Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs)
We combine ground- and space-based observations of long-period comet C/2021 O3 (Panstarrs; perihelion distance 0.287 au) in order to investigate its reported near-perihelion destruction. Preperihelion photometric observations show a remarkably small heliocentric dependence of the scattered light, $\...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-3881/adea4d |
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| author | David Jewitt Jing Li Michael Jaeger Yoonyoung Kim |
| author_facet | David Jewitt Jing Li Michael Jaeger Yoonyoung Kim |
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| description | We combine ground- and space-based observations of long-period comet C/2021 O3 (Panstarrs; perihelion distance 0.287 au) in order to investigate its reported near-perihelion destruction. Preperihelion photometric observations show a remarkably small heliocentric dependence of the scattered light, $\propto {r}_{H}^{-s}$ with s = 2.59 ± 0.21, distinct from values reported in other long-period comets, for which s = 4 is the canonical standard. The index is smaller than expected of coma production by equilibrium sublimation of either supervolatiles (for which s ∼ 4 is expected) or water ice ( s ∼ 6–8) across the ∼4 to 2 au range. The absolute magnitude deduced from the preperihelion data is H = 13.0 ± 0.3 (coma scattering cross section ∼225 km ^2 for an assumed geometric albedo 0.04), while after perihelion the cross section fades by a factor of 25 to H = 16.5 (∼9 km ^2 ). STEREO spacecraft observations near perihelion show a long debris trail whose properties are consistent with forward scattering from radius ∼7 μ m particles. The data show that the nucleus of C/2021 O3 was not destroyed at perihelion. Although the light curve from 3.9 au inbound to 0.8 au outbound is not uniquely determined, a simple explanation is provided by seasonal dimming on a nucleus having high obliquity and an asymmetric distribution of near-surface volatiles. The survival of the nucleus against rotational disruption suggests a preperihelion nucleus radius r _n ≳ 1.0 km, while the photometric limit to the radius of the nucleus after perihelion is r _n < 1.7 km (geometric albedo 0.04 assumed). |
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| spelling | doaj-art-712eab2203f64738a2773276bd9de6f82025-08-20T03:43:03ZengIOP PublishingThe Astronomical Journal1538-38812025-01-01170314210.3847/1538-3881/adea4dDown But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs)David Jewitt0Jing Li1https://orcid.org/0000-0002-0982-7309Michael Jaeger2Yoonyoung Kim3Department of Earth, Planetary and Space Sciences , UCLA, 595 Charles Young Drive, Los Angeles, CA 90095, USA ; djewitt@gmail.comDepartment of Earth, Planetary and Space Sciences , UCLA, 595 Charles Young Drive, Los Angeles, CA 90095, USA ; djewitt@gmail.comAuf der Burg 225 , A-3610 Weißenkirchen, AustriaDepartment of Earth, Planetary and Space Sciences , UCLA, 595 Charles Young Drive, Los Angeles, CA 90095, USA ; djewitt@gmail.comWe combine ground- and space-based observations of long-period comet C/2021 O3 (Panstarrs; perihelion distance 0.287 au) in order to investigate its reported near-perihelion destruction. Preperihelion photometric observations show a remarkably small heliocentric dependence of the scattered light, $\propto {r}_{H}^{-s}$ with s = 2.59 ± 0.21, distinct from values reported in other long-period comets, for which s = 4 is the canonical standard. The index is smaller than expected of coma production by equilibrium sublimation of either supervolatiles (for which s ∼ 4 is expected) or water ice ( s ∼ 6–8) across the ∼4 to 2 au range. The absolute magnitude deduced from the preperihelion data is H = 13.0 ± 0.3 (coma scattering cross section ∼225 km ^2 for an assumed geometric albedo 0.04), while after perihelion the cross section fades by a factor of 25 to H = 16.5 (∼9 km ^2 ). STEREO spacecraft observations near perihelion show a long debris trail whose properties are consistent with forward scattering from radius ∼7 μ m particles. The data show that the nucleus of C/2021 O3 was not destroyed at perihelion. Although the light curve from 3.9 au inbound to 0.8 au outbound is not uniquely determined, a simple explanation is provided by seasonal dimming on a nucleus having high obliquity and an asymmetric distribution of near-surface volatiles. The survival of the nucleus against rotational disruption suggests a preperihelion nucleus radius r _n ≳ 1.0 km, while the photometric limit to the radius of the nucleus after perihelion is r _n < 1.7 km (geometric albedo 0.04 assumed).https://doi.org/10.3847/1538-3881/adea4dComet nucleiComet originsOort cloud objectsComet volatilesLong period comets |
| spellingShingle | David Jewitt Jing Li Michael Jaeger Yoonyoung Kim Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs) The Astronomical Journal Comet nuclei Comet origins Oort cloud objects Comet volatiles Long period comets |
| title | Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs) |
| title_full | Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs) |
| title_fullStr | Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs) |
| title_full_unstemmed | Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs) |
| title_short | Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs) |
| title_sort | down but not out the case of long period comet c 2021 o3 panstarrs |
| topic | Comet nuclei Comet origins Oort cloud objects Comet volatiles Long period comets |
| url | https://doi.org/10.3847/1538-3881/adea4d |
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