The Sun

Introduction Did you know that the sun counts for 99.8 % of our solar system’s mass? Because of this mass the sun exerts a massive amount of gravity. This gravity is strong enough to hold planets much bigger than our own inside an orbit. Neptune is 2,795,084,800 miles away from the sun, but the sun is still able to hold it in its orbit.

The Sun’s Interior So what makes up the sun? The sun is very much different than Earth, but not just because its hot. The sun does not have a solid surface, it is just a big glowing ball of gas held together by gravity. This gas is ¾ hydrogen and ¼ is helium. The sun’s interior includes the core, the radiation zone, and the convention zone.

The Core The core produces enormous amounts of energy. The sun’s energy comes from a process known as nuclear fusion, which is when hydrogen atoms join together to form helium. Nuclear fusion can only occur under high temperatures and on the sun it typically reaches 15 million degrees Celsius in its core. This energy slowly escapes the core through the next layer called the radiation zone.

The Radiation Zone The radiation zone is a region of very tightly packed gas. The energy that radiates from the core comes to this region in the form of electromagnet radiation. This zone is packed so densely some energy can take over 100,000 years to get through the zone!

The Convection Zone Once the energy has finally escaped the radiation zone it comes to the convection zone. This is the outermost layer of the sun’s interior. Hot gases from the bottom rise to the top and gradually cool. The cooler gas sinks back down forming loops of gas that move energy towards the sun’s surface.

Convection Zone

The Sun’s Atmosphere Like Earth the sun also has an atmosphere and each layer has its own unique properties. The layers include the photosphere, the chromosphere, and the corona.

The Photosphere The photosphere is the innermost layer of the atmosphere. It is the visible layer of the sun. It is where sunspots are located. The word photo comes from the Greek word photos meaning light. This is the layer that gives off visible light, the gases in this layer are thick enough and have enough energy to be visible. When you look at an image of the sun you are looking at the photosphere.

The Chromosphere During a solar eclipse is the only time you can view the sun’s chromosphere, but it is still very dangerous to do so. Produces UV radiation If you get the chance and are wearing protection on your eyes you will see a faint red glow around the edge. This is the chromosphere. The word chroma in Greek means color so the chromosphere is the “color sphere”.

The Corona Super hot, outermost layer of the sun’s atmosphere. During a solar eclipse you will also see a faint layer of light outside of the red edge. What you are looking at is the corona. This makes up the halo around the sun. The word corona means crown in latin. This layer extends into space for millions of miles and thins into small electrically charged particles known as solar wind.

Features on the Sun For many years scientists have used telescopes with infrared technology to study the sun. These years of observations have yielded some surprising features about our sun. These features include: sunspots, prominences, solar flares.

Sunspots Scientists began noticing huge dark spots on the sun’s surface and these became known as sunspots. Most sunspots are larger than our entire planet. Sunspots are areas of gas that are cooler than the surrounding gas which is why they are darker than the rest of the photosphere. Sunspots are caused by the twisting of the sun’s magnetic field.

Close-up of sunspot Sunspot cycles by year. Notice how the cycle goes up and down about every 11 years. Image of sunspots taken on 3/29/2001

Prominences Sunspots typically appear in groups around areas of magnetic chaos. Giant reddish loops of gas known as prominences, link sunspots together. These loops can be so large we can see them from Earth. Notice how it makes a “P” shape!

Solar Flares Sometimes prominences can collide causing a huge release of the sun’s energy. This energy release is known as a solar flare. Solar flares eject gas and plasma millions of miles into outer space. Some eruptions can hit Earth causing severe weather, disrupt communications, and cause auroras. They produce X-Rays and Gamma radiation.

Sun’s Rotation Because the Sun is not solid, but is instead a giant ball of gas and plasma, different parts of the Sun spin at different rates.

What do you notice about the sunspots movement over the course of four days in 1612? Hint: look at the movement of the sunspots near the equator versus the spots near the north pole. Remember, the sun rotates more quickly at the equator.

Conclusion The sun is what makes up a majority of the solar system. The sun’s interior consists of the core, the radiation zone, and the convection zone. The sun’s atmosphere consists of the photosphere, the chromosphere, and the corona. Surprising features such as sunspots, prominences, solar flares, and solar wind have fascinated scientists for years.