Disintegration of Near-Sun Comet C/2021 O3 (PANSTARRS)
ATel #15358; Qicheng Zhang (Caltech), Quanzhi Ye (U. Maryland/Boston U.), Tony L. Farnham (U. Maryland), Carrie E. Holt (U. Maryland)
on 2 May 2022; 18:49 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Qicheng Zhang (qicheng@cometary.org)
Twilight observations conducted with the Lowell Discovery Telescope (LDT) on 2022 April 29 (UT) indicate that comet C/2021 O3 (PANSTARRS) has disintegrated. We used LDT's Large Monolithic Imager to obtain 19 x 1 s exposures of the comet through the r′ filter between 02:50 and 02:54 UT at ~6° altitude where the seeing was ~4″ FWHM. The comet would have been 0.38 au from the Sun, 0.70 au from Earth, and at 135° phase angle during these observations. We accounted for the expected, rapid ~7 arcsec/min motion of the comet by aligning and stacking the calibrated frames on the JPL orbit #15 ephemerides positions. A median stack showing the vicinity of the predicted position, with the formal 3σ uncertainty ellipse and a point spread function (PSF) model derived from a separate stack of a background star labeled, is available here: https://near.earth/shared/2022/04/ldt_2021o3_20220429.png
While extrapolation of the earlier pre-perihelion brightening trend (e.g., [1]) projected that the comet would have brightened to a magnitude of V ~ r′ ~ 5 by this time, no objects with the expected motion of the comet are visible within the 3σ uncertainty ellipse. The magnitude limit of r′ > 14 for point sources in the stacked image very roughly constrains dust production activity of a comet in this region to Afρ < 10 cm. However, a diffuse glow ~40″ in diameter with an integrated magnitude of r′ ~ 9 is visible above the noise level ~2′ southeast of the JPL position and appears to be co-moving with the JPL orbital solution. The large offset in both the antisunward and negative heliocentric velocity directions together with the lack of any observed nuclear condensation suggests that this feature is a dust cloud or debris field persisting as a remnant from the disintegration of the nucleus, an event likely associated with the comet's close perihelion passage on April 21 at 0.29 au from the Sun. This conclusion lines up with previous reports the comet had fallen below its earlier brightness trend since a few days before perihelion (e.g. [2], [3]).
These results made use of the Lowell Discovery Telescope (LDT) at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. The University of Maryland observing team consisted of Quanzhi Ye, James Bauer, Michaela Blain, Adeline Gicquel-Brodtke, Tony Farnham, Lori Feaga, Carrie Holt, Michael S. P. Kelley, and Jessica Sunshine.
LDT Median Image Stack of C/2021 O3
