Stars and solar system
Celestial objects :- the moon is the brightest object in the night sky. The stars, the planets, the moon and many other objects in the sky are called celestial objects.
Astronomy :- the study of celestial objects and associated phenomena is called astronomy.
The moon :- the day on which the voltage of the moon is visible is known as the full moon day.
There after, every night the size of the bright part of the moon appears to become thinner and thinner. On the 15th day the moon is not visible. This day is known as 'New moon day'. The Next day only a small portion of the moon appears in the sky. This is known as the 'crescent moon'.
** The various shapes of the bright part of the moon as seen during a month are called phases of the moon.
** The time period between one full moon to the next full moon is slightly longer than 29 days.
** The moon revolves around the earth. The earth along with the moon revolved around the sun.
** The moon completes one rotation on its Axis as it completes one revolution around the earth.
The moon surface :- the moon surface is dusty and Barren. There are many creators of different size. It also has a large number of steep and high mountains.
The moon has no atmosphere, it has no water.
The star :- there is a large number of stars in the sky. The sun is also a star.
** Stars appear to move from east to west.
** The pole star appears to be stationary from the earth, because of it is situated close to the direction of the axis of rotation of the earth.
** Large distance are expressed in a unit known as light year.
Constellations :- the star forming a group that has a recognisable shape is called constellations.
Constellations appear to move from east to west as Earth rotates from west to east.
Ex Ursa major, Leo major, great bear, orion etc.
Orion :- It is another well known constellation that can be seen during winter in the late evening. It is also called the hunter.
* The star Sirius, which is the brightest star in the sky is located close to Orion.
Cassiopeia :- it is another prominent constellation in the Northern sky. It is visible during winter in the early part of the night.
The solar system :- The sun and the celestial bodies which revolve around it form solar system.
It consists of large number of bodies such as planets, comets, asteroids and meteors.
The gravitational attraction between the sun and these objects keeps them revolving around it.
* The eight planets in their order of distance from the sun are mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
The Sun :- It is nearest star from us. It is continuously emitting uuge amounts of heat and light. The sun is the source of almost all energy on the earth.
The planets :- The planets look like stars, but they do not have light of their own. They merely reflect the sunlight that falls on them.
A planet has a define path in which is revolves around the sun is called orbit.
** The period of revolution increase as the distance of the planet increase from the Sun.
** Beside revolving around the sun. A planet also rotates on its own axis like a top.
** The earth can be said to be satellite of the Sun, though generally we call it a planet of the Sun.
Mercury :- It is nearest to the sun. It is smallest planet of our solar system. Because it is very close to the sun.
Venus :- It is earth's nearest planetary neighbours. It is the brightest planet in the night sky.
* Venus has no moon or satellite of its own.
* It is rotate from east to west while the Earth rotates from west to east.
The earth :- It is only planet in the solar system on which life is known to exist. Some special environmental conditions are responsible for the existence and continuation of life on the earth. These include just the right distance from the Sun, so that it has the right temperature range, the presence of water and suitable atmosphere and a blanket of ozone.
* From space, the earth appears blue green due to the reflection of light from water and land mass on its surface.
* The earth has only one moon.
Mars :- The first outside the orbital of the Earth is Mars. It appear slightly reddish and therefore it is also called the red planet. Mars has two small natural satellites.
* ISRO (Indian space research organisation) launched India's first Mars orbiter mission. Mangalyaan on 5 November 2013.
Jupiter :- It is largest planet of the solar system. It rotate very rapidly on its axis.
* It has a large number of satellites. It also has faint rings around it.
* It is so large that about 1,300 earth can be placed inside these giant planet.
Saturn :- It appear yellow in colour, it has beautiful rings around it. These rings not visible with the naked eye. It also has large number of satellites.
* It is the least dense among all the planets.
Uranus and Neptune :-These are the outermost planet of the solar system. They can be seen only with the help of large telescope like Venus. Uranus also rotates from east to west.
* The first for planets mercury, Venus, Earth and Mars are much nearer to the sun than other for planets. So they are called the inner planets.
* The planets outside the orbit of Mars namely Jupiter, Saturn, Uranus and Neptune are much further off then the inner planets. They are called outer planets.
Some other member of solar system :-
Asteroids :- There is large gap in between the orbits of Mars and Jupiter. This gap is occupied by a large number of small objects that revolve around the sun, these are called asteroids.
Comets :- It is also member of our solar system. They revolve around the sun is highly e elliptical orbits. A comets appear generally as a bright head with a long tail. The tail of comet is always directed away from the Sun.
Meteors and meteorites :- Meteor is a brief streak of light in the night sky caused by a materoid. Small meteors melt and burn up creating streaks of light. Few meteoroids which survive as they pass through the earth's atmosphere and reach the Earth's surface are called meteorites.
Artificial satellite :- man made objects sent into space to orbit of the earth.
Ex. IRS, EDUSET, INSAR etc.
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