Fact-Checking Solar Cycle 25: Is the Sun Actually Getting Brighter Every Year?

Are fact-Checking Solar Cycle 25: Is the Sun Actually Getting Brighter Every Year something you want to understand? Read key explanations in our feature story.

The baseline brilliance of our star comes down to deep interior mechanics. At the center of the solar interior, extreme gravitational pressure maintains a core temperature of approximately 15 million Kelvin (27 million degrees Fahrenheit). Under these crushing conditions, protons overcome electrostatic repulsion to initiate the proton-proton chain reaction.

This sustained hydrogen to helium fusion converts roughly 600 million metric tons of hydrogen into helium every second. A fraction of that mass, about 4 million tons per second, converts directly into pure energy under Einstein's mass-energy equivalence equation. That energy originates in the core as high-energy gamma-ray photons.

Those photons do not exit instantly. They undergo a erratic journey through the dense radiative zone, repeatedly absorbed and re-emitted over tens of thousands of years. By the time this energy reaches the outer boundary known as the photosphere, it degrades into a broader spectrum of electromagnetic radiation spanning ultraviolet, visible light, and infrared. Total solar luminosity, the total power output radiating into space, remains remarkably stable at approximately 3.828 × 10²⁶ Watts.