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the speed of sound in the Sun


What have we learnt from projects like SOHO about the inside of the Sun? This picture shows the difference between what we thought the speed of sound was inside the Sun before 1995, and what we have measured it to be with SOHO.


The speed of sound is important because it tells us about the temperature of the Sun's plasma. The hotter the plasma, the faster the speed of sound.

The picture (right) shows that the predictions made before SOHO was launched were pretty good. Blue is slightly cooler and red is slightly hotter than we predicted but only by a very small amount of 0.1%.


That small difference in the centre of the Sun is very important - it suggests that the centre may be slightly cooler than we thought and so might not be providing quite so much nuclear fusion energy.



Cross section of the Sun

How well did we do estimating the Sun's temperature? Put your mouse over the blue and red circles to find out!

Cross Section of the Sun

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Blue is slightly cooler and red is slightly hotter than we predicted.



Using the same observations we can also show how the plasma flows inside the Sun. The red central part is the core and radiative zone. Above this is the convection zone which shows very complicated circulation patterns.




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