Here's why:

* Core Temperature: The Sun's core reaches temperatures of around 27 million degrees Fahrenheit (15 million degrees Celsius). This intense heat is generated by nuclear fusion reactions, where hydrogen atoms fuse to form helium, releasing immense energy.

* Surface Temperature: The Sun's surface, called the photosphere, has a temperature of about 10,000 degrees Fahrenheit (5,500 degrees Celsius).

So, while the Sun's surface is incredibly hot, the core is many times hotter due to the ongoing nuclear fusion reactions.