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Astronomy with an online telescope
Astronomy with an online telescope

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2.2 The energy output of the Sun

The Sun radiates a lot of energy. Think about the warmth of the Sun on a bright summer day; the energy reaching us from the Sun has travelled 150 million km through space, spreading out in all directions.

The Sun as a source of energy

To provide this amount of warmth at such a great distance, the Sun must generate and emit huge quantities of energy every second. But precisely how much? Figure 3 shows the largest power station in the UK, which generates roughly 7% of all the electricity we use.

Described image
Figure 3 The coal-fired Drax power station in Yorkshire, United Kingdom

By way of comparison you would need one hundred thousand million million (or 100 000 000 000 000 000) such power stations to produce the same energy output as the Sun.

The Sun as an active star

Fortunately for life on Earth the overall energy output of the Sun is relatively stable. However, when looked at in more detail the Sun is a highly active and dynamic place.

Satellite telescopes such as NASA’s SDO have revealed the outer atmosphere of the Sun to be in constant turmoil and motion, with vast magnetic fields ejecting millions of tonnes of hot gas and plasma into space. Moreover, the interior of the Sun is thought to be in constant motion, which is revealed to us by regions of the surface layers of the Sun rhythmically pulsating up and down.

If you followed the link to the NASA video in Figure 1, you will have seen images of the churning outer atmosphere of the Sun. In the following activity, you will see more stunning images of the Sun taken using a range of different filters.

Activity 3 Activity on the surface of the Sun

Timing: Allow approximately 10 minutes

Download this video clip.Video player: boc_aot_1_video_week5_nasa_sun.mp4
Interactive feature not available in single page view (see it in standard view).

This video was produced by NASA from data obtained by their Solar Dynamics Observatory (SDO). It captures images of the Sun in ten different wavelengths of light, each of which helps to highlight a different temperature of solar material and in this video is artificially coloured by visible light to enable us to see it. This video shows the first five minutes, but you can also view NASA’s full video [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] if you so wish.

Later, in Weeks 7 and 8 you will look at variable stars, whose energy output and hence luminosity vary in a more dramatic way.