55 Cancri e - the Diamond Exoplanet

Among the exoplanets discovered so far, one of them seems to stand out by a special characteristic. It is located in the constellation Cancer, at a distance of about 40 light-years away from the Earth, which in cosmic terms, is very near to our planet. When the night sky is free of clouds, the host star of this exotic planet is visible to the naked eye. The name of the exotic planet is 55 Cancri e and scientists have concluded that it is made of diamonds. The term exoplanet defines any planet that is situated outside the Solar System. 55 Cancri e revolves in only 18 hours around a star called 55 Cancri A. Its size is twice the size of Earth and its surface is extremely hot, at about 5000 degrees Fahrenheit or 3000 degrees Celsius. 55 Cancri e has eight times the mass of our planet and this is why it is also called the super-Earth. The planet is believed to be a carbon planet. No water has been discovered on its surface, but helium and hydrogen were detected.

The presence of carbon, together with the very high temperature provides the proper conditions for the formation of diamonds. And due to its extremely high surface temperature and the great proximity to the star it orbits, it is very likely that the gases on the planet are in a fluid state.

Since planets do not produce light, the way stars do, the only method of discovering them is to detect the variation in the radial velocity of the star around which the planet revolves. This is how 55 Cancri e was discovered in 2004. The solar system to which 55 Cancri e belongs has at least four other planets which orbit 55 Cancri A.

55 Cancri e has a rate of spin that is tidally locked, which means that one of its sides permanently faces the sun. In other words, it has one side where there is a permanent day, and on the opposite side, there is a permanent night. This phenomenon is similar to the situation of the Moon, which orbits the Earth in such a way that it keeps showing us only one side. Thus its rate of spin is synchronized with the time needed to complete one orbit, which is also called the rate of revolution. Because of this situation, 55 Cancri e rotates exactly once every time it circles its sun, 55 Cancri A.

In a solar system, the planets and the star they orbit, are created from the same primordial disk of material, therefore in the 55 Cancri solar system, they are all richer in carbon, as compared to our Sun and planets. In our solar system, the dominating substances are silicates and oxygen, and this is why the formation of diamonds is less likely, with the exception of the two large gas giants, Jupiter and Saturn, where scientists have concluded that it is very likely that it does rain diamonds.

As I mentioned before, the abundance of carbon in a solar system is a favorable factor, that can lead to the formation of diamonds, under the right circumstances. The fact that one planet that contains diamonds has been discovered in the universe, makes scientists conclude that there must be many similar planets in our galaxy, which will be discovered in the future, in other carbon-rich solar systems.

By observing 55 Cancri e, scientists have concluded that at least a third of the planet's mass is made up of carbon. Due to the high temperature and pressure in its interior, this carbon is likely to take the form of diamonds. 55 Cancri e has thus a surface layer of graphite, which surrounds a thick layer of diamond. If sci-fi writers have been dreaming for a long time about diamond planets, it looks like science has managed to make their dream come true.