The Earth and the Solar System
STD: VI
Knowing about the universe
• All the objects we see
in the sky are called
heavenly bodies or
celestial bodies.
• They include the
stars, planets,
satellites, asteroids,
meteors and comets.
The Universe
Universe means everything that exists in space.
Nobody knows how universe was formed.
Most scientist believe that 2000 crore years ago
universe was formed
by
.
Universe is very vast.
No ordinary units can measure the distance
between two heavenly bodies. Thus,
astronomers have come up with a special unit
called
.
Galaxies
Universe has countless galaxies.
Galaxy means a collection of billion stars, gas and
dust.
Each galaxy vary in size, shape and brightness.
The sun & all stars belong to a galaxy known as the
or the Akash Ganga.
It has about 10,000 crore stars.
Stars
They are formed from the clouds of gas & dust
in space called
Stars
The Sun is also a star. It looks big as it is closer to
the earth.
The other nearest star to the earth is
It is more than 4.24 light years away.
Members of the Solar System
The word ‘solar’ comes from the Latin word ‘sol’
meaning ‘Sun’.
Family of the Sun is called as the solar system.
It consist of the Sun, eight planets and their
satellites, numerous asteroids, meteors &
comets.
The Sun
Largest member of the solar system.
Located in the center..
A huge ball of gases.
It is the main source of light & heat on the
Earth.
Is about 15 crore km away.
Temperature 6000 *C.
Light from the Sun takes about 8 minutes & 20
seconds to reach the Earth.
The Planets
There are eight planets.
Increasing distance from the Sun: Mercury,
Venus, Earth, Mars, Jupiter, Saturn, Uranus &
Neptune.
Decreasing size: Jupiter, Saturn, Uranus,
Neptune, Earth, Venus, Mars & Mercury.
The inner planets (terrestrial) & the outer
planets(gas giants).
Mercury
It is named after the
messenger of the
Roman gods.
Temperature:
Day: about 400 *C
Night: about -170 *C
Venus
Named after Roman god
of love & beauty.
Its almost the same size
as the Earth known as
Earth’s twin.
It shines brightly & is
seen before sunrise as
Morning star & after
sunset as the evening
star.
Earth
It is the largest among the
inner planets.
It is the only planet
to support life.
Also called as the
Blue planet.
Mars
It is named after the
Roman god of war.
It is known as the Red
planet.
It is about half the size
of earth.
Its rotational period is
same as the Earth.
Jupiter
It is named after the
ruler of the Roman
gods.
Jupiter, with its moons,
is described as a mini
solar system by NASA.
Saturn
It is named after
Jupiter’s father in
Roman mythology.
It has bright rings
around its equator.
Uranus
It is named after the
Greek god of sky.
It also has rings around its
equator.
Neptune
It is named after the
Roman god of the sea.
It is similar to Uranus in
size & structure.
The two are called twin
giants.
Satellites
It means an attendant or a companion.
They revolve around the planets from west to
east.
They do not have their light & reflect the light
of the sun.
Until 1610, moon is the only satellite.
Today, there are more than 150 known
satellite.
Mercury & Venus do not have any satellite.
The Moon
It is the closest celestial body to the Earth.
The Sun & the Moon appear to be of the
same size, although the Sun is much bigger.
The Moon is closer. It is about 3,84,400km
away from the Earth.
No life exist there because it neither has
water nor an atmosphere.
Phases of the Moon
Moon reflects the light
of the sun thus, the
visible shape of the
Moon changes from
night to night.
The waxing & waning of
the Moon is known as
the phases of the
Moon.
Phases of the Moon
In its journey from
full moon to new
moon, its visibility
decreases and the
Moon is said to
.
From new moon to
full moon, the visible
portion increases and
the Moon is said to
.
Phases of the Moon
The Moon is always half dark & half bright.
The angle of view from the Earth keeps changing.
On the new moon day the dark hemisphere of
the Moon faces the Earth & on the full moon day
the bright hemisphere is visible to us.
Asteroids
These are small planet like objects also called as
planetoids or minor planets.
Each asteroid follows its own orbit around the Sun.
Billions of asteroids between Mars & Jupiter.
It is believed that asteroids are some broken pieces
of some planets, which exploded soon after their
birth.
Comets
Comets are huge lumps of snow &
rocky dust.
Revolve around the Sun in large
elliptical orbits.
When it reaches close to the Sun its
starts glowing & develops a long
tail.
The most famous comet- Halley’s
comet.
It comes near the Earth every 76
years.
Meteors
Meteors are also known as shooting stars.
These are small pieces of rocks and dust revolving
around the Sun.
Their presence is known only when they enter the
Earth’s atmosphere.
Most of them burn up & disappear as gases.
Some are big & thus they do not burn up
completely.
They strike the Earth & are known
as meteorites.