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Dispersal of Disks Around Young StarsWe review the evidence pertaining to the lifetimes of planet-forming disks and discuss possible disk dispersal mechanisms: 1) viscous accretion of material onto the central source, 2) close stellar encounters, 3) stellar winds, and 4) photoevaporation by ultraviolet radiation. We focus on 3) and 4) and describe the quasi-steady state appearance and the overall evolution of disks under the influence of winds and radiation from the central star and of radiation from external OB stars. Viscous accretion likely dominates disk dispersal in the inner disk (r < or approx. equals 10 AU), while photoevaporation is the principal process of disk dispersal outside of r > or approx. equals 10 AU for low mass stars. Disk dispersal timescales are compared and discussed in relation to theoretical estimates for planet formation timescales. Photoevaporation may explain the large differences in the hydrogen content of the giant planets in the solar system. The commonly held belief that our early sun's stellar wind dispersed the solar nebula is called into question. Finally, we model the small bright objects ("proplyds") observed in the Orion Nebula as disks around young, low mass stars which are externally illuminated by the UV photons from the nearby massive star Theta(sup 1)C.
Document ID
20020050666
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Hollenbach, David
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Astrophysics
Funding Number(s)
PROJECT: RTOP 344-04-10-02
Distribution Limits
Public
Copyright
Other

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