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The Solar System

The Solar System

PoS - describe the movement of the , and other , relative The to the in the solar system NaG - pupils should learn that the Sun is a at the centre of our solar system and that it has eight planets: , , Earth, , , , and ( was reclassified as a ‘dwarf ’ in 2006). WS - pupils could create simple models of the solar system

The Sun

The Sun is a star of average size and . Many

are much bigger and hotter than the Sun, and many stars are

smaller and cooler. There are billions of stars in the like our Sun, but our star the Sun is special because it helps to support the life on our planet - the planet Earth!

The Sun is our source of heat, light and energy; without it we could not exist. The diameter of the Sun is about 1.4 million km across. It has an average surface temperature of 5800oC. The Sun rotates once every 25 days.

The Planets

The planets the Sun. Our solar system contains one star and eight planets. These planets, in order from the sun are:

Mercury Venus Earth Mars Jupiter

Note – up until 2006 our solar system was said to contain 9 planets. This is because Pluto was included in our solar system as our 9th planet. In 2006 astronomers and scientists agreed,

after much debate, that Pluto was too small to be classed as a Planet, so it was Saturn Uranus Neptune reclassified as a ‘’.

Mercury Mercury is a small planet (4,878 km in diameter) only 40% larger than our . It close to the Sun and speeds through a year in just over 88 days (1 orbit). Mercury spins slowly on its axis, taking 58.6 days to turn once. Mercury has a surprising temperature range of -173˚C to 430˚C. It is not a world where life as we know it could be expected to live and survive!

© Sigma Science The Solar System p1 www.sigmascience.co.uk

Venus Venus was at one time thought to be the planet that was most like the Earth. It was often even referred to as Earth's sister planet (12,102 km in diameter). The surface of Venus is a

blistering inferno with exceeding 478˚C and which includes deadly acid rainfall. Venus takes 225

days to complete 1 orbit of the Sun.

Earth Compared to all of the other places in space, our planet is the only one that we know where there is life, not just a little bit of life, but an abundance of life! Earth is not a large planet; it has a diameter of 12,756 km. When viewed from space the Earth looks blue - this is because approximately 70% of the Earth’s surface is covered by . The Earth spins on its axis approximately once every 24 hours. This spin gives us our night time and time. The Earth takes 365 days to travel once around the Sun. This orbit gives us our seasons and our years.

Mars Mars, because of its red colour, is referred to as the ‘Red

Planet’. Mars has a diameter of 6790 km, about half the size of the Earth. A day on Mars is 24 hours 37 minutes long, almost exactly the same as Earth's. The Martian year is 687 days, slightly less than twice the length of a year on Earth. Compared to all the other planets, Mars has the most in common with the Earth. Mars’ tilt is similar to that of the Earth; it also has seasons and ice caps.

Jupiter Jupiter is the fifth and largest planet in our solar system and is made from gases. It has a diameter of 142,980 km. This has a thick and 39 known (the Earth has 1). Jupiter takes 11.5 years to complete one orbit of the Sun. Its most prominent features are bands across its surface and a , which is a that appears to be constantly raging.

© Sigma Science The Solar System p2 www.sigmascience.co.uk

Saturn Saturn is easily recognisable and famous because of its rings.

These rings are extremely wide and incredibly thin. They are largely made from rocks and ice. Saturn is smaller and colder

than Jupiter. The planet has a diameter of 120,660 km, about 9.5 times the diameter of the Earth. Saturn is 1427 million km from the Sun and takes 29.5 years to complete 1 orbit. Saturn has a fast spin, turning on its axis once every 10 hours

14 minutes.

Uranus Uranus is much smaller than Jupiter and Saturn, but with a diameter of 51,118 km, it is still over four times bigger than that of the Earth’s. It would take 15 of our planet to equal the of Uranus. Uranus is a cold world, covered in thick gas with an average temperature of -221˚C. These clouds have made it impossible to see what the actual surface of Uranus is like.

Neptune Neptune is over 30 times further from the Sun than Earth. It is so far out that Neptune takes 165 years to make one orbit around the Sun! It has a diameter of 49,352 km. Neptune turns fast; a day on Neptune lasts 16 hours 3 minutes. Being so far away from the Sun, Neptune is extremely cold with temperatures falling below -220˚C.

Pluto Pluto was discovered in 1930 and classed as a planet. In 2006

astronomers voted to strip Pluto of its status as a planet and

call it a ‘dwarf planet’ because it is so small. Pluto is located at the edge of the solar system and has a diameter of 2294 km (about 85% the size of our moon). It takes Pluto 248 years to

orbit the Sun once. Being so far from the Sun, Pluto is cold

enough (at -230˚C) to freeze most gases. Scientists think Pluto is made from rock and ice.

© Sigma Science The Solar System p3 www.sigmascience.co.uk

1) Read the information about the Solar System and complete this table:



MERCURY 57,910,000

VENUS 108,200,000

EARTH 149,600,000

MARS 228,000,000

JUPITER 778,330,000

SATURN 1,427,000,000

URANUS 2,870,990,000

NEPTUNE 4,500,000,000

PLUTO 5,906,000,000

2) Use the information about the Solar System and the table to answer the following questions:

a) Name the largest and smallest planets (not including Pluto). b) Name two planets which are extremely hot. c) Name two planets which are covered in, or made from thick poisonous gases. d) Which planets have the most severe ? e) Why is the Earth a unique and special planet? f) Why was Pluto downgraded to a ‘dwarf planet’?

3) We know the order of the planets in the Solar System, now sort the planets in order from smallest to largest.

4) Which planet do you think is most like the Earth? Explain your answer.

© Sigma Science The Solar System p4 www.sigmascience.co.uk