Download The Sun Our sun is a star. It is the star we see in the daytime. It is the

The Sun
Our sun is a star. It is the star we see in the daytime. It is the center of our solar system. The sun
is so big that more than a million Earths would fit inside it. It looks small because it is so far
from Earth. Like all stars, our sun is a ball of very hot gases. It gives off light and heat. The sun
makes energy in its center. Huge explosions take place, releasing energy. The outside layer of
the sun is boiling gases. This is why the sun looks like a ball of fire. We couldn’t live without
the sun. It gives us heat to stay warm and gives us light to see by. Plants need the sunlight too. It
helps plants make food for us to eat and oxygen for us to breathe.
The Eight Planets
In ancient times, people did not have telescopes. When they wanted to know what’s there in the
sky, they had just their eyes to use. They could only see the objects close to Earth. When
telescopes were invented, astronomers could see much more. In 1977, some special spaceships
(Voyager 1 and Voyager 2) were sent into space to get information about the far-off planets.
Now the astronomers have discovered that eight planets are orbiting around the sun. The planets
are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Our planet earth is the
third one from the sun. Pluto has been known as the ninth planet of our solar system since it was
discovered in 1930. However, Pluto is different from other planets (it is smaller than Earth’s
Moon). In 2006, the International Astronomical Union re-classified Pluto as a "dwarf planet".
1. Mercury
Mercury is the nearest planet to the Sun and is also the smallest, except for Pluto. It can be seen
for a short time just before sunrise or after sunset because it is so close to the Sun. Mercury has
almost no atmosphere. With no air, and no clouds, the weather forecast on Mercury would be
very simple: unbearably hot by day and freezing cold at night.
about the Mercury
A year on Mercury is as long as
88 days on Earth
A day on Mercury is as long as
58.6 days on Earth
Average surface temperature
117 °C day / -170 °C night
Number of moons
0
Average distance from the Sun
58 million km
2. Venus
Venus is easy to see in the sky because it is very bright – only the Sun and Moon are brighter
than Venus. The thick atmosphere makes Venus a very dangerous place to explore. This is
because it mainly consists of a gas called carbon dioxide; which we cannot breathe. It also traps
the heat so that Venus is even hotter than Mercury.
Days on Venus seem endless. Venus is the second planet from the Sun. One day on Venus is as
long as 243 days on Earth. A year on Venus is only 225 Earth days long. So a day on Venus is
longer than a year!
about the Venus
Average distance from the Sun
108 million km
A year on Venus is as long as
225 days on Earth
A day on Venus is as long as
243 days on Earth
Average surface temperature
457 °C
Number of moons
0
3. Earth
Earth is the third planet from the Sun. It is the only planet that has water on the surface — about
two-thirds of the Earth is covered with oceans of water. In colder parts the water freezes into ice
and there are droplets of water in the clouds. Earth was formed 4.5 billion years ago. When
Earth was formed, it too had a dense atmosphere of carbon dioxide just like Venus.
about the Earth
Average distance from the Sun
150 million km
A year on Earth is as long as
365 days on Earth
A day on Earth is as long as
24 hours on Earth
Average surface temperature
15 °C
Number of moons
1
4. Mars
Mars has a thin and wispy atmosphere made almost entirely of carbon dioxide. At the north and
south poles of Mars there are ice-caps. This kind of ice is known as dry ice (made up of frozen
carbon dioxide). The surface of Mars is a stony desert with sand that is so tiny that you would
need a microscope to see them. The winds of Mars easily stir up vast dust storms, which cause
the pinkish glow in its sky.
about the Mars
Average distance from the Sun
249,2 million km
A year on Mars is as long as
687 days
A day on Mars is as long as
24.6 hours
Average surface temperature
-63.35 °C
Number of moons
2
5. Jupiter
Jupiter is not a solid planet. Unlike the four rocky planets closest to the Sun, Jupiter is a huge
ball of gas. Jupiter rotates very rapidly, once every 10 hours. This is so fast that the planet
bulges at the equator. The rapid rotation also causes high wind speeds in the upper atmosphere,
where the clouds are stretched out into colorful bands. Different parts rotate at slightly different
rates, and these speed differences causes the bands.
about the Jupiter
Average distance from the Sun
778 million km
A year on Jupiter is as long as
11.9 years on Earth
A day on Jupiter is as long as
9 hours 50 minutes
Average surface temperature
14.85 °C - 19.85°C
Number of moons
63
6. Saturn
Saturn is the sixth planet from our Sun. The rings around the planet are made up of millions of
bits of ice and rock. Saturn is a frozen world, with a cloud and wind system similar to Jupiter.
