Proxima B Update

The discovery of the exoplanet Proxima B last year was a landmark revelation for two reasons. The first is its proximity, it orbits the closest star to our solar system, Proxima Centauri, which itself has recently been determined to be a member of the greater Alpha Centauri system. The second reason is that the planet happens to be located within the zone of habitability of its star opening up the possibility that it might be earth-like, at least in some ways and that it may hold the potential for life to have evolved there.

But in a new study published by Vladimir Airapetian and his colleagues there is a model for how red dwarfs act when they're young and how that affects any planets within their zones of habitability. Unfortunately, the implications on Proxima B are not so good.

This study shows that immense solar flares may have removed all oxygen from the planet's atmosphere early in its history, and in fact would affect any planets within the habitability zone of any red dwarf star. These are the most common stars in the galaxy, something on the order of 75 percent of all stars and that holds significant ramifications for answering the Fermi Paradox, or the question of if there are aliens out there, why don't we see them? Well, if three quarters of all stars can't develop life within their zones of habitability, that eliminates a lot of the potential for life in the universe in general.

The reasoning behind the study is that while red dwarfs are among the coolest stars in temperature, they counter intuitively end up more active. They can even fire off superflares early in their history, this is bad news for life. So while they are a very stable kind of star when they age, and live enormously long lives that would give evolution a chance to get a foothold,  their violent past may preclude life from arising in an earth-like way on any planets orbiting them.

Part of the problem is that red dwarfs are tiny and dim, and that means that their zones of habitability are in a different location than a star such as our sun. Planets must therefore be over ten times closer to their star in order to be within the zone. This leaves them wide open to damage caused by solar flares and storms.

Planets that are located in inner solar systems tend to lose hydrogen because the X-Ray and Ultraviolet radiation from stellar flares strips electrons from the atoms which escape into space and drag the ionized atoms with them. When you get much closer to a star, as is the case for habitability zones around red dwarves, oxygen and nitrogen can then escape in the same way. That would leave the planet devoid of two necessary elements for life as we know it to evolve.

But there's even worse news. When you bring hydrogen into that mix, it becomes a situation where the planet would also slowly lose its liquid water as it evaporates and enters the atmosphere. This would leave Proxima B a lifeless, arid world even though it's within a zone of habitability.

But in a way, this is good news. The planet is close to us, so much so that it's within the realm of possibility that if initiatives like Project Starshot see fruition, some of us may see close up images of proxima B within our lifetimes. We may well find a world that we can terraform if there's enough ice in the outer part of the system and then some day call it another home for humanity.