Linnaeus Physics Colloquium: The most explosive events after the Big Bang

Image: Artist impression of the “reverse shock” echoing back though the jets of the gamma-ray burst (GRB 161219B). Credit: NRAO/AUI/NSF, S. Dagnello.

Title: The most explosive events after the Big Bang
Lecturer: Gabriele Ghisellini, dirigente di ricerca at INAF-Osservatorio Astronomico di Brera, Italy

Abstract

Gamma Ray Bursts (GRBs) are flashes of gamma-rays occurring once a day, in an unpredictable direction of the sky. They were discovered in 1967, but their discovery was made public in 1973. For the next 30 years their distance, hence their luminosity, remained unknown. The "aura" of mistery grew.

In 1997, thanks to the italian-dutch satellite BeppoSAX we eventually found that their distance is cosmological: they are the most luminous object in our universe, albeit for the few seconds of their intense gamma-ray emission. Their physics is therefore at the extreme, because in no other place of the universe we have such a large release of energy in so small a volume, with the important exception of merging of black holes or neutron stars generating gravitational waves.

We now know that GRBs are born together with a black hole, either after the collapse of a massive star, or the merging of two neutron stars. Some of the physics is understood, some is still under discussion, and some still challenges our understanding.

About Gabriele Ghisellini

Dirigente di ricerca at INAF-Osservatorio Astronomico di Brera, I am interested in relativistic jets of AGN, supermassive black holes, Gamma Ray Bursts, and high energy radiative processes. PhD in SISSA (Trieste), postdoc in Cambridge (UK), and then back to Italy.