Written for the KidsKnowIt Network by: Gemma Lavender, MPhys, FRAS
If you compare the Sun with the planets in the Solar System, it does not seem very exciting at all, in fact, as it hangs in the sky from day to day it seems quite boring. However, this is very far from the truth; the Sun has quite a few interesting things happening on its surface, but from the Earth and seeing as we are not allowed to look directly at the Sun, it’s not that easy to tell. Remember that you must NEVER look directly at the Sun as you could lose your eyesight!
You probably know that the Sun is very bright. It is also very hot. Think of the hottest day that you can remember; maybe you were on holiday with your family or playing a game in the park with your friends; now imagine it to be thousands of times that temperature - that works out to be a very hot day - your ice cream would melt in seconds! Because of the Sun's brightness, high temperature and the fact that it is not solid, but is made of gas, astronauts are not able to land on its surface. But that doesn’t mean that we cannot pretend what it would be like to go there!
For this mission, you would need a suit that kept you cool and a pair of sunglasses that blocked out more light than any pair that you can find in the shops. With your oxygen supply and spaceship that allows you to get close to the Sun, you are ready to start exploring!
On close approach, you will find that the Sun looks very different, not only does it look like a gigantic fireball, but it is also very spotty. Can you guess what these spots could be? Sunspots is the answer! But far from having a skin problem, these dark regions have quite a different meaning. Sunspots are much cooler than the rest of the Sun and are made from what is known as magnetic activity. These areas have the strongest magnetic activity. You may have come across something that is magnetic, such objects are called magnets. You may have a magnet stuck to your fridge or you may have played with them in class. The first thing that you have probably noticed about them, is that they love sticking to metal objects but are not so keen on other things like wood. The second thing that you might have noticed, is that they have an “N” and an “S” written on them. Do you know what these letters stand for? That’s right, the “N” stands for “North” and the “S” means “South” and they are called the poles of the magnet.
Sunspots are huge and act just like poles. Because there needs to be a “North” sunspot and a “South” sunspot, these spots like to appear in pairs. On your mission, you should be able to see them in pairs or in groups - they are rarely seen on their own! If you look closely from your spacecraft, you might be able to see two sunspots attached to a bright loop of hot gas. This loop is called a solar prominence and such features appear because of the magnetic field of the Sun. Sunspots are also responsible for bright bursts from the surface called solar flares and the more there are, the brighter the Sun appears!
“South” sunspots become “North” sunspots on the next solar cycle. Sunspots can grow to gigantic sizes - some are much bigger than the Earth!
Courtesy of SOHO/MDI consortium. SOHO is a project of international cooperation between ESA and NASA
Sunspots have a dark centre called the Umbra and are surrounded by a lighter coloured region called the Penumbra. Sunspots are around 1,500 degrees Celsius (2,732 degrees Fahrenheit) cooler than the rest of the Sun. The solar corona, or outer most surface, is estimated to be about 1 million Kelvin. That equals 1,799,540 degrees Fahrenheit and 999,727 degrees Celsius.
The Sun is not spotty all of the time, sunspots appear and disappear at around the same time every 11 years. Astronomers call this length of time the solar cycle and the number of sunspots is never the same. How many solar cycles would have happened in your lifetime?
Below is a comparison of solar activity. On the left, there is not much activity. On the right, you can see the solar activity has greatly increased. The Sun appears blue in these images because they were taken in ultraviolet light. Can you see the solar flares arching away from the Sun's surface?
Courtesy of SOHO/EIT consortium. SOHO is a project of international cooperation between ESA and NASA.
The Sun is responsible for the Northern lights, which are also known as the Aurora Borealis. In the Southern Hemisphere, they are known as the Aurora Australis. Click here to learn more.