A recent study challenges the long-held belief that galaxies preceded rocky planets in the universe. Researchers propose that potentially habitable rocky planets could have formed even before the first galaxies emerged.
Following the Big Bang, the universe primarily consisted of hydrogen and a small amount of helium, lacking the heavier elements necessary for rocky planets like Earth. It wasn't until hundreds of millions of years later that the first stars and galaxies appeared. These early stars, which existed for a relatively short cosmic time, exploded as supernovae, dispersing heavy elements throughout the universe.
However, this new research, based on the effects of primordial supernovae, suggests that massive stars—hundreds of times the mass of the Sun—could have created conditions for rocky planets to form before galaxies did. When these massive stars exploded, they produced smaller stars with the right chemical composition to facilitate planet formation.
According to the study, these early stellar explosions generated sufficient heavy elements, allowing for the formation of smaller stars with the right chemical makeup, which in turn became the building blocks for future planets. The modeling indicates that these young stellar systems contained water equivalent to that in our Solar System, a crucial ingredient for life.
The findings imply that supernovae from the earliest stars produced essential elements like carbon, oxygen, and iron, necessary for both planet formation and the emergence of life.
If rocky planets could indeed form before the first galaxies, this could significantly alter our understanding of cosmic evolution. The authors suggest that such habitable planets, although now extinct, may still be detectable around ancient stars with low heavy element content.
Despite the intriguing implications, astronomers have yet to observe these first stars directly, with only indirect evidence of their existence and powerful supernovae. The conditions in the early universe, however, may have permitted the scenarios proposed by the researchers.