The calculations assume that life could form at all on planets in habitable zones surrounding stars as small as 8 percent the size of our sun, but that might not be the case. "There's a lot of papers that say that life may be suppressed around those stars," James Kasting, geoscientist and exoplanet researcher at Penn State, told Popular Science. "My guess is that very few of them have habitable planets." The habitable zone around these small stars would be much closer in, so any planets might be more vulnerable to harmful radiation shooting off of the star. Even worse, the star's gravity could pull much harder on one side of the planet, causing more volcanic activity that could lead to runaway greenhouse effect and the oceans boiling off, according to a paper published by researchers Rodrigo Luger and Rory Barnes.