The planet, GJ 667Cc, lies only 22 light-years from Earth. It circles a relatively cool star (GJ667C), has an orbital period of 28.15 days and a minimum mass of 4.5 times that of Earth, according to a report of the discovery to be published in The Astrophysical Journal Letters.

The new planet receives about 90% of the light that the Earth receives from the Sun. But most of this incoming light is in the infrared, and so more of it will be absorbed by the planet, says Professor Chris Tinney of the University of NSW, a member of the research team. Other UNSW team members include Dr Jeremy Bailey and Dr Rob Wittenmyer.

“This means that overall the planet absorbs about the same amount of energy from its star as the Earth absorbs from the Sun: so that would give the planet the right temperature, if it has a rocky surface and a wet atmosphere, to host liquid water,” says Professor Tinney. “And liquid water is seen as an essential pre-condition for the development of life.”

The planet orbits a star called GJ 667C, which is a member of a triple-star system and orbits a distant pair of brighter, orange K-dwarfs (GJ 667A and B).

“This discovery shows that habitable planets could form in a greater variety of environments than we previously considered,” said Dr Simon O’Toole of the Australian Astronomical Observatory, another team member.

The planet was discovered using the “Doppler wobble” technique, which detects the slight movements of a star as its orbiting planets tug it to and fro in space.

Star GJ 667C had previously been observed to have a “super-Earth” (GJ 667Cb) with an orbital period of 7.2 days, although this finding was never published. But that orbit is too tight, and thus that planet is too hot, to support life.

GJ 667C might also host a distant gas-giant planet, and an additional super-Earth with an orbital period of 75 days, but more observations are needed to confirm this.

Data that led to the finding came from the European Southern Observatory’s 3.6m telescope; one of the two 6.5-m Magellan telescopes of the Carnegie Observatories; and one of the twin 10-m Keck telescopes operated by the University of California and the California Institute of Technology.

Dr Brad Carter of the University of Southern Queensland was one of several astronomers who made observations for the project—in his case, using Magellan in Chile.

This project was part of a larger program to find rocky planets and super-Earths.

The research team was led by Dr Guillem Anglada-Escudé (now University of Göttingen, but at the Carnegie Institution for Science at the time of the observations) and Dr Paul Butler (Carnegie Institution for Science). It also includes researchers from Pontificia Universidad Catolica de Chile, University of California’s Lick Observatory, the Institute for Astronomy & NASA Astrobiology Institute at University of Hawaii-Monoa, the University of Hertfordshire, and the Universidad de Chile.

Media contacts in Australia:

Chris Tinney (+61) 2 9385 5168  or  0416 092 117
    c.tinney@unsw.edu.au and www.phys.unsw.edu/~cgt

UNSW Faculty of Science media liaison Bob Beale 0411 705 435
    bbeale@unsw,edu.au

UNSW Press Release

1. •at the UNSW Faculty of Science Press Office
   

Related International Press Releases

1. •Carnegie Institution
   

2. •Keck Observatory
   

3. •University of Hawaii
   

Supporting material

1. •Copies of the accepted paper for publication in The Astrophysical Journal Letters, is available at http://arxiv.org/abs/1202.0446
   

Graphical Material

1. •GJ667Cc.png : artistic conception of the GJ667C system with planet c in the foreground. Even though it is an artists conception, the size of the star and the binary are on the right scale, color and brightness.
   

2. •GJ667C_TwoPlanets.png  : artistic conception of the two planets we report here : b and c. Planet c is the one that lies in the habitable zone of the star. Planet b is too hot to be habitable.
   

3. •GJ667C_TwoPlanets_withLabels.png : the same figure of the two planets now with labels.
   

4. •GJ667_vs_Sol.avi (movie) : Solar System compared to the two comfirmed planets b and c.
   

5. •GJ667_Constelation.png : Sky location of the GJ 667 system in the constelation of Scorpius. The system is a bit too faint to be seen by eye.
   

All the above images and video were created by G. Anglada using the free software Celestia (http://www.shatters.net/celestia/).