A new study using data from NASA's Kepler spacecraft found that in the Milky Way alone, there are likely 40 billion Earth-sized planets in the habitable temperature zone. The study was published Monday in the journal Proceedings of the National Academy of Science. Of those 40 billion planets, an estimated 8.8 billion orbit a Sun-like star. And that's just our galaxy - there are hundreds of billions of other galaxies in the universe.
And the 8.8 billion Earth-size planets figure is only a start. That's because scientists were looking only at sun-like stars, which are not the most common stars.
An earlier study found that 15 percent of the more common red dwarf stars have Earth-size planets that are close-in enough to be in the not-too-hot, not-too-cold Goldilocks Zone.
Put those together and that's probably 40 billion right-size, right-place planets, Marcy said.