Giant planet of diamonds discovered in Cancer constellation

Astronomers have discovered an interesting exoplanet in the constellation of Cancer near star 55 Cancri. Earlier it was considered a gas giant like Neptune, but recent studies have shown that this is not the case. This planet is carbon, and therefore, most of its mantle is composed of diamonds. Their weigh is twice as much as that of the planet Earth.

Cancer is an ordinary pale constellation. However, there is Cancer 55 star in the constellation (55 Cancri, 55 Cnc) which is Sun-like and has five open exoplanets. So far it is on the third place in terms of the number of distinct defined objects of that type.

In May of 2011, direct measurement of the angular diameter of the star 55 Cancri were taken with a CHARA telescope. It was equal to 0,711 ± 0,004 milliarcseconds, which corresponds to a distance of 12.3 parsecs with the radius of 0,943 ± 0,01 solar radii, and the distance to this star is 40.9 light years. 55 Cancri is a yellow dwarf G8V, and can be seen with the naked eye (magnitude 5.95, and 0.6 solar luminosity). The star system of 55 Cancri is double, and the yellow dwarf has a neighbor - a dim red dwarf separated from a companion by 1,100 astronomical units.

On July 6, 2003, radio astronomers sent a radio message Cosmic Call to 55 Cancri with RT-70 located in Ukraine. The message will arrive at the destination point in May of 2044. Humans are looking for intelligent creatures there because of the five exoplanets there is one "super-Earth" 55 Cancer discovered in 2004. Among the known objects of this type, it is one of the closest to Earth. Its mass is greater than that of Earth by 8.6 times, and its diameter is twice the diameter of Earth. The density of the Earth and the exoplanet is very similar.  

A recent study conducted at Yale University (USA), describes the "super-Earth" 55 Cancer as a typical carbon planet. It should be noted that up to this point, this class of exoplanets was discussed only as a theoretical possibility. The lead author of the report Professor Nikki Madhusudhan emphasized that the surface of the planet is covered with graphite and diamonds rather than water and granite. 

Climate of 55 Cancer is extremely hot. The temperature at the illuminated side of the planet is about 2 thousand degrees Kelvin. This is due to a small distance to the local luminary estimated at 0,01560 ± 0,00011 AU. The exoplanet makes a full rotation around its axis in 0.74 Earth days.

Now the old theory that this exoplanet is a hot gas giant like Neptune is considered erroneous. After determining the radius of the planet (which is very small), and its density, it was obvious that this is one of the first planets that can be confidently called carbon. This was discovered through the study of 55 Cancri. Its chemical composition has very little silicon and a great deal of carbon (incidentally, the sun is very different).

As shown by spectral observations, there are hardly any traces of water on the surface of Cancer 55 e. Consequently, in terms of its composition it is very far from the Earth, which is an ocean planet whose surface is covered in water and that has silicon mantle inside. The mantle of the exoplanet, apparently, consists of carbon, which accounts for a third of its mass. Given the extreme heat and pressure in the inner layers, most likely, it is made of solid diamonds. On Earth, these stones are found only in specific places, and on 55 Cancer e they are located under the surface of the planet. It is assumed that the mass of diamonds there is twice as big as the mass of our planet.  

The discovery of the first carbon planet opens up horizons of chemical diversity of planets similar to the Earth in size. Now it is obvious that there are various exoplanets, the question is how they can affect the chemistry of the processes. Most of the observed yellow dwarfs are closer in composition to the Sun than 55 Cancer. However, because of unimaginable abundance of stars in the galaxy we can assume that there are millions of carbon planets.

Perhaps there will be billions of them if many stars of exoplanets are discovered since one unremarkable star 55 Cancer has at least five planets. There may be two more additional, not yet confirmed planetary objects in the system. Questions about the magnetic field of such planets and tectonics of their plate are discussed with certain skepticism. Their mantles must have no flow of matter, and this is a necessary condition for the magnetic "dynamo" and movement of the surface plates.

The question of the origin of life in such exotic worlds intrigues scientists. After all, to enable life forms like that on Earth a water environment is required along with unique temperature, abundance of chemical elements and their compounds, strong atmosphere and shield protecting from harmful radiation. In a variety of exoplanet worlds on more distant from the Sun carbon planets, such as satellites of exoplanets (e.g., 55 Cancer f), water can exist in liquid form, and the conditions for the emergence of unique forms of life may well exist. There is also a possibility of a discovery of an exact copy of our planet with its biological diversity.

Tatiana Valchuk


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Author`s name Dmitry Sudakov