It seems most likely that to find other forms of life, we must look beyond our solar system. The sun is only one of 100 million stars in  the galaxy. Are not other stars also likely to have planets that support life? We do know that some nearby stars have planets. It is possible that life could exist on them.
	Scientist have made estimates of the number of other civilizations that are likely to exist in the Galaxy, and believe that there could be aboute a million. If this were so, then each civilization would be about 300 light years apart.
	MESSAGES IN SPACE. Talking with the beings of such civilization would take a long time. We could only contact each other by radio signals, which travel at the speed of light. It would therefore take 300 years for a message to travel from our civilization to theirs. To get an immediate reply, we would have to wait 600 years.
	We could send out messages to the stars and hope for a reply. A radio message would not be in English or any other language, but a series of signals that world stand for numbers and diagrams.

	STARS AND CONSTELLATIONS. On a clear nidht, away from the light of a town, you can see about 2000 stars with the naked eye. A teleskope can reveal millions. Like the Sun and the Moon, the stars appear to move slowly accros the sky in fact it is we who are moving as the Earth rotates.
	CONSTELLATOINS. In ancient times, people were reminded of the outlines of animals and gods in the sky gave their names to the groups of stars that they saw. These groups are called constellations.
	These are not in fast actual groups of stars that are near each other in space - some may be near us while others are far away. But dividing the sky into these recognizable patterns helps us to map the sky.
	GALAXIES. Through a powerful telescope, vast groups of stars called galaxies can be seen. Our Sun in fact belongs to a galaxy containing about 100000 million other stars; when we look at the Milky Way, we are looking at our own Galaxy. Millions of other galaxies are scattered throughout space.
	Many are shaped in a flat disc like our Galaxy, and made up of spiral arms of stars reaching out from a central hub of stars. Our Galaxy is rotaiting slowly and edge of the Galaxy, makes one circuit every 225 million years.
	MEASURING DISTANCES. Distances are so vastin astronomy that they are measured in light year - the distance light travels in a year. One light year is nearly 9,5 million kilometres and our Galaxy is 100000 light years across.
	THE LIFE OF A STAR. Stars form as hydrogen comes together in clouds that contact with gravity and eventually begin to burn. Many stars burn for millions of years and then expand into a red giant star before contracting to a cold dwarf star, their fuel used up. But some stars end their lives in a gigantic explosion. An exploding star is called a supernova and is very bright indeed.