Joint Astrophysics Colloquium

The Extravagant Lives of the First Stars

Alexander Heger

University of Minnesota

After the Big Bang, as the light of recombination faded, the universe became a rather unremarkable and dull place without any new sources of light. These “dark ages” lasted some hundred million years. This only changed when the first stars appeared, long before the any galaxy formed, brightening up the skies and introducing the transformation of the universe to the place to which we are acquainted today.

And bright they were. Probably with masses much bigger than most stars that form today, built only from the debris of the big bang, and not polluted by the ashes from earlier generations, they were also much hotter than modern stars, emitting many ionizing photons. Not only were they the first lighthouses marking the over-dense regions of the universe, but they also produced the first heavier elements, carbon and beyond.

I will discuss the evolution and explosive death of these “Population III” stars and how it differs from stars that form today. I will show what specific nucleosynthesis fingerprints they should have left behind, and how we may be able to use this for “stellar archeology”, helping us tell who they really were and how their lives ended - how massive they were, what explosions ended their lives, and what remnants they left behind. To date, no Population III star has ever been identified - potential small sibling that are as old as the universe - nor does it seem to be feasible to directly image them in their cradle in the near future, but looking at the “fossil record” may allow us to uncover at least part of the story.