OUR SOLAR SYSTEM
Have you ever tried to count the stars in the night sky? Nobody knows how many there are. A group of stars is called a galaxy, and there are millonsof galaxies in the universe Our sun is one of the smallest stars on the edge of our galaxy, the Milky Way. Imagine the sun is one grain of sand. Now add a bucket of sand to it – that represents thestars in the Milky Way. Now try to imagine how many buckets of sand there are in the Sahara desert, and you have an idea of how many stars there are in the universe!
Let's imagine a tour of our solarsystem. We begin our journey from the sun, but of course we could never live there – the temperature on the surface is 6000° C! The first planet we see is Mercury. It is strange because the same sidealways faces the sun, so one half of the planet is very hot and the other extremely cold. It orbits the sun once every 88 days. The next planet we see is cloudy Venus. The thick gases in itsatmosphere have created a greenhouse effect', with temperatures of up to 500° C during the day! (The highest temperature recorded on Earth is 57° C in Death Valley.) Our Earth is the next planet we pass onour journey. We Think it is the only planet with life. After Earth is Mars. People used to think there was life on Mars because they thought they could see canals on its surface. We now know this isnot true.
The next four planet are giants. Jupiter, the next stop on our tour, has a mysterious red spot on its surface. The spot, which moves, is many times bigger than our Earth! Next is Satur,famous for its colourful rings of rock and ice which go round it. A person standing on Saturn and looking up at the sky. We know see a beautiful rainbow in the sky. We know very little about the nexttwo giant planets, Uranus and Neptune.
Previously the solar system had an extra planet, Pluto, which is no longer considered a planet by scientists because of its small size.
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