Astronomy Practice Exam 2026 – Complete Preparation Guide

The core of the Sun is the region where nuclear fusion occurs. In this part of the Sun, temperatures reach around 15 million degrees Celsius (27 million degrees Fahrenheit), and the pressure is immensely high. These conditions create an environment conducive to fusion, where hydrogen nuclei can overcome their repulsion due to their positive charges and collide with enough energy to fuse into helium.

This fusion process releases an enormous amount of energy in the form of light and heat, which is what powers the Sun and provides energy to our solar system. The core is essentially the heart of the Sun's energy production, driving all subsequent processes that occur in the outer layers of the Sun. Other regions like the convection zone and radiation zone also play critical roles in the transport of energy generated, but they do not initiate nuclear fusion. The photosphere, being the visible surface of the Sun, is the layer where sunlight is emitted and does not have conditions suitable for nuclear fusion.