Big News for Exoplanet Enthusiasts

It's one thing whenever Kepler finds a potentially habitable exoplanet around a star several hundred light years away. That's cool, but there's nothing we can realistically do about it. The technology to move things fast enough to get that far in human amounts of time doesn't exist, won't exist anywhere in the near future, and is barely even theoretically possible outside of your crazier fringe physics. Those planets will most likely remain mere curiosities for the rest of our lives. It's another thing entirely when we find a potentially habitable exoplanet orbiting the star Proxima Centauri, which if you couldn't deduce it from the name, is the Sun's closest stellar neighbor.

Credit: ESO/M. Kornmesser

Now, this is no slam dunk, "oh, it's definitely Earth 2.0" moment. The habitability of planets orbiting red dwarfs has always been in dispute, and the Proxima Centauri system features many of the red dwarf flaws. Proxima Centauri b orbits just 4.7 million miles from its star, which is okay since Proxima Centauri is a wet match compared to the Sun's 60 watt bulb, but it does mean that the planet will be tidally locked, either showing only 1 side to its sun or, if we're lucky, in a 3:2 resonance like Mercury (3 planetary rotations for every 2 orbits). If Proxima Centauri b is tidally locked in a 1:1 resonance like the Moon is, it means that one side of the planet will be constantly in the sun, and the other will never see sunlight. An atmosphere mitigates most of the vast temperature differential this situation causes, but we're not sure a planet formed in these conditions can maintain an atmosphere, which brings us to our second problem.

Many red dwarfs have issues with solar flares. They shoot off big, powerful flares at a much higher rate then the Sun does. Proxima Centauri has this issue, and as a result, Proxima Centauri b currently experiences high level radiation 100 times more intense then Earth currently does. A powerful magnetic field would protect the planet, but we don't know if it has one, or if the solar flares were even more intense earlier in the star's history. It's possible intense solar radiation stripped the planet of any atmosphere when the the planet was young, and there's nothing there now but barren rock.

So, what should you take away from this? First, anyone who says we found a new Earth right next door are wrong. We don't know what this is, and even if it does turn out to be habitable, it won't be anything like Earth. Habitable doesn't necessarily mean pleasant, and I can pretty much guarantee that life on Proxima Centauri b would be hard, for us or for native life. Plant life would be black instead of green, since most available light would be in the infrared rather then risible spectrum, and high winds would constantly blow from where the sun is directly overhead towards the night side. But you know what? If Proxima Centauri b does turn out to be this hard-scrabble, bleak world where life has to struggle to get by, it would still be the discovery of the century. I hope it works out, I really do, but let's wait until we get more information before we start planning a trip out there.