A new study shows that a nearby exoplanet seems to be comprised of a substantial amount of diamond. The diamond planet, 55 Cancri e, was first discovered passing in front of its parent star in 2011. 55 Cancri e is only two times bigger than Earth but has eight times the Earth’s mass; its diamonds alone are at least three times the Earth’s mass. The exoplanet has a thin surface of mainly graphite encompassing a thick mantle of mainly diamond. The diamond mantle makes up an astounding 1/3 of the planet’s radius. It is possible that diamonds can be found on the surface as well due to the geophysical movements of the planet’s interior.
At first, researchers proposed that 55 Cancri e was an Earth-like planet, composed of iron, silicates, and water. However, this model was not adequate because it did not match the planet’s mass. To be a planet with a composition similar to that of Earth, 55 Cancri e would have to be surrounded by an enormous layer of water that is neither liquid nor gas, in a supercritical state and thus unlikely. Later, spectrographic data showed that 55 Cancri e’s parent star contains an inordinate amount of carbon, much more than our sun, leading to the suspicion that 55 Cancri e itself is also carbon-rich and therefore diamond-rich.
Nikku Madhusudhan, leader of the study and a postdoctoral researcher at Yale University clarifies, “If we make the assumption that the star and its surrounding planets are all born from the same primordial disk of material, then it makes sense that the entire planetary system would be carbon rich.” The journal Astrophysical Journal Letters will publish the study in an upcoming issue.
55 Cancri e is located only 40 light years away from Earth, which is a very short distance in astronomical terms. The rocky planet is one of five planets orbiting its parent star, 55 Cancri A. 55 Cancri A is a star found in the northern constellation Cancer that is clearly visible to the naked eye at certain times. Out of the star’s five planets, the diamond planet has the closest orbit around its host star. 55 Cancri e’s orbit around its parent star takes only 18 hours while Earth’s orbit around our sun takes an entire year. Relative to Earth, the gem-like exoplanet is situated very near its parent star.
The diamond planet’s extreme proximity to its host star means that its surface temperatures reach an incredible 2, 150 degrees Celsius, scorching the exoplanet. While this alone would make the existence of life forms impossible, there is also a lack of water and oxygen. The intense heat along with the presumed abundance of carbon on the planet, however, creates the perfect recipe for diamonds.
It is possible that 55 Cancri e is the first of a new class of planets with strange, never-before-seen chemistry. The discovery of a diamond planet is especially important because it gives astronomers insight on the creation of planetary systems and the diversity of planets. Acknowledging that something as questionable as a planet made of diamonds exists allows astronomers to expand their thinking and consider possibilities that they may have otherwise dismissed.