Stars and the solar system

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This the small presentation on Class 8th Chapter: Stars and the solar system.

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Stars, planets, the moon and other bodies in the sky are called celestial bodies. The different shapes of the disc of the moon observed during a month are called the phases of the moon. Nearly fifteen days after the new moon can be seen approximately once a month. The new moon is seen when the moon is in between the sun and the earth. The full moon can be seen when the sun and the moon are on either side of the earth. The surface of the moon is dusty and full of craters. The moon has a very thin atmosphere. This is why sound transmission is not possible on the moon. The moon has a very thin atmosphere. This is why sound transmission is not possible on the moon. A Light year is used to measure very large distances. It equals the distance travelled by light in one year. Sunlight takes about 8 light minutes to reach the earth.

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There are 8 planets in the solar system that revolve around the sun. The sun is a major source of heat and light for all the planets in the solar system. Planets reflect the Sunlight that is incident on them. They have no light of their own so they don’t tinkle like stars. Planets have definite paths called orbits in which they revolve around the Sun. The time taken by a planet to complete one full revolution around the Sun is called its period of revolution. The taken by a planet to rotate a full 360 degrees on its axis is called its period of Rotation. A celestial body that revolves around another celestial body is called a satellite.

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Mercury is the smallest planet in the solar system as well as the closest to the Sun. It takes about 88 days to complete one revolution around the Sun. Venus is the second closest planet to the Sun. It takes about 225 days to complete one revolution around the Sun. It has no satellite or moons. It rotates from East to West. Earth is the only planet on which life is known to exist. It takes 365 days for the Earth to complete one revolution around the Sun. Mars completes one revolution around the Sun in about 687 days. It has to Moons of its own. Jupiter is the largest planet in the solar system. Jupiter’s four larger Moons are called lo, Europa, Callisto and Ganymede. It rotates the fastest among all planets. The rings of Saturn are made of ice particles and dust. Saturn is the only planet that is lighter than water. The largest of Saturn’s Moon is Titan. Uranus is the coldest planet. Neptune as discovered through mathematical calculation.

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Mercury, Venus, Earth and Mars are called the Inner Planets. Jupiter, Saturn, Uranus and Neptune are called the Outer Planets. The Outer Planets have several Moons and a system of rings.

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Apart from the sun and the planets, the solar system also comprises of celestial bodies such as meteors, comets and artificial satellites. A meteor is made of debris. It enters the Earth’s atmosphere at a very high speed. The friction with the atmosphere at a very high speed the friction with the atmosphere makes the meteor hot and it burns till it disintegrates. As it falls to the ground, it glows brightly. This is why it is called shooting star. Some meteors reach the ground before they burn completely and evaporate. These are called meteorites . Asteroids are made of rubble and are found in the gap between the orbits of Jupiter and Mars. The gap is called asteroid belts. An asteroid does not have a tail. However, a comet is made up of a bright head and a long tail. A Comet is comprised of rock, dust, water, ice frozen gases. Artificial Satellites are man-made and are launched from the Earth. They are used for transmission of television and radio signals, telecommunication and remote sensing.

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Constellation is a group of stars that form a recognizable shape. Ursa Major is in the shape of a bear. The Big Dipper is a group of stars that from part of this constellation, it represents the black half of the bear’s torso and its long tail. It can be used to locate the position of the Pole Star. Orion has seven or eight bright stars. The three middle stars make stars make up the belt of Orion. The four other stars are in form of a quadrilateral. Cassiopeia resembles a distorted W or M. Stars appear to move from east to west through the night because the Earth rotates from west to east.

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