Supernova lights up galaxy at the end of the Universe’s dark ages

A depiction of a gamma ray burst and the clouds of gas that absorbed some of the light it emitted.

Harvard

Early in the Universe's history, before the formation of the first stars, nearly all of the regular matter existed in the form of the three lightest elements: hydrogen, helium, and lithium. Initially, the Universe was so energetic that these elements couldn't hang on to any electrons; instead, all of the normal matter existed as a plasma. When the Universe finally cooled enough to allow atoms to come into existence, the photons that resulted formed the cosmic microwave background, which provides us with a detailed look at the physics of the Big Bang.

At that point, the Universe entered what's called its dark ages. Stars and small galaxies started to form, but the dense fog of atoms they were born in kept any record of the events from being visible for hundreds of millions of years. It was only later, once enough stars had formed, that their emissions re-ionized the interstellar gas, making the Universe transparent again. By that time, many of the most interesting events in the Universe's history had already happened.

Scientists have lately been able to make observations that are beginning to shed light on the Universe's dark ages. In the latest example, they looked at how an early supernova lit up the galaxy it occurred in, revealing the presence of heavier elements, but in much smaller quantities than we currently see.