A team of astronomers have used data from observations of Gliese 667C and combined it with existing data from HARPS at ESO’s 3.6-metre telescope in Chile which has revealed a system with at least six planets. Three of the planets are super-Earths where liquid water could exist, making them candidates for the presence of life. This is the first system found with a fully packed habitable zone.
Gliese 667C is one third of the mass of the Sun, it is part of a triple star system known as Gliese 667 , 22 light-years (about 129,329,761,907,465 miles) away in the constellation of Scorpius . In the relativity of the Universe, this is close to us.
A team of astronomers led by Guillem Anglada-Escudé of the University of Göttingen, Germany and Mikko Tuomi of the University of Hertfordshire, UK, has reexamined the system. They added new HARPS observations, along with data from ESO’s Very Large Telescope (VLT), the W.M. Keck Observatory and the Magellan Telescopes to the equation . The team has found evidence for up to seven planets around the star!
“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!” – Mikko Tuomi (University of Hertfordshire, UK).
Three of these planets are confirmed to be super-Earths and are within their star’s habitable zone, where water may be present in liquid form. This is the first time that three planets have been seen orbiting 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,” adds co-author Rory Barnes (University of Washington, USA).
There are many compact systems around sun-like stars in our own Milky Way Galaxy but these stars are far too hot for the planets to be habitable. This is not true for Gliese 667C, where the the habitable zone lies within an orbit the size of Mercury’s, much closer. This is the first example where a low mass star has several rocky planets in the habitable zone.
The ESO scientist responsible for HARPS, Gaspare Lo Curto, remarks: “This exciting result was largely made possible by the power of HARPS and its associated software and it also underlines the value of the ESO archive. It is very good to also see several independent research groups exploiting this unique instrument and achieving the ultimate precision.”
And Anglada-Escudé concludes: “These new results highlight how valuable it can be to re-analyse data in this way and combine results from different teams on different telescopes.”
This research was presented in a paper entitled “A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone”, to appear in the journal Astronomy & Astrophysics.
The team is composed of G. Anglada-Escudé (University of Göttingen, Germany), M. Tuomi (University of Hertfordshire, UK), E. Gerlach (Technical University of Dresden, Germany), R. Barnes (University of Washington, USA), R. Heller (Leibniz Institute for Astrophysics, Potsdam, Germany), J. S. Jenkins (Universidad de Chile, Chile), S. Wende (University of Göttingen, Germany), S. S. Vogt (University of California, Santa Cruz, USA), R. P. Butler (Carnegie Institution of Washington, USA), A. Reiners (University of Göttingen, Germany), and H. R. A. Jones (University of Hertfordshire, UK).