nuclei.

→ nuclear; → magnetism.