Planet Definition–noun | 1. | Astronomy. | a. | Also called major planet. any of the nine large heavenly bodies revolving about the sun and shining by reflected light: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto in the order of their proximity to the sun. | | b. | a similar body revolving about a star other than the sun. | | c. | (formerly) a celestial body moving in the sky, as distinguished from a fixed star, applied also to the sun and moon. | | | 2. | Astrology. the sun, moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto: considered sources of energy or consciousness in the interpretation of horoscopes. | |
From Dictionary
Related topics from Britannicaplanet
(from Greek planetes, "wanderers"), broadly, any relatively large natural body that revolves in an orbit around the Sun or around some other star and that is not radiating energy from internal ...
extrasolar planet
any planetary body that orbits a star other than the Sun. The first extrasolar planets were discovered in 1992, and within 15 years some 250 were known.Trojan planets
two groups of asteroids named for heroes of Greece and Troy in Homer's Iliad. These minor planets revolve around the Sun in the Lagrangian points of Jupiter's orbit. These are positions where a ...
dwarf planet
body, other than a natural satellite (moon), that orbits the Sun and that is, for practical purposes, smaller than the planet Mercury yet large enough for its own gravity to have rounded its shape ...
Astronomers Reclassify Pluto as a Dwarf Planet
"What's in a name? That which we call a rose by any other word would smell as sweet." These lines, spoken about Romeo by Shakespeare's Juliet, encapsulated the debate that peaked in 2006 over the ...
asteroid
any of a host of rocky small bodies, about 1,000 km (600 miles) or less in diameter, that orbit the Sun primarily between the orbits of Mars and Jupiter in a nearly flat ring called the asteroid ...
extraterrestrial life
The atmosphere of Jupiter is composed of hydrogen, helium, methane, ammonia, some neon, and water vapour. These are exactly the gases used in experiments that simulate the early Earth. Laboratory and ...
Cosmos
Useful summaries are found in Bruce Murray (ed.), The Planets (1983), a collection of Scientific American articles. Also recommended is J. Kelly Beatty and Andrew Chaikin (eds.), The New Solar ...
solar system
The eight planets can be divided into two distinct categories on the basis of their densities (mass per unit volume). The four inner, or terrestrial, planets-Mercury, Venus, Earth, and Mars-have ...
Cosmos
Clues as to how the planets were formed lie in the regularities of their orbital motions, their satellite systems, and their chemical compositions. Compared to their sizes, the separations of planets ...
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