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THE SOLAR SYSTEM
o
What is solar system?
o Planets
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
o The
Sun
o The
Moon
What is Solar system?
ü
The Sun +
ü The Nine Planets (Now 8) +
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The satellites of the Planets +
ü
The Asteroids +
ü The Meteoroids +
ü The Comets +
ü The interplanetary dust +
ü
Plasma (The electrically charged gases)
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The 8 (9) planets are
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Mercury
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Venus
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Earth
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Mars
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Jupiter
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Saturn
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Uranus
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Neptune
ü Pluto
(Note: The planet PLUTO lost the status of a planet in the year 2006. This is
announced by International Astronomical Union. Now, the Pluto has been named as
a dwarf planet).
According
to the new definition given by International Astronomical Union in the year
2006, a planet is a celestial body that
v is
in orbit around the sun
v as
sufficient mass for its self gravity to overcome rigid body forces so that it
assumes a hydrostatic equilibrium i.e. nearly round shape
v Has
cleared the neighborhood around its orbit
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The Planets have no light of their own.
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They take the light from the Sun.
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All the planets move on their axis from West to East direction.
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Venus and Uranus rotate on East to West direction. (Remember this).
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The planets revolve around the Sun in elliptical orbit.
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Each planet takes different time to complete the orbit round the Sun.
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Satellites revolve around the planets.
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Jupiter has 63 satellites. (Highest
number of satellites for a planet).
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Earth has only one satellite i.e. Moon.
ü Do all the
Planets have satellites?
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No, the two planets that are nearer to the Sun have no
planets.
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They are Mercury and Venus.
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Mercury and Venus have no satellites. (These are the first two planets
from the Sun).
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The Sun is at the center of the Solar system.
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The Sun is the largest body in the solar system.
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The distance of the Sun from the earth is 150,000,000 km.
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The Mercury and the Venus that are near to Sun are called inferior
planets.
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All other planets are at a greater distance from the Sun than the earth
are called superior planets.
Celestial Bodies:
v The Sun, the Moon and all objects that shine in the sky are
called celestial bodies.
v They are made up of gases and emit heat and light in large
amount.
v These are called stars.
v The SUN is a star.
v The celestial bodies that do not have heat and light and are
lit by the light of the stars are called planets.
v The word planet means Wonder.
v Billions of stars put together is called galaxy.
v Millions of such galaxies are called Universe.
v Our solar system lies in the Milky Way
v Earth is present is a galaxy is called Milky Way or
Akashaganga.
v Constellations: Group of stars is called constellations.
v The most easily recognizable constellation is the small bear
or saptarishi.
v North Star or Pole star indicates the north direction.
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Inferior Planets: Mercury and Venus
Superior Planets: Mars, Jupiter, Saturn, Uranus and Neptune.
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Inner Planets: Mercury, Venus, Earth and Mars.
Outer Planets: Jupiter, Saturn, Uranus and Neptune.
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Now
let us know more about each planet.
MERCURY:
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This is also the smallest planet in the Solar system.
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Mercury has no satellites.
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The Mercury has no atmosphere.
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Mercury is also called inferior planet.
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Mercury is one of the inner planets.
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The Mercury rotates from West to east direction.
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The Mercury takes the least time to complete the orbit round the Sun.
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The Mercury completes the orbit in 88 days.
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This means 1 year on Mercury is 88 days.
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The Mercury has craters.
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The longest crater of the Mercury is Carolis Basin.
VENUS:
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Venus has no satellites.
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Venus is considered to be the Greek God.
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The Venus is the nearest planet to the earth. (Remember).
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This rotates in the East to West direction. (Uranus also rotates in the East
to West direction and the remaining planets in West to East direction).
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Venus is considered to be earth’s twin.
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Venus is also called inferior planet.
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The Venus is one of the inner planets.
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This is also called Morning and Evening star.
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This is the brightest of all the planets.
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Venus is the hottest planet. (The surface temperature is 4000 C).
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Venus has 98% of Carbon dioxide in its atmosphere.
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The revolution of the Venus is faster than the rotation.
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Due to this Venus has long day than the years.
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This is the 3rd nearest planet to the Sun.
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The earth is also one of the inner planets. (Others being Mercury, Venus
and Mars).
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The earth contains 2/3rd of water. Hence it looks blue from
the top.
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The earth is called living planet.
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This is also called blue planet.
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This is the only known planet where the life exists.
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This is the only planet with plate tectonic observations. (What is this?
We come to know in the later chapters).
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The earth has one satellite, the Moon.
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The Sun is the nearest star to the earth.
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The brightest star near to the earth is Sun.
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The “Proxima Centuari” is the brightest star near to the earth after the
Sun.
MARS:
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This is also called Red planet.
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The red colour comes with the presence of Iron oxide in the soil.
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This is one of the inner planets.
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This is one of the superior planets. (Others being Jupiter, Saturn,
Uranus and Neptune).
