2.13 Understanding our Universe 10 January 2011 What is this image?
Key terms Orbit: the path of an object moving through space such as the path of the Earth as it goes around the sun
The Solar System The Solar System consists of the Sun and all the objects that are attracted to the Sun by gravity These include the eight planets and other objects such as asteroids and meteroids The Sun is the brightest star and is the centre of the Solar System Because the Sun is so huge, its gravity holds the planets in their orbits around it
Objects in the night sky (1) If you look at a clear night sky, you will see that it is filled with various objects With the naked eye you can see the light of thousands of stars, which seem to be arranged in patterns, called constellations Because the Earth rotates, the stars rise and set like the Sun You will also see planets These do not shine their own light but reflect light from other sources Because they are close to the Earth, they shine brightly and do not twinkle
Objects in the night sky (2) If you are lucky you may see an object with a bright tail This is likely to be a comet, which are made from rock, dry ice and frozen gases such as CO 2 and CH 4 .They come from outside our Solar System You may also see ‘shooting stars’ which are meteors, these are bits of dust and rock which enter the Earth’s atmosphere Astronomers have also discovered hundreds of stony objects called asteroids , which also orbit the Sun The Earth’s moon is clearly visible and its appearance changes through the month as it orbits the Earth With a good telescope you can see that other planets have moons. Jupiter has 63 moons, one of which has volcanoes.
Origin of the Solar System Astronomers believe that the Solar System was formed when clouds of gas and dust collided Eventually our sun was formed, together with other objects such as planets Asteroids and meteoroids are believed to be remains of that cloud. Geologists have investigated meteorites and estimate they are 4.5 billion years old The effect of meteoroids and asteroids that hit the surface of the moon can clearly be seen even with the naked eye Some astrophysicists believe that the Earth was formed by collisions of asteroids and meteoroids
Assessment Activity You are an astronomer working for an observatory. You are invited to a primary school to describe our Solar System to young children Working in groups of three, construct a model of the solar system, showing the distances of the eight planets from the Sun In your groups, investigate the theory described above of how the Solar System was formed. Present your results in the form of a poster