Date: 8 Jun 2026
Topic: Science
Codebreakers are a fun way to build numeracy skills.
The Sun, our nearest star, has a toasty surface temperature of 5,500 degrees Celsius. Its core temperature is closer to 15 million degrees Celsius. For context, water boils at a mere 100 degrees, which pales in comparison to the heat of the Sun. Even from a distance of 1 AU, a small portion of the Sun's energy is sufficient to power all of humanity.
The Sun is currently halfway through its 10-billion-year lifespan. At a ripe 4.6 billion years old, it has another 5 billion years or so before it enters its end-of-life phase. It is a main-sequence star, which makes it fairly ordinary - not big enough to supernova or turn into a black hole. Instead, our star fuses hydrogen in a continuous nuclear fusion process until eventually there is none left. At this time, the Sun's core engine falters, allowing gravity to crush the star inwards. As everything gets crushed together, its core temperature spikes to roughly 100 million degrees Celsius, which ignites helium fusion and pushes the outer layers of gas outwards. This increases its radius until it becomes a red giant, engulfing the orbits of Mercury, Venus, and likely Earth, though Mars will likely escape direct consumption.
As this outer layer continues to expand, our Sun eventually forms a beautiful planetary nebula. The intense radiation from the exposed core interacts with the expanding shells of gas, causing them to glow in a myriad of magnificent colors. As the nebula dissipates, we are left with just the hot carbon and oxygen core - a white dwarf about the size of the Earth, but containing over half the mass of the original Sun. Because the white dwarf no longer generates heat, it gradually radiates away its remaining thermal energy over trillions of years until it turns into the theoretical corpse of a star: a black dwarf, a cold, dark ball in empty space.