Quirks & Quarks

The universe's dark age ended with the first stars - and we've found them

The fingerprint of the stars that first shone on a dark universe has been detected
Artist's rendering of how the first stars in the universe may have looked. (N.R.Fuller, National Science Foundation)

The first stars lit up the universe

Astronomers have detected a tiny "hole" in the background radiation from the Big Bang, that represents the silhouette of the first generation of stars born in our universe. This is the earliest glimpse we've ever had of these stars, which would have been large, bright, short-lived and very different from the stars in our "mature" modern cosmos.

Astronomers think that just after the universe was born, nearly 14 billion years ago, the entire universe was full of superheated plasma - the kind of thing we see on the surface of the Sun. Then as the universe cooled and expanded, about 400,000 years after the Big Bang, the fire went out and the universe when dark.  For tens of millions of years there was nothing but cooling gas floating in the blackness.  And then the first stars were born - and once again there was light.

The modest EDGES radio spectrometer in the Australian outback that was used to detect the signs of the earliest stars (CSIRO Australia)
Detecting signs of stars we can't see

We know those first stars once existed - but we've never seen them.  They're too old and too far away to be spotted by even our most powerful telescopes. But now a team of Astronomers led by Dr. Judd Bowman, an astrophysicist from Arizona State University, has detected signs of those first stars.

These brand-new stars, composed of only hydrogen and helium, would have produced a great deal of powerful ultraviolet light. That light, in turn, would have excited the plentiful hydrogen gas in the relatively dense early universe. That excited gas would in turn have acted like a kind of cosmic fog, absorbing a particular frequency of the radio waves that saturated the early universe.  What Dr. Bowman and his colleagues detected was the absence of this radio light - a sign of the radio "fog" created by these early stars.

A date for when the first stars emerged

Their observation provided evidence that these early stars were present no later than 180 million years after the Big Bang - and were probably there much earlier. No telescope we have today can see the light from this generation of stars, but the new James Webb Space Telescope - due to launch in 2019 - may be powerful enough to see that far back in time and space.