Washington: Scientists have discovered a potentially habitable super-Earth orbiting a nearby star.
The star is a member of a triple star system and has a different makeup than our Sun, being relatively lacking in metallic elements.
This discovery demonstrates that habitable planets could form in a greater variety of environments than previously believed.
The international team of scientists led by Carnegie’s Guillem Anglada-Escude and Paul Butler used public data from the European Southern Observatory and analyzed it with a novel data analysis method.
They also incorporated new measurements from the Keck Observatory’s High Resolution Echelle Spectrograph and the new Carnegie Planet Finder Spectrograph at the Magellan II Telescope.
Anglada-Escude and his team focused on an M-class dwarf star called GJ 667C, which is 22 light years away. It is a member of a triple-star system. The other two stars (GJ 667AB) are a pair of orange K dwarfs, with a concentration of heavy elements only 25 percent that of our Sun’s.
GJ 667C had previously been observed to have a super-Earth (GJ 667Cb) with a period of 7.2 days, although this finding was never published.
This orbit is too tight, and thus hot, to support life. The new study started with the aim of obtaining the orbital parameters of this super-Earth.
But in addition to this first candidate, the research team found the clear signal of a new planet (GJ 667Cc) with an orbital period of 28.15 days and a minimum mass of 4.5 times that of Earth.
The new planet receives 90 percent 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 would allow surface temperatures similar to Earth and perhaps liquid water, but this extreme cannot be confirmed without further information on the planet’s atmosphere.
“This planet is the new best candidate to support liquid water and, perhaps, life as we know it,” Anglada-Escude said.
The team notes that 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.
The Astrophysical Journal Letters will publish details of the discovery.