A Brief Guide to the Sun

The Sun is our nearest and most important star in space. This great ball of gas, mainly hydrogen, has a diameter of 1,392,000 km (865,000 miles) which is more than 100 times that of the Earth.

The diagram above shows a cross-section of our Sun. Beginning deep in the centre, the core, we find a very high temperature indeed. You may think it's hot outside sometimes with the Sun blazing down from the clear blue sky. For the British Isles, we find anything above 40 degrees (or so) Celcius almost unbearable. I don't think we would survive the Sun's core then, with temperatures around 15 million °C! Here, under intense pressure and heat, the hydrogen gas is forced together to make another gas, helium. This process produces a small (but very important) amount of energy - including heat and light. The Sun loses 4 million tonnes of mass every second in this conversion, but still has enough fuel to continue happily shining away for about 5,000 million more years.

Meanwhile, back in the core... all this heat and stuff is trying to get out of the Sun, first through the Radiation zone - a solidy type of area made of compressed gas. Next it finds the Convection zone, where currents of hot gas are constantly rising, as they are heated from below, and falling as they let out the heat and energy out into space.

The bright visible bit of the Sun we see is called the Photosphere. The temperature here is just under 6000 degrees Celcius. Then the energy flies though the atmosphere, zooming through the Chromosphere and, further out, the Corona, the tenuous atmosphere of the Sun only visible during a Total Solar Eclipse.

Because the Sun is a big ball of gas it actually rotates at different speeds. The equator rotates faster at 25 days, while the poles are slowest at about 35 days.

The Spotty Sun

At times, on the bright photosphere, darker lower temperature patches called Sunspots can appear. Their position and number change with the rotating Sun and with the eleven year Solar Cycle. At the start of each cycle spots appear at the higher latitudes (near the poles) but as the cycle moves on newer spots are seen slowly working their way towards the equator. The number of spots on the Sun increases over this time as well. This Solar Cycle is all to do with the action of magnetic fields as they weave, warp and smash their way through the Sun. Sunspots can appear on their own, but more commonly appear in pairs and in groups lasting anything from a few days to a few weeks. As for observing these sunspots, please remember the Sun is very dangerous. You can feel the heat and see its brightness on a sunny day, just imagine how this is strengthened through a telescope or binoculars:

Some Sunny Facts

The temperature at the centre of the Sun is around 15 million degrees Centigrade.

The Sun is losing 4 million tonnes of mass every second.

One square centimetre of the Sun's surface shines with the brightness of 60,000 candles.

The Sun's diameter is 109 times that of the Earth.

It would take you over 2,100 years if you wanted to walk to the Sun!

© Anton Vamplew 2008