The Earth and the Solar System STD: VI

Knowing about the universe All the objects we see in the sky are called heavenly bodies or celestial bodies. They include the stars, planets, satellites, asteroids, meteors and comets.

The Universe

Galaxies

Stars

Members of the Solar System The word ‘solar’ comes from the Latin word ‘sol’ meaning ‘Sun’. Family of the Sun is called as the solar system. It consist of the Sun, eight planets and their satellites, numerous asteroids, meteors & comets.

The Sun Largest member of the solar system. Located in the center.. A huge ball of gases. It is the main source of light & heat on the Earth. Is about 15 crore km away. Temperature 6000 *C. Light from the Sun takes about 8 minutes & 20 seconds to reach the Earth.

The Planets There are eight planets. Increasing distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus & Neptune. Decreasing size: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars & Mercury. The inner planets (terrestrial) & the outer planets(gas giants).

Mercury It is named after the messenger of the Roman gods. Temperature: Day: about 400 *C Night: about -170 *C

Venus Named after Roman god of love & beauty. Its almost the same size as the Earth known as Earth’s twin. It shines brightly & is seen before sunrise as Morning star & after sunset as the evening star.

Earth It is the only planet to support life. Also called as the Blue planet. It is the largest among the inner planets.

Mars It is named after the Roman god of war. It is known as the Red planet. It is about half the size of earth. Its rotational period is same as the Earth.

Jupiter It is named after the ruler of the Roman gods. Jupiter, with its moons, is described as a mini solar system by NASA.

Saturn It is named after Jupiter’s father in Roman mythology. It has bright rings around its equator.

Uranus It is named after the Greek god of sky. It also has rings around its equator.

Neptune It is named after the Roman god of the sea. It is similar to Uranus in size & structure. The two are called twin giants.

Satellites It means an attendant or a companion. They revolve around the planets from west to east. They do not have their light & reflect the light of the sun. Until 1610, moon is the only satellite. Today, there are more than 150 known satellite. Mercury & Venus do not have any satellite.

The Moon It is the closest celestial body to the Earth. The Sun & the Moon appear to be of the same size, although the Sun is much bigger. The Moon is closer. It is about 3,84,400km away from the Earth. No life exist there because it neither has water nor an atmosphere.

Phases of the Moon Moon reflects the light of the sun thus, the visible shape of the Moon changes from night to night. The waxing & waning of the Moon is known as the phases of the Moon.

Phases of the Moon

The Moon is always half dark & half bright. The angle of view from the Earth keeps changing. On the new moon day the dark hemisphere of the Moon faces the Earth & on the full moon day the bright hemisphere is visible to us.

Asteroids These are small planet like objects also called as planetoids or minor planets. Each asteroid follows its own orbit around the Sun. Billions of asteroids between Mars & Jupiter. It is believed that asteroids are some broken pieces of some planets, which exploded soon after their birth.

Comets Comets are huge lumps of snow & rocky dust. Revolve around the Sun in large elliptical orbits. When it reaches close to the Sun its starts glowing & develops a long tail. The most famous comet- Halley’s comet. It comes near the Earth every 76 years.

Meteors Meteors are also known as shooting stars. These are small pieces of rocks and dust revolving around the Sun. Their presence is known only when they enter the Earth’s atmosphere. Most of them burn up & disappear as gases. Some are big & thus they do not burn up completely. They strike the Earth & are known as meteorites.