Could There be 100 Billion Potentially Habitable Planets in the Galaxy?

As we’ve reported recently, the likelihood of findings habitable Earth-sized worlds just seems to keep getting better and better. But now the latest calculations from a new paper out this week are almost mind-bending. Using what the authors call a “very careful extrapolation” of the rate of small planets observed around M dwarf stars by the Kepler spacecraft, they estimate there could be upwards of 100 billion Earth-sized worlds in the habitable zones of M dwarf or red dwarf stars in our galaxy. And since the population of these stars themselves are estimated to be around 100 billion in the Milky Way, that’s – on average – an Earth-sized world for every red dwarf star in our galaxy.

Image 1 | A visualization of the “unseen” red dwarfs in the night sky. Credit: D. Aguilar & C. Pulliam (CfA)

Image 2| The graphic shows optimistic and conservative habitable zone boundaries around cool, low mass stars. The numbers indicate the names of known Kepler planet candidates. Yellow color represents candidates with less than 1.4 times Earth-radius. Green color represents planet candidates between 1.4 and 2 Earth radius. Credit: Penn State.