Scientists disagree on planet habitability definition

The discovery of an Earth-like planet that may contain life has the scientific community abuzz, yet scientists are still not in agreement about what makes a planet habitable.

The debate resurfaced Thursday as NASA announced its Kepler telescope found a planet, referred to as Kepler-452b, that might be at the right temperature to contain liquid water and orbits a star similar to Earth’s sun.

The Kepler was launched in March 2009 to identify possible Earth-like planets and look at plant habitability, which measures the likelihood a planet could sustain life.

“Briefly speaking, it’s a rocky planet at the distance where water can exist on the surface,” said Paul Hertz, director of NASA’s astrophysics division.

On specifics, though, Hertz said planet habitability lacks a clear definition.

“What people argue about is how far away from the star or how close to the star might the edges of that habitable zone might be and people think of all sorts of stranger combinations,” Hertz said. “Scientists don’t have a crisp definition where they all agree on where the lines are that divide a habitable zone from the rest of the planetary system.”

By contrast, the International Astronomical Union set forth a controversial definition of a planet in 2006. The new definition resulted in Pluto being demoted from a full-fledged planet to a dwarf planet.