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

A → Fermat number, 2²ⁿ + 1, that is a → prime number. The only known Fermat primes are: 3, 5, 17, 257, and 65537, corresponding to n = 0, 1, 2, 3, and 4.

→ Fermat's principle; → prime.

A → prime number of the form 2^p - 1, where p is a prime. As of February 2013, 48 Mersenne primes are known. The largest known prime number is 2^57,885,161 - 1. Each prime gives rise to an even → perfect number.

Marin Mersenne (1588-1648), French theologian, philosopher, mathematician and music theorist; → prime.

The line connecting the Moon's north pole with its south pole, and passing through the center of the lunar disk. The longitude of the Moon's prime meridian is zero degrees.

→ Moon; → prime meridian.

1) Of the first importance; of the highest rank.
2) Same as → prime number.

M.E., from L. primarius "of the first rank, principal," from primus "first."

Naxost, naxostin, naxosti, from Mid.Pers. naxust "the first," Parthian Mid.Pers. nxwšt, from naxu, Manichean Parthian nwx "beginning" + -ist superlative suffix, Av. -išta-, cf. Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost.

The focal point of a large primary reflecting mirror. This focus actually falls at a point just within the upper structure of the telescope and provides a large field of view.

→ primary; → focus.

The meridian at which longitude is defined to be 0°. The meridian running through Greenwich.

→ primary; → meridian.

A number which is divisible by no whole number other than itself and one.

→ prime; → number.

The great circle through the observer's zenith that intersects the horizon at the west and east points. → vertical circle.

→ primary; → vertical.

Lemaître's (1931) name for the early dense Universe, which later became known as the → Big Bang theory.

From L. primaevus "early in life," from primus "first," → prime, + aevum "an age," + → -al; → atom.