9-13 September 2019
University of GenevaA100 Sciences II
Europe/Zurich timezone

The beginning of the stellar era in the Universe is a singularly

fascinating phase in the history of the Cosmos. The baryonic material

filling the Universe at that time, having a composition inherited from

Big Bang nucleosynthesis, has its physical characteristics modified by

the very first stars. Indeed, the first stars will change the degree of

ionized material in their vicinity, and, through their winds and/or

supernova explosion, will inject energy, momentum, and newly-synthesized

elements. Some pockets of gas, enriched by the first stars, will in turn

form new stars, whose initial composition is inherited from the first

nucleosynthetic events. These low-mass stars can live sufficiently long

to be observed today in halo of the Galaxy, providing the opportunity to

obtain information about the very high redshift Universe by the study of

nearby stars.


How did these processes happen? How were these processes different from

similar ones occurring in the present Universe? What can they teach us

about the infancy of the Universe during the reionization era? These are

the questions that will be discussed during this workshop, questions

that are particularly topical at a time when new facilities, such

as SKA, JWST, and the next generation of extremely large telescopes have

as one of their prime objectives to probe this very period. 


At present, observational constraints on these first stars are scarce

and/or indirect. Important constraints come from observations of the

elemental abundances of very, extremely, and ultra iron-poor stars that

likely formed from the ejecta of the first stellar generations. Of

course the full story can be complex, as some elements might be formed

by more than one source, and others may be somewhat altered by in-situ

processes that occurred in the star that is observed today.

Nevertheless, through the accumulation of observational data, progress

made in numerical simulations, and in our deeper understanding of the

physical processes involved, a much more complete and detailed story can

be told.

University of GenevaA100 Sciences II
A100 Sciences II
30 quai Ernest Ansermet
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