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★ science

solar system & planets

The Solar System consists of the Sun with planets in orbit around it. Most planets have at least one satellite in orbit around them. Gravity provides the centripetal force needed to keep objects in orbit.

We can explore space using manned or unmanned spacecraft

Solar systems consist of:

a star (the Sun)

planets and dwarf planets in orbit around the Sun

satellites (moons) in orbit around most of the planets

comets and asteroids in orbit around the Sun.

There are eight planets in our solar system, including the Earth, and smaller dwarf planets such as Pluto, Ceres and Eris.

You need to know the position of the planets in order from the Sun. Starting with the closest to the sun, the order is:

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

It may help to remember My Very Easy Method Just Speeds Up Naming.There are many other smaller objects that orbit the Sun. Three of these are Ceres, Pluto ansd Eris, known as 'the dwarf planets'. Ceres orbits between Mars and Jupiter. Pluto orbits further away from the Sun than Neptune, while Eris orbits further out still.

Stars and galaxies

Stars are very hot and give off their own light, which is why we can see the Sun during the day, and the stars in the night sky. A galaxy is large group of many millions of stars.

Our Sun is just one of at least 200 billion stars in our galaxy, the Milky Way. The observable universe contains around 80 billion galaxies. The universe also contains other objects, such as black holes.

Gravity and orbits

The orbits of the planets in the Solar System are almost circular - with the Sun near the centre. Many diagrams (including these here) show the orbits very squashed from top to bottom. This is to give a sense of perspective, or to fit the diagram into a page in a book.