A Planet Made of Diamond

Far beyond our solar system lies exoplanet 55 Cancri e, a world of extremes orbiting its star at a dizzying pace, completing a full year in a mere eighteen hours. This "super-Earth" is nearly twice the size of our home planet and boasts a mass almost eight times greater, leading to incredibly high pressures within its interior. Its proximity to its sun-like star results in scorching surface temperatures, likely rendering its surface a global ocean of molten rock.

For a time, 55 Cancri e captured the imagination of scientists and the public alike with the intriguing moniker of a "diamond planet." This hypothesis emerged from a 2012 model that inferred the planet's chemical makeup by analyzing its substantial mass and radius without assuming an Earth-like composition. Given its carbon-rich environment and the immense pressures deep within, researchers suggested that a significant portion of its interior, perhaps as much as one-third of its mass, could be composed of diamond and graphite.

While subsequent research in 2013 challenged the initial "diamond planet" designation by suggesting the host star's oxygen-to-carbon ratio might not support such a diamond-rich world if the planet formed from the same material, the broader scientific principle remains. Laboratory experiments using diamond-anvil cells have demonstrated that under the right conditions of high heat, pressure, and the presence of water, carbon-rich materials like silicon carbide can indeed transform into diamonds and silica. This ongoing research highlights the diverse and exotic geologies possible on exoplanets, far beyond anything found in our own solar system.