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Measurements of the properties of gravitational lenses have the power to tellus what sort of universe we live in. The brightest known radio Einsteinring/gravitational lens PKS 1830-211 (Jauncey et al., 1991), whilst obscured byour Galaxy at optical wavelengths, has recently been shown to containabsorption at the millimetre waveband at a redshift of 0.89 (Wiklind andCombes, 1996a). We report the detection of a new absorption feature, mostlikely due to neutral hydrogen in a second redshift system at z = 0.19.Follow-up VLBI observations have spatially resolved the absorption and revealit to cover the NE compact component and part of the lower surface brightnessring. This new information, together with existing evidence of the unusual VLBIradio structure and difficulties in modeling the lensing system, points to theexistence of a second lensing galaxy along our line of sight and implies thatPKS 1830-211 may be a compound gravitational lens.

PKS 1830−211: A Possible Compound Gravitational Lens