A protoplanetary nebula is the result of a star that is near the end of its life, just before the final planetary nebula (PN) phase. They are considered to be a type of reflection nebula, although for some of these objects I have captured narrowband images which indicates that they also have characteristics of emission nebulae.
During this phase, the central star's temperature is supposed to be too cool to ionize the shell ejected during the preceding AGB phase. The star produces high-speed winds which shape the shell into axially symmetric jet-type patterns. This phase is short lived and examples are hard to find because the nebula are tiny (less than 1 arc-minute) and their visibility is highly dependent upon our viewing angle.
The phase continues until the central star reaches about 30,000 K, which is hot enough to ionize the circumstellar nebula. The nebula then becomes a type of emission nebula commonly called a planetary nebula.
The poster contains 7 protoplanetary nebulae that I have found to be bright enough and large enough to image. I have had many unsuccessful attempts over the years at imaging other protoplanetary nebulae, most of which were just too small and faint.
The technical data for the objects on the poster is shown in Revision F.
If you would like to read more about any of these objects, each of the objects in the poster has previously been uploaded and described individually on Astrobin. They all reside in my
Astrobin Protoplanetary Nebula Collection .
Comments