The Solar System

The Solar System

Our Solar System is 4.6 billion years old and was formed inside a diffuse cloud of gas and dust called a nebula. At the center is a giant ball of exploding hydrogen and helium called the Sun, containing 99.86% of the mass of our solar system. It is a yellow dwarf star whose gravity is so strong it overpowers all other objects around for a distance of two light-years. These objects rotate around the Sun in nearly circular orbits and include the 8 planets, as well as asteroids, comets, moons, dust, gas and some dwarf planets.


In astronomy, an AU, or Astronomical Unit, is the mean Earth–Sun distance roughly equal to 93 million miles (150 million kms). To put things into perspective our Solar System has a diameter of around 100,000 AU such that if you imagine our Sun as a basketball and Pluto (39 AU) a grain of sand located 1,000 meters away, the edge of our Solar System (50,000+ AU) would then extend 1,000 times beyond Pluto.


Planets (0.39 To 30 AU): There are 4 inner, terrestrial planets consisting of Mercury, Venus, Earth and Mars, which are all basically balls of rock and metal. Next are the 4 outer, ringed, gas giants of Jupiter, Saturn, Uranus and Neptune, which are essentially gigantic balls of gas and liquid. In general, the nearer the Sun the hotter the planet will be therefore Mercury, for instance will be hotter than the furthest planet Neptune.

Asteroid Belt (2 to 4 AU): Between inner planet Mars and outer planet Jupiter lies the asteroid belt, a region occupied by millions of rocky objects including over 90,000 asteroids.

Structure Of The Solar SystemKuiper Belt (30 To 50 AU): The Kuiper Belt is the first of our Solar System’s two reservoirs of cometary material consisting mainly of icy debris, and lies 30 to 50 AU distant.

Oort Cloud (5,000 To 50,000 AU): There is a massive thick “bubble” of up to a trillion comets encompassing our solar system known as the Oort Cloud. If Neptune lies 30 AU away, then the Oort Cloud may extend beyond 50,000+ AU or nearly a light-year from our sun. The distance to our nearest star Proxima Centauri is 272,061 AU or 4.3 light years.

Proceed To Step 2: Galaxies

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