Gamma rays shed light on ancient star formation

Agenda
The history of star formation
The conventional way to estimate star-formation
Difficulties of usual method
Absorbing gamma rays

Looking back in time: Marco Ajello gazes at the stars. (Courtesy: Pete Martin/Clemson University)
Researching of ultraviolet (UV) light from galaxies
Emission from short-lived stars with a mass more than 10 times that of our Sun
Two corrections

Early universe
Ionized hydrogen
Faint galaxies invisibility
https://en.wikipedia.org/wiki/Chronology_of_the_universe

Not emission but its absorption
Gamma-telescope
Outcome of research