Habitable planets existed even before the formation of the first galaxies. How is this possible?

Which came first: galaxies or planets? The answer can only be one: galaxies. However, a new study challenges this notion. Scientists believe that rocky, habitable planets could have formed even before the first galaxies emerged in the Universe and could potentially be detected. The research was published on the arXiv preprint server, as reported by Universe Today.

After the Big Bang, the Universe lacked heavy chemical elements, as it was primarily composed of light hydrogen and a small amount of light helium. This means there were no heavy elements from which rocky planets similar to Earth could be formed. It was only several hundred million years post-Big Bang that the first stars appeared, followed by galaxies. These initial stars existed for a relatively short time on cosmic scales and exploded as supernovae. These explosions dispersed heavy chemical elements created in the cores of the first stars throughout the Universe, which then formed the next generations of stars. Around these stars, in the formed galaxies, rocky planets, including those potentially suitable for life, began to emerge.

However, the new study suggests that potentially habitable planets may have formed even before the first galaxies were created. The research is based on primordial supernovae, which are the explosions of the very first stars. These stars had masses several hundred times greater than that of the Sun and existed for only a few million years.

According to scientists, when these massive stars exploded, they created stars with much lower masses, approximately several dozen times greater than that of the Sun, as modeling indicates. Around these stars, planetesimals formed, which then gave rise to potentially habitable rocky planets. But all of this occurred before the formation of the first galaxies.

Scientists state that after the explosion of a massive star, a sufficient amount of heavy chemical elements was produced, allowing for the formation of a smaller star with the right chemical composition, the material of which became the foundation for future planets. The modeling also showed that such a young stellar system contained as much water as our Solar System, and water, as we know, is essential for life.

The study revealed that the explosions of the first supernovae allowed for the creation of chemical elements such as carbon, oxygen, and iron, which are all necessary ingredients for not only planet formation but also the emergence of life.

If planets could have formed even before the appearance of the first galaxies, this changes our understanding of the Universe's evolution.

The authors of the study believe that such habitable planets, although now extinct worlds, could be found near ancient stars that contain few heavy chemical elements.

It should be noted that astronomers have yet to directly observe the very first stars; there is only some evidence that they existed and exploded as very powerful supernovae. However, these supernovae have also not been directly observed, as they are located very far away.

Yet, perhaps the conditions in the early Universe allowed for the scenario proposed by the researchers.