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Download The Sun Our sun is a star. It is the star we see in the daytime. It is the
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The Sun Our sun is a star. It is the star we see in the daytime. It is the center of our solar system. The sun is so big that more than a million Earths would fit inside it. It looks small because it is so far from Earth. Like all stars, our sun is a ball of very hot gases. It gives off light and heat. The sun makes energy in its center. Huge explosions take place, releasing energy. The outside layer of the sun is boiling gases. This is why the sun looks like a ball of fire. We couldn’t live without the sun. It gives us heat to stay warm and gives us light to see by. Plants need the sunlight too. It helps plants make food for us to eat and oxygen for us to breathe. The Eight Planets In ancient times, people did not have telescopes. When they wanted to know what’s there in the sky, they had just their eyes to use. They could only see the objects close to Earth. When telescopes were invented, astronomers could see much more. In 1977, some special spaceships (Voyager 1 and Voyager 2) were sent into space to get information about the far-off planets. Now the astronomers have discovered that eight planets are orbiting around the sun. The planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Our planet earth is the third one from the sun. Pluto has been known as the ninth planet of our solar system since it was discovered in 1930. However, Pluto is different from other planets (it is smaller than Earth’s Moon). In 2006, the International Astronomical Union re-classified Pluto as a "dwarf planet". 1. Mercury Mercury is the nearest planet to the Sun and is also the smallest, except for Pluto. It can be seen for a short time just before sunrise or after sunset because it is so close to the Sun. Mercury has almost no atmosphere. With no air, and no clouds, the weather forecast on Mercury would be very simple: unbearably hot by day and freezing cold at night. about the Mercury A year on Mercury is as long as 88 days on Earth A day on Mercury is as long as 58.6 days on Earth Average surface temperature 117 °C day / -170 °C night Number of moons 0 Average distance from the Sun 58 million km 2. Venus Venus is easy to see in the sky because it is very bright – only the Sun and Moon are brighter than Venus. The thick atmosphere makes Venus a very dangerous place to explore. This is because it mainly consists of a gas called carbon dioxide; which we cannot breathe. It also traps the heat so that Venus is even hotter than Mercury. Days on Venus seem endless. Venus is the second planet from the Sun. One day on Venus is as long as 243 days on Earth. A year on Venus is only 225 Earth days long. So a day on Venus is longer than a year! about the Venus Average distance from the Sun 108 million km A year on Venus is as long as 225 days on Earth A day on Venus is as long as 243 days on Earth Average surface temperature 457 °C Number of moons 0 3. Earth Earth is the third planet from the Sun. It is the only planet that has water on the surface — about two-thirds of the Earth is covered with oceans of water. In colder parts the water freezes into ice and there are droplets of water in the clouds. Earth was formed 4.5 billion years ago. When Earth was formed, it too had a dense atmosphere of carbon dioxide just like Venus. about the Earth Average distance from the Sun 150 million km A year on Earth is as long as 365 days on Earth A day on Earth is as long as 24 hours on Earth Average surface temperature 15 °C Number of moons 1 4. Mars Mars has a thin and wispy atmosphere made almost entirely of carbon dioxide. At the north and south poles of Mars there are ice-caps. This kind of ice is known as dry ice (made up of frozen carbon dioxide). The surface of Mars is a stony desert with sand that is so tiny that you would need a microscope to see them. The winds of Mars easily stir up vast dust storms, which cause the pinkish glow in its sky. about the Mars Average distance from the Sun 249,2 million km A year on Mars is as long as 687 days A day on Mars is as long as 24.6 hours Average surface temperature -63.35 °C Number of moons 2 5. Jupiter Jupiter is not a solid planet. Unlike the four rocky planets closest to the Sun, Jupiter is a huge ball of gas. Jupiter rotates very rapidly, once every 10 hours. This is so fast that the planet bulges at the equator. The rapid rotation also causes high wind speeds in the upper atmosphere, where the clouds are stretched out into colorful bands. Different parts rotate at slightly different rates, and these speed differences causes the bands. about the Jupiter Average distance from the Sun 778 million km A year on Jupiter is as long as 11.9 years on Earth A day on Jupiter is as long as 9 hours 50 minutes Average surface temperature 14.85 °C - 19.85°C