Class 9 Science Note
The Earth in the Universe
Universe is a huge space which contains everything that exists including solar system, constellations, Galaxies etc.
Constellations are the group of stars having fixed shapes. Examples: Aries, Cancer, Aquarius, Leo, Libra etc.
Galaxy is the system of stars that consists star, star clusters, dust and gases held together by gravity.
Solar system is composed of the sun, eight planets including the earth, satellites, asteroids, comets, meteorites etc. The distance in the space is measured in the term of light year.
Planets are the heavenly bodies which revolve around the sun in elliptical path without being intersected by path of other planets.
There are major eight planets in the solar system. They are: Mercury Venus Earth Mars Jupiter, Saturn, Uranus and Neptune.
The closest planet and the farthest planet from the sun is mercury and Neptune respectively
Mercury is the fast rotating planet. Venus is the brightest planet. Mars is red planet. Jupiter is the largest planet. Earth is the only one planet where the life is possible.
Motion of earth
The earth revolves around the sun which is called revolution of the earth. The revolution of the earth causes the changes in the season. Earth takes 365.5 days to complete one rotation. It also rotates about its own axis which causes the change in day and night. To complete its one rotation about its own axis, it takes 23 hours 50 minutes and 4 sec.
When the earth comes in between the sun and the moon and they lie in a straight line, the shadow of the moon falls on the moon. At this stage, we cannot see the moon and this phenomenon is known as lunar eclipse.
The solar eclipse occurs when the moon comes in between the earth and the sun and in a straight line and the shadow of the moon falls on the surface of the earth.