10317(  1) - 04/02/04 11:48  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10317
                                                       Version: 1
                                                       Check-in Date: 02-Apr-2004
                                                                      11:48:21

1.Proposal Title:
The Hydrodynamics of Collimated Flow Interactions around Dying Stars
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
AR               13        <none>
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5. Investigators
                                                                                     Contact?
    PI: Dr. Raghvendra Sahai              Jet Propulsion Laboratory
   CoI: Dr. Vikram Dwarkadas              University of Chicago                         N
   CoI: Dr. Chin-Fei Lee                  Smithsonian Institution Astrophysical         N
                                          Observatory

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6. Abstract

The Hubble Space Telescope (HST) has imaged a substantial and growing number of
young planetary (PNe) and proto-planetary nebulae (PPNe), with unprecedented high
angular resolution and dynamic range. These objects represent the last phases of
evolution of 1-8 solar mass stars. The data show that young PNe have highly
aspherical morphologies, characterised by multipolar bubbles distributed roughly
point-symmetrically around the central star, and that complex morphological
structures begin emerging during the PPNe phase. We have hypothesised that the data
support a model for the formation of PNe in which high-speed collimated outflows or
jets operate during the late AGB/ early post-AGB evolutionary phase. In order to
test our hypothesis, detailed theoretical models are needed to study the
hydrodynamical interactions of post-AGB collimated fast winds with the slow AGB
winds, and understand the nature of the collimated outflows. The subsequent
evolution of these PPNe to young PNe, as the central star evolves towards higher
temperatures, also needs to be followed. The underlying jets which produce the
nebula shapes are generally not detectable in their pristine state (i.e. before they
have interacted with the ambient circumstellar medium) - theoretical modeling is
needed to derive their basic physical characteristics. Since magnetic fields may be
important in the collimation process, numerical simulations using magneto-
hydrodynamic codes are needed. However, very little work has been done in these
areas. Thus the enormous scientific potential of HST's rich legacy of morphological
and (to a lesser extent) kinematical data on dying stars, remains virtually
untapped. We propose a 2-year study to model existing HST images of PPNe and PNe.
Our work will lead to a better understanding of astrophysical jets and their
interaction with the surroundings, as well as the physical mechanisms which shape
the circumstellar environment of dying stars.
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                                                10317(  1) - 04/02/04 11:48  - [  2]

            Summary Form for Proposal  10317

  Item                         Used in this proposal
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  Proposal Category            AR
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