Artist's impression of the first stars in the universe

By 180 million years after the Big Bang, the first stars (artist’s rendering) had appeared in the Universe. Credit: N. R. Fuller/National Science Foundation

Astronomy and astrophysics

Dark matter’s nature is illuminated by the earliest stars

Long-elusive particles might have left their mark on the primordial cosmos.

Researchers have long theorized that dark matter makes up about 85% of the Universe, but the elusive material has never been directly detected.

Rennan Barkana at Tel Aviv University sought to bring dark matter out of the shadows by analysing the first direct evidence of the ‘cosmic dawn’ — a period some 13.5 billion years ago when the first stars burst into existence. Barkana’s findings, which are based on recent observations by a separate research team, suggest that the gases permeating the early Universe were cooler than predicted.

Barkana attributes the unexpected cooling to collisions between the gas molecules and cold particles of dark matter. He estimates that each dark-matter particle is no heavier than a few protons — much lighter than previous suggestions.

Further observations of the cosmic dawn could shine more light on the properties of dark matter, the author says.

See related News & Views: A surprising chill before the cosmic dawn