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The Solar System

The limitless expiries of space around usconsisting of solar system empty space (97%), Stars, Nebulae, Galaxies etc… is called the (Universe= cosmos) + logos = Science(Cosmology)
The study of Universe is known as Cosmology
The sun, the moon, there objects shining in the night Sky are called celestial bodies.

Astronomy: The science which deals with the nature and motion of celestial bodies is called astronomy.

Galaxies:A galaxy is a large group ofstars, dust and gas held together by natural gravitational forces.
  • Thy are about 100 billion (1011) galaxies in the universe.
  • Milky way or Akasha ganga is one such galaxy in which we liven The milky way is a galaxy containing as many as 1,00,000 stars.
  • The sun is a medium sized star in the milky way galaxy.
  • There are millions of such galaxies in the universe which can be seen through large telescope.
  • Each galaxy has on average 100 billionsstars (1011stars)

  • Some celestial bodies are made up of gases and firely luminous.
  • They have their own heat and light, which they emit in large amounts. There celestial bodies are called stars.
  • The Universe is commonly defined as the totality of everything that exits, including all the physical matter and energy, the planets, stars, galaxies.
  • Our sun is one of the nearest stars that Weser. It’s light reaches the Earth 8.3minutes.
  • The star continuously emit energy in the form of light and heat and the planet receives that energy. The Earth on which we live is a planet.
  • The Sun is the nearest star to the Earth .
  • ‘Proxima centauri’ is the second nearest star in the Universe to the Earth.
  • Hydra galaxy is the biggest galaxy in the universe.
  • Nearest galaxy to the milky way galaxy is the ‘Andromedha’nMilky way shape is spiral
  • Brightest star in the Universe- Series ‘A’(Dog star)
  • Biggest star in the Universe- Betting Links
  • In stars- Hydrogen (71%),  Helium(26.5%)
  • Stars are born in Nebulae. A nebulae is a cloud of gas (Hydrogen) and dust in space.
  • Huge clouds of dust and gas collapse under gravitational forces, forming stars.
  • The study of universe on a ground scale is called ‘Cosmology’.

A light year
  • It is the distance covered by light on one year in vacuum travelling at a speed of 29,97,925 Km/sec
  • A light year distance= 9.3 ×1012km
  • One Astronomical Unit (IAU) represents the mean distance between the sun and the Earth.
  • IAU= 1,49,60,000 km
  • One per sec (IPS) = 3.26 ×light years. To measure in between sun and earth distance. Origin of Universe
  • Geocentric theory is proposed by‘ ptolemy’ in 149 AD. Which states that the earth is centre of Universe.
  • Heliocentric theory proposed by Copernicus in AD 1456, according to which the sun is the centre of the Universe.
  • In 1805, British astronomer ‘Herschel’studied Universe with the help of telescope and stated that the solar system is merely small part of a galaxy (milky way).
  • An American astronomer ‘Edin p Hubble’ in 1925 said that the Universe has a diameter of 2.5 billion light-year and is composed of several galaxies

The sun and bodies revolving around it,which includes 8 planets, number of satellites, comets, asteroids meteors,together constitute ‘the solar system’ The solar system formed from cloud of dust and gas or nebula, about 4.6 billion years ago.
The sun:It is the nearest star that we can see.
  • It contains 71 % hydrogen and 26 %helium by mars.
  • The sun is about 150 million kms away from the earth.
  • The light of the sun takes about 8.3minutes to reach the earth.
  • The sun takes 250 million years to complete one revolution around the center. This period in now called a Cosmic year.
  • Sun is mainly composed of hydrogen. It’s energy is generated by nuclear fusion.

Structure of Sun::  Dived in to 4 parts.

Centre:The pert of the sun is smallest.
  • Sun is composed of hydrogen.
  • Sun energy is generated in this part.

The photo sphere:The part of the sun,that we can see is known as photosphere. The temperature at the photosphere is about 60000c

The chromosphere:It is the third outer most layer of sun’s atmosphere which isonly visible at the morning and evening time in the colour of bright red. The temperature at on this part is about320000c On this black lines are called ‘fraunhoferlines’.

