What are fast radio bursts and where do they come from?

The answer

Fast radio bursts (FRBs) are intense pulses of radio emission lasting milliseconds that originate from distant galaxies. First detected in 2007 by Duncan Lorimer in archival data from the Parkes telescope, over 800 FRBs have been cataloged. The CHIME radio telescope in Canada detects several per day. In 2020, the mystery partially unraveled when magnetar SGR 1935+2154 in our own galaxy produced an FRB-like burst alongside an X-ray flare, confirming magnetars as at least one source. However, the repeating source FRB 20121102A produces thousands of bursts, suggesting diverse mechanisms. Some FRBs are localized to specific galaxies, with one traced to a globular cluster - an unexpected environment. FRBs are now being used as cosmological tools: their radio signals interact with intervening matter, allowing scientists to detect and weigh the 'missing' baryonic matter between galaxies, solving a decades-old cosmic accounting problem.