Real-time detection of an extreme scattering event: constraints on Galactic plasma lenses

Understand

Extreme scattering events (ESEs) are distinctive fluctuations in the brightness of astronomical radio sources caused by occulting plasma lenses in the interstellar medium.

• The inferred plasma pressures of the lenses are $\sim 10^3$ times the ambient pressure, challenging our understanding of gas conditions in the Milky Way.
• Using a new survey technique, we have discovered an ESE while it was in progress.
• We report radio and optical follow-up observations.