17291( 3) - 27-Dec-2022 11:40:20 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17291 Version: 3 Check-in Time: 27-Dec-2022 11:40:20 STScI Edit Number: 1 Title Investigating a Vanishing Active Centaur ------------------------------------------------------------------------------------ Type Cycle GO/DD 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Colin Orion Chandler University of Washington Y CoI: Dr. Chad A. Trujillo Northern Arizona University N CoI: Dr. Stephen Tegler Northern Arizona University N CoI: Dr. William Romanishin Northern Arizona University N CoI: William Oldroyd Northern Arizona University N ------------------------------------------------------------------------------------ Abstract Centaurs are minor planets found between the orbits of Jupiter and Neptune. In this region temperatures are too cold for water ice to be sublimate, yet a rare (<20) subset of Centaurs display cometary activity such as a tail or coma. Observations by our team of one such active Centaur, P/2020 MK4, revealed the object had dimmed dramatically, by over 4 magnitudes. A distinct cloud of material has been consistently observable, even in the absence of a clearly discernible nucleus. We present two hypotheses to explain the vanishing of active Centaur P/2020 MK4: (1) the object is disintegrating or dissipating, or (2) the object is much smaller than previously estimated and is now entering a quiescent phase. Notably, the object has a nearly circular orbit (e=0.01), so a decrease in temperature alone cannot account for sublimation cessation, thus disintegration or material exhaustion may be more plausible. In order to test our hypotheses we propose to observe P/2020 MK4 with the WFC3 instrument with the F350LP filter in a sequence of four images acquired during a single orbit. With these observations we will (1) search for the presence of a nucleus (or nuclei, in case of breakup), (2) characterize the activity morphology, (3) measure the size of the debris cloud, and (4) describe the changes in mass loss rates through an observationally informed model of our own construction. In addition to furthering our understanding of active Centaurs, our findings will significantly enhance our understanding of the Centaur population if a fraction of the objects vanish prior to discovery, a possibility enhanced by their recent arrival to the Centaur region and short dynamical lifetimes. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request 4 X 432 s WFC3 exposures with the F350LP filter, all within a single orbit (though our science can be carried out with observations spanning multiple orbits if necessary). The target is P/2020 MK4, and it should be tracked non-siderealy. ------------------------------------------------------------------------------------ 17291( 3) - 27-Dec-2022 11:40:20 - [ 2] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: COMET-P-2020-MK4 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET P/2020 MK4 ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=6.023599722627209, E=0.02054475958444175, I=6.691382147221793 , O=1.888050999838472, W=169.9937011228537, T=06-MAY-2015:10:29:43, TTimeScale=TDB, EQUINOX=J2000, EPOCH=07-SEP-2020:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 24.5 +/- 0.5 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 17291( 3) - 27-Dec-2022 11:40:20 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17291( 3) - 27-Dec-2022 11:40:20 - [ 4] Visit: 01 (377s X 4) Visit Requirements: BETWEEN 02-JAN-2023:00:00:00 AND 08-JAN-2023:16:00:00; BETWEEN 08-JAN-2023:22:00:00 AND 10-JAN-2023:09:00:00; BETWEEN 10-JAN-2023:15:00:00 AND 11-JAN-2023:00:00:00; TOO RESPONSE TIME 19.0D On Hold Comments: Additional Comments: expanded via "auto-adjust" to 432 s each to maximize usable time of orbit Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 COMET-P-202 WFC3/UVI ACCUM UVIS2 F350LP 1 377 S SEQ 1 NON-INT; PATTERN 2 0-MK4 S (1508 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ COMET-P-2020-MK4 1 WFC3/UVI ACCUM UVIS2 F350LP 1 none none none 1 N/A S COMET-P-2020-MK4 1 WFC3/UVI ACCUM UVIS2 F350LP 2 none none none 1 N/A S COMET-P-2020-MK4 1 WFC3/UVI ACCUM UVIS2 F350LP 3 none none none 1 N/A S COMET-P-2020-MK4 1 WFC3/UVI ACCUM UVIS2 F350LP 4 none none none 1 N/A S 17291( 3) - 27-Dec-2022 11:40:20 - [ 5] Summary Form for Proposal 17291 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 02-JAN-2023:00:00:00 AND 08-JAN-2023:16:00:00, BETWEEN 08-JAN-2023:22:00:00 AND 10-JAN-2023:09:00:00, BETWEEN 10-JAN-2023:15:00:00 AND 11-JAN-2023:00:00:00, PATTERN 2 1, SEQ 1 NON-INT, TOO RESPONSE TIME 19.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F350LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names COMET-P-2020-MK4 ------------------------------------------------------------------------------------------------------------------------------------