The Water World of Gliese 1214 b

A Puffy Planet Unlike Our Own

Gliese 1214 b is one of the most intriguing exoplanets discovered, often nicknamed the "Water World." Orbiting a dim red dwarf star about 48 light-years away in the constellation Ophiuchus, this planet challenges our conventional understanding of planetary compositions.

Unlike the four terrestrial (rocky) planets in our solar system, Gliese 1214 b is classified as a mini-Neptune or a super-Earth, with a mass about seven times that of Earth and a radius 2.7 times larger. Its density suggests that a huge fraction of its mass—perhaps up to 50%—is composed of water. To compare, water makes up less than 0.05% of the Earth's mass.

Exotic Ice and Steam

Because of the extreme pressures and temperatures deep within the planet, this water wouldn't exist in the familiar liquid or frozen states we see on Earth. Instead, scientists predict it is composed of exotic phases of water, such as hot ice (Ice VII or Ice X) and supercritical fluid (a state where water is neither liquid nor gas) under its thick, steamy atmosphere.

The planet orbits its star every 1.58 Earth days, which means it is tidally locked—one side is eternally hot, and the other eternally cold. While the surface temperature is estimated to be around 280°C (536°F), the thick atmosphere helps distribute the heat, potentially leading to stable, long-lasting cloud formations composed of steam and exotic materials.

Gliese 1214 b serves as a prime example of the diversity of planets in our galaxy and provides an important target for follow-up observations by the James Webb Space Telescope (JWST) to characterize its unique atmosphere.