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Introduction: The Earth in the Universe

Notes, Exercises, Videos, Tests and Things to Remember on Introduction: The Earth in the Universe

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The universe

The universe has unlimited size and unknown shape. All the existing things include galaxies, planets, satellites, comets, and meteors. The solar system is located in Milky Way galaxy. The Milky Way galaxy is a medium sized galaxy, which consists of about 150 billion of stars. Astronomers believe that there are 1012 such galaxies in the universe. Astronomical unit (AU), Lightyear (LY) and parsec are used to measure the distance in the universe.

1 AU = 1.5 × 1011 m
1 LY = 9.46 × 1015 m
1 parsec = 3.26 LY

Solar system

Only the sun is known star, which has a group, like solar family and only one planet the earth of it has suitable conditions for organisms to survive on it. The eight planets of the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Countless meteors, meteorites, and comets also revolve around the sun beside planet. Drifting particles called interplanetary dust and an electrically charged gas known as plasma exist in the space of the solar system.

According to international convention of astronomers held on 2005 AD following criteria should be fulfilled by revolving planets:

  • A planet should have its own orbit around the sun.
  • Its shape must be round.
  • Its orbit must not cross the orbit of other planets.

Pluto was removed from the planet as it crosses the orbit of Neptune.



  • The Milky Way galaxy is a medium sized galaxy, which consists of about 150 billion of stars.
  • Pluto was removed from planet as it was not massive(large) enough to become a planet and it crosses the orbit of Neptune.
  • The eight planets of the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. 
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Questions and Answers

Click on the questions below to reveal the answers

The distance travelled by a light in a year is called light year.
1 light year = 1 x 3.0 x 108 x 60 x 24 x 365 m
= 9.46 x 1015m
Therefore, 1 light year = 9.46 x 1015 m

Astronomical unit is defined as the average distance between the sun and the earth. It is used to measure the distance between two heavenly bodies in the solar system. The distance between the sun and the earth is about 1.5 x 108 km.

The spiral shaped galaxy including solar system along with other planets, comets, meteorites, constellations, etc. is called milky way galaxy. In constellation, milky way is at the center. The sun lies in the 2/3rd. length of milky way galaxy.

The universe is a huge space which contains of planets, stars, satellites, asteroids, comets and meteorites.
The system containing the sun and its family members including the earth is called solar system.

Light year is the unit to measure the distance between any two heavenly bodies.

There are eight planets in solar system. They are as follows:
i) Mercury
ii) Venus
iii) Earth
iv) Mars
v) Jupiter
vi) Saturn
vii) Uranus
viii) Neptune

Mercury and Venus don't have their own satellites.

In Greek word the meaning of planet is 'Wanderer'.

The rotation of the earth on its own axis from west to east is called diurnal motion.
The revolution of the earth around the sun is called annual motion of the earth.

In constellation, milky way is at the center. The sun lies in the rd length of the milky way.

Universe is a huge space which consists of planets, stars, satellites, asteroids, comets and meteorites.

Light year is the unit used to measure the distance between any two heavenly bodies.

There are 8 planets in the solar system. They are:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Jupiter
  6. Saturn
  7. Uranus
  8. Neptune

Mercury and Venus do not have their own satellite.

Jupiter (63 satellites) has largest number of satellites.

The heavenly bodies which have their own source of light are called stars. Stars have their own light because of the thermonuclear fission reaction in which the hydrogen gas is converted into helium at very high temperature and pressure.

The space contains billions of stars. They have different clusters or groups. These clusters of stars is called galaxy. Thus a galaxy is a vast system of stars, dust particles and gases isolated from similar system in the space.

The nearest star from our solar system is α - century. It is 2.42 light years far from the solar system.

