Near Super Earth is a diamond planet

55 Cancri e is the first known carbon planet around a sun-like star

This illustration shows the Super Earth 55 Cancri e in size comparison with Earth; The blue color of the planet dates back to the time when it was supposed to have a dense water cover. © NASA / JPL-Caltech
Read out

A supergiant only 41 light-years away could consist of at least one-third diamond. The planet 55 Cancri e is about twice the size of the earth, but has a fundamentally different chemical composition than the earth. An international team of astronomers has found this out on the basis of new observations. "The surface of this planet is probably covered with graphite and diamond instead of granite and water like Earth, " says first author Nikku Madhusudhan of Yale University in New Haven. 55 Cancri e opens a completely new geochemical and geophysical class of rock planets, the researchers report in a publication that will soon be published in the journal "Astrophysical Journal Letters".

Last year, a team of researchers had already discovered a suspected diamond planet in the Milky Way, but this orbited a pulsar and thus a very special, exotic star type. 55 Cancri e is now the first known diamond planet around a sun-like star, the astronomers say.

55 Cancri e is the innermost of five planets orbiting the Sun-like star 55 Cancri. This lies in the constellation of Cancer and is even visible to the naked eye in the night sky. 55 Cancri e has eight times the mass of the earth and circled its star at breakneck speed, for a round it takes only 18 days. Because of its proximity to its sun, it is also extremely hot, on its surface more than 2, 100 degrees Celsius prevail.


Carbon instead of silicon, oxygen and iron

Last year, astronomers first saw the planet pass in front of its central star. From the data obtained, initial conclusions could be drawn on the size, density and mass of 55 cancres. "At first it was assumed that the planet is made of iron, silicates and a thick shell of water, " report Madhusudhan and his colleagues. Just assume the typical structure of the rocky planets in the solar system. Recent measurements and models have shown, however, that the observed features of the planet rather pointed to an extremely carbon-rich composition. display

According to the researchers, 55 carbon could consist of carbon in the form of graphite and diamond, iron, the carbon compound silicon carbide and possibly some silicates. "The Earth's interior, on the other hand, is extremely low in carbon - it's less than one-thousandth of the Earth's mass, " says co-author Kanani Lee of Yale University. At least one-third of 55 Cancri could be diamond, say the scientists. This amount of diamond would be at least three times the mass of our earth. Water was contrary to previous assumptions probably not available at all.

Planets are more diverse than thought

The discovery of a carbon-rich super-earth throws a completely new light on the diversity of foreign planets, says Madhusudhan. For now one can no longer assume that distant rocky planets of the earth must be similar in terms of their composition and also the processes running on them. If a planet is largely made up of the highly thermally conductive carbon, it also influences geological processes such as plate tectonics, volcanoes, earthquakes, and the formation of mountains.

"Stars are simple - if you know their age and mass, you can deduce their structure and history, " comments David Spergel of Princeton University on the study of his colleagues. By contrast, planets are far more complex. "This diamond-rich super-earth is just one example of the many other discoveries that await us in the search for alien planets, " says the astronomer.

(Astrophysical Journal Letters, 12.10.2012 - NPO)