Definition

1. Noun:
   • A large celestial body in orbit around a star: A "major planet" is a large, non-stellar astronomical object that orbits a star, is massive enough for its own gravity to make it nearly spherical, and has cleared its orbital region of most other debris.
   • Specifically, one of the classical planets of the Solar System: Historically, the term refers to the large, traditionally recognized planets in our solar system that orbit the Sun, distinguished from smaller bodies like asteroids or dwarf planets.

Usage Examples

• Noun:
  • Astronomers study each major planet to understand the formation of our solar system.
  • Jupiter is the largest major planet.
  • The definition of a major planet was refined after the discovery of many Pluto-like objects.

Advanced Usage

• In historical/classical context: Refers specifically to the bodies known from antiquity through the early 20th century: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto's status has been reclassified.

  • In 2006, the International Astronomical Union created a new definition that reclassified Pluto from a major planet to a dwarf planet.

• "The major planets": Used as a collective term for these large bodies.

  • The gas giants are the four largest major planets.

Variants and Related Words

• Planet (n): The more general term. "Major planet" is often used to specify the largest planets, especially in contrast to "minor planet" (an asteroid) or "dwarf planet."
• Dwarf Planet (n): A celestial body that orbits the Sun and is spherical but has not cleared its orbital neighborhood (e.g., Pluto, Ceres).
• Gas Giant (n): A type of major planet composed largely of gaseous hydrogen and helium (Jupiter, Saturn).
• Ice Giant (n): A type of major planet composed largely of elements heavier than hydrogen and helium, like water, ammonia, and methane (Uranus, Neptune).
• Terrestrial Planet (n): A type of major planet with a solid rocky surface (Mercury, Venus, Earth, Mars).

Synonyms

• Primary planet: A less common synonym.
• (Classical) planet: Often used interchangeably, especially before the formal definition of "dwarf planet."

Related Phrases

• Inner planets: Refers to the major planets whose orbits lie within the asteroid belt (Mercury, Venus, Earth, Mars).
• Outer planets: Refers to the major planets whose orbits lie beyond the asteroid belt (Jupiter, Saturn, Uranus, Neptune).

Noun

1. (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction