A massive parsec-scale dust ring nebula around the yellow hypergiant Hen 3-1379

On the basis of far-infrared images obtained by the Herschel Space Observatory, we report the discovery of a large and massive dust shell around the yellow hypergiant Hen 3-1379. The nebula appears as a detached ring of 1 pc diameter which contains 0.17 M[SUB]&sun;[/SUB] of dust. We estimate the total gas mass to be 7 M[SUB]&sun;[/SUB], ejected some 1.6 × 10[SUP]4[/SUP] years ago. The ring nebula is very similar to nebulae found around luminous blue variables (LBVs) except it is not photoionized. We argued that Hen 3-1379 is in a pre-LBV stage, providing direct evidence that massive LBV ring nebulae can be ejected during the red supergiant phase.