Astronomers have discovered a potentially habitable exoplanet, Gliese 12 b, located 40 light-years away in the constellation Pisces. The finding, detailed in a new paper published today in Monthly Notices of the Royal Astronomical Society, has scientists excited about the possibility of life beyond our solar system.
As per the research paper, Gliese 12 b is slightly smaller than Earth and similar in size to Venus. With an estimated surface temperature of 107 degrees Fahrenheit (42 degrees Celsius), it's warmer than Earth's average but cooler than many other exoplanets. This temperature range raises the possibility of liquid water existing on the planet's surface, a key ingredient for life as we know it.
However, the big question remains: does Gliese 12 b have an atmosphere? The planet could have an Earth-like atmosphere, making it a potential haven for life. But it could also have a scorching atmosphere like Venus, or no atmosphere at all. The possibility of an entirely different kind of atmosphere is also on the table.
"Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on planets across our galaxy," said Shishir Dholakia, a doctoral student at the Centre for Astrophysics at the University of Southern Queensland in Australia, in a press release. Dholakia co-led the research team that made the discovery alongside Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London.
The exoplanet's host star is about 27 per cent of the size of our Sun and has a surface temperature that is around 60 per cent of our own star.
However, the distance separating Gliese 12 and the new planet is just 7 per cent of the distance between Earth and the Sun. Gliese 12 b therefore receives 1.6 times more energy from its star as Earth does from the Sun and about 85 per cent of what Venus experiences.
This difference in solar radiation is important because it means the planet's surface temperature is highly dependent on its atmospheric conditions. As a comparison to Gliese 12 b's estimated surface temperature of 42°C (107°F), Earth has an average surface temperature of 15°C (59°F).
"Atmospheres trap heat and - depending on the type - can change the actual surface temperature substantially," Dholakia explained. "We are quoting the planet's 'equilibrium temperature', which is the temperature the planet would be if it had no atmosphere.
"Much of the scientific value of this planet is to understand what kind of atmosphere it could have. Since Gliese 12 b gets in between the amount of light as Earth and Venus get from the Sun, it will be valuable for bridging the gap between these two planets in our solar system."
Palethorpe added: "It is thought that Earth's and Venus's first atmospheres were stripped away and then replenished by volcanic outgassing and bombardments from residual material in the solar system.
"The Earth is habitable, but Venus is not due to its complete loss of water. Because Gliese 12 b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the habitability pathways planets take as they develop."
