New calculations show that for every five sun-like stars, there might be one Earth-like planet, meaning there are about 6 billion Earth-like planets in the universe. 

While a majority of the Earth-like exoplanets discovered so far have been gas and ice giants, calculations released by Michelle Kunimoto, astronomer at the University of British Columbia, suggest that 7% of the Milky Way’s 400 billion planets fit the G-type classification. 

Planets that fit into the G-type classification must be rocky, about 0.75 to 1.5 times the size of the earth, and orbit around the habitable zone of a Sun-like star. 

“My calculations place an upper limit of 0.18 Earth-like planets per G-type star. 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,” Kunimoto said. 

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Kunimoto and fellow researcher Jaymie Matthews established these findings using a technique called ‘forward modeling’ in conjunction with data from the Kepler planet-hunting mission led by NASA. 

“I started by simulating the full population of exoplanets around the stars Kepler searched,” Kunimoto explains in a new study published in The Astronomical Journal. “I marked each planet as ‘detected’ or 'missed' depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalog of planets.”

Kunimoto had previously been credited with discovering 17 new exoplanets. One of those planets also happened to be in the habitable zone, and had ice on its surface, promising new possibilities in the search for habitable planets and life beyond the earth.