- Some planets, called terrestrial planets, have a surface of solid rock. Others, called gas planets, have a surface of liquid or airy gas.
- The solar system has nine planets including Pluto. But Pluto may be an escaped moon or an asteroid, not a planet. More interesting facts
- Giant planets have now been detected orbiting stars other than the Sun. These are called extra-solar planets.
- Extra-solar planets are too far away to see, but can be detected because they make their star wobble.
- The Milky Way is the faint, hazy band of light that you can see stretching right across the night sky.
- Looking through binoculars, you would see that the Milky Way is made up of countless stars.
- Neptune is so far from the Sun that its orbit lasts 164.79 Earth years. Indeed, it has not yet completed one orbit since it was discovered in 1846.
- The Milky Way is 100,000 light-years across and 1000 light-years thick. It is made up of 100 billion stars.
