Early Universe Stars May Have Spawned Rocky Planets Just 300 Million Years Post-Big Bang

Recent computational models indicate that the fundamental components for forming Earth-like planets might have emerged merely 100 million years following the Big Bang. This groundbreaking insight shifts back the timeline for rocky planet formation by billions of years, proposing that the infant universe began generating planetary matter far earlier than previously assumed.

Creating rocky planets requires elements heavier than hydrogen and helium, including carbon, oxygen, iron, and silicon. These heavier elements were not produced during the Big Bang itself but were generated deep within stars and dispersed throughout space when those stars exploded.

The universe’s first generation of stars, classified as Population III stars, were crucial in altering early cosmic chemistry. Their explosive deaths expelled freshly synthesized heavy elements into surrounding gas clouds, setting the stage for new stars and planetary systems to arise.

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Scientists at the University of Portsmouth performed simulations to investigate the aftermath of these primordial stellar explosions. Their findings suggest that planetesimals—the initial solid clumps that lead to planet formation—could have formed around smaller stars in the universe's earliest epochs.

First Supernova Explosions Forged Rocky Planet Precursors

The research examined pair-instability supernovae, exceptionally energetic stellar explosions occurring in some of the universe’s massive earliest stars. Unlike typical supernovae, these can obliterate stars entirely, distributing vast amounts of heavy elements across space. The team, including Daniel Whalen, discovered that several Population III pair-instability supernovae likely dispersed over 100 solar masses worth of elements heavier than hydrogen and helium.

These materials enriched adjacent gas clouds, enhancing their metal content—a critical factor for dust grain formation, which is essential for rocky planet development in regions previously deficient in heavy elements.

Over time, these dust grains could collide and agglomerate into planetesimals, representing the earliest solid structures that serve as planet-building blocks.

The simulations hint that rocky planet formation may have commenced far sooner than traditionally thought, coinciding with the dawn of star-driven chemical enrichment.

Early Stars Hosted Planet-Forming Materials

The models tracked enriched gas collapsing under gravity to produce a young star encircled by a rotating protoplanetary disc, reminiscent of the one that gave rise to our Solar System. This simulated star held roughly 70% of the Sun’s mass. Within its disc, the team identified sufficient solid matter to form several Earth-mass planetesimals located between 0.5 and 1 astronomical unit from the star.

Whalen noted that the simulations revealed a protoplanetary disc containing enough substance "to form several Earth masses’ worth of building blocks for planets" at distances akin to Earth’s orbit around the Sun.

While this planetesimal formation doesn't guarantee complete planet development, which relies on subsequent collisions and gravitational dynamics, the results confirm that the raw materials for rocky planets were present far earlier than formerly assumed.

The study also explored water presence in these primordial systems. Previous research by Whalen and colleagues demonstrated that water could emerge in dense gas clouds enriched by early supernovae within 100 to 200 million years after the Big Bang.

Traces of Ancient Planetary Systems May Persist Today

The simulations further indicated that the early protoplanetary disc held considerable water quantities—only modestly less than those observed during the Solar System’s formation—implying that planets forming in such settings could have acquired water through mechanisms similar to Earth's early developmental processes.

Moreover, the research highlights the longevity of low-mass stars. A star possessing roughly 40% of the Sun’s mass from this early epoch might still be orbiting within the Milky Way, offering astronomers potential targets to detect remnants of ancient planetary systems.

Although these simulations do not confirm the existence of habitable planets in the universe’s infancy, they do reveal that the essential conditions for rock-rich worlds likely emerged well earlier than previous theories suggested.

“Our findings suggest that the conditions for planet formation may have existed much earlier than previously thought. If that’s the case, it raises an intriguing question: could potentially habitable worlds have appeared far earlier in the Universe’s history as well?” noted Whalen.

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