The Big Bang should have created equal amounts of matter and antimatter, which would have annihilated each other and left only empty space and energy. Yet an infinitesimal imbalance allowed matter to exist.

In a study published in Physical Review Letters, physicists Rishav Roshan of the University of Southampton and Sudipta Show of the Indian Institute of Technology Kanpur propose that an overlooked, hypothetical 'sterile neutrino' was the cosmic savior.

In the seesaw framework, two right-handed neutrinos are usually enough to explain the data, so the third is often ignored as too heavy or too feeble — but ScienceAlert reports this neglected particle decayed so slowly that it temporarily took over the universe's energy density and triggered a matter-dominated period.

Sterile neutrinos ignore every force that acts on ordinary matter, feeling only gravity and an extraordinarily weak pull from the Higgs, ScienceAlert explains.

Live Science reports that the particle in the team's main example would have been about 100 trillion times as heavy as a proton, and that as the cosmos cooled, its energy shifted from fading like light into mass locked in place, so its share of cosmic energy grew until it dominated and sped up cosmic expansion.

That faster expansion delayed key Standard Model interactions — including the Higgs-driven switch that shapes how the matter-antimatter imbalance was built up — allowing a lighter right-handed neutrino, about 100 billion times a proton's mass, to produce the observed amount of matter.

According to both outlets, the slowly decaying neutrino's decay shortchanged antimatter, creating slightly more matter particles — a surplus of leptons, the family that includes electrons.

ScienceAlert reports that a strange 'sphaleron' process in the cooling quantum soup then converted part of that lepton excess into a matching excess of quarks, which coagulated into protons and neutrons, complementing the surviving electrons.

The extra matter went on to form today's galaxies and gas clouds.

The same hypothetical particles could also solve two other puzzles at once: the seesaw mechanism explains why ordinary neutrinos are so staggeringly light, and sterile neutrinos remain a proposed culprit for some of the universe's dark matter.

The heavy neutrino is far too massive to create in any particle accelerator, so tests must be indirect, Live Science notes.

Because the era of matter domination would have left distinct imprints on primordial gravitational waves, Show says the research 'offers us a new explanation for how matter won' and that the signatures 'open up new avenues for us to unravel the evolution of the early universe after the Big Bang,' per ScienceAlert.