Planet

A large, rounded astronomical body in orbit around a star, stellar remnant, or brown dwarf.

A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets by the most restrictive definition of the term: the terrestrial planets Mercury, Venus, Earth, and Mars, and the giant planets Jupiter, Saturn, Uranus, and Neptune.

Quick Facts

Type: Collectible object (largest mass tier)
Franchise: Katamari Damacy
First appears: Katamari Damacy (2004)
Creator: Keita Takahashi (Bubsy)
Publisher: Namco
Player character: The Prince
Issuer of tasks: King of All Things

Lore & Background

The word planet comes from the Greek. In antiquity, this word referred to the Sun, Moon, and five points of light visible to the naked eye that moved across the background of the stars—namely, Mercury, Venus, Mars, Jupiter, and Saturn. Planets have historically had religious associations: multiple cultures identified celestial bodies with gods. Earth itself was recognized as a planet when heliocentrism supplanted geocentrism during the 16th and 17th centuries.

With the development of the telescope, the meaning of planet broadened to include objects only visible with assistance: the moons of the planets beyond Earth; the ice giants Uranus and Neptune; Ceres and other bodies later recognized to be part of the asteroid belt; and Pluto, later found to be the largest member of the Kuiper belt. In 2006, the IAU adopted a definition of a planet in the Solar System, placing the four terrestrial planets and the four giant planets in the planet category; Ceres, Pluto, and Eris are in the category of dwarf planet.

Many planetary scientists have nonetheless continued to apply the term planet more broadly, including dwarf planets as well as rounded satellites like the Moon.

Reader's Guide

According to the IAU definition, there are eight planets in the Solar System, which are (in increasing distance from the Sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Jupiter is the largest, at 318 Earth masses, whereas Mercury is the smallest, at 0.055 Earth masses. The planets can be divided into categories based on composition: terrestrials (Mercury, Venus, Earth, Mars) and giant planets (Jupiter, Saturn, Uranus, Neptune). The gas giants, Jupiter and Saturn, are primarily composed of hydrogen and helium; the ice giants, Uranus and Neptune, are primarily composed of low-boiling-point materials such as water, methane, and ammonia. Dwarf planets are gravitationally rounded but have not cleared their orbits; examples include Ceres, Pluto, and Eris.