Earth-Like Planets Inhabitable, Experts Claim

Till now, the condition for life to thrive on a planet was considered to be its position which must be in the habitable zone of its host star.

"We have pessimistic results for planets around young red dwarfs in this study, but we also have a better understanding of which stars have good prospects for habitability", NASA solar scientist Vladimir Airapetian, lead author of the paper, said.

Atmospheric erosions involve high-energy particles that drag molecules of liquid water - oxygen and hydrogen - out into space.

The new model for habitable zones now takes this effect into account.

Because Proxima b orbits its red dwarf host star, Proxima Centauri, 20 times closer than the Earth is to our sun, the scientists expect that the exoplanet is most likely not habitable. The proposed change would likely mean Proxima b, and other exoplanets orbiting red dwarf stars, probably aren't habitable after all. "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". However, a study published in the journal "The Astrophysical Journal Letters" said that some of the habitable zones are exposed from stellar eruptions from young red dwarf stars. 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. Proxima b, for example, orbits its star 20 times closer than Earth orbits our Sun.

The research has implications for the recently discovered planet orbiting the red dwarf Proxima Centauri, our nearest stellar neighbour. Furthermore, RT reported that frequent stellar eruptions deplete the oxygen levels in the atmosphere. As more electrons are generated, they start attracting positively charged ions, thus causing ions to escape from atmosphere. Hydrogen, which, along with oxygen, is needed to create water on a planet's surface, is already known to be extremely vulnerable to ion escape.

"To assess the habitability of planets around these stars, we need to understand how these various effects balance out".

"Considering oxygen escape alone, the model estimates a young red dwarf could render a close-in exoplanet uninhabitable within a few tens [of millions] to a hundred million years", NASA officials wrote in the same statement.

"Scientists have long suspected that extreme space weather might make these dwarf stars less than hospitable, but the NASA team put numbers to those impressions, showing that even relatively "'quiet' dwarfs are more active than previously thought", he says. Rather, it is subjected to high doses of X-rays and extreme UV radiation from superflares that occur on average every two hours, which the team estimates would see the planet's atmosphere stripped of any oxygen within 10 million years.

What's more, intense bouts of stellar wind and magnetic activity worsen harsh space conditions on the exoplanet.

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.

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