To discover the secrets of exploding stars or black holes, scientists have been focusing on the gamma rays they emit. However, gamma rays don't pass through the Earth's atmosphere, making them difficult to study. To find what high-energy process a gamma ray originates from, scientists have been observing the cascades of secondary particles produced when these rays hit the atmosphere. The cascades—which create blue flashes of light called Cherenkov light after the Russian physicist who discovered them—only last a few billionths of a second and are invisible to the naked eye. What's more, they're very rare, producing one gamma-ray photon per m2 yearly (for bright sources) or per century (for faint sources).
* This article was originally published here
