Earth and Beyond
Solar system:
Our solar system consists of the Sun and
eight planets.
The Sun:
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Sun is around 93 million miles far
away from Earth.
Sun makes 99 % of the mass in the
solar system.
The gravity of the Sun holds the solar
system together.
Sun is a ball of Helium and Hydrogen
gases.
Sun burns a million degrees in its
Centre.
1. Mercury:
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Mercury is the first planet after the Sun.
Mercury is the smallest planet.
We can see Mercury at night by naked eye.
Mercury is very hot in the day and very cold at the night.
Mercury is the fastest planet to go around the Sun. It takes 88
days to complete one orbit.
2. Venus:
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Venus is the second planet away from the Sun.
Venus is the sister of Earth as it has the same size and gravity.
Venus is the hottest planet in the solar system.
Venus’ atmosphere is made up of CO2 (Carbon-dioxide) so it is
easy for it to trap the heat.
Venus have clouds of Sulphuric acids.
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Venus is the second brightest thing in the night sky.
Venus completes one orbit in 225 days.
3. Earth:
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Earth is the third planet from the Sun.
Earth is the place where life exists.
Earth isn’t too hot or too cold, it is balanced.
Earth takes 365 days (1 year ) to orbit the Sun.
4. Mars:
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Mars is the fourth planet away from the Sun.
Mars is called the “Red planet” because Iron oxide in the soil
gives it a reddish color.
Mars is smaller than Venus and Earth but larger than Mercury.
Mars completes one orbit in 2 years.
Mars is cold and rocky.
Mars has an atmosphere made up of CO2 and oxygen.
Mars have two moons.
5. Jupiter:
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Jupiter is the fifth planet away from the Sun.
Jupiter is the largest planet in the Solar system.
Jupiter has around 67 moons.
Jupiter has the largest moon in the solar system.
Jupiter takes 12 years to orbit the Sun.
Jupiter is called the “Gas giant” because it is made up of gas.
It has the strongest storm in the solar system called “Red
spot”.
It is the third brightest planet in the solar system.
6. Saturn:
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Saturn is the sixth planet in the solar system.
Saturn has a ring around it made up of ice, rocks and dust.
Saturn is made up of gas.
Saturn has more than 60 moons.
Saturn is the least dense planet.
Saturn’s orbital period is 29 years.
7. Uranus:
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Uranus is the seventh planet in the solar system.
Uranus is made up of gas.
Uranus is smaller than Saturn and Jupiter but bigger than Earth.
Uranus actually spins sideways.
Uranus has rings around it, they are much smaller than
Saturn’s.
Uranus has around 27 moons.
Uranus has blue clouds which is made up of methane.
Uranus completes one orbit in 84 years.
8. Neptune:
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Neptune is the eighth planet from the Sun.
Neptune is made up of gas.
Neptune clouds are made up of methane which makes it blue.
Neptune color is darker than Uranus.
Neptune has few thin rings.
Neptune has 14 moons.
Neptune take over 164 years to orbit one time around the Sun.
Source: Exploring our solar system
Gravitational force:
There is a gravitational pull between all masses. Larger masses give a
stronger pull. And the further the distance away, the smaller the
gravitational pull.
The gravitational pull of Sun holds the Planets around the it in the Solar
system. As well as the gravitational pull of the Planets keep their
moons on the orbit around them.
1. Sun – Earth System:
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Different phases of Moon can be seen from Earth as the light
from the Sun reflects from the Moon.
2. Earth – Moon system:
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The Moon revolves around the Earth in 27 days.
The Moon completes only one spin (rotation) while revolving
around the Earth (It takes 27 days to spin once). This is why we
can see only one side of the Moon from the Earth.
3. Satellites:
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Satellites revolve around the planets.
Satellites must have the right speed to stay at a certain height
above planet.
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Low Satellites travel faster and Higher Satellites take longer to
complete one orbit.
A satellite above Earth takes 24 hours to orbit, so that it seems
to be stand still.
Satellites are used for different purposes:
1. Communication satellites :
- use microwaves as signals
- telephone, television, internet etc. are using
communication satellites to send signals across the world.
2. Weather satellites:
- used for weather forecasting.
3. Earth observation satellites:
- Used for taking detailed picture of Earth’s surface.
- Help in warning about forest fires and locust swarms,
show up diseased crops, hurricanes and oil leaks.
4. Military satellites:
- used for spying.
5. Navigation satellites:
- used for locating the positions in ships, cars & planes.
- GPS (Global Positioning System).
6. Astronomical satellites:
- used for taking sharper photographs outside the
Earth’s atmosphere.
- can travel to the other planets.
PRACTICE QUESTIONS :
1.
Give the time taken for (in days)
a) one rotation of Earth in its axis.
b) one rotation of Moon in its axis.
c) one orbit (revolution) of the Earth around the Sun.
d) one orbit of the Moon around the Earth.
2. In the solar system,
a) which planet has the highest surface temperature?
b) which is largest planet?
c) which planet orbits at highest speed?
d) why does Mars have a lower surface temperature than Earth?
e) which planet is the brightest in the night sky?
f) which planet is the second brightest in the night sky?
g) which planet is the lightest (least density)?
h) which planets have rings around them?
i) which planet has the lowest orbital period?
3. The diagram below shows the orbits of Earth and Venus.
a) What causes these planets to orbit the Sun?
b) Suggest why the orbital period (time) for Venus is less than that
of Earth.
c) Why Venus is called the “Sister Planet of Earth”?
4. a) What is gravitational force?
b) It is observed that, the objects with greater mass will have reater
gravitational force. What will happen to the gravitational force
between two objects if the distance between them tripled?
5. Give reasons for the following.
a) A satellite seems to be stand still above one place of Earth.
b) We can see only one side of the Moon from the Earth.