THE EVOLUTION OF PLANETARY NEBULAE(PN) AND FADING TIME ACCORDING TO SYNTHETIC MODEL

Abstract

Planetary nebulae (PN) represents the short phase in the life of stars with masses
(0.89-7) M☉. Several physical processes taking place during the red giant phase of
low and intermediates-mass stars. These processes include :1) The regular (early )
wind and the envelope ejection, 2) The thermal pulses during Asymptotic Giant
Branch (AGB ) phase. In this paper it is briefly discussed how such processes affect
the mass range of Planetary Nebulae(PN) nuclei(core) and their evolution, and the
PN life time, and fading time for the masses which adopted. The Synthetic model is
adopted. The envelope mass of star (MeN ) and transition time (ttr) calculated
respectively for the parameter (MeR =1.5,2, 3×10-3 M☉). Another time scale is of
capital importance for the understanding of PN and their nuclei, it is the fading time
( tf). The results indicated that for each observed nebulae( ttr < tPN) also the fading
time is sensitive to mass core(MH) of star, the mass with 1.2 M☉ takes only (25 yr )
to fading, while the mass with (0.66 M☉) takes about ( 4715 yr) years to fading. The
calculations showed that (ttr) increases with the increasing of final mass( Mf). The
initial nebulae radius will also increase with (Mf) thus will correlate with the
location of nucleus on the HR diagram.