There might be two billion Earth-like planets just in our galaxy

Illustration for article titled There might be two billion Earth-like planets just in our galaxy

The recent exoplanet spotting by NASA's Kepler probe revealed there might be more than a million Earth-like planets in our galaxy. Now a new estimate says as many as 1 out of every 37 sun-like stars has an Earth-like world.


When we last checked in on exoplanets, astronomers had set 500 million as a conservative estimate for the number of Earth-like, potentially habitable planets in the Milky Way. Now scientists at NASA's Jet Propulsion Laboratory have crunched the numbers again, and we're up to at least two billion Earth-like worlds.


Here's how the math works. Based on the data from Kepler, the JPL scientists estimated that 1.4 to 2.7 percent of all stars with the same basic properties as our Sun are home to Earth-like planets. That means a planet between 0.8 and two times the mass of Earth that lies within the habitable zone of its star. When you total up the amount of sun-like stars in the galaxy, that gives you two billion stars. And, of the hundred or so sun-like stars within a few dozen light-years of Earth, at least two of them should be home to habitable worlds.

JPL researcher Joseph Catanzarite points out just how many Earth-like planets there might really be:

"This means there are a lot of Earth analogs out there - two billion in the Milky Way galaxy. With that large a number, there's a good chance life and maybe even intelligent life might exist on some of those planets. And that's just our galaxy alone - there are 50 billion other galaxies."

And even then, this estimate restricts us to just Earth-like planets that orbit stars like our own. Much smaller, dimmer stars - the red dwarfs - could also support habitable planets, and they're far, far more numerous than sun-like stars. If the percentage of red dwarfs with habitable planets is anything like that of sun-like stars, then that two billion planets estimate could skyrocket.

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Dr Emilio Lizardo

This is wonderful news but it doesn't answer the Fermi paradox.

So where is everybody?