The Hunt for Alien Life Becomes Easier with New 'Habitability Index' for Exoplanets

Finding life beyond Earth has been a major project for scientists across the world. Now, more powerful telescopes are being created to learn a bit more about exoplanets and other galaxies; but where exactly should researchers point these telescopes? Scientists are now comparing and ranking exoplanets to determine which ones most likely host life.

The new metric that researchers are creating is called the "habitability index for transiting planets." Essentially, researchers have devised a way to take all the observational data that are available and develop a prioritization scheme. This allows researchers to focus on objects when there are hundreds of targets available.

This is especially important for the James Webb Space Telescope, which is set for launch in 2018. This telescope will be the first to be able to actually measure the atmospheric composition of a rocky, possibly Earthlike planet far off in space. This, in turn, will vastly enhance the search for life.

Researchers detect some planets when the worlds pass in front of their host star, causing a brief shadow. With the Webb telescope and its "transit transmission spectroscopy," researchers will be able to study planets closely to hunt for life.

In order to figure out which planets are most likely to host life, the researchers created an index that factored in estimates of a planet's rockiness. They also accounted for a phenomenon called "eccentricity-albedo degeneracy," which comments on a sort of balancing act between a planet's albedo, which is the energy reflected back to space from its surface, and the circularity of its orbit, which affects how much energy it receives from its host star.

In the end, the researchers found that the best candidates for habitability and life are planets that get about 60 to 90 percent of the solar radiation that the Earth receives from the sun. This is in line with current thinking about a star's habitable zone.

"This innovative step allows us to move beyond the two-dimensional habitable zone concept to generate a flexible framework for prioritization that can include multiple observable characteristics and factors that affect planetary habitability," said Victoria Meadows, one of the researchers, in a news release. "The power of the habitability index will grow as we learn more about exoplanets from both observations and theory."

The findings are published in The Astrophysical Journal.

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