The star GJ 667C has three potentially habitable planets

Diagrama of the planetary system of the star GJ 667C, also known as Gliese 667C (Image ESO)
Diagrama of the planetary system of the star GJ 667C, also known as Gliese 667C (Image ESO)

The star GJ 667C (also known as Gliese 667C) rose to the spotlight a little more than a year ago, when a scientific study led to the identification of three planets and the one called GJ 667Cc was in the habitable zone of its star. Some doubt was expressed regarding this discovery but a new research, conducted by Guillem Anglada-Escudé of the University of Göttingen, Germany, and Mikko Tuomi of the University of Hertfordshire, UK, led to the conclusion that the star has at least 6 planets of which 3 in its habitable zone.

The researchers used data from the HARPS (High Accuracy Radial Velocity Planet Searcher) spectrograph of ESO’s telescope in Chile together with data from the W.M. Keck Observatory, the Magellan telescope and ESO’s VLT (Very Large Telescope) to examine the star GJ 667C, a small red dwarf that is part of a triple star system with two other stars a little smaller than the Sun. The smallest star orbits at a considerable distance from its two companions so it can have a stable planetary system, which turned out really extraordinary.

The discovery is remarkable because the planetary system of the star GJ 667C is very compact since the farthest planet has a distance that is approximately half that of the Earth from the Sun. All the planets have orbits close to each other and thanks to this peculiarity three of them are within the habitable zone of the system, which is quite limited because of the star’s small size. In that zone the environmental conditions are potentially favorable to the life of the type that we know starting from the possibility that water is in its liquid state.

Those three planets that are so interesting are super-Earths, more massive than the Earth but smaller than Uranus and Neptune. The one already known, GJ 667Cc, has a mass about four times the Earth, GJ 667Cf has a mass nearly twice the Earth while GJ 667Ce has a mass just over two and a half times the Earth.

If there was any living creature on at least one of these planets, they could enjoy an amazing show because the other two stars of the system at night would shine like the full Moon but they would be visible even in daylight. However, it’s clear that potential is the key word because we actually know too little about their characteristics.

If on one of these planets there were astronomers who are watching our solar system, they might think that here there are three potentially habitable planets as well: Venus, Earth and Mars. This is to say that the conditions on the surface of a planet depend not only on the distance from its star but also on other factors.

The investigation on the system of the star GJ 667C will go on, regardless of its results the latest discoveries confirm that it’s worth looking for planets around red dwarfs, which are by far the most numerous stars.

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