How do we know the temperature of a star if it is millions of kilometers away? The answer is in the light. ✨ At the end of the 19th century, physicists discovered that every heated object emits radiation in a predictable way. As a material heats up, its light changes color: first reddish, then yellowish, and at extreme temperatures, whitish or bluish. Stars obey the same physics. They behave, with excellent approximation, like heated bodies radiating energy. When scientists break a star’s light