  1. Name the gas present excess in sun = Hydrogen
  2. No of satellites of Saturn = 60
  3. largest planet = Jupiter
  4. Smallest planet = Mercury
  5. Nearest planet to sun = Mercury
  6. Planet with ring = Saturn
  7. Evening or morning star = Venus
  8. Red planet = Mars
  9. Living planet = Earth
  10. Fifth largest planet = Earth
  11. Planet with narrow ring = Saturn
  12. Time taken by moon to complete its revolution around the earth = Sideral month
  13. Distance travelled by light in one year = 1 light year
  14. Average distance between sun and the earth = Astronomical unit
  15. Inner planets = Mercury, Venus, Earth and Mars
  16. Outer planets = Jupiter, Saturn, Uranus and Neptune

There are 88 constellations known till yet. Example: Ursa major, Ursa Minor, Drecoficious, etc.

After supernova explosion, if the mass of the remaining core is three times the mass of the sun, it will contract rapidly so that gravity becomes infinite and even the light cannot escape from it. This resulting object is called black hole.

These are streak of light in the sky at night which disappears within a second. It is called shooting star or falling star. They actually are small rock fragments coming from outer space.

The moon revolves round the earth in elliptical orbit. Hence, the distance between the earth and the moon is not constant throughout the year.

It is because sun has its own light.

The solar system is formed by the combination of sun, earth, other planets, satellites, asteroids, meteors, comets and dust particles, plasma, etc.

The major purposes of launching artificial satellites in the space are as follows:

  • Communication
  • Weather forecasting
  • Surveying of natural resources
  • Military purposes
  • Study of other planets and outer space

Pluto has been removed from the category of planets because of the following reasons:

  1. It is so small than the size of other planets
  2. Its orbit crosses with the orbit of Neptune

The differences between stars and planets are as follows:
Stars Planets
The heavenly bodies which have their own source of light are called stars. The heavenly bodies which revolve round the sun and do not have their own source of light are called planets.
Stars are luminous objects Planets are non-luminous objects
They are bigger in size. They are smaller

The differences between galaxy and constellation are as follows:
Galaxy Constellation
It is the collection of billions of stars. It is the collection of limited number of stars.
It has no regular pattern. It has regular pattern
There are about 1010 galaxies in the universe. There are about 88 constellations known.

The differences between Meteors and Stars are as follows:
Meteors Stars
They are made up of stone, iron or both They are made up of gases like helium, hydrogen, etc.
They are not luminous. They are luminous

The differences between comets and meteors are as follows:
Comets Meteors
The broom shaped shining objects with bright head which is made up of ice mass is called comet. The pieces of stone or metal entering the earth's atmosphere are called meteors.
It has long glowing tail like structure It has streaks of light falling down towards earth surface

The differences between planets and asteroids are as follows:
Planets Asteroids
The heavenly bodies which revolve around the sun are planets. The heavenly bodies which revolve round the sun mainly between mars and jupiter are called asteroids.
They are bigger. They are smaller.

The planets which are present inside the asteroid belt are known as inner planets. These planets have similar structure as that of the earth. So, they are also known as terrestrial planets.

The planets which are present outside the asteroid belt are known as outer planets. These planets have similar structure as that of the Jupiter. So, they are also known as jovian planets.

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  • What is the full form of AU?

    Atomic Unit
    Astronomical unit
    Asteroids Unit
    Astronomers Union
  • 1 AU is equals to ______.

    9.46 x 1015 m


    1.49 x 1011 m


    7.5 x 100 m


    0.06 x 1015 m


  • Pluto crosses the orbit of ______.

    Neptune


    Saturn


    Jupiter


    Earth


  • A complete round around the sun is called ______.

    revolution


    evolution


    tropic of cancer


    rotation


  • 22 March is called ______.

    summer equinox


    monsoon equinox


    autumn equinox


    spring equinox


  • You scored /5


    Take test again

ASK ANY QUESTION ON Introduction: The Earth in the Universe


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Forum Time Replies Report

What is defination of persec


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Computer

Explain me in brief about the black hole?


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Rom Kandel

What should happen if the axis of the earth made an angle 0° instead of 66.5° with the plane of orbit?


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Sudaan

It is also possible that pluto can bang with other planet.We only remove it from our studuies but what about solar family.. It can harm other planets too


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