Conspiracy theories aside, the existence of intelligent lifeforms on other planets has yet to be proven. With that being said, many of those planets may actually be capable of sustaining human life -- if we can somehow travel the distance to inhabit them. Scientists have been searching for other planets that could be conducive to life for quite some time. In fact, NASA's Kepler mission recently confirmed the first near-Earth-size planet in the “habitable zone” around a star that is considered very similar to the sun that we know and love. Planets like this that orbit relatively close to small stars most likely have magnetic fields to protect their surface and any possible life on it from radiation, according to researchers at the University of Washington. But it gets a little more complex than that.

Magnetic Fields and Habitable Planets

The magnetic field of a planet begins in the core -- created by the motion of molten material in the outer core. The molten material possesses electric charges whose motion is believed to produce the magnetic field. This is how Earth’s atmosphere keeps us safe from radiation and how other Earth-like planets could do the same. Low-mass stars are fairly common in the universe and the planets that orbit near those stars are much easier for scientists to study because when they pass in front of their host star, they block a larger fraction of the light than they would if they revolved a larger sun. The relative dimness of a low-mass star gives it more of a “habitable zone,” meaning that orbiting planets receive less heat, but enough to maintain liquid water on the surface.

Gravitational Tides

The primary issue with planets that revolve too closely to their star is gravitational pull. This pull can cause planets to become tidally locked, meaning they forever face the host star, kind of like the moon in relation to the Earth. On planets with liquid water, that tug can also create tidally-generated heat inside the planet, or tidal heating, which is a welcome sign for volcanic activity. This scenario is apparent with Jupiter’s moon Io -- the most volcanically active body in our solar system. So, the big balance for scientists researching habitable planets is that, though the planet must be close enough to its star to have a magnetic field, it cannot currently be subject to tidal locking, which would decimate any life on the planet’s surface.

The Waiting Game

Luckily, some tidal heating is far from harmful, in fact, it can actually make the planet more habitable. Though it’s somewhat counterintuitive, the more tidal heating a planet experiences, the better it is at dissipating that heat, cooling the core and creating the magnetic field. For planets whose orbits don’t follow a perfectly circular pattern (like Earth) scientists have found that their orbits tend to become more circular during the time of extreme tidal heating. Once the orbit becomes more circular, the planet stops experiencing any tidal heating, making it more habitable and maybe even capable of sustaining human life. Earthlings still have a long way to go before venturing off into the stars and inhabiting another, post-tidally heated planet with a magnetic field, but who know’s what humanity could accomplish in the next few hundred years? Kepler-186f, here we come.