A recent story that’s still making waves is the detection of Kepler 186f, a planet the size of Earth and in the so called “habitable zone” of its host star. It would seem K186f is then very much like Earth but that’s not exactly true. The “habitable zone” is defined as the region around a star where liquid water can exist (the bedrock of life as we know it). For a star like our sun, the Earth is in this “goldilocks region,” not too hot, not too cold. But K186f’s sun is a lot cooler than ours, so it’s much closer in! The host star, Kepler 186 is an M1 star, a cool star around 3800 Kelvin, compared to our sun’s 6000 Kelvin temperature.
So if K186f is in the habitable zone, is it habitable? Part of the problem with answering this question is that we don’t understand how the radiation and activity of M dwarfs will weigh on the habitability of liquid-water-containing planets around it. Just because it’s at the right temperature, doesn’t mean if can support life. And as far as our new friend K186f goes, we may never know if it’s habitable or inhabited and we’ll probably never visit; it’s very very far away. Before we fret, consider that the major success of the Kepler mission has been a huge statistical sample of planets helping us understand how often planets of different sizes and orbits occur in our galaxy. K186f is a sort of proof of concept; we know they’re out there. Kepler has taught us that we can expect to see more of these potential Earth counterparts, close enough to study and characterize. We’re getting that much closer to finding other Earths — and who knows what else!
Read the paper for more information and background.
Many thanks to Alexandra Greenbaum from Johns Hopkins for her insight and commentary!
Managing Editor: Steph Hays