Understanding the Connection Between Carbon Rich AGB Stars & Bipolar Planetary Nebula




Stribling, Finis L. IV
Speck, Angela

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UTSA Graduate School




Asymptotic Giant Branch (AGB) stars are variable stars are late type stars for low to intermediate mass stars. They have relatively high mass loss rates and are major contributors to the interstellar medium. Their mass loss is symmetric as the star ejects its circumstellar envelope in shells. When the mass of the hydrogen envelope Me = 10^(-3) M☉ , the envelope is so thin there is no more large scale mass loss and the star is no longer pulsating (Volk & Kwok 1989). This will mark the end of the AGB phase.


Planetary Nebula (PN) phase is the next stage in a low to intermediate mass star’s life. At 30,000 K the star will begin to ionize the gas around the central star. This is the beginning of the planetary nebula phase. The central star will increase in temperature up 200,000 K. At this stage, the star develops a fast, low density, wind that travels from a few hundred kms^(-1) to thousands of km s^(-1). There are 3 main classifications of PN: Elliptical, Bipolar, and Irregular. Bipolar PNe have a torus ring of molecular material with 2 high velocity outflow poles. The big question is how does a star go from symmetrical mass loss during the AGB phase to an asymmetric structure during he PN phase





Physics and Astronomy