11232( 3) - 25-Apr-2008 15:05:23 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11232 Version: 3 Check-in Time: 25-Apr-2008 15:05:23 STScI Edit Number: 0 Title Determination of Angular Expansion Velocities in the Ring Nebula ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. C. Robert O'Dell Vanderbilt University CoI: Dr. Franco Sabbadin Osservatorio Astronomico di Padova N CoI: Dr. William J. Henney Universidad Nacional Autonoma de Mexico N (UNAM) ------------------------------------------------------------------------------------ Abstract The Ring Nebula (NGC 6720) represents an important stage in the evolution of planetary nebulae, being large enough that it has entered the post fast-wind stage yet has not reached the late ballistic phase of objects like the Helix Nebula. Understanding this nebula well presents the opportunity to determine how nebulae transition from their creation phase into the form they have as their material enters the interstellar medium. A recent study based on ground-based spectroscopy has derived a new and accurate model for the Ring Nebula. A well defined characteristic of this model is that it predicts a tangential velocity of 20 km/s whereas the application of its quite uncertain trigonometric parallax distance of 700 (+450/-200) pc with the angular expansion velocity determined from HST observations with a 2 year time base indicates a tangential velocity of 69 (+45/-20) km/s. This disagreement indicates that either the distance is even more uncertain than thought or that the earlier angular velocity is incorrect. We propose to make a new set of observations of the Ring Nebula in the diagnostic emission line filters F469N (HeII), F502N ([OIII]), and F658N ([NII]) that will produce much more accurate angular velocities than the previous study by having a time base of 8.8 years and imaging the nebula entirely within a single CCD of the WFPC2. The primary result from this study will be an accurate distance to this important nebula and from this to be able to use this object to refine our picture of how planetary nebulae evolve during middle-age. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will make WFPC2 observations of the Ring Nebula (NGC 6720) in the F502N and F658N filters for the purpose of determining the tangential expansion velocities within this nebula. Real Time Justification ----------------------- Calibration Justification 11232( 3) - 25-Apr-2008 15:05:23 - [ 2] ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11232( 3) - 25-Apr-2008 15:05:23 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6720 ISM, EMISSION LINE RA=18H53M35.5400S +/- 1", J2000 V = 15 +/- 1 NEBULA, PLANETARY DEC=+33D01'48.00" +/- 1" NEBULA Reference Frame: ICRS Comments: ------------------------------------------------------------------------------------------------------------------------------------ 11232( 3) - 25-Apr-2008 15:05:23 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 258.0D TO 260.0 D On Hold Comments: Additional Comments: This visit uses the same target and orientation as the PI's Visit 1 of program 11231 and optimally would be executed immediately after Visit 1 of program 11231. If that is done, then the exposure times of this program (11232) should be increased to take advantage of not having to do a new guidestar acquisition. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6720 WFPC2 IMAGE WF3-FIX F502N CR-SPLIT=NO 3 260.0 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6720 WFPC2 IMAGE WF3-FIX F658N CR-SPLIT=NO 3 260.0 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 1 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 2 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 3 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 1 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 2 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 3 none 1 N/A 11232( 3) - 25-Apr-2008 15:05:23 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENT 258.0D TO 260.0 D On Hold Comments: Additional Comments: This visit uses the same target and orientation as the PI's Visit 1 of program 11231 and optimally would be executed immediately after Visit 1 of program 11231. If that is done, then the exposure times of this program (11232) should be increased to take advantage of not having to do a new guidestar acquisition. Repeat of visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6720 WFPC2 IMAGE WF3-FIX F502N CR-SPLIT=NO 3 260.0 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6720 WFPC2 IMAGE WF3-FIX F658N CR-SPLIT=NO 3 260.0 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 1 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 2 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 3 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 1 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 2 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 3 none 1 N/A 11232( 3) - 25-Apr-2008 15:05:23 - [ 6] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: This visit uses the same target and orientation as the PI's Visit 1 of program 11231 and optimally would be executed immediately after Visit 1 of program 11231. If that is done, then the exposure times of this program (11232) should be increased to take advantage of not having to do a new guidestar acquisition. Repeat of visit 1 - no orient Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6720 WFPC2 IMAGE WF3-FIX F502N CR-SPLIT=NO 3 260.0 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6720 WFPC2 IMAGE WF3-FIX F658N CR-SPLIT=NO 3 260.0 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 1 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 2 none 1 N/A NGC6720 1 WFPC2 IMAGE WF3-FIX F502N none none 3 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 1 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 2 none 1 N/A NGC6720 2 WFPC2 IMAGE WF3-FIX F658N none none 3 none 1 N/A 11232( 3) - 25-Apr-2008 15:05:23 - [ 7] Summary Form for Proposal 11232 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 258.0D TO 260.0 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F502N, F658N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6720 ------------------------------------------------------------------------------------------------------------------------------------