The carona:The outer most part of sunwhich is visible only at the time of a solar eclipse is known as carona.
The temperature at the carona is about 2,70,0000c
Planets:: Planets, which are revolving around the sun and does not emit its own light. But reflects some of the incident light of the sun.
  • There are 8 planets, which are revolving around the sun in elliptical path known as orbits.
  • In order of 8 plants of their distance from the sun, they are Mercury (5.1/3500c),Venus (5.3/4750c), Earth (5.4/200c), Mars(3.9/-500c), Jupiter (1.3/1200c), Saturn(0.7/-1800c), Uranus (1.5/-1280c), Neptune(2.2/-2280c).
  • In order of their decreasing sizes…Jupiter> Saturn > Uranus > Neptune >Earth > Venus > Mars > Mercury.
  • The inner planets are Mercury, Venus,Earth, Mars. There are small in size.
  • The outer planets are Jupiter, Saturn,Uranus, Neptune. There are large in size.

Mercury:: It is the closest planet to the sun. It completes one revolution around the sun in 88 days.
  • It is fastest revolution in the solar system.
  • It is the smallest planet.
  • It has no satellite.

Satellites: There are small bodies, which rotate on their axis and revolve around the planets.
  • There is no atmosphere and  water on the surface of the mercury and hence there is no possibility to life on this planet. 
  • It is called as ‘Apollo’
  • It takes one rotation on the axis 176 days. Venus
  • It is a second planet of the solar system next to the mercury in order of increasing distance from the sun.
  • It is the brightest planet of solar system and also know as morning star and evening star.
  • It is mars, density and radius are comparable to those of earth. Hence, it is called earth’s twin.
  • It has no satellite.
  • It is the hottest planet and nearest planet to earth.
  • On this planet you would find that it rotation its axis from east to west.
  • The day and night temperature are almost the same.
  • Its atmosphere contains 90% carbon dioxide. There is no possibility of life on this planet.

Earth :: It is the third planet of the solar system.
  • It completes one revolution around the sun in 365 1/4days. 
  • The blue planet, called so because of the presence of water.
  • There is atmosphere and water on the surface of the Earth and so life is there on the earth’s surface. 
  • The distance between the sun and the earth is 149.5 m.k.m
  • It takes 8.3 minutes for the light from the sun to reach the earth.

The Moon  ::  Moon is the satellite of the Earth.
  • Moon’s distance from the Earth is 3.84 x105km
  • The gravity of moon is 1/6 x the Earth(9.8)
  • It revolves around of earth in 27days 7 hours 43 minutes and rotates on its own axis inexactly the same time.
  • The moon always keeps the same face towards the Earth.
  • There is no atmosphere and water on the moon’s surface, hence there is no possibility of life on it. 
  • Neil Armstrong and Edwin Aldrin were the first humans to set foot on the Moon’s surface in 1969 July 21. The landing spot was later called the sea of Tranquility. 
  • Earth is the densest (5.4) of all and is unique for the presence of higher forms of life.
  • Length of day – 24 days.
  • Length of year (revolution)- 365 days.

MARS::  It is a radish planet of solar 84
  • It has two satellites photos and Deimos.
  • The only possibility of life other than the earth is on this planet.
  • Mars changes colour in different seasons.
  • The Asteroids are tiny planets found between mars and Jupiter.
  • Length of day (rotation)- 24 Earth hours
  • Length of year (revolution)- 687 earth days.

JUPITER::  It is the largest planet of the solar system.
  • Jupiter is the 5th planet from the sun and first in size.
  • It is also called as the Lord of Heavens.
  • One special feature of this planet is the great Red patches planet.
  • It has 63 satellites like Europa, IO, Callisto and Ganymede (largest in solar system)
  • Length of day (rotation)- 10 Earth hour (9hour 50 minutes)
  • Length of year (Revolution)- 12 Earth year
  • The mass of Jupiter is 318 times that of Earth.
  • The Jupiter is the fourth brightest object in the sky after the sun, moon and Venus.

SATURN::  Saturn is the 5 th planet from the sun and the second largest.
  • Its satellites Titan has an atmosphere like Earth
  • It is most beautiful planet in the sky,chiefly on account of the three broad rings around it. 
  • Length of days (rotation)- 10 hours
  • Length of year (revolution)- 29 year
  • This is also called cruel planet of golden planet.

URANUS::  Uranus named after the Greek God of the sky. Is the 7th planet from the sun.
  • Uranus the first planet discovered in modern times was discovered has William Herschet on 1781nIt is called Lopsided planet and Green Planet.
  • Uranus has 21 satellites, they are Titania,oberona, miranda, etc..
  • Length of year (revolution)- 84 Earth years

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