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Encyclopedia > Solar system II


Classification of the different bodies 

The bodies of the Solar system are named by different words often similar. For example, Jupiter is named as a giant planet, a gaseous planet or an outer planet... Moreover, what is the difference between an asteroid and a minor planet? And between a meteor and a meteorite? The table below will try to answer these questions.

We have to note that, since 2006, astronomers decided to keep only three official categories of bodies:
- the planets (they are eight: Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus and Neptune)
- the dwarf planets (the other spherical bodies)
- the small bodies (astéroids and comets).  

planet :  body orbiting around the Sun, having a spherical body (most of time diameter larger than 800 km), whose orbit has a small eccentricity (quite a circle)), a small inclination (on the orbital plane of the Earth) and dominating gravitationally its environment
satellite :  body orbiting around a planet or a satellite (providing that the center of mass is inside the planet)
asteroid :  small body (diameter smaller than 2000 km) orbiting around the Sun on any trajectory. Most of the known asteroids are in the Main belt (between Mars and Jupiter). They are also named "Minor planets".
comet : 

very small body made of rocks and ice orbiting around the Sun on an eccentric trajectory bringing the body near the Sun where the ices will melt and sublimate making visible a coma
Pluto : 

body considered first as a planet being in fact a large asteroid maybe a previous satellite of Neptune. Similar bodies on a similar orbit are named "plutinos".

Since 2006, the International Astronomical Union introduced a new class of bodies, the dwarf planets which are in fact the larger asteroids such as Ceres, Pluto and some transneptunian objects. They all have a spherical shape due to an hydrostatic equilibrium. Here, you may have the new official definition of a planet.

Other classifications:

terrestrial planets : 
rocky planets, dense with a solid surface
Mercury, Venus, Earth, Mars
gaseous planets : 
planets made mainly of hydrogen (missed stars due of a lack of mass)
Jupiter, Saturn, Uranus, Neptune
giant planets : 
large planets (diameter larger than 40  000  km); the gaseous planets
Jupiter, Saturn, Uranus, Neptune
minor planet : 
another name of the asteroids

inner planets : 
planets between the main belt of asteroids and the Sun
Mercury, Venus, Earth, Mars
outer planets :  planets beyond the main belt of asteroids
Jupiter, Saturn, Uranus, Neptune
inferior planets : 
planets between the Earth and the Sun
Mercury, Venus
superior planet : 
planets beyond the Earth
Mars, Jupiter, Saturn, Uranus, Neptune
old planets : 
planets observable with naked eye known since antiquity
Mercury, Venus, Mars, Jupiter, Saturn

Meteors and meteorites
events affecting Earth
piece of asteroid, comet, planet or space dust falling on Earth

Meteor : 
light phenomenon in the atmosphere as the trace left by a meteorite falling on Earth

More on the meteoritic swarms