Researchers Build New Model to Identify Habitable Zone for Alien Planets

Researchers from Penn State Department of Geosciences have developed an updated model to find out whether a planet discovered falls within the habitable zone.

A habitable zone is where liquid water can exist on the planet's surface and thus sustain life. The previous habitable zone model was developed by Penn State researcher James Kasting about 20 years ago. Now Penn State scientists, including Kasting, have built their work on the previous model to give a more precise calculation of where habitable zones around a star can be found.

The new definition was built based on updated absorption databases of greenhouse gases called HITRAN (high-resolution transmission molecular absorption) and HITEMP (high-temperature spectroscopic absorption parameters). The databases provided accurate information on water and carbon dioxide than what was previously available. This helped the researchers to build new estimates from the prior model.

Using the information, the team was able to calculate habitable zones around parent stars. When they compared the new estimates with the prior model, they found that the habitable zone is actually farther away from the stars than what was earlier thought. "This has implications for finding other planets with life on them," Ravi Kumar Kopparapu, a lead investigator on the study from Penn State University, said in a statement.

Based on the new definition, scientists have found that some extrasolar planets that were earlier believed to be in a habitable zone might actually not be. The boundaries of the habitable zone in our solar system have also shifted from between 0.95 astronomical units (AU, or the distance between Earth and the sun) and 1.67 AU, to the new range of 0.99 AU to 1.7 AU. With the change in the boundaries, the Earth appears to be situated at the very edge of the habitable zone, reports Space.com.

Researchers said the model could help in finding out if the alien planets discovered by NASA Kepler mission are within a habitable zone.

The findings of the study will appear in the Astrophysical journal.