New super-earth detected within the habitable zone of a nearby star
An international team of scientists has discovered a potentially habitable super-Earth orbiting a nearby star. The host star, called GJ 667C, is a M-class dwarf member of a triple-star system and has a different makeup than our Sun, with a much lower abundance of elements heavier than helium, such as iron, carbon, and silicon.
The other two stars (GJ 667AB) are a pair of orange K dwarfs, with a concentration of heavy elements only 25% that of our Sun’s. Such elements are the building blocks of terrestrial planets, so it was thought to be less likely for metal-depleted star systems to have an abundance of low-mass planets.
The new found planet (GJ 667Cc) has an orbital period of 28.15 days and a minimum mass of 4.5 times that of Earth. It receives 90% of the light that Earth receives. However, because most of its incoming light is in the infrared, a higher percentage of this incoming energy should be absorbed by the planet.
When both these effects are taken into account, the planet is expected to absorb about the same amount of energy from its star that the Earth absorbs from the Sun. This planet is the new best candidate to support liquid water and, perhaps, life as we know it.
GJ 667C also has a super-Earth (GJ 667Cb) with a period of 7.2 days, previously detected. This planet orbits so close to the star that it would be too hot for liquid water. The system might also contain a gas-giant planet and an additional super-Earth with an orbital period of 75 days. However, further observations are needed to confirm these two possibilities.
This was expected to be a rather unlikely star to host planets. Yet there they are, around a very nearby, metal-poor example of the most common type of star in our galaxy. The detection of this planet, this nearby and this soon, implies that our galaxy must be teeming with billions of potentially habitable rocky planets.