Solar System

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The Solar System refers specifically to our Sun's star system. A star system is the area around a star containing bodies which orbit that star. The Solar System consists of the terrestrial planets, the gas giants, moons, dwarf planets, asteroids, comets, and vast amounts of dust and debris. Also, Mars.

Orbital Bodies

The Solar System mostly consists of the vacuum of space, but there are many countless bodies out amongst it.


At the heart of our Solar System is our star the Sun. It is by far the most massive object in the Solar System, and is why all other bodies in the solar system orbit it.

The Sun is constantly sending out Solar energy in the form of radiation and charged particles, a minor percentage of which intersects with the bodies across the Solar System.

Major Planets

The Sun has many bodies orbiting and gravitationally bound to it, but the most significant of these bodies are the eight major planets. These include the terrestrial planets Mercury, Venus, Earth, Mars and the gas giants Jupiter, Saturn, Uranus and Neptune (although there are several moons larger than Mercury).

The terrestrial planets are mostly composed of rock but with a thin atmosphere of gas. The gas giants are the biggest objects in the Solar System, after the Sun and are almost entirely composed of a thick gaseous atmosphere around a small solid body.

All of the planets orbit in the same plane of the Solar System as each other.

Dwarf Planets

The next biggest objects in the Solar System are the Dwarf Planets. Pluto is the most well known of the dwarf planets and orbits out at around 40 AU, but many others exist throughout the solar system, including Ceres in the asteroid belt at 2.7 AU just beyond Mars' orbit, and Eris orbiting well beyond Pluto out at 67 AU.

Many of the dwarf planets, orbit in their own unique plane, above or below the plain that contains the planets.

Moons / Satellites

Many of the largest bodies in the Solar System are actually moons orbiting the major planets. The Moon which orbits Earth is one of the largest in the Solar System, but the biggest moon in the Solar System is Ganymede which orbits around Jupiter. This has a diameter of 5,268 km and is actually larger than the planet Mercury.

There are also many moons which orbit around dwarf planets and other minor bodies. These are often comparable in size to the objects they orbit.

The planet Mars has two very small moons called Phobos and Deimos. But both of these are thought to be captured asteroids which at some point passed close enough to Mars to be captured by its gravity.

Asteroid Belt and asteroids

The Asteroid Belt exists between the orbits of Mars and Jupiter and consists of many small rocky bodies (i.e asteroids) of different shapes and sizes. However, collisions between objects are quite rare because the distances between objects are quite large.

Although there are many individual asteroids, the total mass of all the objects in the Asteroid Belt is not even thought to exceed the mass of the dwarf planet Pluto. It is believed Jupiters influence on the asteroids is the reason they have never coalesced into a single body. Mars has more meteor impacts than Earth because it is closer to the asteroid belt.

The asteroids in the Asteroid Belt all orbit on the same plane as the major planets.

Kuiper Belt and comets

The Kuiper Belt consists of many, many cold, icy bodies as the distance from the Sun means they receive very little radiation.

Occasionally these objects will be perturbed in someway and their trajectory will change enough so that they enter the inner solar system. These objects are known as comets and iconic "tail" is produced as they get closer to the sun, heat up and break up.

Oort Cloud

At the edge of the solar system, exists the Oort Cloud. Unlike other objects in the Solar System which orbit in a single plane the objects in the Oort cloud completely surround the Solar System.


The edge of the Solar System is difficult to detect but has been defined as the point where the Sun's influence ends. This is the point where the Sun's solar wind equals that of the background value of our galaxy.

The extend of the Solar System is calculated to be at around 120 AU.


The Solar System is thought to have been created from the collapse of a massive gas cloud. The Sun first capturing most of the mass and triggering the creation of the other bodies through countless collisions.

The collapse of the gas cloud and the startof the Solar system is believed to have happened around 4.6 billion years ago.