Astronomers have made a mind-blowing discovery about the early universe. Using the Murchison Widefield Array (MWA) in Western Australia, a team from Curtin University and ICRAR found that the universe was warm, not freezing, even before the first stars and galaxies appeared.

This period, called the Epoch of Reionization, marks when the Cosmic Dark Ages ended and light could finally travel across space. Scientists expected the gas between galaxies to be extremely cold—but new signals reveal it was already heated nearly 800 million years after the Big Bang.

To detect this faint signal, researchers had to remove all other radio interference, including emissions from nearby stars, galaxies, Earth’s atmosphere, and even the telescope itself. After subtracting these “foreground signals,” the hidden warmth of the early universe emerged.

Professor Cathryn Trott explains that this heating likely came from early black holes and stellar remnants emitting X-rays, spreading energy across the cosmos.

By combining a decade of MWA data, the team achieved the cleanest radio sky image ever, bringing scientists closer than ever to finally detecting the Epoch of Reionization. These breakthroughs will guide the next-generation SKA telescopes in Australia and South Africa.