Ph.D. Thesis

From Red Giants to Planetary Nebulae: Asymmetries,

Dust and Polarization

by Joni Jayne Johnson

Under the supervision of Professor Terry Jones

ABSTRACT

In order to investigate the development of aspherical planetary nebulae, we obtained polarimetry of a group of planetary nebulae and of objects that will evolve into planetary nebulae, i.e. red giants, late AGB objects, proto-planetary nebulae, and young planetary nebulae. To study the dust around the objects in our sample, we also used data from the IRAS mission. The youngest objects in our survey, red giants, had the hottest dust temperatures while planetary nebulae had the coolest.
 
Most of the objects were intrinsically polarized, including the red giants. This indicated that the circumstellar dust shells of these objects were aspherical. Both carbon- and oxygen-rich objects could be intrinsically polarized. The intrinsic polarizations of a sample of our objects were modeled using ellipsoidal circumstellar dust shell.
 
The findings of this study suggest that the asphericities that leas to an aspherical planetary nebula originate when a red giant begins to undergo mass loss. The polarization and thus the asphericity as the star evolves.
 

Master's Thesis

An Infrared Study of OMC-2

by Joni Jayne Johnson

Under the supervision of Professor Tom Jones

ABSTRACT

Infrared photometry of the sources in the Orion Molecular Cloud-2 is used to model the internal objects. They are found to be young stars embedded in a cold dust cloud. The findings are consistent with current theories of stellar formation.