THE EARTH IN THE SOLAR SYSTEM Stars, Constellations & the Solar System

Stars They are huge balls of very hot gaseous matter. They are self- luminous heavenly/ celestial bodies that emit heat & light (SUN). They are formed from huge cloud of dust & gas. They are found in very large groups/clusters called galaxies. Our galaxy is called the Milky way/Akash Ganga.

The Constellations A group of stars that resemble a figure. E.g. Ursa Major/ The Great Bear/ The Big Dipper & Orion. Orion

The Solar System The Sun and the various objects that moves around it together form the Solar System. Earlier astronomers thought it was geocentric by Claudius Ptolemy in AD140. Later Nicolas Copernicus introduced heliocentric theory in 1543.

The Sun 5 billion yrs old. It is made up of hot gases like helium & hydrogen. Its surface temperature is 5700 degree C. The distance from the Sun to Earth is 149 million km. Temperature at the centre of the Sun is 15 million degree C. The Sun’s diameter is 1, 392, 000 km. It is 109 times bigger than the Earth. Sunlight reaches the Earth in about 8 minutes.

The Planets They are the celestial bodies that revolve around a star. They are spherical in shape. They are non- luminous. Every planet spins on its own axis. There are 8 major planets in the Solar System. Jupiter, Saturn, Uranus & Neptune- Outer Planets. Mercury, Venus, Earth & Mars – inner planets.

The Earth It is unique because life is possible here. It is the largest among the inner planets. It is called the blue planet. The favorable conditions that facilitate life on Earth- optimum distance from the Sun, an average surface temperature of 14 degree C, suitable seasons & weather conditions, adequate availability of liquid water, the presence of atmosphere.

The Moon The Celestial body that revolves around Earth. It is a natural satellite. Except Mercury & Venus, all the other planets have natural satellites. It is about 384,400 km away from the Earth. There is no air but recently minute amount of water has been discovered. It gets hot (100 degree C ) in the day & cold (- 150 degree C)in the night.

SSS Stages of the moon

Asteroids The celestial bodies that revolve around the Sun between the orbits of Mars & Jupiter are called asteroids. These are the parts of planets which exploded millions of years ago.

Meteors They are the pieces of rock moving at tremendous speed around the Sun. As the meteor come near the Earth, they are pulled in by the Earth’s gravity. As they enter the Earth’s atmosphere they begin to glow as a result of the heating due to friction. (shooting star).