Welcome to The Solar System Wiki, where you come to fill your mind with the joys of the Solar System. We all live in it. Why not learn about it? How did the planets become how they are today? Why is there a Sun? Who discovered Uranus? Find it out here. And for all of you children who have reading logs filled out for homework, you better get to it. If you want to be an astrophysicist when you grow up, better get to it. If you clicked the wrong button or are just bored and want to leave now but is so intrigued to continue reading, leave! Just kidding. We accept all Wikians to this Wiki (except for spammers). And if you have an account, why not make this Wikia a better place. Or, just leave a message on my message wall. (I'm MrScience12 by the way; kind of a founder here). And besides, you can earn cool badges and achievements by editing as well. You're welcome.

Formation of the Solar System

The Solar System was formed approximately five billion years ago by a nebula cloud. When this cloud began a process of rotating, it began to compact due to a force known as accretion, a force caused by matter compacting together and forming layers that create pressure and create a solid or gaseous-like material depending on the amount of gravity reacting on the object from a nearby gravitational emitting source (in this case, the Sun). After this process, the gas created the Sun, using up 99.86% of all of the Solar System's matter and mass. The rest of the cloud was used to form the inner and outer planets.

There are two main regions in the Solar System: the inner planets and the outer planets. These regions are seperated by a region known as the Asteroid belt. This belt is bordered by Mars and Jupiter.

Inner Planets

800px-Terrestrial planet size comparisons
The inner planets of the Solar System, Mercury, Venus, Earth, and Mars, are the four innermost planets of the Solar System. These planets are rocky due to their distance from the Sun and since their portion of the cloud was exposed to more accretion during their formation. The inner planets are also referred to as the terrestrial, or rocky, planets. Only one of these inner planets, Earth, is known to support life, which is the planet we live on. These planets have been known since ancient times.

Outer Planets

466px-Gas giants in the solar system
The outer planets of the Solar System, Jupiter, Saturn, Uranus, and Neptune, are the four outermost planets of the Solar Sysrem. These planets are all gaseous and are the largest planets in the Solar System. In fact, Jupiter is the largest planet in the Solar System. These planets also harness the most of amount of moons, with Jupiter having the most at 66 known satellites, and is also home to Ganymede, the largest moon in the Solar System, being larger than the planet of Mercury. The outer planets are referred to as the gas giants. None of these planets have been known since ancient times. In fact, the earliest date these planets were found were by Galileo Galilei, who found the two planets Jupiter and Saturn, not to mention the Great Red Spot and four of Jupiter's moons. William Herschel found Uranus and three astronomers (listed in Neptune article) found Neptune.

Dwarf Planets

The dwarf planets of the Solar System, Pluto, Eris, Ceres, Makemake, and Haumea, are the second smallest celestial bodies in the Solar System, just barely surpassing the satellites belonging to the much larger planets. These bodies are so small, they are actually asteroids that were large enough to sustain themselves in a spherical shape. These bodies are even too small to pull in their own satellites, although Pluto, Haumea, and Eris have attracted some asteroids that they have been able to sustan in their gravitational pulls and are classified as satellites. Before more classifications for celestial bodies were established, there were fifteen planets in the Solar System, with the other seven made up of various dwarf planets. Ceres, the innermost of the dwarf planets, is actually inside of the Asteroid belt, while the others, such as Pluto and Eris, belong or even surpass the Kuiper Belt, another region surpassing the planet of Neptune. These objects surpassing Neptune are known as Trans-Neptunian objects. These planets also have not been known since ancient times because of their distance Earth, let alone the Sun. In fact, Eris is more than 40 Astronomical Units (AU) from the Sun (see the discoverers and discovery dates in the dwarf planet's articles). These dwarf planets are also known as minor planets.


The satellites of the planets are the smallest bodies in the Solar System (despite the dwarf planet, Pluto, being smaller than Earth's Moon). This definition is sometimes irrelevant though. Ganymede, the largest moon in the Solar System, is larger than the planet of Mercury. The Earth's moon is the largest natural satellite in the Solar System, being only a fourth smaller than its home planet, Earth. Yet, most of Jupiter's moons are asteroids from the Asteroid belt or loose asteroids from the same region. To see all of the satellites in Solar System and their articles (all 179 of them), click here.

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