Seeing stars born at the dawn of the Universe

Astronomers have found six galaxies that look to be at the thin hairy edge of the observable Universe, so far away that we see them not long after their very first stars were born — the cosmic dawn.

Incredibly, just seeing stars in them at all means we can learn about what they were like even earlier in their history, perhaps around 100 million years after the birth of the Universe itself!

There are two key physical properties of the Universe needed to make an observation like this. One is tha...