The first generation of stars in our Universe were represented by very massive and bright luminaries that consisted of almost pure hydrogen. They quickly went through all the stages of their evolution, exploded like supernovae and filled space with the first water molecules.
Water is the basis of life
Water is the essence of life. Every living being on Earth contains water inside of it. The Earth is rich in life because it is rich in water. This fundamental connection between water and life is partly due to the extraordinary properties of water, and partly due to the fact that water is one of the most abundant molecules in the Universe.
Water is made up of one part oxygen and two parts hydrogen, and its structure is simple and strong. Hydrogen comes from the primordial fire of the Big Bang and is the most abundant element. Oxygen is formed in the cores of large stars together with carbon and nitrogen in the process of thermonuclear fusion of CNO.
Because of its origins, we generally thought that oxygen (and therefore water) became more prevalent over time. From the first stars to the present day, each generation has released oxygen into space at the moments of its death. So, if water was rare in the early universe, it is now a relatively common phenomenon. But a new study suggests that’s not the case.
Stellar populations and water formation
Astronomers categorize stars into groups based on their age and metallicity, where “metals” are any elements other than hydrogen and helium. The youngest and most metal-rich stars, such as the Sun, are called Population I. Older stars with lower metal content belong to Population II. The oldest stars, the very first stars to appear in the Universe, are known as Population III.
Although we have not observed Population III stars directly, they would have to be huge stars composed entirely of hydrogen and helium. The first embryos of everything we see around us, from oceans to trees and favorite friends, formed in those first stars. A new study published on the arXiv preprint server claims that Population III stars have also filled the cosmos with water.
In their study, the team modeled the explosions of small (13 solar masses) and large (200 solar masses) early stars. The larger stars would have been the very first stars to form from primary clouds, while the smaller stars would have been the first stars to form in early stellar nurseries. Not quite Population III stars, but with very low metallicity. When smaller stars died, they exploded as typical supernovae, but when larger stars died, they exploded as brilliant supernovae with pair instabilities.
Simulation of water concentration in the early Universe
According to the modeling, these stars would have greatly enriched the environment with water. Molecular clouds formed from the remnants of these stars had 10 to 30 times the proportion of water than the diffuse molecular clouds observed in the Milky Way today. Based on this, the team argues that 100-200 million years after the Big Bang, there was enough water and other elements in the molecular clouds for life to originate.
Whether life really appeared so early in the Universe is an unanswered question. There is also the fact that although water formed early, ionization and other astrophysical processes may have broken up many of these molecules. There may have been plenty of water in the beginning, but the Universe entered a dry period before the Population II and Population I stars created the water levels as we see today. But it’s quite possible that most of the water that surrounds us comes from the very first stars.
According to phys.org
