June 27, 2014
Potentially Habitable Exoplanet With Earth-Like Temperatures Found
redOrbit Staff & Wire Reports - Your Universe Online
Astronomers have discovered a new, potentially habitable Super-Earth believed to possess temperatures comparable to those found here, but with much larger seasonal shifts, provided the atmosphere is similar to our planet's own.Dr. Robert A. Wittenmyer, a researcher at UNSW Australia specializing in the detection and characterization of extrasolar planets, and his colleagues located the new Super-Earth in orbit around the nearby red dwarf star Gliese 832 some sixteen light years away.
In 2009, a cold Jupiter-like planet identified as Gliese 832b was discovered orbiting this star, and according to the researchers, the newly discovered Gliese 832c is believed to be the closest quality habitable world discovered to date. It has been added to the Habitable Exoplanets Catalog, along with 23 other objects of interest.
According to the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo, Gliese 832c has a mass at least five times that of Earth’s and an orbital period of 36 days. While it possesses Earth-like temperatures, the large seasonal shifts combined and a denser atmosphere could make it too hot to support life, essentially meaning that it is closer to being a Super-Venus than a Super-Earth.
“The Earth Similarity Index (ESI) of Gliese 832c (ESI = 0.81) is comparable to Gliese 667Cc (ESI = 0.84) and Kepler-62e (ESI = 0.83),” the laboratory explained. “This makes Gliese 832c one of the top three most Earth-like planets according to the ESI (i.e. with respect to Earth's stellar flux and mass) and the closest one to Earth of all three, a prime object for follow-up observations. However, other unknowns such as the bulk composition and atmosphere of the planet could make this world quite different to Earth and non-habitable.”
Artistic representations of Gliese 832c depict it as a temperate world covered in clouds. Based on the relative size of the planet, it is assumed that it possesses a rocky composition, but if it is larger it could consist primarily of ice and gas, the researchers said. It orbits near the inner edge of the conservative habitable zone.
In terms of temperature, it possesses an average equilibrium temperature of 253K, which is similar to Earth’s average equilibrium temperature of 255K. However, it has a high eccentricity (based on an estimated 0.3 albedo) that causes large temperature shifts of up to 25K.
A research paper detailing the findings of Dr. Wittenmyer’s team has been accepted for publication by The Astrophysical Journal.
At this point, the two planets orbiting Gliese 832 include an inner, Earth-like world and an outer Jupiter-like giant planet, making it appear as if it is a scaled-down version of our own Solar System. The outer giant could fill a dynamical role in the Gliese 832 system as Jupiter plays in our Solar System, the researchers said, noting that it will be interesting to discover whether or not there are any other objects that follow this particular configuration.
Image 2 (below left): Artistic representation of the potentially habitable exoplanet Gliese 832 c as compared with Earth. Gliese 832 c is represented here as a temperate world covered in clouds. The relative size of the planet in the figure assumes a rocky composition but could be larger for a ice/gas composition. Credit: PHL @ UPR Arecibo.
Image 3 (below right): The Habitable Exoplanets Catalog now has 23 objects of interest including Gliese 832 c, the closest to Earth of the top three most Earth-like worlds in the catalog. Credit: PHL @ UPR Arecibo.