The aggregate of all existing things or the whole creation including all celestial bodies(heavenly bodies) and all of the space is called universe.The earth, the sun, the moon, etc whatever we see around us are in the universe.
It is defined as the distance traveled by the light in one year. Its value is about 9.5*10^15 m or 63066 AV. The sun takes 2.5*10^8 years to revolve around the galactic center. This time is called cosmic year.
It is defined as the distance between the sun and the earth and its value is about 1.5*1011. This unit is suitable for measuring the distance of the planets and satellites in the solar system 1AU=1.5*1011. the diameter of the solar system is about 78.1 AU.
A galaxy is a huge assembly of stars, dust and gasses, mutually held together by gravitational force. Millions of stars are present in the galaxy and the diameter of galaxy ranges from 1000 light years to one million light years. Our universe contains 10galaxies and each galaxy has about 1011 stars.
Some of the stars in the galaxy stay in a group called constellation such group of stars staying in certain patterns can be seen clearly in clear moonless night. As looking from the earth, the group of stars resembles with some animals, a group of people, some object, etc. On the basis of what they resemble, they are given different names.About 88 constellations are known sufor and 12 of them are considered as zodiac. E.g. Ursa major, Scorpio, Orion, etc.
The star is self glowing heavenly bodies which generate the energy themselves by nuclear fusion reaction. The temperature of star is very high.About 3000 stars can be seen in the sky in clear night with naked eyes.The sun is the nearest star of earth. Alpha Centauri is the nearest star to the sun.
It is a medium sized star whose surface temperature is about 6000 degree Celsius. Sun revolve around the galactic center once in 2.5 x 108 years. Sun consist of 3 layers which are photosphere, chromosphere, and corona.
Importance of sun in solar system:
i) It is the center of solar system.
ii) All the planets revolve around the sun in their own orbit. iii) It provides light to all the planet to shine as they have no light of their own. iv) It provides heat and light energy for the lives of the planets if the life
iii) It provides light to all the planet to shine as they have no light of their own. iv) It provides heat and light energy for the lives of the planets if the life
iv) It provides heat and light energy for the lives of the planets if the life exists there.
Solar system: The giant family of sun including planets, asteroids, comets etc is called solar system.The diameter of the solar system is 10.5 light hour.
Planets: In solar system, eight planets are out of them first four planets which are present inside asteroid belt are called planets.They are Mercury, Venus, Earth and mars. But the remaining four planets are out of the asteroid belt are called inner planet. They are Jupiter, Neptune, Saturn and Uranus.
Some important facts about planet: 1) Nearest planet to sun = Mercury 2) Farthest planet to sun = Neptune 3) Fastest rotating planet = Mercury 4) Morning and evening star = Venus 5) Hottest planet = Venus 6) Green planet or living planet = Earth 7) Red planet = Mars 8) Largest planet = Jupiter 9) Planet having ring = Saturn 10) Planet that can float in water = Saturn
a) Natural satellite:
They are those members of the solar system which revolve around the planets in their elliptical orbits. There are about 163 natural satellites. All the planets do not have satellites. Mercury and Venus have no satellite.Satellite are non-luminous bodies but they appear bright by reflecting the sunlight. The number of a satellite are different and are given below:
1) Mercury = 0 2) Venus = 0 3) Earth = 1 4) Mars = 2 (Phobos and Deimos) 5) Jupiter = 63 (Europa,Callisto) 6) Saturn = 60 (Titan) 7) Uranus = 27 (Miranda, Ariel) 8)Neptune = 13(Nereid)
b)Artificial satellite: An artificial satellite is made on the earth which moves continuously around the earth. The orbit of artificial satellite is elliptical and characterized by the parameters, apogee, perigee and inclination. Satellites are launched for different purposes.
Asteroid: The piece of rocks revolving around the sun between variable size and about 200 asteroids are present in a solar system. The diameter of asteroids varies from 100m to 700 km.The largest asteroid is Ceres which takes 4.6 years to revolve around the sun.
Comet: A comet is a frozen chunk of gas, dust and ice which when approaching the sun it begins to resemble a foggy star with a long shiny tail. They are block of icy rock materials and surrounded by a large mass of substance like water, ammonia, methane, etc. They make round the sun in highly elongated oval orbit, so they spend most of their time away from the sun.
Meteors and meteorites: Small pieces of rocks or metals which enter the earth atmosphere from outer space with very high speed are called Meteors. They are also called shooting star. If meteors is too big, then it will not burn completely and reach on earth. Some objects which land on the earth from the outer space are called a meteorite.
1) Formation of star: Scientist believed that stars are formed by the nebula. The nebula will make the collection of inter seller objects into various places into smaller parts. By any means, any one of the mass will develop the gravitational force and stars to attract the other patches towards itself. As a result of which its mass increases and the pressure on the circle also increases. And when the temperature of center reaches 5 x 106 degree Celsius then it is called a protostar. In protostar gradually, nuclear fusion reaction starts, due to excessive gravitational force, and it converts into stars.
2) Destruction of stars
The four differences between a star and a meteor are:
The two differences between comet and meteor are: