Earthlike Planets Could Have Formed at Almost Any Time in the Milky Way’s Evolution
Building a terrestrial planet requires raw materials that weren’t available in the early history of the universe. The Big Bang filled space with hydrogen and helium. Chemical elements like silicon and oxygen - key components of rocks - had to be cooked up over time by stars. But how long did that take? How many of such heavy elements do you need to form planets, especially rocky, Earthlike planets?