Hi Chelsea,

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Temperature varies greatly in different parts of the Sun.

The hottest part of the Sun is its core. The solar core is extremely hot (about 27,000,000 Fahrenheit!), so hot (and dense) that hydrogen is fused to helium. Temperature in the core can be approximated in different ways. One is to estimate the temperature that is needed for the fusion to take place. The other way is to balance the heat expansion and the gravitational compression, i.e. to find out what temperature is needed to get this balance.

When moving up from the core to the surface the temperature decreases. At the surface of the Sun the temperature is about 9900 Fahrenheit. The temperature also defines the colour we see the Sun. E.g. if the Sun’s surface would be cooler Sun would appear us more red. Solar surface defined by investigating the light that Sun emits. Interesting is also that part of the atmosphere of the Sun is hotter than its surface. In a region called chromosphere the temperature starts to rise very sharply. It is not yet clear why this happens.