First Stars May Have Filled the Universe with Water, Study Finds

Water is a cornerstone of life. Every organism on Earth depends on it, and our planet thrives with life due to its abundance of water.

The link between water and life comes from both water’s unique properties and its abundance in the cosmos.

The Origins of Water: Hydrogen and Oxygen

Water, with its simple structure of two hydrogen atoms bonded to one oxygen atom, is remarkably resilient. Hydrogen formed in the Big Bang, while oxygen, carbon, and nitrogen are forged in massive stars.

Traditionally, scientists believed oxygen—and by extension, water—became more prevalent as the Universe evolved. Successive generations of stars enriched the cosmos with oxygen during their explosive deaths.

Thus, while water was scarce in the early Universe, it has since become relatively abundant. However, a new study challenges this perspective.

Star Populations and Their Cosmic Impact

Astronomers classify stars into three populations based on their age and metallicity (where “metals” refer to elements heavier than hydrogen and helium).

Population I: Younger stars rich in metals, like the Sun.

Population II: Older stars with fewer metals.

Population III: The Universe’s first stars, made entirely of hydrogen and helium.

Although Population III stars have not yet been observed directly, they are theorized to have been massive and short-lived, sowing the seeds of everything we see today—oceans, forests, and even ourselves.

Simulating the Deaths of Early Stars

A recent study published on arXiv suggests that these primordial stars may have also been responsible for spreading water throughout the cosmos.

The researchers modeled the deaths of early stars, both small (13 solar masses) and massive (200 solar masses). The larger stars, likely the first in the Universe, formed from pure hydrogen and helium, while the smaller ones emerged in early stellar nurseries with very low metallicity.

When these smaller stars died, they exploded as standard supernovae. In contrast, the massive stars ended their lives in dazzling pair-instability supernovae.

According to the simulations, these explosions significantly enriched the surrounding molecular clouds with water. The remnants of these early stars contained 10 to 30 times more water than the diffuse molecular clouds observed in the Milky Way today.

Early Water and the Potential for Life

The researchers propose that within 100 to 200 million years after the Big Bang, the molecular clouds in the early Universe held enough water and other essential elements for life to potentially emerge.

Whether life actually arose so early remains an open question. It’s also possible that ionization and other cosmic processes destroyed much of this early water.

While water may have been abundant in the Universe’s infancy, the cosmic environment likely entered a “dry spell” before the next generations of stars, Populations II and I, replenished it. Still, some of the water we see today might trace its origins back to the very first stars.

Read the orginl article on: Science Alert

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