Scientists use 3D climate model to narrow search for habitable exoplanets

We are now closer to answering whether ‘we are alone in the universe’

Photo: NASA

For the first time, scientists used a 3D climate model that incorporates photochemistry to study and redefine the habitability of exoplanets surrounding M dwarf stars, which comprise about 70% of the total galactic population. The findings - published Thursday in the Astrophysical Journal - could help planetary scientists know what to look for when surveying potentially habitable exoplanets.

The team from Northwestern University collaborated with researchers from the University of Colorado Boulder, NASA’s Virtual Planet Laboratory and the Massachusetts Institute of Technology (MIT). Using this tool, astronomers were then able to redefine the conditions that make a planet habitable by taking the star’s radiation and the planet’s rotation rate into account.

“For most of human history, the question of whether or not life exists elsewhere has belonged only within the philosophical realm,” said Northwestern’s Howard Chen, the study’s first author. “It’s only in recent years that we have had the modelling tools and observational technology to address this question.”

As a result, the collaboration discovered that only planets orbiting active stars, those that emit a lot of ultraviolet (UV) radiation, lose large amounts of water to vaporisation. Thus, planets around inactive, or quiet stars are more likely to maintain liquid water. The researchers also found that planets with thin ozone layers, which have otherwise habitable surface temperatures, receive dangerous levels of UV dosages, making them hazardous for complex surface life.

The team also found that many planets in the circumstellar habitable zone could not sustain life due to their thin ozone layers. Despite having otherwise habitable surface temperatures, these planets' ozone layers allow too much UV radiation to pass through and penetrate to the ground, making them hazardous for complex surface life.

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