Protoplanetary nebula

To avoid any possible confusion, Sahai, Sánchez Contreras & Morris 2005 suggested employing a new term preplanetary nebula which does not overlap with any other disciplines of astronomy.

At this point, the effective temperature of the star, T*, will be around 5,000 K and it is defined to be the end of the LAGB and the beginning of the PPN.

(Davis et al. 2005) During the ensuing protoplanetary nebula phase, the central star's effective temperature will continue rising as a result of the envelope's mass loss as a consequence of the hydrogen shell's burning.

Observations and high-resolution imaging studies from 1998 to 2001, demonstrate that the rapidly evolving PPN phase ultimately shapes the morphology of the subsequent PN.

Complementarily, theorists (Soker & Livio 1994; [6] Reyes-Ruiz & Lopez 1999;[7] Soker & Rappaport 2000;[8] Blackman, Frank & Welch 2001[9]) investigated whether accretion disk scenarios, similar to models used to explain jets from active galactic nuclei and young stars, could account for both the point symmetry and the high degree of collimation seen in many PPN jets.