The planet has a mass of 23 Earth-masses and an orbital period of 2.64385 days. It orbits a red dwarf star 33 light years away. The temperature on the planet is somewhere in the oven-cleaning neighborhood of 600K (327K, 620F). No habitability news stories on CNN for this fine fellow. The transit depth is a healthy 0.6%, which implies that the the planet’s radius is ~25,000 km. That’s four times that of the Earth, and essentially identical to the 24,764 km radius of Neptune.

As the planet is close to its host star, its surface temperature is expected to be at least 300 C (600 F). The water in its atmosphere would therefore be in the form of steam. Inside, the water is crushed under intense pressure and adopts states unknown on Earth, except in physicist’s laboratories. Says Frédéric Pont: “water has more than a dozen solid states, only one of which is our familiar ice. Under very high pressure, water turns into other solid states denser than both ice and liquid water, just as carbon transforms into diamond under extreme pressures. Physicists call these exotic forms of water ‘Ice VII’ and ‘Ice X’. If Earth’s oceans were much deeper, there would be such exotic forms of solid water at the bottom.” Inside GJ 436’s planet, this strange ice is moreover heated to many hundred degrees.