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We report new observations of "Hanny's Voorwerp" (hereafter HV) taken fromthe second data release of the LOFAR Two-metre Sky Survey (LoTSS). HV is ahighly-ionised region in the environs of the galaxy IC2497, first discovered bythe Galaxy Zoo project. The new 150MHz observations are considered in thecontext of existing multi-frequency radio data and archival narrow-band imagingfrom the Hubble Space Telescope, centred on the [Oiii] emission line. Thecombined sensitivity and spatial resolution of the LoTSS data -- which farexceed what was previously available at radio frequencies -- reveal clearevidence for large-scale extended emission emanating from the nucleus ofIC2497. The radio jet appears to have punched a hole in the neutral gas halo,in a region co-located with HV. The new 150MHz data, alongside newly-processedarchival 1.64GHz eVLA data, reveal that the extended emission has a steepspectrum, implying an age $>10^8$yr. The jet supplying the extended 150MHzstructure must have "turned off" long before the change in X-ray luminosityreported in recent works. In this picture, a combination of jet activity andthe influence of the radiatively efficient active galactic nucleus areresponsible for the unusual appearance of HV.

Relic jet activity in "Hanny's Voorwerp" revealed by the LOFAR Two metre Sky Survey