51 L6-All About Space

该页暂无翻译

Oxford Read and Discover level 6 All About Space by Alex Raynham

Introduction Space is everything that's around planet Earth, and it's bigger than we can imagine. When you look at the sky at night, you can see thousands of stars. Did you know that the Sun is a star, too? There are also billions of other stars in space, and billions of planets! How many planets do you know? What do you know about them? What can you see below? Discover! Now read and discover more about space!

Chapter 1 Our Solar System Stars are huge balls of hot gas. A star with planets around it is called a solar system. Our Sun has eight planets— this is our solar system. Our Galaxy Groups of stars are called galaxies. Each galaxy has billions of stars. Our solar system is in a galaxy called the Milky Way that has 200 billion stars. There are billions of other galaxies in the universe. Discover! The universe is everything that exists all the stars in all the galaxies. It appeared in a single moment, called the Big Bang, about 14 billion years ago. Before then, there were no stars. Our Amazing Sun The Sun and all other stars are made of two gases called hydrogen and helium. The hydrogen changes into helium in a process called nuclear fusion. This process produces heat and light. Our Sun is about 150 million kilometers away from Earth, but it's hot enough to burn you at the beach! Plants on Earth use energy from the Sun to grow. Animals and people also get their energy from the Sun because they eat plants. Earth and the Sun A planet goes around, or orbits, a star. It takes our planet Earth one year to orbit the Sun. A planet also turns on its axis. It takes Earth 24 hours to do a complete turn on its axis. When a place on Earth is opposite the Sun, it's daytime in that place.

The Planets in Our Solar System All the planets in our solar system orbit the Sun. A year is the time that it takes a planet to orbit the Sun— it's 365 days for Earth. Mercury and Venus are near the Sun, so they have shorter years because they travel a shorter distance around the Sun. A year on Mercury is the same as 88 days on Earth. Planets that are further from the Sun have longer orbits. A year on Neptune is the same as 165 years on Earth. Each planet in our solar system is different, but Mercury, Venus, and Mars are rocky planets like Earth. If you landed on these planets, you would find rocks, and you could walk around on them. Jupiter, Saturn, Uranus, and Neptune are called gas giants. They are much bigger than the rocky planets, and they are made mostly of gas. Dwarf Planets Astronomers have discovered five dwarf planets in our solar system. Dwarf planets are like very small planets and they orbit the Sun. The biggest dwarf planet is called Eris, and it's 2,500 kilometers across. Discover! The most famous dwarf planet is Pluto. It was discovered in 1930, and for more than 70 years, it was called the ninth planet in the solar system. Now it's called a dwarf planet.

Chapter 2 The Inner Planets The inner planets in our solar system are Mercury, Venus, Earth, and Mars. They are the nearest planets to the Sun and they are made of rocks and soil. Venus, Earth, and Mars have gas around them, called atmosphere. Mercury Mercury is the smallest planet in the solar system and it doesn't have an atmosphere. A planet's atmosphere traps the Sun's heat, and keeps the temperature warm at night. Mercury is very hot in the daytime because it's the nearest planet to the Sun, but it's very cold at night. When the temperature on one half of Mercury is 427 degrees centigrade, the other half is minus 173 degrees! Venus Venus is the second planet from the Sun, and the nearest planet to Earth, but it would not be a nice place to visit! Pressure is the force or weight of something on your body. Venus has more gas in its atmosphere than Earth, and all that gas creates pressure. If astronauts visited Venus, the pressure would kill them. In the atmosphere around Venus, a gas called carbon dioxide traps heat from the Sun. The temperature on Venus is 462 degrees centigrade— that's hotter than a pizza oven! The sky on Venus is yellow because there are clouds of sulphuric acid. This dangerous chemical can burn metal. Discover! Venus turns very slowly on its axis, but it orbits the Sun very quickly, so a day is longer than a year on Venus!