Proxima Centauri is the closest star to our own, roughly 4.2 light-years away. Last August, scientists discovered an Earth-like planet, Proxima B, orbiting that star. The finding has captured the imagination of astronomers everywhere, particularly when thinking about where else humanity might eventually call home. Avi Loeb of the Harvard-Smithsonian Center for Astrophysics says, “A habitable, rocky planet around Proxima would be the most natural location to where our civilization could aspire to move after the sun will die, five billion years from now.”
Alpha Centauri and the Southern Cross. Credit: ESO/Claus Madsen
In an article in Astronomy & Astrophysics, University of Exeter scientists describe taking the next step in determining whether Proxima B could support life—studying its climate.
Proxima B’s location in the star system suggests its potential habitability—it’s in the “Goldilocks” zone, meaning it’s not too close or too far from Proxima Centauri to contain liquid water and livable temperatures. Astronomers and meteorologists used the Unified Model, a weather and climate-predicting approach that simulates atmospheres. The team conducted climate models for Proxima B—for one they assumed the planet to have at atmosphere like Earth’s; for another, they assigned the planet a more nitrogen-rich atmosphere. They also modified the orbit of the planet in the models, gathering results for different variables. “One of the main features that distinguishes this planet from Earth is that the light from its star is mostly in the near infrared,” explains Dr. James Manners, one of the papers’ authors. “These frequencies of light interact much more strongly with water vapor and carbon dioxide in the atmosphere which affects the climate that emerges in our model.”
Proxima Centauri relative to the Sun. Credit: Illustration adapted from Pale Red Dot/ESO; Background: A. Fujii/ESO
The study indicates that Proxima B could potentially be habitable. In all orbital configurations tested, the planet appears able to sustain liquid water. While the climate simulations varied depending on orbit, the team also found indications that Proxima B’s climate might not only be livable, but stable. The 3:2 orbital configuration (a planet rotates three times for every two trips around its host star, like Mercury) in particular generated the largest temperate areas on the planet. While this doesn’t mean Proxima B has been proven as definitively habitable, it means the team didn’t discover anything to rule out habitability. The process of assessing a planet’s livability is a long and difficult one given the amount of information necessary, the distance, and the fact that one can’t truly be sure of a planet’s survivability until or unless someone or something alive goes or is found there. But this is a start.
Artist’s interpretation of Proxima B. Credit: ESO/M. Kornmesser
The study not only aids our understanding of exoplanets and their conditions but could also allow scientists to better understand Earth’s climate and how it has and will change over time. Given the results of this study, we can expect to see more about Proxima B from researchers continuing to gauge whether the planet has ingredients necessary for life.