Residing in a triple star system in the Scorpius constellation some 23-23 light-years away, Gliese (GJ) 667 Cc orbits within the habitable zone of its red dwarf star. Astronomers at the European Southern Observatory discovered Gliese 667 Cc in 2011 (announced 2012) using the radial velocity method, also called Doppler spectroscopy. This indirect method of planet hunting involves measuring a star’s Doppler effect, or change in wavelength frequency, which may reveal the presence of planets in orbit. Its namesake derives from Christian Doppler, the Austrian physicist who first described this phenomenon in 1842. The radial velocity method accounts for about 30% of confirmed exoplanet discoveries.
Classified as a super-Earth, Gliese 667 Cc has a surface temperature near 277.4 K (4.3 C, 39.6 F), strikingly comparable to our planet’s climate. The exoplanet appears heavier than Earth, at a minimum at least 3.7 times its mass. Gliese 667 Cc orbits its star every 28 days, and astronomers believe it tidally locked, with one side of the planet facing its star, the other hemisphere in perpetual night. The terminator line divides these two extreme regions, providing a sliver of ideal conditions that could allow water to exist.
Curiously enough, a 2013 paper published in The Astrophysical Journal revealed that Gliese 667 Cc remains exposed to tidal heating at a rate 300 times more than on Earth, casting doubts whether this world offers suitable conditions for habitability. Despite all this, the Planetary Habitability Laboratory ranks it high on the list of candidate exoplanets with the most promising characteristics. These findings leave us with speculation until our technology progresses.
Above Image: Artist impression of a hypothetical sunset on Gliese 667 Cc, its three suns appearing at various levels of brightness. Credit: ESO/L. Calçada
Star: Gliese (GJ 667 C)
Distance From Earth: 22.18 Light-years
Habitable Zone: YES
Planet Radius: 1.54⊕ (Super-Earth)
Orbital Period: 28 days
Temperature: 277.4 K (4.3 C, 39.6 F)
Discoverer: European Southern Observatory
Discovery Method: Radial Velocity