A team of astronomers led by Dr Robert Wittenmyer of the University of New South Wales has discovered a super-Earth orbiting near the inner edge of the habitable zone of Gliese 832 (GJ 832), a red-dwarf star previously known to host a cold Jupiter-like exoplanet.
Gliese 832, also known as HD 204961 or LHS 3685, is a M1.5 dwarf located in the constellation Grus, about 16 light-years from Earth. It has about half the mass and radius of the Sun.
This star is already known to harbor Gliese 832b, a cold Jupiter-like planet discovered in 2009.
“With an outer giant planet and an interior potentially rocky planet, this planetary system can be thought of as a miniature version of our Solar System,” said Prof Chris Tinney, an astronomer with the University of New South Wales and a co-author of the discovery paper accepted for publication in the Astrophysical Journal (arXiv.org pre-print).
The newly discovered exoplanet, labeled Gliese 832c, has an orbital period of 35.68 days, a mass 5.4 times that of Earth’s and receives about the same average energy as Earth does from the Sun.
Gliese 832c might have Earth-like temperatures, albeit with large seasonal shifts, given a similar terrestrial atmosphere.
“If the planet has a similar atmosphere to Earth it may be possible for life to survive, although seasonal shifts would be extreme,” Prof Tinney said.
A denser atmosphere, something expected for Super-Earths, could easily make this planet too hot for life and a Super-Venus instead.
The Earth Similarity Index of Gliese 832c (0.81) is comparable to exoplanets Gliese 667Cc (0.84) and Kepler-62e (0.83). This makes it one of the top three most Earth-like planets according to the ESI and the closest one to Earth of all three, a prime object for follow-up observations.
Gliese 832c was discovered from its gravitational pull on its star, which causes the star to wobble slightly.
Dr Wittenmyer, Prof Tinney and their colleagues used the Anglo-Australian Telescope, the 6.5-m Magellan Telescope and the European Southern Observatory 3.6-m telescope to make this new discovery.
Gliese 832b and c are a scaled-down version of our own Solar System, with an inner potentially Earth-like planet and an outer Jupiter-like giant planet. Gliese 832b may well played a similar dynamical role in the system to that played by Jupiter in our Solar System.
“It will be interesting to know if any additional objects in the Gliese 832 system follow this familiar Solar System configuration, but this architecture remains rare among the known exoplanet systems,” the scientists said.
R.A. Wittenmyer et al. GJ 832c: A super-earth in the habitable zone. ApJ, accepted for publication; arXiv: 1406.5587