Planetary Nebula HuBi 1 (IMAGE) The University of Hong Kong Caption Planetary nebula HuBi 1 shows a double-shell structure -- a hydrogen-rich outer shell and a nitrogen-rich inner shell, after its central star experienced a "born-again" event. Credit (Image adopted from Guerrero, Fang, Miller Bertolami, <em>et al</em>., 2018, <em>Nature Astronomy</em>, tmp, 112) Usage Restrictions Please credit (Image adopted from Guerrero, Fang, Miller Bertolami, et al., 2018, Nature Astronomy, tmp, 112) when using the image License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.