Earth-like exoplanets are the ones that get astronomers (and the rest of us) really excited. These rocky worlds are about the same size as our planet—give or take a little—and many orbit in the “Goldilocks zone” where it’s not too hot and not too cold for liquid water to exist on the surface. Water is the key ingredient for life as we know it, so these planets are our best bets for finding places that might have oceans, clouds, or even alien life one day.

Scientists have found hundreds of them using telescopes like Kepler, TESS, and the James Webb Space Telescope. Some orbit Sun-like stars, others circle cooler red dwarfs. A few are close enough that future missions could study their atmospheres for signs of biology. They’re not perfect twins—some might be tidally locked with one eternal day side, others could have thick greenhouse atmospheres—but they prove Earth isn’t unique. Out there in the Milky Way, there could be billions more just waiting to be discovered.