Friday, April 23, 2010

THE PLANETS


THE PLANETS

The nine planets are the most important members of the Sun’s family. In order of distance from the Sun , they are Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uranus , Neptune and Pluto. The first four are small rocky bodies. The next four are giants , made up mainly of gas . Pluto is a tiny ball of rock and ice.

Which is the biggest planet?

Jupiter is by far the largest of the planets. It has more mass than all other planets put together. It measures nearly 143,000 kilometres across, which is 11 times bigger than Earth. Even though it is so big, it takes less than 10 hours for it to spin round once. This means that its surface round at a speed of 45,000 kilometres an hour. This is 30 times faster than Earth spins.

Which planets have rings?

Once it was thought that Saturn was the only planet that had rings around it because they were the only one that can be seen through a telescope. But close up photographs taken by the Voyager space probes have shown us that the other three gas giants- Jupiter, Uranus and Neptune-have rings too. The rings around the these other planets are much thinner , narrower , and darker than Saturn’s.

Why is Uranus sometimes called ‘new’?

Astronomers have been studying the planets for thousand of years. They have watched the way they move, or ‘wander’ across the night sky, unlike the stars. But the ancient astronomers could only see five planets in the night sky. It was not until 1781 that someone built a telescope powerful enough to spot another planet, which came to be called Uranus. Uranus was the first of three ‘new’ planets to be discovered. Neptune was discovered in 1846, and Pluto in 1930.

What is special about Saturn?

Two things are outstanding about Saturn. One is obvious when you look at the planet through telescope. The planet is surrounded by a set of bright, shining rings. Many people think that these make Saturn the most beautiful object in the Solar System. The other special thing about Saturn is that it is the lightest(least dense) of all the planets. It is lighter even than water. This means that if you could place it in huge bowl of water, it would float.

Which planet is furthest from the sun?
As far as we know, the most distant planet from the Sun is Pluto, the last ‘new’ planet to be discovered after Neptune. But Pluto is not always the furthest away. For 20 years between 1979 and 1999, Neptune was further still because during this time Pluto was travelling inside Neptune’s orbit. Neptune will become the furthest planet again in a little over 200 years’ time. Pluto travels more than 7000 million kilometres away from the Sun. It takes nearly 248 Earth-years to circle the Sun once.

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