/sci/ - Science & Math

protoplanetary nebula or preplanetary nebula is an astronomical object which is at the short-lived episode during a star's rapid stellar evolution between the late asymptotic giant branch phase and the subsequent planetary nebula (PN) phase. A PPN emits strongly in infrared radiation, and is a kind of reflection nebula. It is the penultimate high-luminosity evolution phase in the life cycle of intermediate-mass stars (1-8 solar masses).