Astronomers measure distances in 'light years'. Each light year is the distance travelled by a ray of light in one year, which is 9,500,000 km. The M13 clusters is 22,500 light years from Earth.
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| Stars | ||||||||||||||||
| Beyond our Solar System lie countless billions of stars. Some are over 100 times bigger than our Sun. They are called SUPERGIANTs. GIANTs are about ten times smaller than the Sun. We can tell how hot a star is by its colour. Red stars are slightly cooler than the Sun, which is yellow. Hotter stars are white or blue-white. Some stars seem bright to us on Earth. This may because they really are bright, or because they are near to us. | ||||||||||||||||
| Do stars last forever ? | ||||||||||||||||
| Do other stars have planets ? | ||||||||||||||||
| New stars are born from clouds of dust and gas spinning in space. Big stars burn up their gases in a few millions years. However a medium-sized star like the Sun may lost about 10,000,000,000 years. The Sun itself is halfway through its life. Before the Sun dies it will turn into a red giant. Its gases will drift away into space. A white dwarf will be left at the centre, which will slowly fade away. A big star may go out with a huge bang. Such an explosion is called supernovae. Any nearby planets would be instantly melted down. | When our Sun was being formed in space, some of the gas and dust on the edge of the spinning cloud was not sucked into the centre. It was the material which formed the planets. It is thought that maybe one out of ten of the stars we see at night also hae\ve planets. We have not been able to see any of these planets through telescopes. However pictures taken by the Infra-Red Astronomy Satellite in 1983 seem to slow planets being formed around the star Beta Pictoris. | |||||||||||||||
| Stars grouping | ||||||||||||||||
| Twin Stars | ||||||||||||||||
| Many stars cling together in groups of two and threes. They are held in place by the force of gravity. Sometimes large numbers of stars are bunched together in groups called clusters. The M13 cluster appeard in the constellation Hercules. It contains thousands of stars. The group is shaped like a globe, and so it known as a globular clister. Star groups which have no particular shape are called open clusters. Astronomers measure distances in 'light years'. Each light year is the distance travelled by a ray of light in one year, which is 9,500,000 km. The M13 clusters is 22,500 light years from Earth. |
Many of the stars we see in the sky turn out be double stars when viewed through a telescope. Some of these may simply appear to be close together when viewed from Earth. Others really are pairs, held together by gravity. They are called binaries. In a binary, each star orbit the others. Sometimes one of the twins in faint and blocks the light of its brighter neighbour. | |||||||||||||||
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