THE SOLAR SYSTEM// GENERAL KNOWLEDGE // GEOGRAPHY
● Our solar system is a part of Milky Way galaxy. In ancient
India, it was imagined to be a river
of light
flowing in the sky. Thus, it was named Akash Ganga.
● A solar system consists of a sun at the centre and the eight
planets, moons, asteroids,
comets
and meteoroids that revolve it. The gravitational attraction between the Sun
and
these objects
keeps them revolving around it.
● The sun, the moon and all those objects shining in the night
sky are called celestial bodies.
● The study of universe is known as cosmology.
● The size of the solar system has been estimated to at about
10^5 AU.
● The eight planets, namely the Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus and
Neptune,
revolve around the sun in fixed elliptical paths known as ‘orbits’.
● Pluto is a dwarf planet.
● The light-year is a unit of length used to express astronomical
distances
Sun
● The sun is in the centre of the solar system.
● The sun is the ultimate source of heat and light for the solar
system.
● The sun is about 150 million km away from the earth.
● Light takes about 8.5 minutes to reach the earth from the sun.
● Hydrogen and helium are the main gases present in the sun.
● The boundary between the Sun's interior and the solar
atmosphere is called the
photosphere.
It is the visible ‘surface’ of the Sun.
● The core is at the centre of the sun. It is the hottest region,
where the nuclear fusion
reaction
takes place to give the sun power.
● The outer layer of sun atmosphere made up of thin hot gases is
called corona. Corona is
visible
only during a total eclipse of the sun.
● Sun has a surface temperature of 6000 degree Celsius.
● The temperature at the centre of sun is around 1.5*10^7 K
Planets
The
planets are classified in order of their distance from the sun and based on
their characteristics.
They
are:
● The inner planets or terrestrial planets or rocky planets.
Mercury, Venus, Earth and Mars are
called
inner or terrestrial planets.
● The outer planets or gaseous planets or giant planets. Jupiter,
Saturn, Uranus and Neptune
are
called outer or gaseous planets.
● All the eight planets of the solar system move around the sun
in fixed paths. These paths are
elongated.
They are called orbits.
● A night planet has been recently discovered by NASA named as
Carla .
Mercury
● Mercury is nearest to the sun and it is the smallest planet in
the solar system.
● Mercury has no satellite of its own.
● It rotates on its own axis in 58.65 earth days while it takes
88 Earth days to complete one
revolution
around the sun.
● The sunlight takes 3.2 minutes to travel from the Sun to
Mercury.
● Mercury has no protective blanket like Ozone around it to
prevent us from harmful
radiations.
Venus
● Venus is the second planet in distance from the sun.
● Venus is earths nearest planetary neighbour. It is the
brightest planet.
● Venus has no moon or satellite of its own. Rotation of Venus on
its axis is somewhat
unusual.
It rotates from east to west. Only Venus and Uranus have this backwards
direction.
● It completes one rotation in 243 Earth days which is the
longest day of any planet in our
solar
system.
● The Venus takes 224.7 Earth days to complete one revolution
around the sun, and it has no
natural
satellites.
● Venus is 0.7 astronomical units away from the sun.
● Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that
of the
earth. It’s also called as ‘Earth sister’.
● Venus is known as the evening star as well as Morning star.
● Venus is hotter than Mercury because Venus has an atmosphere
which is thicker and made
almost
entirely of carbon dioxide.
● The sunlight takes 6 minutes to travel from the sun to Venus.
Earth
● The earth is the third nearest planet to the sun. In size, it
is the fifth largest planet.
● The axis of rotation of the Earth is not perpendicular to the
plane of its orbit. The Earth is
23.5 degrees
tilted on its axis and thus makes 66.5 degrees angle. The tilt is responsible
for
the
change of seasons on the Earth. The Earth has only one moon.
● The Earth rotates from west to east.
● It is also known as the ‘Blue Planet’ because of the presence of water.
● Earth has only one natural satellite called the Moon.
● The Earth takes 365.25 days to complete one revolution around
the Sun. It takes 23 hours 56 minutes and 4 seconds for the earth to complete
one rotation on its own axis.
● The sun light takes about 8.3 minutes to reach the earth.
● Earth has a protective blanket of ozone layer high up in its
atmosphere to save life from
harmful
ultraviolet radiations coming from the sun.
Mars
● Mars is the fourth nearest planet to the sun and it is the
second smallest planet in the Solar
system.
● It is also described as the “Red planet”. It is reddish in colour due to the presence of iron
oxide on
its surface.
● The landmass of Mars and Earth are very similar.
