The planets of the solar system A planet is a body with three characteristics: it must be in orbit around a star; it must have a roughly spherical shape; it must not have a body of comparable size in a near orbit. A planet is a spherical celestial body that does not produce light and orbits a star. The solar system has eight planets that are, in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto is a dwarf planet. In order to retain the order of the planets, there are different mnemotechnical tricks. Here is a sentence that makes it easy to remember the order of the planets of the solar system: « My Very Excellent Mother Just Served Us Nachos ». In this sentence, the first letter of all words represents the name of a planet. It also represents the order of the planets in the solar system. Mercury – Venus – Earth – Mars – Jupiter – Saturn – Uranus - Neptune Representation of the different planets of the solar system. Inner planets The terrestrial planets are Mercury, Venus, Earth and Mars. These are the four planets closest to the Sun and precede the asteroid belt. They are classified in this category because their surface is made up of solid rocks and they have solid envelopes interlocking together (usually three: crust, mantle and center, core). Comparison of the sizes of the four terrestrial planets. The outer planets The giant planets, also known as gas giants, are the largest planets in the solar system. They have a large number of satellites. In addition, in our solar system, these planets have planetary rings. The giant planets all have a thick atmosphere. Although these planets are mainly composed of gas, scientists' observations indicate that they probably have a solid rock core. They are also the furthest from the Sun from the asteroid belt. These are Jupiter, Saturn, Uranus and Neptune. Comparison of the sizes of the four giant planets. The dwarf planets For the time being, there are five celestial objects in the category of dwarf planets. Eris, the most massive dwarf planet known, located beyond the Kuiper Belt, discovered in 2003 and identified in 2005; Pluto, the largest known dwarf planet, located after Neptune in the Kuiper Belt, discovered in 1930; Makemake, the third largest known dwarf planet, located in the Kuiper Belt (after Neptune), discovered in 2005; Haumea, located in the Kuiper Belt (after Neptune), discovered in 2004; Ceres, located in the asteroid belt between Mars and Jupiter, discovered in 1801.
