A pair of new studies is debunking the assumptions made by the scientists while determining whether an exoplanet is habitable or not. Till now, only two star systems have been discovered that are said to host planets in the habitable zone thus hinting about the possibility of life on them. The most preferred exoplanet candidate to support alien life is the Proxima Centauri b. It is the closest potentially habitable planet as per the researchers. But the scientists of the latest studies argue that the planet might not be habitable at all because its host star might be blowing huge amount of strong solar winds towards its atmosphere.
Proxima Centauri b is one of the three planets of the red dwarf star Alpha Centauri which is the closest star to our solar system. Proxima Centauri b is just about 4.2 light years away from Earth, and it is one of those dozen rocky exoplanets that orbit in the habitable zone of their parent star. That means there is a chance that liquid water might be flowing o the surface of Proxima Centauri, But the latest pair of studies say that only water is not enough to decide whether a planet is habitable or not. The habitability depends mainly on the parent star that the exoplanets revolve around.
The models of the latest studies talk about the influence of the stellar winds or the charged X-ray or UV ray particles that a host star emits or injects towards its planets. The models revealed that if the parent star emits strong stellar winds towards its closely orbiting planet, then it destroys its atmosphere for over hundreds of millions of years, and thus it becomes impossible for the planet to support life irrespective of its presence in the habitable zone.
Lead author Chuanfei Dong of Princeton University said, “Traditional definition and climate models of the habitable zone consider only the surface temperature. But the stellar wind can significantly contribute to the long-term erosion and atmospheric loss of many exoplanets, so the climate models tell only part of the story.” Among both the studies, one study analyzed how long an atmosphere would survive on Proxima Centauri b which faces frequent stellar winds, and another study tried to examine how long the oceans of the so-called ‘watery world’ could survive under different stellar wind conditions.
Both studies indicated that stellar winds can severely affect both the atmosphere as well as the ocean world of an exoplanet. If the intense stellar winds continue to attack the atmosphere of the Proxima Centauri b the, the atmosphere will get very thin, and the evaporated water will not be able to fall as rain. “Our results indicate that Proxima Centauri b and similar exoplanets are generally not capable of supporting an atmosphere over sufficiently long timescales when the stellar wind pressure is high,” Dong informed. He also said that as the planets are tidally locked so one part is always exposed to the parent star and hence it results in the weak global magnetic field.
So, the atmosphere of Proxima Centauri can be retained if the intensity of the stellar winds becomes low and if the planet manages to have a strong magnetic field that could deflect the charged particles.