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Introduction: The Earth in the Universe

Subject: Science

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Overview

The Milky Way galaxy is a medium sized galaxy, which consists of about 150 billion of stars. Pluto was removed from the planet as it was not massive (large) enough to become a planet and it crossed the path of Neptune. This note gives us more information about the universe and solar system.
Introduction: The Earth in the Universe

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.

Things to remember
  • 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. 
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
Videos for Introduction: The Earth in the Universe
Planets in our solar system | Sun and solar system | Solar System for children | 8 planets elearnin
Spaceship Earth - An animated documentary of how Earth works 1/52
Questions and 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.

In Greek, the meaning of planet is 'wanderer'.

Planets hare heavenly masses or bodies that do not have their own light an also revolves around the sun.

A satellite is a heavenly body which is revolving round a planet in its own orbit. The types of satellites are natural satellite and artificial satellite.

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 groups of stars forming a fixed shape or pattern which do not change their position with respect to each other are called constellations. Till now, 88 constellations are known.

The distance travelled by light in 1 second is called light second. Light can travel 3.0 x 108 m distance in one second.

The distance travelled by light in 1 hour is called light hour. Light can travel 1.08 x 1012 m distance in 1 hour.

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

The time taken by the planet to complete one rotation on its own axis is one day or solar day of planets.

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.

When we observe the sky at night, we can see the tailed structure revolving round the sun. The broom shaped shining objects with bright head is called comet.

The rock and metal objects which are present between the orbits of mars and jupiter and revolves round the sun are called asteroids or minor planets.

The head part of the comet is made up of ice, this head part is called coma.

When a neutron, star moves very fast radiating radio wave, it is called pulsar.

The pieces of stone or metal which enters the earth's surface are called meteors.

Sometimes, the big meteors do not burn completely and may reach the surface of the earth. This object is called meteorite.

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.

Very big and dizzling meteorites are called fire balls.

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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