How did the team build the model?

Dr. Daniel Whalen, of the University of Portsmouth's Institute of Cosmology and Gravitation, led the project. PhD student Chris Jessop ran the first stage of the simulation chain.

Their model followed the aftermath of one pair-instability supernova and tracked the chemistry of the gas it enriched. Gravity then pulled the metal-rich gas into a rotating disk around a young, low-mass star.

The setup resembles, in many ways, the disk of gas and dust that eventually produced our own Solar System — only this one began forming before the first galaxies had fully taken shape.

What did the disk contain?

The team found a disk circling a star about 70 percent as massive as the Sun. Inside that disk, enough solid material collected to build several Earth-masses of planetesimals — the small rocky bodies that collide and merge to form full-sized planets — at roughly Earth's orbital distance.

Whalen described the result directly: "Within that disc, enough solid material accumulated to create several Earth-masses' worth of planetary building blocks at roughly the same distance from the star as Earth is from the Sun."

The disk also held a substantial water reservoir, only a few times smaller than the supply that helped build Earth's oceans.

Could these planets have been habitable?

The water finding raises a sharper question. Whalen noted: "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 researchers stop short of claiming life existed that early. Their models show only that the raw ingredients and physical conditions appeared unusually soon in cosmic time.

Why does the early timing matter?

If rocky planets could indeed condense around low-mass stars just 100 million years after the Big Bang, the Universe may have been a planet-forming machine almost from the moment the first lights switched on.

"Our findings suggest that the conditions for planet formation may have existed much earlier than previously thought," Whalen said. The result, he added, raises an "intriguing question: could potentially habitable worlds have appeared far earlier in the Universe's history as well?"

To put this into perspective, the Universe today is about 13.8 billion years old, so a 100-million-year window sits less than 1 percent of the way through cosmic history.

Other researchers will need to extend the simulations, vary the supernova masses and check whether such disks survive long enough to actually form planets. The Portsmouth team frames the work as a starting point, not a confirmed history of the early cosmos.