The idea of a brightly colored planet, particularly one with a vibrant hue like pink, has long captured the public imagination. While planetary colors are governed by predictable physics and chemistry, the search for exoplanets has revealed a surprising spectrum of celestial bodies. Astronomers have found that a world’s surface and atmospheric composition dictates its appearance, leading to diverse results. Although a true, bubblegum-pink planet remains fictional, one real-life exoplanet displays a distinct magenta shade, offering the closest known candidate to the “pink planet.”
The Closest Real-Life Candidate: GJ 504b
The exoplanet GJ 504b, orbiting the star GJ 504 about 57 light-years away, is the celestial body most often associated with the color pink. Discovered in 2013 by the SEEDS survey, this gas giant was captured using direct imaging, a technique that blocks the host star’s light to photograph the faint companion. Astronomers described the planet’s appearance as a dark, dull magenta, reminiscent of a dark cherry blossom. This unique coloration is not a simple reflection of starlight but rather a glow from the planet’s own internal heat.
GJ 504b is relatively young, with its star system estimated to be only about 160 million years old. The planet is still radiating thermal energy from its formation, giving it an effective temperature of approximately 237 degrees Celsius (460 degrees Fahrenheit). This residual heat allows it to be directly imaged in the infrared spectrum, resulting in the magenta hue. The atmosphere of this massive world, which is about four times the mass of Jupiter, is theorized to contain fewer clouds than expected for its temperature. The planet’s unique color signature also comes from the confirmed presence of methane gas, which absorbs light at specific infrared wavelengths, leaving the observed magenta color dominant.
How Planetary Atmospheres Create Color
A planet’s color is fundamentally determined by two interacting factors: the light it receives from its star and the chemical composition of its outer layers. Starlight, which is composed of a spectrum of colors, strikes the planet, and the atmosphere dictates which wavelengths are absorbed and which are scattered back into space. This scattering of light by gas molecules and particles is the primary mechanism that creates the perceived color.
Specific molecules absorb certain parts of the light spectrum while reflecting others. For example, methane is a powerful absorber of red and infrared light, creating the bluish-green colors of the ice giants in our solar system. The presence of hazes, clouds, and aerosols further complicates the interaction by causing Mie scattering, which tends to scatter all visible wavelengths more evenly, often resulting in a whitish or duller appearance. The specific temperature and pressure conditions of a planet determine the state of these chemicals, influencing whether they exist as gas, liquid droplets, or solid crystals.
Comparing Other Planetary Hues
The distinct magenta of GJ 504b highlights the variety of coloration possible among planets. The blue appearance of Earth is a result of its vast oceans and the scattering of blue light by nitrogen and oxygen molecules in the atmosphere. By contrast, the reddish-orange color of Mars is not due to atmospheric effects but to the iron oxide, or rust, prevalent in its surface dust and rocks.
The gas giants in the outer solar system display a different range of colors. Jupiter’s iconic bands of white, yellow, and brown are formed by clouds of ammonia, water ice, and other compounds that react with sunlight, while Saturn shares a similar composition but appears a paler gold. Uranus and Neptune appear blue and cyan, respectively, because their upper atmospheres contain higher concentrations of methane. This methane absorbs the red portion of incoming sunlight, leaving the unabsorbed blue light to be reflected back, a mechanism that contrasts with the internal heat and atmospheric composition creating GJ 504b’s rare pinkish glow.