There’s possibly 20 billion other Earths in our galaxy

By Casey Frye, CCNN Writer

Earth-like planets come in many sizes.

The Sun is a priceless life-giving star for people on Earth, but in our Milky Way galaxy, it’s really just one burning ball of gas among billions. Doesn’t seem so special when I say it like that, right?

Well, according to researchers from the Harvard-Smithsonian Center for Astrophysics and a more recent study by the University of Hawaii at Manoa and the University of California, Berkeley, Earth isn’t all that rare either, since there are around 20 billion other planets like ours in the galaxy!

For their studies, scientists wanted to know how many Earth-like planets were orbiting stars in a “habitable zone” –  a region that’s not too close and not too far from its host star. If it’s too close, it’ll turn into a boiling planet, but if it’s too far, the frosty temperatures are hostile to life. If it’s in the habitable zone, though, then liquid water can exist, which is a key ingredient for biological life.

In order to find out just how many Earth-like planets are orbiting that sweet spot, researchers ran a computer program that analyzed starlight fluctuations – changes in brightness – collected at the Kepler space observatory. Basically, the idea is that if a planet passed in front of a star from our point of view, the shadow would make the star appear a little less brighter.

So, how many Earth-like planets did they discover? Well, of the 42,000 stars they observed, about 10 seem to have some sort of planet like ours! I know it seems like a low number, but the scientists say there’s probably a whole lot more that were missed because they weren’t big enough to make a significant shadow or didn’t completely round their orbits to block light.

If they take these into account, then generalize the data to the billions of stars in the Milky Way, you’re left with a lot of Earth-like planets. “The high abundance of Earth-sized planets appears to be a general feature of nature,” says lead study author Erik Petigura. “With about 100 billion stars in our Milky Way galaxy, that’s about 20 billion such planets.”

I wonder if there are other intelligent beings on those planets. If so, greetings! We come in peace.

Images courtesy of NASA.