Geo Chap-1 Structure of Solar System keypoints
Universe
Ø Heavenly
bodies or Celestial bodies-The
Sun, The Moon, The Stars.
Ø includes stars, planets, satellites, asteroids,
meteoroids and comets.
Ø Universe was formed due to a cosmic explosion The BIG BANG, led to the
formation of giant clouds of gases and dust particles called nebulae.
Ø Within each nebulae, particles or atoms collided
with one another at tremendous speed.
Ø Generation of enormous heat and led to formation
of glowing bodies known as
STARS.
STARS
Ø
self luminous
celestial bodies that emits light and heat.
Ø
When these stars
are found in a very large group or cluster, they form GALAXIES.
Ø
Billions of stars
with gas and dust and held together by gravitational attraction.
Ø
Universe is made
up of infinite galaxies and still expanding because every moment new stars are
being born.
Ø
Our solar system
is a part of galaxy called MILKYWAY
or AKASHGANGA.
Constellations
Ø
Astronomers have
joined stars with imaginery lines giving them a definite shape.
Ø
Group of stars
forming recognisable patterns are called CONSTELLATIONS.
Ø
Two easily
recognisable constellations-URSA
MAJOR (GREAT BEAR) and ORION
(HUNTER).
Ø
Others are CANIS MAJOR (THE GREAT DOG), LEO (THE
LION), TAURUS (THE BULL).
Ø
THE NORTH STAR indicates the north direction. Also known as POLE STAR .Remains in same
position in the sky.
The Solar System
Ø Family of
Sun is called Solar System.
Ø Word Solar is derived from latin word 'Sol'
means Sun.
Ø 4.6 billion yrs old.
Ø Our solar system consists of one sun, planets,
satellites & some celestial bodies known as asteroids, meteoroids, comets.
The SUN
Ø
Head of Solar
system.
Ø
Huge ball of fire.
Ø
Made up of hot
gases mainly helium & hydrogen.
Ø
About 150 km away
from earth.
Ø
Diameter-109 times
and mass 3,33,000 times of earth.
Ø
Light reaches from
sun to earth in 8 min 20 secs.
Ø
Because of
gravitational pull Sun holds earth and other planets in their fix orbit.
Ø
Main source of
heat and light for all life forms.
The Planets
Ø Derived from Greek word 'planetia' means
wanderer.
Ø Non luminuous, don't produce light of their own
but reflects sun's light.
Ø Rotation- Planet spins on its own axis.
Ø Revolution-One complete movement of planet around the sun
in its fixed orbit.
Ø Inner planets- Mercury,Venus,Earth & Mars.
Ø Outer planets- Jupiter, Saturn, Uranus, Neptune.
Criteria for planets-
Ø
Celestial body
orbits around the Sun.
Ø
Have sufficient
mass that is its own gravity pulls it
into a roughly spherical shape.
Ø
cleared neighbourhood
around its orbit. Became gravitationally dominant. No other bodies of
comparable size other than its own satellites or those under its gravitational
influence.
The Earth- A unique planet
Ø 3rd nearest planet of solar system.
Ø Shape of earth is nor perfect sphere.
Ø Flattened from poles and bulge in middle-Geoid shape.
Ø 2/3rd of earth is covered with water. So it is
called 'Blue Planet'.
Ø Water is available in 3 states- solid, liquid and gas.
Favourable conditions
Ø Earth is optimum distance from Sun. Neither too
hot nor too cold.
Ø surrounded by blanket /cover of air composed of
life supporting gases such as oxygen, Co2, nitrogen etc.
Ø Ozone layer present in atmosphere protects from
harmful ultra violet radiations.
Ø Presence of adequate amount of water favours the
evolution of life.
Ø Suitable seasons and weather conditions also
supports existence of life.
Moon
Ø
A natural
satellite revolves around a planet.
Ø
Earth has only one
natural satellite.
Ø
Moon's diam. is
earth's 1/4
Ø
Distance -3,84,400
km away.
Ø
Completes one
revolution in 27 days and 8 hrs.
Ø
Time taken of
rotation and revolution is same, thats why we see only one side of moon from
earth.
Ø
Moon is non luminous . Moonlight is the light
of Sun reflected by moon.
Phases of Moon
Ø When the moon appears to be growing,
it is called the waxing period; and when its shape appears to be reducing, it is
called the waning period.
Ø The first visible phase of the moon is the crescent phase.
Ø Then, the moon grows till half of it is visible
and this is called the first quarter
phase.
Ø The day when the moon looks like a full disc in
the sky, it is the full moon day or Purnima.
Ø In between the first quarter and the full moon
phase, lies the gibbous phase (waxing).
Ø From then onwards, the moon starts disappearing
slowly every day and after 15 days, it disappears completely.
Ø Before disappearing completely, the moon passes
through the gibbous phase (waning) and
reaches the last quarter phase and the crescent
(waning) phase.
Ø When the side of the moon that we can see from
the earth does not receive sunlight, we cannot see the moon. This day is known
as the new moon day or Amavasya.
Eclipses
Ø The Sun, a luminous body casts a
shadow
of opaque body in its path of
light.
Ø
Formation of
shadow is known as
Eclipse.
Ø
Two types of
eclipses- Lunar eclipse
and Solar Eclipse.
Lunar
Eclipse
Ø Moon, Earth and Sun comes in a
straight line.
Ø
When Earth in
between Sun and
Moon, the shadow of earth falls on
moon is Lunar eclipse.
Solar
Eclipse
Ø Sun, Moon and Earth comes in a
straight line .
Ø
Moon in between Earth
and Sun, the
shadow of moon falls on a portion of
Earth's surface is Solar Eclipse.
Asteroids
Ø Also known as Planetoids because scientists believe that these are parts of
planets which exploded millions of years ago.
Ø These are celestial bodies which revolve around
the Sun between orbit of Mars and Jupiter.
Meteoroids
Ø
Pieces of rocks
moving with high speed around the Sun.
Ø
On entering
earth's atmosphere, they produce heat and begin to glow and are known as Meteors or Shooting stars.
Ø
Most meteors burnt
out, but some do not completely & fall on earth's surface causing huge
dents or craters. Rocks fragments are called Meteorites.
Ø
Ex- Arizona USA
Comets
Ø Huge lumps made of snow and rocky dust.
Ø
When reached near
the Sun, heat up and start glowing and developing long tail.
Ø
Comets follow its
own elliptical orbit around the Sun.
Ø
Comets are
Periodical and Non periodical.
Ø Most famous comet-Halley's Comet, every 76 yrs.
Last seen in 1986.
