Rocky Planets Could Form 100M Years After the Big Bang

The cosmos has been growing planets for far longer than anyone suspected. A groundbreaking new study from the University of Portsmouth suggests that rocky, Earth-like planets could have begun forming just 100 million years after the Big Bang — remarkably early in the 13.8-billion-year history of the Universe.

The research, led by Dr. Daniel Whalen and PhD student Chris Jessop from Portsmouth's Institute of Cosmology and Gravitation, used computer simulations to model conditions present in the earliest moments of cosmic history. What they found upends longstanding assumptions about when planet formation first became possible.

For decades, scientists believed that planets required billions of years of stellar evolution before the necessary chemical ingredients could accumulate. The conventional view held that the first few generations of stars lacked the heavy elements — carbon, oxygen, iron — needed to build rocky worlds. The Portsmouth team found a much earlier path.

The key lies in a class of ancient stars known as Pop III stars. These were the Universe's first generation of massive stars, and they burned fast and died violently. When they exploded as supernovae, they scattered heavy elements across surrounding gas clouds. One especially energetic variant, called a pair-instability supernova, could eject more than 100 times the Sun's mass worth of heavy elements in a single blast. That material dramatically enriched nearby gas clouds, setting the stage for the next generation of stars — and potentially, the first planets.

In the simulations, the researchers found one young star about 70% as massive as the Sun. Surrounding it was a rotating disk of gas and dust rich in carbon, iron, and oxygen — the building blocks of terrestrial planets. Within that disk, enough solid material had accumulated to create several Earth-masses worth of planetary building material, at roughly the same distance from the star as Earth orbits the Sun.

Perhaps most striking: the disk contained substantial amounts of water.

"Most surprisingly, the disc also contained substantial amounts of water, only a few times less than what was available when our own Solar System formed," said Dr. Whalen. "This means that any planets forming there could potentially have received water in a similar way to Earth, which is thought to have gained much of its water from material left over during the planet-building process."

The implications are staggering. If rocky planets with water could form just 100 million years after the Big Bang, the Universe's window for life may be vastly wider than previously imagined. Potentially habitable worlds could have appeared billions of years before Earth, around some of the oldest and most long-lived stars in the cosmos.

"To put this into perspective, the Universe is about 13.8 billion years old, so this is remarkably early in cosmic history," said Dr. Whalen. "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?"

The findings don't prove that such ancient planets hosted life. But they do show that the raw ingredients for planets, including water, were present far earlier in cosmic history than most models predicted. For the scientific community, the discovery reframes fundamental questions about when and where life might first have emerged in the Universe.

If the seeds of rocky worlds were scattered by the Universe's first explosions, then the long story of planets — and possibly of life — may have begun far earlier than Earth's relatively late arrival, some 4.5 billion years ago. The Universe, it seems, has been in the planet-making business for almost as long as it has existed.