The apparent angular diameter of the hotspots of the radio galaxy cygnus a at 81.5 MHZ

Scintillation observations of the radio galaxy Cyg A have shown that, at 81.5 MHz, its hotspots had diameters greater than 6 arcsec, much greater than the 2 arcsec observed at 5000 MHz. One possible explanation is that scattering by inhomogeneities in the interstellar medium will lead to a size that increases with increasing wavelength, and this would imply that the medium in the direction of Cyg A is highly turbulent, with a fluctuation in electron density about two orders of magnitude greater than the typical value inferred from pulsar observations.