Number of moons 63 6. Saturn Saturn is the sixth planet from our Sun. The rings around the planet are made up of millions of bits of ice and rock. Saturn is a frozen world, with a cloud and wind system similar to Jupiter. Saturn’s beautiful rings do not touch the planet. The rings are tilted at an angle of 29°. This means that they slowly change their appearance when viewed from Earth. The rings are mainly made of billions of tiny particles and each particle is orbiting Saturn! They all orbit the planet as if they were wandering satellites. about the Saturn Average distance from the Sun 1,457 million km A year on Saturn is as long as 29.5 years on Earth A day on Saturn is as long as 10 hours 39 minutes Average surface temperature -139.15 °C Number of moons 46 7. Uranus Uranus is mainly made of hydrogen and helium, but one-seventh of its atmosphere is methane. This gas makes it appear bluish in a larger telescope. The axis of Uranus is tilted by more than a right angle, which means its north pole actually points below the planet’s orbit. This gives Uranus rather strange seasons. One pole faces the Sun and has a constant sunlight for about 40 years. This end of the planet then goes into complete darkness for about another 40 years while the other pole of the planet faces the Sun. about the Uranus Average distance from the Sun 2,870 million km A year on Uranus is as long as 84 years on Earth A day on Uranus is as long as 17 hours 14 minutes on Earth Average surface temperature -197.15 °C Number of moons 47 8. Neptune You could not breathe on Neptune, and the fierce winds would blow you away. Even without the winds, you could not walk on Neptune because the planet has no solid surface. A thick layer of clouds surrounds Neptune. The clouds are part of the planet’s atmosphere. Neptune’s atmosphere is made mostly of hydrogen and helium gases. Some methane gas high in the atmosphere gives Neptune its bluish color. You could not breathe the gases in Neptune’s atmosphere. There is no oxygen in Neptune’s atmosphere. Neptune has the fastest winds in the solar system. The winds on Neptune can blow at 1,200 miles per hour. about the Neptune Average distance from the Sun 4,498 million km A year on Neptune is as long as 164 years on Earth A day on Neptune is as long as 19 hours 3 minutes on Earth Average surface temperature -200 °C Number of moons 8 Pluto Our Sun would look like a small dot of light if you were standing on the surface of Pluto. But Pluto is so far away that no spacecraft has ever visited it. Pluto is the “dwarf planet” (tiny) in our solar system. It is farthest of all other planets. It is the smallest of all the planets. Its size is smaller than even our Moon. Astronomers know less about Pluto than about any other planet. This is because no spacecraft could ever reach the Pluto. about the Pluto Average distance from the Sun 5,906 million km A year on Pluto is as long as 248 years A day on Pluto is as long as 6 days 9 hours Average surface temperature -215.35 °C Number of moons 1 ASTEROIDS, COMETS, AND DUST There are thousands of asteroids in the solar system. Asteroids are small pieces of rock and metal. Most of them orbit the Sun between Mars and Jupiter. Asteroids that crash into Earth are called meteors. Sometimes they burn up as they fall toward Earth. They make tails of light in the night sky. Pieces that land on the ground are called meteorites. Comets are another type of object in the solar system. Comets are like dirty snowballs. They are made of ice and dust. Comets are usually far out in the solar system. Sometimes a comet comes in close to the Sun. When it comes in close, the comet starts to melt and looks like it has a long tail streaming out behind it. In 1994 pieces of a comet called Shoemaker-Levy 9 crashed into Jupiter. The crash made huge explosions and sent up fireballs that were larger than Earth. The geocentric system was the first model of our solar system-dating back to the ancient times. This model predicted a earth-centered system hence geocentric and it was the most favorable until about the late 15 hundreds. However some astronomers were not concurring to the geocentric model, in the light of that a guy known as Nicolaus Copernicus devised a secret (this was against the teachings of the church and it was death punishable) heliocentric system with the sun at the center of our solar system and that was later mastered by Galileo and Kepler. Some Facts about this 1) Copernicus publish this model on his bed of death 2) Galileo was held under house arrest for the last 10 years of his life for publishing the heliocentric system. The word "helios" in Greek means "sun." Heliocentric means that the sun is at the center. A heliocentric system is one in which the planets revolve around a fixed sun. Thus Mercury, Venus, the Earth, Mars, Jupiter and Saturn all revolve around the sun. This theory was first proposed by Nicolaus Copernicus.