Our Solar System

The Solar System we live in contains the Sun, its eight orbiting planets and any other astronomical bodies that are under its gravitational pull such as comets and asteroids.

Comets originate from the Oort Cloud and Kuiper Belt, beyond Neptune, while most asteroids orbit in a region between Mars and Jupiter.

Mercury, Venus, Earth and Mars - the four planets closest to the Sun - are called terrestrial planets because they have solid rocky surfaces. Jupiter, Saturn, Uranus and Neptune are known as gas giants. Pluto, a dwarf planet, has a solid surface but is much icier than the terrestrial planets.

Our Solar System is just one star system among many within the Milky Way galaxy. There are 300 billion stars in the Milky Way and the nearest, Alpha Centauri, is 4.3 light years away. One light year is approximately 9,500 billion km, the distance travelled by light in one year.

There are around 100 billion galaxies in our Universe. So far, no one has detected life outside our home planet.

Earth

Earth is the fifth largest planet in the solar system, third in order of distance from the Sun. It is the largest of its planetary system's terrestrial planets and the only place in the universe known to support life.

The most prominent features of the earth's climate are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region. Precipitation patterns vary widely according to location, ranging from several meters of water per year to less than a millimeter. About 70 percent of the surface is covered by salt-water oceans. The remainder consists of continents and islands, with the vast majority of the inhabited land in the Northern Hemisphere.

Earth has evolved through geological and biological processes that have left traces of the original conditions. The outer surface is divided into several tectonic plates that gradually migrate across the surface over geologic time spans, which at least several times have changed relatively quickly. The interior of the planet remains active, with a thick layer of molten Earth mantle and an iron-filled core that generates a magnetic field