Four hundred thousand years after the big bang, the universe was a cold, dark fog of hydrogen and helium atoms. Less than 400 million years later, it had begun to shine with the light of infant galaxies. Sometime in between, the first stars must have formed.
What were these stars made of? How big and bright were they? How long did they live, and what happened to them when they died? Do any still exist?
The fact is, no one really knows exactly what the first stars were like. Not even the most powerful telescopes operating today—space telescopes like Hubble, Spitzer, and Chandra, and ground-based telescopes like Keck and ALMA—have been able to detect them. But we do have some ideas.
Credit: NASA/STScI
