August
2026
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2026PSJ.....7..186M
Authors
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Murtagh, Joseph
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Schwamb, Megan E.
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Kelley, Michael S. P.
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Knight, Matthew M.
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Lehmann, Thomas
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Milani, Giannantonio
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Gillan, A. Fraser
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Fitzsimmons, Alan
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Lyttle, Ryan R.
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Dobson, Matthew M.
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Holt, Carrie E.
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Lister, Tim
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Chatelain, Joseph P.
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Greenstreet, Sarah
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Ye, Quanzhi
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Hsieh, Henry H.
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Bodewits, Denis
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Chen, Tracy X.
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Dekany, Richard G.
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Graham, Matthew J.
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Groom, Steven L.
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Helou, George
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Kasliwal, Mansi M.
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Mahabal, Ashish A.
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Riddle, Reed
Abstract
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Comets and Centaurs trace the evolution of trans-Neptunian objects (TNOs) into the inner solar system. Their activity reflects the interplay between volatile sublimation, dust dynamics, and, in some cases, ring scattering. Yet the long-term behavior of individual objects remains less constrained. To probe this evolutionary transition, we use wide-field survey photometry from the Asteroid Terrestrial-impact Last Alert System (ATLAS), Zwicky Transient Facility, and targeted Las Cumbres Observatory observations of the Jupiter-family comet (JFC) 103P/Hartley 2 during its 2023/24 apparition, and the Centaur (2060) Chiron across 2020─2025, including its 2021 outburst. For 103P, heliocentric activity slopes are asymmetric about perihelion, with a steep inbound index ( nr,pre=−3.48±0.08 ) and flatter outbound value (nr,post = −1.16 ± 0.04), consistent with enhanced relative dust contribution postperihelion. With reduced brightness versus prior apparitions, this behavior matches reported secular fading trends. Dust mass-loss rates are ∼4─16 kg s−1 for assumed grain properties. Colors exhibit a blueward trend near perihelion, consistent with enhanced gas contamination of the g band, with possible phase-dependent scattering. Periodogram analysis recovers a ∼18.7 hr activity-linked period near perihelion. For Chiron, subtracting a quiescent baseline reveals exponential decay from the 2021 outburst on a ∼1.4 yr timescale. Seasonal phase curves flatten from βo = 0.150 ± 0.034 mag deg−1 in 2021 to ≲0.09 mag deg−1 by 2023─2025, converging with quiescent behavior. Broadband colors remain unchanged at ATLAS (c − o) = 0.22 ± 0.09 mag. The extended duration of this activity suggests a new epoch of persistent, low-level activity and/or evolving ring scattering. These two objects bracket the TNO-to-JFC evolutionary sequence, with 103P near the volatile-depleted end, and Chiron still volatile-rich and capable of episodic activity.
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