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

A triple star system in which the (inner) binary is orbited by a third body in a much wider orbit. → hierarchical multiple system.

→ hierarchical; → stellar; → system.

Any group of three → integers that satisfy the relations specified by the → Pythagorean theorem. Some examples: 3, 4, and 5; 5, 12, and 13; 8, 15, 17.

→ Pythagorean theorem; → triple; → triplet.

Threefold; consisting of three parts. → triple alpha process; → triple conjunction; → triple point; → triple star.

M.E., from M.L. triplare "to triple," from L. triplus "threefold, triple," from tri-, → three, + -plus "-fold."

Setâyi, from setâ, from sé→ three + tâ "fold, plait, ply; piece, part," Mid.Pers. tâg "piece, part."

A chain of nuclear fusion reactions by which three helium nuclei (→ alpha particles) are transformed into → carbon. First two nuclei of helium collide, fuse, and form a nucleus of → beryllium: ⁴He + ⁴He ↔ ⁸Be, which is unstable and will decay back into two helium nuclei within a few 10^-17 seconds. However, due to sufficiently high density and temperature in the stellar core, during a third collision between beryllium and helium, carbon is formed: ⁸Be + ⁴He → ¹²C + γ. The triple-alpha process is possible owing to the existence of the → Hoyle state. It is the main source of energy production in → red giants and → red supergiants in which the core temperature has reached at least 100 million K. Also called → Salpeter process.

→ triple; → alpha particle; → process.

A rare event involving a particularly intricate set of movements of two planets or a planet and a star where they meet each other three times in a short period either in opposition or at the time of inferior conjunction, if an inferior planet is involved. The visible movement of the planet or the planets in the sky is therefore normally prograde at the first conjunction, retrograde at the second conjunction and again prograde at the third conjunction.

→ triple; → conjunction.

The definite pressure and temperature at which all three phases of a substance coexist in → phase equilibrium. The triple point of water has a pressure of 4.58 mm of Hg and a temperature of 273.16 °K.

→ triple; → point.

Noqté, → triple; segâné, from sé→ three + -gâné suffix forming plural entities, from Mid.Pers. -gânag, -gâna.

A group of three stars visually or physically associated with each other. → triple system.

→ triple; → star

A system of three stars which are physically associated among them.

→ triple; → system

A group or set of three of one kind.
Optics: A compound lens made up of three elements that may or may not be cemented.

From trip-, from → triple + -et, from → doublet.

Setâyé, from setâ, → triple, + -(y)é nuance suffix.

The electronic state of an atom or molecule which has two unpaired electrons, and therefore whose total spin angular momentum is equal to 1.

→ triplet; → state.