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The atmosphere contains mostly Carbon dioxide.
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The Mars has volcanoes. Tharsis and Olympus
mons are the most important volcanoes of the Mars.
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The Mars has two satellites.
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They are
ü
Deimos
and
ü
Phobos.
ü The
first spacecraft to visit Mars was Mariner 4 in 1965.
ü In 2008, Phoenix was sent and it landed in
the northern plains to search for water
Asteroids:
v
These are also called planetoids.
v
These are fragments of planets.
v
Asteroids revolve around the Sun.
v
Asteroids are present between the Mars and Jupiter.
v
Ceres is the largest body in the asteroid belt.
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JUPITER:
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The Jupiter is the largest planet in the solar system.
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The Jupiter has 63 satellites.
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The 4 important satellites of the Jupiter are Ganymede, Callisto, Lo and
Europa.
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The Ganymede is the largest satellite in the solar system.
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The Ganymede is larger than the planet Mercury.
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The Jupiter is mainly composed of Hydrogen and Helium.
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Jupiter is the least rotating planet in the solar system.
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NASA (National Aeronautics and Space Administration) sent an artificial
satellite called Galileo on to Jupiter.
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The rotation time of Jupiter is 10 hours and this is the shortest of all
the planets.
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This is the second largest planet in the solar system.
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The Saturn is distinguished by extensive ring system.
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This is also called ringed planet. (This consists of golden rings around it).
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This is also called beautiful planet.
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The rings are made up of small ice and rock particles.
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The Saturn has 61 satellites.
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The two important satellites are Titan and Enceladus.
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The Titan is the only satellite with substantial atmosphere.
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Galileo Galilei was the first person to turn the Telescope towards the
Saturn in the year 1610.
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This is called the green planet.
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This is the coldest planet.
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The Uranus has 27 known satellites.
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The Uranus rotates in East to West direction.
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The important satellites are Titania, Oberon, Umbriel, Ariel, Miranda.
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The Titania is the largest satellite of Uranus.
(Note:
Only Venus and Uranus rotate in East to West direction. Remaining planets
including earth rotate in West to East direction.)
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This is the farthermost planet from the Sun.
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This is the coldest planet.
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This has 13 known satellites.
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The largest satellite is “Triton”.
THE SUN:
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The Sun is also a star.
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The Sun is the major source of energy in the World.
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The time taken for the Sun rays to reach the earth is 8 minutes.
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The Sun is divided into three layers.
·
Photosphere (Outer most layer, the temperature is 60000 C).
·
Chromo sphere (Intermediate layer, the temperature is 320000 C).
·
Corona (The innermost layer, the temperature is lakh0 C).
·
The core of the Sun is 2,700, 0000 C.
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The Corona is visible during eclipses.
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The major gas constituents of the Sun
·
Hydrogen (71 %)
·
Helium (26.5 %).
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The Sun accounts for 99.8 percent of the total mass of the Solar system.
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The Sun is 109 times bigger than the earth.
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The weight of the Sun is 2 * 10 ^ 27 tonnes.
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The Sun rotates and revolves.
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The Sun rotates on its own axis in 25 days.
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The Sun revolves in 250 million years.
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The nearest star to the Sun is “Alpha Centauri”. This is located 4.25 light years
away from the Sun.
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The expansion of the gases away from the Sun is called Solar wind.
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The distance between the Sun and the earth is called Astronomical Unit.
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Aphelion is the maximum distance of the earth from the sun. This is 152,000,000
km.
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Perihelion is the minimum distance of the earth from the Sun. This is 147,000,000
km.
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Quasars: These are the stars that emit more light and more energy.
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Pulsars: These are the stars that emit less light and less energy.
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Comets: These are formed by dust particles and hot gases. (Halley comet appears
every 76 years. It was last appeared in 1986).
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This is the satellite of the earth.
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The Moon is the only satellite of the earth.
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The Moon revolves round the earth.
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The moon also rotates on its own axis.
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The diameter of the Moon is 3480 km.
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The mass of the Moon is about 1/81th that of the earth.
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There is no
atmosphere on the moon.
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There is also no
gravitational pull on the Moon.
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The Moon light reaches the earth in 1.03 sec.
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SYNODIC MONTH: The Moon’s period of revolution with reference to the Sun is about
29.53 days. This period is called Synodic month.
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SIDEREAL MONTH: The Moon’s period of revolution about the earth with
respect to stars. This takes about 27 ½ days.
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As we discussed the Moon also rotates on its own axis. The time taken by
the Moon to rotate on its own axis is also exactly one sidereal month.
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The person from the earth always sees the same face of the Moon.
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Only 59 percent of the total surface of the moon is seen from the earth.
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APOGEE: This is the farthest distance of the Moon from the Earth. This is
407,000 km
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PERIGEE: This is the nearest distance of the Moon from the Earth. This is 3, 56,
00 km.
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