The Cosmic Savannah - Ep. 81: One Last Burst: Gamma Rays & Afterglows

Gamma ray bursts (GRBs) are the most energetic explosions in the universe—so powerful that a single burst can release as much energy as the Sun does over its entire 10-billion-year lifespan, all in just two seconds. These cosmic events, often linked to the collapse of massive stars or merging neutron stars forming black holes, are detected not by visible light but by the cascading particles they create when hitting Earth’s upper atmosphere. Despite their danger—potentially capable of wiping out life if one occurred nearby—most GRBs happen so far away that Earth’s ozone layer protects us. The real breakthrough in understanding GRBs came in the 1990s when astronomers discovered their 'afterglows' in optical, X-ray, and radio wavelengths, allowing precise localization and distance measurement. Dr. Simon DeVette, a recent PhD graduate from the University of Cape Town, played a key role in this research by using the Mierlicht Optical Telescope in Sutherland to capture optical afterglows of 29 GRBs, detecting 10 of them—some with unusual light curves and even a never-before-seen re-brightening in millimeter wavelengths observed by ALMA. This discovery hints at complex physics, possibly involving reverse shock waves, and underscores how much remains unknown about these extreme events.