Water World or Diamond Planet

Figure 1: Earth and 55 Cancri e shown to scale.55 Cancri e is a planet orbiting a Sun-like star 41 light years from Earth. This planet takes just 17 hours 41 minutes to orbit its host star and its distance from its host star is only 1/20th the distance of Mercury from the Sun. Being so close to its parent star, the dayside of 55 Cancri e is scorched to a temperature of over 2000 °C. 55 Cancri e is in a class of exoplanets known as “super-Earths”. It has about 8 times the mass of Earth and a diameter just over twice that of Earth. Knowing both the size and mass of 55 Cancri e allows the planet’s internal composition to be predicted. When 55 Cancri e is being plotted onto a mass-radius relationship diagram, it seems that the planet is too large for its mass to be made up of just rock material.A study done by M. Gillon et al. (2012) suggests that 55 Cancri e has a rocky interior with a thick overlying envelop of water comprising ~30 percent of the planet’s total mass. Such a layer of water is expected to be a few thousand kilometres ...