Iron condensation and the formation of planetary nebulae

Journal Article · Thu Mar 01 04:00:00 EST 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156874· OSTI ID:6178701

Scalo, J M; Shields, G A

Theories about the existence of dust in planetary nebulae (PN) are reviewed and it is concluded that most of the observed dust forms during the expansion of the prenebula. The observed gas-phase iron depletion in PN is used as a fundamental constraint on two specific models for PN formation and grain evolution. The two models are ejection of the entire shell in a single event (ejection model), and buildup of the nebula by steady mass loss during the red-giant phase (wind model). In both models condensation along predicts essentially infinite gas-phase depletion, contrary to observations. This suggests that some grain-destruction mechanism must operate. Relative gas-grain drift velocities are far below the threshold for sputtering in the ejection model, and marginally below threshold in the wind model, if carbon or iron atoms are the sputtering projectiles. However, in the latter model the sputtering yields are much too small to account for the observed gas-phase iron abundances. Shattering accompanied by vaporization in grain-grain collisions is ineffective in the ejection model because, in order to exceed the relative kinetic energy needed for shattering, the density must be so low that the collision time scale is much larger than the PN lifetime. Shattering-vaporization in the wind model is found to successful in accounting for the observed degree and uniformity of the iron depletions if about 1% of the grain material is vaporized in each shattering event. These results favor the idea that PN originate from a wind at the end of red-giant evolution.

• Research Organization: Department of Astronomy, University of Texas
• OSTI ID: 6178701
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 228:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
COLLISIONS
COSMIC DUST
COSMIC GASES
DUSTS
ELEMENTS
FLUIDS
GASES
GIANT STARS
INTERSTELLAR GRAINS
IRON
METALS
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
NEBULAE
PARTICLES
PLANETARY NEBULAE
SPUTTERING
STAR EVOLUTION
STARS
STELLAR WINDS
TRANSITION ELEMENTS