The Planets and Space Exploration

The four rocky planets at the center of the solar system Mercury, Venus, Earth, Mars, are known as the inner planets. Jupiter, Saturn, Uranus, and Neptune are all composed primarily of gas and are known as the outer planets.

There are thousands of smaller, icy not-quite-planets in the space beyond Neptune. They include the dwarf planets Pluto, Haumea, Eris, and Makemake.

The asteroid belt, between Mars and Jupiter, is made of thousands of chunks of rock which travel around the Sun. The largest asteroid, Ceres, is also a dwarf planet. Comets are small icy bodies that travel past the Sun and give off gas and dust each time they pass by.

Unmanned spacecraft have travelled to all the planets in the solar system (except Pluto) and taken pictures of the planets and many of their moons. They have also taken measurements that tell us what the planets are like inside.

Big, Bigger, Biggest

A Solar System Model Builders Guide

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Dwarf Planets

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Pluto

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Eris - a dwarf planet

Eris is a dwarf planet in our Solar System. Eris was one of the first three objects classified as a dwarf planet, along with Pluto and Ceres. Eris was first spotted in January 2005. Eris is a large sphere...more

Makemake: a Dwarf Planet

Makemake is a dwarf planet in our Solar System. Makemake was discovered in March 2005 by a team of astronomers led by Mike Brown. Makemake officially became a dwarf planet in July 2008. There were three...more

The Solar System

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Solar System Formation

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