What does PPN stand for?

PPN stands for "Proto-Planetary Nebula"

How to abbreviate "Proto-Planetary Nebula"?

"Proto-Planetary Nebula" can be abbreviated as PPN

What is the meaning of PPN abbreviation?

The meaning of PPN abbreviation is "Proto-Planetary Nebula"

What does PPN mean?

PPN as abbreviation means "Proto-Planetary Nebula"