3rd Class Science Our Universe Planets


Category : 3rd Class

*     Planets


There are eight planets, which revolve around the Sun. Mercury, Venus, earth, and Mars are called inner planets, as they are very close to the Sun. Jupiter, Saturn, Uranus and Neptune are called outer planets as they are far away from the Sun.


*         Mercury

Mercury is the smallest planet in the solar system. It looks like our moon. The surface of mercury is covered with craters. Though it is nearest to the Sun, but it is less hottest than Venus. The reason is that the mercury has no atmosphere to retain Sun's heat on it.


Look at the following picture of the Mercury:



*         Venus

Venus is named after roman goddess of beauty and love. Venus is very beautiful object in the sky. It is called the evening star. Venus is also the brightest and hottest planet. This is because it has atmosphere containing more amount of carbon dioxide, which traps Sun's heat and doesn't allow it to go back. It can be seen in the sky just after the sun sets.


Look at the following picture of the planet Venus:



*        Earth

This is the only planet in the solar system that has life on it. Earth looks blue from the space because water covers about ¾th of the planet’s surface. This is the only planet with an atmosphere containing oxygen. Water and oxygen are the essential components for life. Earth like all other planets revolve around the Sun which is called the revolution of the earth. The time duration that the earth takes to complete its one revolution around the Sun is known as year.

Earth also rotates on its own axis, known as rotation. It takes around 24 hours to rotate once on its own axis. Days and nights are formed due to rotation and different seasons occurs due to revolution of the earth around the Sun.

Planets revolve around the Sun, similarly moon of the planets revolves around the planets. Earth has one moon. Like planets, moons are also non luminous object. They glow because they reflects Sun's light.

Earth has strong force of gravity that pulls every objects towards itself. Because of this influence only we sit, stand, eat, or do all kinds of activities, otherwise we all would have been floating in the sky.

The most beautiful object in the night sky as seen from the earth is moon.

Moon is the natural satellite of the earth. Moon revolves around the earth and along with it, moon also revolves around the Sun. Our earth is 80 times bigger than the moon. It is at a distance of about 3,84,000 km from the earth.


*       Phases of Moon

Moon appears to change gradually from crescent to gibbous moon, and then back again to its original form.


Look at the following pictures of different phases of the moon:



Different parts of the moon receive sunlight at different period. New moon occur when moon lies exactly between the sun and the earth. The sun and moon are aligned on the same side of the earth. Slowly the face of moon, visible from the earth grows larger and larger, till the full moon is formed.

During revolution around the earth, sometimes moon comes into the earth shadow. This is called as lunar eclipse. Moon has many craters on its surface.

Neil Armstrong and Edwin Aldrin were the first men to land on the moon.  


*          Mars


Look at the following picture of the plant Mars:

Mars is the fourth inner planet. Mars is red in colour, hence is named after the Roman god of war. Mars has two moons, named as phobos and deimos. There is no sign of water and life on this planet. Olympus mons is the largest volcano of Mars.


*         Jupiter


Look at the following picture of the planet Jupiter:

Jupiter is the biggest planet in the solar system. There are strips on the surface of this planet, also a great red spot on its surface which can accommodate two earths in it. Jupiter is not made up of solid matter. It consists of light gases only.

lo, Ganymede, Europa, Callisto are special moons of this planet (it has a total of 17 moons). Ganymede is the largest moon in the solar system.


*         Saturn


Look at the following picture of the planet Saturn:

It is the second largest planet in the solar system, with a system of rings along its equator. Rings are made up of dust and ice. Saturn is made up of liquid and gases, with a small rocky center. Hence it is light enough to float like a boat.

Titan is one of the moons of this planet which is the second largest moon in the solar system.


*       Uranus


Look at the following picture of the planet Uranus:

It is a blue planet because of the presence of methane in its atmosphere. Uranus is also a giant planet. It revolves around the Sun in a horizontal manner. This is the only planet which was found by accident. William Herschel was pointing his telescope at a star when he discovered Uranus at random. It is named after Greek god of the sky.


*           Neptune


Look at the following picture of the planet Neptune:

The size of the Neptune is smaller than that of the Uranus. Neptune is the last planet in the solar system and its only moon triton has cool surface. Fast wind and storm blow across the planet, Neptune.    





     Which one of the following is the biggest planet of our solar system?

(a) Mars

(b) Jupiter

(c) Saturn

(d) Earth

(e) None of these


Answer: (b)


Jupiter is the biggest planet of our solar system. Therefore, option (b) is correct and rest of the options is incorrect.  



     On 24th august 2006, one of the planets from the solar system has been demoted from the status of a planet by IAU. Name the planet.

(a) Earth

(b) Neptune

(c) Saturn

(d) Pluto

(e) Mars


Answer: (d)


Pluto is demoted because ft is too small even smaller than Russia.

Therefore, option (d) is correct and rest of the options is incorrect..

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