planetとは

発音

• (Received 発音, General American) IPA^(key): /ˈplænɪt/
• (General Australian) IPA^(key): /ˈplænət/
• • 韻: -ænɪt

名詞

planet (複数形 planets)

1. (now historical または astrology) Each of the seven major bodies which move relative to the fixed stars in the night sky—the Moon, Mercury, Venus, the Sun, Mars, Jupiter and Saturn. [from 14^thc.]
   • 1603, John Florio, transl.; Michel de Montaigne, Essayes, printed at London: Edward Blount, OCLC 946730821:
     , II.12:

     Be they not dreames of humane vanity, […] to make of our knowne earth a bright shining planet [transl. astre]?

   • 1749, Henry Fielding, Tom Jones, Folio Society, published 1973, page 288:

     The moon […] began to rise from her bed, where she had slumbered away the day, in order to sit up all night. Jones had not travelled far before he paid his compliments to that beautiful planet, and, turning to his companion, asked him if he had ever beheld so delicious an evening?

   • 1971, Keith Thomas, Religion and the Decline of Magic, Folio Society, published 2012, page 361:

     Another of Boehme's followers, the Welshman Morgan Llwyd, also believed that the seven planets could be found within man.

2. (astronomy) A body which orbits the Sun directly and is massive enough to be in hydrostatic equilibrium (effectively meaning a spheroid) and to dominate its orbit; specifically, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. (Pluto was considered a planet until 2006 かつ has now been reclassified as a dwarf planet.) [from 17^thc.]
   • 1640, John Wilkins, A Discovrse concerning a New Planet. Tending to prove, That 'tis probable our Earth is one of the Planets, title:

     A Discovrse concerning a New Planet. Tending to prove, That 'tis probable our Earth is one of the Planets

   • 2006 December 22, Alok Jha, The Guardian:

     Their decision will force a rewrite of science textbooks because the solar system is now a place with eight planets and three newly defined "dwarf planets"—a new category of object that includes Pluto.

3. A large body which directly orbits any star (または star cluster) but which has not attained nuclear fusion.
4. In phrases such as the planet, this planet, sometimes refers to the Earth.
   • 1907, Robert William Chambers, chapter VIII, in The Younger Set (Project Gutenberg; EBook #14852), New York, N.Y.: D. Appleton & Company, published 1 February 2005 (Project Gutenberg version), OCLC 24962326:

     "My tastes," he said, still smiling, "incline me to the garishly sunlit side of this planet." And, to tease her and arouse her to combat: "I prefer a farandole to a nocturne; I'd rather have a painting than an etching; Mr. Whistler bores me with his monochromatic mud; I don't like dull colours, dull sounds, dull intellects; […]."

   • 2013 June 7, David Simpson, “Fantasy of navigation”, in The Guardian Weekly, volume 188, number 26, page 36:

     It is tempting to speculate about the incentives or compulsions that might explain why anyone would take to the skies in [the] basket [of a balloon]: […]; perhaps to moralise on the oneness or fragility of the planet, or to see humanity for the small and circumscribed thing that it is; […].

使用する際の注意点

The term planet originally meant any star which wandered across the sky, and generally included comets and the Sun and Moon. With the Copernican revolution, the Earth was recognized as a planet, and the Sun was seen to be fundamentally different. The Galileian satellites of Jupiter were at first called planets (satellite planets), but later reclassified along with the Moon. The first asteroids were also thought to be planets, but were reclassified when it was realized that there were a great many of them, crossing each other's orbits, in a zone where only a single planet had been expected. Likewise, Pluto was found where an outer planet had been expected, but doubts were raised when it turned out to cross Neptune's orbit and to be much smaller than the expectation required. When Eris, an outer body more massive than Pluto, was discovered, the International Astronomical Union (IAU) officially defined the word planet as above. However, a significant minority have refused to accept the IAU definition. Many simply continue with the nine planets that had been recognized prior to the discovery of Eris. Others are of the opinion that orbital parameters should be irrelevant, and that any equilibrium (≈spherical) body in orbit around a star is a planet; there are likely several hundred such bodies in the Solar system. Still others argue that orbiting a star should also be irrelevant, thus re-accepting the Galileian satellites (as well as a dozen other moons) as planets.

Note that the 2006 IAU definition defines a planet in respect to the Sun, and is thus technically inapplicable to exoplanets.

同意語

• wandering star
• wanderstar

上位語

• planemo

下位語

派生語

関連する語

参考

• (planets of the Solar System) planets of the Solar System; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• moon
• orbit

参照

• planet on Wikipedia.
• First Steps to Astronomy and Geography, 1828, (Hatchard & Son: Piccadilly, London).

アナグラム

• Plante, pental, platen