An international team of researchers, led by Dr. Paul Butler of the Carnegie Institution and Dr. Guillem Anglada-Escudé of the University of Gottingen, has discovered a potentially habitable super-Earth orbiting a star, which is a member of a triple system.
M-class dwarf star GJ 667C (CDS / ESO)
In their study, which will appear in the Astrophysical Journal Letters, the team focused on an M-class dwarf star called GJ 667C. The other two stars (GJ 667A and GJ 667B) in this triple system, located in the constellation Scorpius about 22 light years away, are a pair of orange K dwarfs.
GJ 667C had previously been observed to have a super-Earth, called GJ 667Cb, although this finding was never published.
The researchers started with the aim of obtaining the orbital parameters of this super-Earth. They analyzed public data from the European Southern Observatory, and new data from the Keck Observatory and the Carnegie Planet Finder Spectrograph at the Magellan II Telescope.
But in addition to GJ 667Cb, the team found the clear signal of a new planet, called GJ 667Cc. It has an orbital period of 28.15 days and a minimum mass of 4.5 times that of Earth.
The researchers suggest that this planet receives about 90% of the light that Earth receives from the Sun. However, it should absorb a higher percentage of the incoming energy, because most of the incoming light is in the infrared part of the spectrum.
GJ667C system with three super-Earth exoplanets (University of Puerto Rico at Arecibo)
When these effects are taken into account, GJ 667Cc is expected to absorb the same amount of energy from its star that the Earth absorbs from the Sun. This would allow surface temperatures similar to Earth and perhaps liquid water.
“This planet is the new best candidate to support liquid water and, perhaps, life as we know it,” Dr. Anglada-Escudé said.
The team also notes that the system might also contain a gas-giant planet and an additional super-Earth with an orbital period of 75 days. Further observations should help confirm these two candidates.
“With the advent of a new generation of instruments, researchers will be able to survey many M dwarf stars for similar planets and eventually look for spectroscopic signatures of life in one of these worlds,” Dr. Anglada-Escudé concluded.
