An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The time required for a star to exhaust its hydrogen (H) supply in → nuclear fusion. The nuclear time scale is given by the relation t = E/L, where E is the total nuclear energy that can be generated by a star and L is the stellar → luminosity. Assuming that the end point of fusion is → iron (Fe), the → atomic mass difference between H and Fe is Δm = 0.008 m_H. Therefore, the maximum amount of energy a star with a hydrogen mass M can release is Δ M = 0.008 Mc². The nuclear time scale is then: t = 0.008 c²M/L. However, stars use up only a fraction of their hydrogen supply, because only the inner part of the star is hot enough for fusion. For example, the Sun will spend only about 10% of its hydrogen supply before evolving into a → red giant. In other words, the solar life time on the → main sequence is about 10¹⁰ years.

→ nuclear; → time; → scale.

A change in the → energy level or state of an atomic → nucleus involving a → quantum of energy.

→ nuclear; → transition.

The changing of atoms of one element into those of another by suitable nuclear reactions.

→ nuclear; → transmutation.

A particular type of radioactive waste that is produced as part of the nuclear fuel cycle. These include extraction of uranium from ore, concentration of uranium, processing into nuclear fuel, and disposal of byproducts.

→ nuclear; → waste.

A constituent of the atomic nucleus, i.e. a proton or a neutron.

From nucle(us), → nucleus, + -on a suffix used in the names of subatomic particles, probably extracted from → ion.

Haston, from hast(é)→ nucleus + -on, as above.

The practical applications of nuclear physics, and the techniques associated with those applications.

From → nucleon + → -ics.

The process by which → nuclear reactions at very high temperatures and pressures produce the various → chemical elements of the → periodic table, either in the → Big Bang or in stellar interiors. See also → primordial nucleosynthesis, → stellar nucleosynthesis, → explosive nucleosynthesis.

From nucleo-, combining form of → nucleus + → synthesis.

Haste-handâyeš, from hasté→ nucleus + handâyeš→ synthesis.

Produce through → nucleosynthesis.

→ nucleosynthesis; → -ize.

Of, pertaining to, proceeding by, or involving → nucleosynthesis.

Adj. of → nucleosynthesis.

The era following the leptonic era, between 1 second and 1000 seconds after the Big Bang, when neutrons were abundant and helium and deuterium were synthesized.

→ nucleosynthetic; → era.

A process involving → nucleosynthesis, such as → r-process and → r-process.

→ nucleosynthetic; → process.

1) Core of an atom, where most mass and all positive charge is concentrated. It consists of protons and neutrons.
2) Of a comet, the stellar-appearing frozen core, containing most of the cometary mass, in the head of a comet.

From L. nucleus "kernel," from nucula "little nut," diminutive of nux "nut," from PIE *knu(k) "lump" (cf. M.Ir. cnu, Welsh cneuen, M.Bret. knoen "nut," O.N. hnot, O.E. hnutu "nut").

Hasté, variants asté "kernel, fruit stone," ostoxân "bone," from Mid.Pers. astak "fruit stone, bone," ast "bone;" Av. ast- "bone;" cf. Skt. asthi- "bone;" Gk. osteon; L. os; Hittite hashtai-; PIE base *os-.

A species of atom characterized by the constitution of its nucleus, i.e. by the numbers of protons and neutrons it contains.

From nucl(eo), → nucleus, + -ide, from Gk. eidos "shape."

Hastevâr, from hasté, → nucleus, + -vâr a suffix meaning "resembling, like," from Mid.Pers. -wâr, Av. -vara, -var, cf. Skt. -vara.

1a) General: Being or amounting to nothing; nil; nonexistent; without value, effect, or significance.
1b) Math.: Of a set, empty. Of measure zero.
1c) Electronics: A point of minimum signal reception, as on a radio direction finder or other electronic meter.
2) To make null; cancel.

From M.Fr. nul, from L. nullus "not any, none," from ne- "not, no" → non- + illus "any," dimunitive of unus "one."

Nul, from na-, → non-, + -ul a variant of the Pers. suffix → -al. Nulidan, infinitive from nul.

1) The path taken by a light ray in a curved → space-time just as a → timelike geodesic describes the path of a material particle.
2) A → geodesic of length zero.

→ null; → geodesic.

Statistics: The assumption of the absence of a particular pattern in a set of data. The null hypothesis, denoted by H₀, is put forward to be rejected in order to support an → alternative hypothesis.

→ null; → hypothesis.

A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface, it reverses its path and, if the surface is perfect, results in a perfect emerging spherical wavefront, which is easily evaluated.

→ null; → lens.

An m × n matrix whose elements are all zeros. Also known as zero matrix.

→ null; → matrix.

A method of comparing, or measuring, forces, electric currents, etc., by so opposing them that the pointer of an indicating apparatus remains at, or is brought to, zero, as contrasted with methods in which the deflection is observed directly. Same as zero method.

→ null; → method.

A device using the → nulling interferometry technique.

Agent noun of the verb → null.