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The Gliese 667 system
Our galaxy, the Milky Way, is home to many compact systems centered around stars similar to our Sun. However, planets in orbit close to these stars are generally too hot to be habitable.
Gliese 667, a triple stellar system located about 23 light-years from Earth in the Scorpio constellation, contains the first known example of a system where a low-mass star has several potentially habitable rocky planets. Like Alpha Centauri, this system consists of three stars.
The three stars of Gliese 667
GJ 667 A is an orange-red K-type dwarf star, the largest in the system, with a mass of 73% of that of the Sun and a visual brightness of about 12% of that of our star.
Its companion, GJ 667 B, is also an orange-red K-type dwarf with a mass of 69% of that of the Sun and emitting about 5% of its luminosity.
The third, most interesting star is Gliese 667 C, a red M-type dwarf with a mass of only 33% of that of the Sun and an extremely low luminosity of 1.4% of that of the Sun. It has a surface temperature of approximately 3,775 Kelvin.
The planets of the Gliese system
Despite its small size, GJ 667 C is home to a rich planetary system. Scientists initially believed that there were only three exoplanets around GJ 667 C, but additional observations revealed that there could be six planets, three or even four of which are potentially habitable.
Super-Earths
A "super-Earth" is a planet larger than Earth, but not as huge as gas giants like Jupiter and Saturn. These planets can be composed of rocks or a mixture of rocks and ice, and they can have atmospheres capable of supporting various forms of life.
An overview of the planets of the system
- Gliese 667 Cb - A burning planet (200 degrees Celsius) with a mass 5.5 times that of the Earth, it probably has a very thick atmosphere and orbits around its star in just 7 days.
- Gliese 667 Cc - Located at 0.12 AU from its star, this planet, nicknamed the "Holy Grail" of exoplanets, has a mass 3.8 times that of the Earth and an index of similarity to the Earth of 0.85. It receives a little less light than the Earth but is irrigated mainly by infrared, which could maintain liquid water and temperatures similar to those of the Earth.
The other planets, Gliese 667 Ce and Gliese 667 Cf, have masses and rays 2.7 times and 1.45 times the Earth's respective rays. They are located further away from their stars, which could make them too cold to be habitable as we understand it, unless they have thick atmospheres capable of trapping heat.
Living conditions on Gliese 667 Cc
Living on Gliese 667 Cc would be very different from Earth. Because of its proximity to its star, the planet is probably gravitated, with one face always exposed to light and another dive into an eternal night. This would lead to drastic temperature differences influencing the overall climate.
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