Cosmic dawn

A VHF absorption signal at 78 MHz in the sky-averaged spectrum has been interpreted as a result of the formation of the first stars, a process that illuminated the universe with UV radiation and is called the cosmic dawn, as reported in a comment and article in Nature. The UV radiation would modify the excitation state of the 1420.4  MHz hydrogen spin atomic transition and would indicate the universe temperature. The linewidth suggest that the first stars appear 180 Myears after the Big Bang, while the flatten line profile has been connected speculatively with the interaction between normal matter and dark matter, which, if confirmed, would be truly remarkable.