Radiation from the intense light of the first stars, in particular Lyman alpha, altered giant clouds of gas 180 million years after the Big Bang. These clouds then blocked the light of the afterglow of that Big Bang, the Cosmic Microwave Background (CMB). We see these clouds silhouetted against the fireball all around us. The continuing growth of stars, and the first galaxies, eventually heated that gas until it itself began to glow within just 100 million years.
The silhouette detected (see Nature, https://goo.gl/nJ5Ykv) would be a first of its kind, one of the earliest detections of stars and galaxies forming, and acts as a trailblazing observation in low frequency radio astronomy for years to come. Yet that’s not even the most exciting part. It could be the very first confirmation of the dark matter particle – a hidden component of our universe outweighing everything we can see five times over.
In the billions of years since the silhouette blocked this light from the Big Bang afterglow, the universe has expanded and the fireball has long since cooled to just 2.7K above absolute zero. It’s now visible in microwaves by radio telescopes such as EDGES (the Experiment to Detect the Global Epoch of Reionizaton Signature). This searches at low frequencies of radio, from 50–100 MHz, similar to...
