Astronomy Packet: 7
In our journey through the Solar System, we have not talked about one very important member, the King of the Solar System our Sun.
What is the Sun?
It is important that we understand what the Sun is, because it helps us to better understand our own place in the Universe. For thousands of years people thought that the Earth was at the center of the Universe. The Sun, they thought, was a unique ball of fire found nowhere else.
In modern times we have discovered that the Sun is not unique at all. It is just one star in a universe with trillions of other stars. The Sun is a normal star just like every other star in the sky.
Many of the stars in our sky have names, such as Antares and Betelgeuse. Similarly, the Sun also has a name. The name of our sun is Sol. Think about that for a moment. Why does that name sound familiar? Our planet sits in the Solar System, or the System around the star Sol. Would another star's planets be in a Solar System? No, each star's system is named after the star. If Antares has a system, its name would be The Antares System.
The sun has three layers. The first layer is a super hot core where hydrogen fuel is burned into helium. On top of the core lies a thick layer of churning gases. Finally, above this sits a thin surface.
The churning which takes place in the middle layer is also called convection. The hot gases rise up to a certain point. As they rise they cool down. Eventually they become so cool that they begin to sink again deeper into the Sun where they slowly heat up. Then the process starts all over again. Just like a spinning wheel, the gases in this layer are always churning up and down in giant circles.
This convection creates a huge magnetic field around the Sun. In other words, it turns the Sun into a giant magnet. This magnetic field is what causes Sun spots as well as Solar flares. Incidentally, the same thing happens here on Earth. As the molten lava under the Earth's crust churns up and down it creates a magnet. This is why a compass always points North.
The Sun follows an eleven year cycle. Over an eleven year period it slowly gets more and more active. As the eleven years go on we see more and more Sun spots, solar flares, and solar storms which send atomic particles at the Earth. Then suddenly, after eleven years, the cycle starts all over again. Right now we are at the height of the cycle, meaning that the Sun is covered with many Sun Spots. It also means that occasionally our satellite systems go out. Solar storms can cause disturbances in satellites making them useless for a few hours, or days.
Is the Sun big?
Compared to everything else in the Solar System the Sun is huge. It is so big, that if it were hollow you could fit one million Earths inside of it. The Sun contains 99.9% of all the mass in the Solar System.
However, while it is true that the Sun is bigger than anything else in our Solar System and also bigger than most of the stars in the Universe, compared to other stars the Sun is not large. It is a middle sized star.
Assignment # 1:
What is the Sun?
Describe some of its characteristics.