There Could Be Up to 10 Billion Earth-Like Planets in Our Galaxy Alone

Our galaxy could be littered with warm, watery planets like Earth.

That’s the conclusion of researchers at Penn State University, who used data from NASA’s Kepler telescope to estimate the number of Earth-like planets in the Milky Way.


Their results, published in The Astronomical Journal this week, suggest that an Earth-like planet orbits one in every four Sun-like stars. Totalled up, that means there could be up to 10 billion Earth-like worlds in our home galaxy.

The estimate is an important step in the search for alien life, since any potential life on other planets would most likely be found on an Earth-like world warm enough to hold liquid water.

So a better understanding of the potential number of Earth-like planets in the galaxy can inform projects like the Wide-Field Infrared Survey Telescope, which will launch into space in the mid 2020s and hunt for signs of oxygen and water vapour on distant planets.

“We get a lot more return on our investment if we know when and where to look,” Eric Ford, a professor of astrophysics and co-author of the new study, told Business Insider.

Ford’s team defined an Earth-like planet as being anywhere from three-quarters to one-and-a-half times the size of Earth, and orbiting its star every 237 to 500 days.

That’s presumably within the star’s habitable zone – the “range of orbital distances at which the planets could support liquid water on their surfaces,” as Ford described it in a press release.

“For astronomers who are trying to figure out what is a good design for the next major space observatory, this piece of information is an integral part of that planning process,” he said.


5 to 10 billion planets like Earth

The researchers’…

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