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The question “how hot is the sun?” can be seen from many different angles. How hot is the sun’s core, or how hot is the sun’s interior? Or how hot is the surface of the sun? Perhaps you’re wondering how hot the sun’s corona is? You can be calm. Whatever your question is about, you’ll find the answer here.
The interior of the sun
The sun is mostly hydrogen. Heat is generated in the sun’s core by a process called fusion. The nuclei of hydrogen atoms are merged in this fusion to form heavier nuclei – and thus a new substance – helium.
The process releases huge amounts of energy in the form of heat. For natural reasons, it is not possible to measure the heat directly in the Sun’s interior, but calculations have shown that it is around 15 million degrees in the Sun’s core.
The way out and the surface of the sun
The fusion process inside the Sun also gives rise to radiation due to the formation of photons that are extremely rich in energy. These photons travel outwards towards the surface of the Sun – amazingly, it can take them up to 50 million years to get there!
By the time the photons reach us, they have lost so much power that the energy they have left is equivalent to the light we see. At the sun’s surface, the temperature has thus dropped to a modest 6 000 °C.
solar corona
How hot is the sun’s corona? (The corona is the outermost atmosphere around the Sun – the one visible, for example, during a solar eclipse when the entire globe of the Sun itself is hidden.) Oddly enough, the temperature here is rising again compared to the surface of the sun.
The corona has a temperature of over 1 000 000 °C. It’s not known for sure why it gets warmer further out, but it’s thought to be due to the magnetic field emitted by the sun.
Celsius or Kelvin
“How hot is the sun in Kelvin?” asks the even more inquisitive. The answer is that since the difference between Celsius and Kelvin is only 273 degrees, the answers given above will be equally valid whatever unit you put after them. The accuracy of the figures is not high enough for plus or minus 273 degrees to have any meaning.
