0I. The Earth and the Solar System:
1. The sun, the moon and all those objects shining in the night sky are called celestial bodies.
2. Some celestial bodies are very big. They are made up of gases. They have their own heat and light which they emit in large amounts. They are called stars.
3. Various patterns formed by different groups of stars in the sky. These are called constellations. Big bear or Ursa major and small bear or saptrishi (seven sages) are examples of such constellations.
4. The north star or pole star indicates the north direction.
5. The word 'planet' has been derived from the Greek word 'Planetai' that means wanderers.
II. The Solar System:
1. The sun, eight planets, and other celestial bodies like asteroids, meteoroids form together the Solar System.
2. In roman mythology, 'Sol' means the Sun-god. Solar means related to the sun.
III. The sun:
1. It is a huge ball of gases. It provides the pulling force that binds the whole solar system. The sun is about 150million kms. away from us.
IV. Planets:
1. There are eight planets in the Solar System- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
2. A new planet 2003 UB313 has been discovered in our solar system.
V. The Earth:
According to size, it is the fifth largest planet. It's slightly flattered at the poles. That is why it's shape is described as Geoid, which means earth-like shape.
VI. The moon:
1. Its diameter is only one-quarter that of the Earth. It is about 3,84,400 km away from the Earth. The moon takes about 27days to complete one rotation and revolution of the Earth. It has no air or water available but it has mountains, plains and depressions on its surface.
VII. Asteroids:
1. Numerous tiny bodies (except stars, planets and satellites) which moves around the sun are called asteroids. They are mainly found between the orbit of mars and Jupiter.
2. The largest asteroid is called the Ceres. Scientists believe that te asteroids are also part of the planets.
VIII. Meteoroids:
1. Small pieces of rocks which move around the sun are called meteoroids. They come near the Earth and tend to drop and during this they warm up and burn due to friction. A flash of light is often seen in the sky as a result of it. Sometimes, a meteor falls on the Earth and creates a hollow.
IX. Extra points to remember:
1. Human made satellites are designed by scientists to gather information about the universe or for communication purpose. It is carried out by the rocket and placed in the orbit of the Earth.
2. INSAT, IRS, EDUSAT are few examples of indian satellites.
3. Neil Armstrong was the first man to step on the surface of the moon on July 29, 1969.
4. Satellites: As the planets move around the sun, satellites move around the planets.
5. The speed of light is about 300,000km per second. It takes 8 light minutes to reach sun from the Earth.
