Planets can appear pink due to their intense heat causing them to glow with a magenta hue. Specifically, the exoplanet GJ 504b is an excellent example.
The Case of GJ 504b
GJ 504b, a gas giant several times the mass of Jupiter, orbits the star GJ 504. What makes GJ 504b unique is its color. Astronomers describe it as magenta or pink.
Heat and Color
The pink color of GJ 504b isn't due to surface composition like the rusty red of Mars. Instead, it is a result of its intense heat. The planet is still relatively young and radiates a significant amount of energy in the form of infrared and visible light. The specific temperature, and hence the wavelengths of light emitted, create the observed magenta color.
Analogy
Think of heating a piece of metal. As it gets hotter, it first glows red, then orange, then yellow, and eventually white-hot. GJ 504b is radiating at a temperature that produces a magenta glow.
Other Factors
While intense heat is the primary reason for GJ 504b's pink appearance, atmospheric composition could also play a role in influencing the exact color we observe. However, the dominant factor is the heat emitted by the young planet.
