There could be as many as six billion Earth-like planets in our galaxy

Each with the potential for hosting life.

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Is humanity alone in the universe? It’s a question that mankind has grappled with for literal ages, and while Hollywood has spent decades feeding our curiosity with depictions of little green men and pew-pewing lasers, scientists have taken a more cautious approach. For life (at least as we know it) to exist on other planets, those planets must be capable of supporting life. Now, new research shows there are considerably more of these types of planets out there than previously thought.

Such planets, known as Earth-like planets or ocean worlds, must be a similar size to Earth, orbit a sun-like star and be a rocky (or terrestrial) planet. It needs to orbit its star (called G-type stars) within a habitable zone, so the temperature is not too hot or too cold, and it’s able to host liquid water. Typically, such planets are hard to find, given their small size and distance from their stars, but thanks to new research techniques, scientists now think there could be as many as six billion earth-like planets across our galaxy.

The study, published in The Astronomical Journal, shows that previously, it was thought there were around 0.02 Earth-like planets for every G-type star. Now, drawing on data from NASA’s Kepler planet-hunting program, researchers from the University of British Columbia have established up to 0.18 Earth-like planets for every G-type star.

According to researcher Michelle Kunimoto, the findings could have big implications for life-seeking space missions. NASA has designs on visiting ocean worlds such as Jupiter’s moon Europa, for example, to see if life could exist beneath its icy crust. "Estimating how common different kinds of planets are around different stars can provide important constraints on planet formation and evolution theories, and help optimize future missions dedicated to finding exoplanets," she said.