Double-shell planetary nebula HuBi 1 has an inner shell that emits in low ionization potential species, and an outer shell that emits in high-ionization species. This is the inverse of the usual case. The cause is the nebula’s rapidly fading central star that went through a ‘born-again’ event.
- Martín A. Guerrero
- Xuan Fang
- Saúl A. Zavala
