Using more than two years of radio telescope observations, astronomers have observed a distant fast radio burst (FRB) being briefly “eclipsed” by a clump of highly magnetized plasma. This unusual event was potentially the result of a massive coronal mass ejection (CME) from a nearby star. The detection provides a rare window into the magneto-ionic environment surrounding FRBs, and suggests that, in some cases, these mysterious objects reside in binary systems in which their signals can be affected by stellar activity from nearby companions. Fast radio bursts are incredibly powerful yet brief flashes of radio waves from distant galaxies. Occasionally, these bursts repeat at remarkably high rates, and although their origins aren’t fully understood, growing evidence suggests that at least some FRBs are linked to highly magnetized neutron stars called magnetars. Observations of their polarization, particularly their Faraday rotation measure (RM), can reveal clues about the extreme environments surrounding these objects, such as clouds of turbulent plasma or possible binary companions. Here, Ye Li, S. B. Zhang, Yuan-Pei Yang, and colleagues monitored the repeating FRB 20220529 for more than two years – from June 2022 to September 2024 – and tracked its polarization properties. According to the findings, for nearly a year and a half (17 months), the RM of the FRB remained low and stable, with a median of 17 radians per square (rad m^-2). However, in December 2023, the FRB’s RM suddenly increased by nearly two orders of magnitude, reaching as high as ~1977 rad m^-2. RM measurements remained high before returning to the previous baseline range after 14 days, where they stayed for the remaining duration of the observation period. This dramatic yet short-lived RM flare signals a rapid change in the magnetized plasma along the FRB’s line of sight, perhaps due to a CME from a companion star. This would imply that FRB20220529 likely resides in a binary system.