Sun is an important part for all of us,
Because a lot of people use sun in their daily lives.
Wash and then dry them under the sun.
Plants and animals can not live without the sun.
Then, why the sun can get hot?
The sun has heat because of nuclear fusion.
Source image from : google.com

Sun has a very high temperature.
The pressure was too high, and the high-voltage gas form.
In the existing cycle, nuclear fusion keep moving and moving in the core.
The center of the sun's temperature 15 million degrees Celsius. (Maybe the reason why there is currently no one can reach the sun).
The results of the 4 nuclear fusion of hydrogen atoms into 1 helium atom.
Because the result of nuclear fusion is the energy produced, causing the sun at high temperature.

Can you imagine if the hydrogen atoms out?
Then thats article about How the sun can be hot .