Exoplanet Proxima b may be habitable?

Dimitra Atri, an astrobiologist at the Blue Marble Institute of Space Science, has published a paper outlining his work running simulations of planet Proxima Centauri b (or Proxima b). He thinks the exoplanet Proxima b could be habitable if it has a thick protective atmosphere or a strong magnetic field.

Proxima b is an exoplanet circling the red dwarf star Proxima Centauri, the closest star to the Sun. Proxima Centauri, distanced 4.22 light years away, is not visible to the unaided eye from Earth because of its low luminosity.

Last August, astronomers announced that Proxima Centauri hosts a planet, named Proxima b, in its habitable zone. Since that time, Professor Atri created many simulations to measure the impact of stellar flares from the Proxima Centauri. To discern if Proxima b might be capable of supporting life, Atri considered three main factors—the type and size of stellar flares, various thicknesses of the planet’s atmosphere and the strength of its magnetic field. He reports that if Proxima b turns out to have an atmosphere similar to Earth’s, life on the surface could very well survive most of the flares occurring on its star.

Proxima b

Artist’s conception of Proxima Centauri b, with Proxima Centauri and the Alpha Centauri binary system in the background. Source: Wikipedia

Kepler observations have uncovered the existence of a large number of close-in exoplanets. Proxima b is one of them. This exoplanet is orbiting within Proxima Centauri’s habitable zone. That is the region where liquid water may exist on its surface. This Earth-like planet is considered a good candidate for supporting life, but there are several concerns.

The scientists think the planet might be tidally locked. That means the one side of the planet permanently faces its star, as the moon does Earth. Astronomers believe planetwide atmospheric winds would transport heat around the planet. Professor Atri claims that the planet still may be habitable if it has an atmosphere thick enough to transfer heat to the side facing away from the star.

Proxima Centauri also has a large stellar activity, occasional dramatic increases in brightness and high-energy emissions because of magnetic activity. That results in creating large solar flares and storms. Those flares could burn away the surface of the exoplanet and any life on it, if it does not have a strong magnetic field or a protective atmosphere.

Another concern is the brightness of its host star since the Proxima Centauri is comparatively dim. But scientists think that the Proxima Centauri’s brightness evolution has been slow. “Proxima’s brightness evolution has been slow and complicated,” Rory Barnes, UW research assistant professor of astronomy, states. “Stellar evolution models all predict that for the first one billion years Proxima slowly dimmed to its current brightness, which implies that for about the first quarter of a billion years, planet b’s surface would have been too hot for Earth-like conditions.”

The challenges of exploring Proxima b are huge, but it may be the first exoplanet to be directly characterized by powerful ground and space-based telescopes planned.