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It rises in the morning, giving light to the land below it.
It sets in the evening, leaving the world in darkness.
It even provides the heat and energy necessary for life to survive on Earth.
You know what I'm talking about - the Sun!
Because it is so important to us, the sun has been studied and observed since ancient times.
Astronomers today still study it, and are constantly learning new things about the sun,
the center of the solar system.
The Sun is a star, not so different from the stars that can be seen in the night sky.
It may look different, but that is because the sun is many times closer to us than any
other star, which allows us to see how hot and bright it is.
The sun may be close to us compared to other stars, but it is still very far from the earth:
about 93 million miles or 150 million kilometers away.
Although the sun is so far away, it only takes sunlight about 8 minutes to reach the earth
because light travels so fast.
Because the sun is so far away, however, it seems much smaller than it really is - more
than 100 times the width of the earth.
The sun is so large that if it were empty, more than a million earths could fit inside!
The sun is the largest object in the solar system.
In fact, if you collected everything in the solar system including the sun, the planets
and dwarf planets, comets, asteroids, and moons, the sun would account for more than
99% of it, with everything else adding up to less than one percent of the solar system.
As far as stars go, however, the sun is average or even small in size.
It is called a yellow dwarf, and there are billions of stars like it in the Milky Way.
Like other stars, the sun is made of gasses: mostly hydrogen with a little helium, and
only traces of other elements.
These gasses are held together by the sun's gravity, which creates such intense heat and
pressure that it causes nuclear fusion - a process in which hydrogen atoms fuse to create
helium - at its core.
The sun's core is about 27 million degrees Fahrenheit or 15 million degrees Celsius.
By the time heat from the sun's core reaches its surface, temperatures have dropped considerably.
The surface of the sun is only about 10,000 degrees Fahrenheit or 5500 degrees Celsius.
Unlike the Earth, the sun does not have a solid surface.
You may be surprised to learn that the sun's gassy surface is not calm and quiet.
Instead, the sun is constantly moving and changing, with sunspots - or dark patches
of cooler temperatures - and solar flares - or eruptions of high-energy radiation - frequently
marking its surface.
All of the planets in the solar system, including the earth orbit around the Sun.
In turn, the solar system orbits around the center of the galaxy in which we live, the
Milky Way.
It only takes the earth one year to complete an orbit around the Sun, but scientists estimate
that it will take the Sun about 230 million years to complete an orbit of the galaxy.
Since ancient times, humans have understood how important the sun is for life on Earth.
Without the energy provided by the sun's radiation, the earth would be dark, cold, and uninhabitable.
Although it has been studied for thousands of years, there is still much to learn about
the sun.
I hope you enjoyed learning about the sun, the center of our solar system.