One of the key incentives behind hunting down exoplanets is to find alien worlds with qualities similar to Earth. Named Gliese 832 c, the super earth planet takes 16 days to orbit its red-dwarf star, GJ 832. The mass of this exoplanet is at least five times that of Earth.
Gliese 832c orbits a red dwarf star and it was discovered by the international Anglo-Australian Planet Search team led by Robert Wittenmyer of the University of New South Wales, Australia. The discovery has been accepted for publication in the Astrophysical Journal.
Red dwarfs are small, dim stars that generate far less energy than our sun. Therefore, for a red dwarf-orbiting planet to maintain water in a liquid state on its surface, it must orbit much closer to the star. In the case of Gliese 832c, its habitable zone is very compact and Gliese 832c has an orbital period of just under 36 days. The possibly rocky world which is around 5 times the mass of Earth is therefore considered habitable. In fact, Gliese 832c is considered to be the third most habitable world known so far on the Earth Similarity Index (ESI).
The researchers said that the average stellar energy received by this exoplanet is similar to Earth because red dwarfs shine more dimly than our Sun. The scientists said that though this celestial body can be put among the top three most Earth like planets according to the Earth Similarity Index but it is unlikely that it is habitable. Team member and Head of the University of New South Wales Exoplanetary Science research group, Professor Chris Tinney said in a press release that life can survive if the planet has a similar atmosphere to Earth but seasonal shifts would be extreme.
“However, given the large mass of the planet, it seems likely that it would possess a massive atmosphere which may well render the planet inhospitable,” Tinney said.”A denser atmosphere would trap heat and could make it more like a super-Venus and too hot for life,” he added.
The researchers managed to locate this planet from its gravitational pull on its parent star which forced the star to wobble slightly. The Anglo-Australian Telescope was used by the researchers to make observations of the planet.
They combined their data with observations from the 6.5m Magellan Telescope and the European Southern Observatory 3.6m telescope to make this new discovery.
Like Venus, Gliese 832c is probably enduring intense warming caused by a runaway greenhouse effect. In this case, although the planet’s orbital location should allow liquid water to persist, any water would likely be ripped apart on a molecular level by intense atmospheric heating and ultraviolet light from the star, a process known as dissociation.
Of course the astronomers have no idea what chemicals are contained within Gliese 832c’s atmosphere. The world was discovered through its gravitational pull on its parent star, so no information about its atmosphere (if it indeed has one) and any water it contains is known.
“The issue of habitability depends on the atmosphere,” said Wittenmyer, “and the only way we can know that is if the planet transits. IF Gliese 832c is found to transit, then we can get radius and then an idea of the bulk density and likely composition. That will tell us whether we have a super-Earth, a super-Venus or a mini-Uranus.”
Irrespective of 832c’s ESI, Gliese 832c has at least a likely rocky inner planet and a giant outer planet present and accounted for. That makes this nearby system is a good spot to search for other familiar sites.
As more and more exoplanets are discovered the rules of planetary formation and habitability are being continually rewritten. An ESI score is just the beginning. In the end, with more time and much more information, we may discover that it takes an entire Solar System to produce a habitable planet.