● It takes 24 hours and 37 minutes to complete one rotation on
its axis and its takes 687 days
to
complete one revolution around the Sun.
● Mars has two satellites namely Phobos and Deimos.
Jupiter
● Jupiter is the largest planet in the solar system. It is made
primarily of gases and is
therefore
known as ‘Giant Gas planet’.
● Jupiter is also known as winter planet.
● It takes 9 hours 55 minutes to complete one rotation on its
axis and it takes 11.86 years to
complete
one revolution.
● Jupiter has the shortest day in the solar system.
● Jupiter has a faint ring system around it. They are mostly
comprised of dust particles.
● Jupiter has 67 confirmed satellites orbiting the planet.
Ganymede, the satellite of Jupiter,
is the
largest natural satellite in the solar system (even bigger than the planet
Mercury).
Saturn
● Saturn is the sixth planet from the sun and the second largest
planet in the solar system.
Saturn
is called as the Ringed Planet.
● Saturn is the only planet in our solar system whose average
density is less than water.
● The Saturn has 30 rings and 53confirmed natural satellites.
● The Saturn takes 10 hours 34 minutes to complete one rotation on
its axis and it takes 29.4
years to
complete one revolution around the sun.
● Titan is Saturn’s largest moon and the second largest (after Ganymede of
Jupiter) in the
solar
system. It is the only moon in the solar system with clouds and a dense,
planet-like
atmosphere.
Uranus
● Uranus is the seventh planet from the sun and it is not visible
to the naked eye.
● Uranus rotates on its axis from east to west.
● Uranus is inclined on its axis at an angle of 98 degrees.
● Hydrogen, helium and methane are the major gases of its
atmosphere.
● It is very cold due to its great distance from the sun.
● This planet appears greenish in colour because of methane gas
present in its atmosphere.
● Uranus also has rings and twenty-seven satellites.
● Uranus is the first planet to have been discovered by the use
of telescope.
Neptune
● Neptune is the eighth planet from the sun.
● It takes 16 hours to complete one rotation on its own axis and
it takes nearly 165 years to
revolve
around the sun.
● It is the coldest planet in the Solar System because it is the
farthest planet from the Sun.
● It has 13 natural satellites and 5 rings.
● Neptune is surrounded by methane rings of sub-zero temperature.
IMPORTANT TERMS
Dwarf Planets
● Dwarf planets are tiny planets in our solar system. Any
celestial body orbiting around
the sun,
weighing for the self-gravity and nearly be round in shape is called ‘Dwarf
Planet’.
● It should not be a satellite of any planet.
● Ceres, Pluto, Heumea, Makemake and Eris are dwarf planets.
Asteroids
● Asteroids are small rocky celestial bodies that revolve around
the Sun, like other planets.
They are
also called ‘Minor Planets’.
● Larger asteroids are called Planetoids. These are found in
between the planets Mars and
Jupiter.
This belt is known as ‘Asteroid belt’.
● The diameter of the asteroids varies from 100 km to a size of a
pebble .
Comets
● They revolve around the Sun. But their orbits are irregular.
Sometimes they get very close
(Perihelion)
to the sun and in other times they go far away (Aphelion) from the sun.
● These are generally found in Kuiper Belt. They travel towards
the sun.
● The best known Comet, Halley’s Comet, appears once in every 76 years. The Halley’sComet was seen last in 1986.
Meteors
● The small pieces of rocks which move around the sun are called
meteoroids.
● They are the removed pieces of rocks mainly from the Asteroid
belt. They are called
Meteoroids
before they enter into our atmosphere.
● They enter into the atmosphere with great speed. But most of
them are burnt when they
enter
into the atmosphere.
● After entering into our atmosphere they are called as Meteors.
Some pieces do not burn
fully
and they fall on the earth and make craters.
● Examples for Meteorite Fall: Meteor crater in Northern Arizona
and Lake Lonar in Buldhana
District
of Maharashtra in India were created by meteor impacts.
Satellites
● The satellites move around a planet from West to East.
● They have no atmosphere and water.
● Number of natural Satellite in solar system
Moon:
The Earth’s Satellite
● The moon is located at a distance of 8, 84,401 km from the
earth. The moon revolves around
the
earth.
● The moon takes 27 days and 7 hours and 43 minutes for both its
rotation and revolution
around
the earth.
● The moon is the fifth largest natural satellite in the solar
system.
● The light which is reflected by the Moon will reach the Earth
in just one and a quarter
second.
● The moon is smaller than the earth and it has 1/6 of the
gravitational pull of the earth.
● Apollo 11 was the first manned mission to land on the Moon sent
by NASA.
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