Astrophysics (index)

Protoplanetary Nebula

(PPN, Preplanetary Nebula)
(AGB phase before planetary nebula)

A Protoplanetary Nebula (PPN) is neutral gas around an Asymptotic Giant Branch (AGB) star that is not yet sufficiently hot to ionize it. When sufficient Temperature is reached, a Planetary Nebula (PN) is formed. The term Preplanetary Nebula is sometimes promoted for this sense of the term to reduce confusion.

The terms can confuse because the words "planetary", "protoplanetary" and "nebula" suggest a relation to planets and Planet Formation and the Nebular Hypothesis, and "protoplanetary nebula" is indeed occasionally used in that respect.


(stars,gas,object type)
http://en.wikipedia.org/wiki/Protoplanetary_nebula

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