In the night sky: Orion
In the night sky: Orion

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

4.2.5 The asteroid belt

An image of a view from the asteroid belt looking towards the Sun.
Figure 16 Artist’s concept of a view from the asteroid belt looking towards the Sun.

Marking the boundary between the innermost rocky planets (Mercury, Venus, Earth and Mars) and the outer planets is a belt of rocky and metallic bodies, known as the asteroid belt.

The asteroids, also called minor planets, are not a planet that has been broken up; rather, they are the building blocks of a planet that was never assembled. The reason that the building blocks never clumped together was that Jupiter’s gravitational attraction kept pulling them apart.

An image of a meteor.
Figure 17 A meteor from the Geminid shower passing by the Taurus constellation with Orion also visible to left of the photo

The asteroids are in stable orbits around the Sun, but they do occasionally collide with each other. Fragments of broken asteroids can leave the asteroid belt, and fall towards the Sun. Asteroid fragments which land on Earth are meteorites. More often than not, a meteorite falls unnoticed – but sometimes they make a dramatic entry through the Earth’s atmosphere, as was seen with the Chelyabinsk meteorite that landed in Russia in February 2013. You can read how the BBC reported the event in the article ‘Meteor strike injures hundreds in central Russia’ [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .

The final objects in the Solar System that you will encounter are comets – read on to find out about these spectacular visitors.

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371