Saturn’s beautiful rings do not touch the planet. The rings are tilted at an angle of 29°. This
means that they slowly change their appearance when viewed from Earth. The rings are mainly
made of billions of tiny particles and each particle is orbiting Saturn! They all orbit the planet as
if they were wandering satellites.
about the Saturn
Average distance from the Sun
1,457 million km
A year on Saturn is as long as
29.5 years on Earth
A day on Saturn is as long as
10 hours 39 minutes
Average surface temperature
-139.15 °C
Number of moons
46
7. Uranus
Uranus is mainly made of hydrogen and helium, but one-seventh of its atmosphere is methane.
This gas makes it appear bluish in a larger telescope. The axis of Uranus is tilted by more than a
right angle, which means its north pole actually points below the planet’s orbit. This gives
Uranus rather strange seasons. One pole faces the Sun and has a constant sunlight for about 40
years. This end of the planet then goes into complete darkness for about another 40 years while
the other pole of the planet faces the Sun.
about the Uranus
Average distance from the Sun
2,870 million km
A year on Uranus is as long as
84 years on Earth
A day on Uranus is as long as
17 hours 14 minutes on Earth
Average surface temperature
-197.15 °C
Number of moons
47
8. Neptune
You could not breathe on Neptune, and the fierce winds would blow you away. Even without
the winds, you could not walk on Neptune because the planet has no solid surface. A thick layer
of clouds surrounds Neptune. The clouds are part of the planet’s atmosphere. Neptune’s
atmosphere is made mostly of hydrogen and helium gases. Some methane gas high in the
atmosphere gives Neptune its bluish color. You could not breathe the gases in Neptune’s
atmosphere. There is no oxygen in Neptune’s atmosphere. Neptune has the fastest winds in the
solar system. The winds on Neptune can blow at 1,200 miles per hour.
about the Neptune
Average distance from the Sun
4,498 million km
A year on Neptune is as long as
164 years on Earth
A day on Neptune is as long as
19 hours 3 minutes on Earth
Average surface temperature
-200 °C
Number of moons
8
Pluto
Our Sun would look like a small dot of light if you were standing on the surface of Pluto. But
Pluto is so far away that no spacecraft has ever visited it. Pluto is the “dwarf planet” (tiny) in
our solar system. It is farthest of all other planets. It is the smallest of all the planets. Its size is
smaller than even our Moon. Astronomers know less about Pluto than about any other planet.
This is because no spacecraft could ever reach the Pluto.
about the Pluto
Average distance from the Sun
5,906 million km
A year on Pluto is as long as
248 years
A day on Pluto is as long as
6 days 9 hours
Average surface temperature
-215.35 °C
Number of moons
1
ASTEROIDS, COMETS, AND DUST
There are thousands of asteroids in the solar system. Asteroids are small pieces of rock and
metal. Most of them orbit the Sun between Mars and Jupiter. Asteroids that crash into Earth are
called meteors. Sometimes they burn up as they fall toward Earth. They make tails of light in
the night sky. Pieces that land on the ground are called meteorites.
Comets are another type of object in the solar system. Comets are like dirty snowballs. They are
made of ice and dust. Comets are usually far out in the solar system. Sometimes a comet comes
in close to the Sun. When it comes in close, the comet starts to melt and looks like it has a long
tail streaming out behind it. In 1994 pieces of a comet called Shoemaker-Levy 9 crashed into
Jupiter. The crash made huge explosions and sent up fireballs that were larger than Earth.
The geocentric system was the first model of our solar system-dating back to the ancient times.
This model predicted a earth-centered system hence geocentric and it was the most favorable
until about the late 15 hundreds. However some astronomers were not concurring to the
geocentric model, in the light of that a guy known as Nicolaus Copernicus devised a secret (this
was against the teachings of the church and it was death punishable) heliocentric system with
the sun at the center of our solar system and that was later mastered by Galileo and Kepler.
Some Facts about this
1) Copernicus publish this model on his bed of death
2) Galileo was held under house arrest for the last 10 years of his life for publishing the
heliocentric system.
The word "helios" in Greek means "sun." Heliocentric means that the sun is at the center. A
heliocentric system is one in which the planets revolve around a fixed sun. Thus
Mercury, Venus, the Earth, Mars, Jupiter and Saturn all revolve around the sun. This theory was
first proposed by Nicolaus Copernicus.