"If we want to find an exoplanet that can develop and sustain life, we must figure out which stars make the best parents", said Vladimir Airapetian, lead author of the research, and a solar scientist at NASA's Goddard Space Flight Center.
NASA researchers took into account all these space weather, investigating the impact of stellar eruptions on exoplanets and effectively producing a new model for habitable zones.
Proxima B, one of the exoplanets that was discovered in 2016, located four light-years away from the Earth and was given the name of "second Earth, ' gave hopes to scientists that life may be possible on the planet as its position was in the 'habitable zone" from its host star. The question was, how big was the red-dwarf habitable zone - i.e., the "Goldilocks zone" - and could Proxima b fall within it? Because they are cooler than yellow dwarfs like our sun, traditional thinking puts the habitable zone much closer to the star than in our solar system. "Sometimes we use a loose terminology such as a "habitable zone" or just a "water zone" or "super Earth" or "mini-Neptune" that have no quantitative physics behind them". Frequent stellar eruptions spew massive quantities of stellar material and radiations into space, especially from young red dwarf stars.
In short, things are not looking good for life on Proxima B-or other planets around red dwarf stars, which are the most common stars in the galaxy; Roughly 20 to 30 of the stars closest to our solar system are red dwarfs.
"By the classical definition, the habitable zone around red dwarfs must be 10 to 20 times closer-in than Earth is to the sun". As the number of electrons generated through this process increases, the number of positively charged ions escaping the atmosphere also rises - a process that takes place on a smaller scale on Earth, whose middle-aged star is less prone to superflares. During ionization, electrons are knocked off from atoms, and because electrons are much lighter, they escape gravity's pull and move into space.
"We know oxygen ion escape happens on Earth at a smaller scale since the sun exhibits only a fraction of the activity of younger stars", said Alex Glocer, a Goddard astrophysicist and co-author of the paper. This new paper slams that door shut, showing that even relatively quiet dwarfs eject enough planet-frying radiation to strip off atmosphere-forming oxygen in the astronomical blink of an eye. "This effect is very sensitive to the amount of energy the star emits, which means it must play a strong role in determining what is and is not a habitable planet". NASA researchers conclude that it is unlikely exoplanet Proxima B is habitable and that oxygen would escape its atmosphere in 10 million years. After performing calculations, they expect that the exoplanet is often subjected to extreme ultraviolet radiation and superflares that occur every two hours. Space weather conditions would also be exacerbated by intense magnetic activity and stellar wind.
For the goal of their study, the researchers focused on red dwarfs, which are the most common and the longest-lived stars in the universe, and are, therefore, most likely to have planets locked in orbit around them.