An international team of researchers has used new observations of Gliese 667C to find evidence of up to seven planets circling the star, including three super-Earths that orbit in the habitable zone.
Gliese 667C is part of a triple star system known as Gliese 667. Located in the constellation of Scorpius only 22 light-years away, the star is just over one third of the mass of the Sun.
Previous studies had found that it hosts three planets – Gliese 667 Cb, Gliese 667 Cc and Gliese 667 Cd, including one in the habitable zone.
Now, the team led by Dr Guillem Anglada-Escudé of the University of Göttingen re-examined the system, and found evidence of seven planets around Gliese 667C.
The new planets completely fill up the habitable zone of Gliese 667C, as there are no more stable orbits in which a planet could exist at the right distance to it.
“We knew that the star had three planets from previous studies, so we wanted to see whether there were any more. By adding some new observations and revisiting existing data we were able to confirm these three and confidently reveal several more. Finding three low-mass planets in the star’s habitable zone is very exciting!” said Dr Mikko Tuomi of the University of Hertfordshire, UK, second author of the paper reporting the discovery in the journal Astronomy & Astrophysics (paper in .pdf).
“Three of these planets are confirmed to be super-Earths that are within the habitable zone.”
“This is the first time that three such planets have been spotted orbiting in this zone in the same system.”
“The number of potentially habitable planets in our galaxy is much greater if we can expect to find several of them around each low-mass star — instead of looking at ten stars to look for a single potentially habitable planet, we now know we can look at just one star and find several of them,” said study co-author Dr Rory Barnes from the University of Washington.
Gliese 667C’s habitable zone lies entirely within an orbit the size of Mercury’s, much closer in than for our Sun. The system is the first example of a system where such a low-mass star is seen to host several potentially rocky planets in the habitable zone.
“These new results highlight how valuable it can be to re-analyze data in this way and combine results from different teams on different telescopes,” Dr Anglada-Escudé concluded.
Bibliographic information: G. Anglada-Escudé et al. 2013. A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone. Astronomy & Astrophysics, in press; doi: 10.1051/0004-6361/201321331