Broadband polarized radio emission detected from Starlink satellites below 100 MHz with NenuFAR

Aims. We evaluate the impact of Starlink satellites on low-frequency radio astronomy below 100 MHz. We focus on challenges of the data processing and on scientific goals. Methods. We conducted 40 hours of imaging observations using NenuFAR in the 30.8–78.3 MHz range. Observations included both the targeted tracking of specific satellites based on orbital predictions and the untargeted searches focused on high-elevation regions of the sky. Images in total intensity and polarimetry were obtained, and full Stokes dynamic spectra were generated for several hundred directions within the field of view. The detected signals were cross-matched with satellite orbital data to confirm the satellite associations. We performed detailed analyses of the observed spectra, polarization, and temporal characteristics to investigate the origin and properties of the detected emissions. Results. We detected broadband emissions from Starlink satellites, predominantly between 54–66 MHz, with flux densities exceeding 500 Jy. These signals are highly polarized and unlikely to originate from ground-based radio frequency interference or reflected astronomical sources. Instead, they are likely intrinsic to the satellites, and distinct differences in the emission properties are observed for the different satellite generations. These findings highlight significant challenges to the data processing and scientific discoveries at these low frequencies and emphasize the need for effective mitigation strategies, in particular, through collaboration between astronomers and satellite operators.