Date: 21 Jun 2026
Topic: Science
Codebreakers are a fun way to build numeracy skills.
Stars are the largest continuous fusion bombs constantly exploding in the universe. These fusion reactions start by energizing hydrogen atoms until they are buzzing around so fast that when they collide, they fuse to form the heavier element helium. This nuclear reaction is highly exothermic, meaning it releases a supreme amount of energy. This immense power is why nuclear reactions are so dangerous, but it is also the very reason why all of life on Earth can be powered by the Sun.
When a star is at least 8 times the mass of our Sun, it has enough gravity and heat to progressively fuse heavier and heavier elements. While our Sun will die after creating carbon and oxygen, these massive stars keep going, fusing those elements into neon, magnesium, silicon, and eventually creating a core of iron.
Iron is the ultimate dead end for a star. Fusing elements lighter than iron releases energy (exothermic). However, iron is so incredibly stable that trying to fuse iron atoms into anything heavier becomes endothermic, meaning it consumes more energy than it releases. Instead of acting as fuel, iron acts like a sponge, soaking up the star's energy.
This is essentially poison for the star, stopping its nuclear heart. Without the outward pressure of fusion to fight against gravity, the star's core collapses in less than a second. The outer layers of the star crash inward at a quarter the speed of light, creating phenomenal heat and pressure that force protons and electrons to fuse into neutrons.
When this collapsing matter hits the ultra-dense neutron core, it rebounds violently outward in a supernova—an explosion so bright it can temporarily outshine an entire galaxy of 400 billion stars. In the unimaginable heat of this blast, the universe finally forces elements heavier than iron to form, creating precious metals like gold and platinum.
The remnant left behind is a neutron star—the dead, leftover core. It is no longer fusing elements to produce light, but it is packed so tightly and is so superheated that it will continue to glow across the cosmos for billions of years.