New Estimates Say 6 Billion Earth-Like Planets Exist in Our Milky Way Galaxy

New Estimates Say 6 Billion Earth-Like Planets Exist in Our Milky Way Galaxy

Plenty to colonize...if humanity could ever get there.


Canadian astronomers have estimated that there are as many as 6 billion Earth-like planets in our own galaxy—some of which could harbor alien life.

The exciting new findings, which were published in The Astronomical Journal, were extrapolated from data from NASA’s now-retired Kepler telescope, which spent nearly a decade in space looking for exoplanets all across the galaxy.


To be considered an Earth-like planet, the world must be rocky, roughly the same size as Earth and should orbit in the habitable zone of a sun-like (G-type) star. At such a distance from a star, the planet might possess water in liquid form, which could potentially provide a habitable environment.

“My calculations place an upper limit of 0.18 Earth-like planets per G-type star,” the study’s co-author Michelle Kunimoto, a researcher at University of British Columbia (UBC), said in a release.

“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.”

According to UBC astronomer Jaymie Matthews, our Milky Way galaxy “has as many as 400 billion stars, with 7% of them being G-type.”

Some previous estimates regarding the number of Earth-like planets started as low as 0.02 potentially habitable worlds per sun-like star.

Generally, smaller distant worlds that resemble Earth are missed more often by telescopes and planet hunters, which means that a planet catalog represents only a small subset of the planets that are actually in orbit around the stars that are being studied.

The UBC team tapped into a technique known as “forward modeling” to overcome such obstacles.

“I started by simulating the full population of exoplanets around the stars Kepler searched,” Kunimoto said.

“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. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars.”

Previously, Kunimoto searched archival data from 200,000 stars of the Kepler mission to discover 17 new exoplanets, in addition to recovering thousands of already-known planets.

These new findings come in the same week that astronomers at the University of Nottingham estimated that there could be 36 intelligent civilizations in our galaxy.

Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek and Arirang TV. Follow or contact him on LinkedIn.

Image: Reuters