why is the sun hot

The Sun is hot because immense pressure in its core creates continual nuclear fusion. In the core, hydrogen atoms are fused together to form helium, releasing a tremendous amount of heat and energy. This process is powered by the Sun's massive gravity, which squeezes the core so tightly that temperatures reach around 15 million degrees Celsius (27 million degrees Fahrenheit). The heat produced radiates outward from the core through the Sun's layers and into space, making the Sun hot and bright. The Sun is essentially a giant ball of hydrogen gas undergoing nuclear fusion at its core, which generates the massive heat and light we receive on Earth.