Download The Sun There are billions of stars that fill up our skies every night

The Sun
There are billions of stars that fill up our skies every night.
Which star do you think matters the most to the people living on Earth?
Here’s a clue! Without this star’s heat and light, life on Earth as we know it would not
exist.
We’re talking about the huge glowing ball at the center of our solar system. The Sun!
Compared to the other stars in the universe, the Sun is actually just a medium-sized
star.
However, compared to everything else in our solar system, the Sun is the largest
object.
The Sun is so large that about 1 million Earths could fit inside it easily.
Its diameter is about 10 times larger than Jupiter’s, the largest planet in the solar
system.
What are the two main elements that make up the Sun?
The Sun is made up of hydrogen and helium. But as the Sun is so hot, most of these
elements are not in their gaseous state.
Instead, the atoms of these elements break apart into smaller particles and form
plasma.
Plasma is the fourth phase of matter after solid, liquid, and gas. Just like liquid changes
into gas when heated, gas changes into plasma when it’s heated to a super high
temperature.
How does the Sun produce all this heat and light energy?
The Sun is like a huge nuclear reactor. The incredibly high temperatures at the Sun’s
core cause millions of tons of hydrogen nuclei to fuse and produce helium nuclei.
This continuous process, called nuclear fusion produces vast amounts of heat and light.
It is this energy that sustains life on Earth.
The temperature in the Sun’s core, where fusion takes place, can be as high as 15
million degrees Celsius. The density of the core of the Sun is 20 times that of metal
iron.
The radiative envelope is that part of the Sun where the energy transfers from the
super hot core to the cooler outer layers of the Sun. This zone comprises about 85%
of the Sun’s radius.
In the outer, convective envelope of the Sun, energy from the radiative zone transfers
to the surface through a process called convection.
The surface of the Sun is known as the photosphere.
Even though this region is gaseous, it is regarded as the Sun’s surface because at this
point, light from the Sun is finally able to escape into the solar system.
The Solar System
Can you guess what the temperature is like on Mercury, which is right next to the Sun?
As Mercury is right next to the Sun, temperatures on the side closest to the Sun can
get as hot as 430 degrees Celsius.
What do you think the temperature is on the darker side of Mercury?
The temperature on the side away from the Sun can get as low as minus 183 degrees
Celsius.
Even if we could withstand the extreme temperatures, we wouldn’t be able to live on
Mercury as scientists have not found any traces of water or oxygen there.
Is there water or oxygen on Venus?
Scientists have also not found any traces of water or oxygen on Venus.
Despite its similar chemical composition and density to Earth, scientists feel that any
water Venus may have had, evaporated long ago.
Venus is said to be surrounded by thick, yellowish clouds made of poisonous sulfuric
acid.
Its surface is covered by lava flows, oozing out from the many large, active volcanoes
on the planet.
The third rocky planet from the Sun is our very own Earth.
While the temperatures at Earth’s center, or core, are hotter than the surface of the
Sun, temperatures on Earth allow water to exist in its liquid form.
Recently, NASA’s Phoenix Mars Lander has discovered water in a soil sample from
Earth’s neighboring planet, Mars.
This rocky planet named after the Roman god of war, Mars, is also called the “Red
Planet” because of its soil which is full of red iron oxide or rust.
Mars has permanent ice caps on both poles that are made of solid carbon dioxide.
This planet also has the largest mountain in the solar system which is over 2 ½ times
taller than Mount Everest, the largest mountain on Earth.
Of the eight planets in the solar system, the four inner planets, Mercury, Venus, Earth,
and Mars are also known as the terrestrial planets because they are made up of mostly
rock and metal.
The larger outer planets are called the gas planets as they are mostly made up of the
gases hydrogen and helium.
The first gas planet, Jupiter, is more massive than all the other planets combined.
Jupiter has many moons. The four largest of these moons are called the Galilean
moons.
Why are they called the Galilean moons?
Io, Europa, Ganymede, and Callisto are called Galilean moons as they were discovered
about 400 years ago by the astronomer Galileo Galilei.
Saturn, the second gas planet, has many colorful rings made up mostly of ice and icecoated rocks, and its atmosphere is filled with yellow clouds of ammonia.
The atmospheres of Uranus and Neptune, on the other hand, have methane. Scientists
believe it’s the presence of this gas that gives these planets their blue color.
Unlike other planets in the solar system, Uranus rotates as though it has been tipped on
it’s side.
Because Uranus is so far from the Sun, it takes 84 years to complete one orbit.
As Neptune is the farthest planet from the Sun, it takes 165 years to complete one
orbit.
Between the inner and outer planets we can find the asteroid belt which contains over
7,000 asteroids.
These asteroids are the rock and metal debris left over from the early formation of the
solar system.
Any space debris that is larger than 100 meters in diameter is normally classified as an
asteroid.
Like asteroids, meteoroids are smaller chunkc of rocks and debris that orbit the Sun.
They can be as small as a grain of sand or as large as a boulder.
What do you think shooting stars are?
Shooting stars are small meteors that enter the Earth’s atmosphere and heat up due to
air friction causing them to glow brightly. Those meteors that hit the Earth are called
meteorites.
The outermost members of the solar system are comets. These icy leftovers from the
formation of the solar system can sometimes be seen in our skies when they whiz past
our planet.