Early to the Party
A theoretical study from the Space Telescope Science Institute (STScI) proposes that the Earth is among the first of its kind in terms of habitability. The study states that when our solar system was born 4.6 billion years ago, only 8 percent of potentially habitable planets existed and that the bulk of those planets (92 percent) haven’t even been born yet. Study author Peter Behroozi said: "Compared to all the planets that will ever form in the universe, the Earth is actually quite early."
More Earths to Come
Based on assessed data from the Hubble Space Telescope and the Kepler Space Observatory, researchers say that future Earth-like planets are likely to evolve in galaxies that have yet to use up all their hydrogen and helium gas to build stars and planets. The Milky Way galaxy has conversely used up much of this gas already. STScI co-investigator Molly Peeples adds: "There is enough remaining material [after the big bang] to produce even more planets in the future, in the Milky Way and beyond."