The Ongoing Decline in Activity of Comet 103P/Hartley 2
Abstract
We report photometric observations of Comet 103P/Hartley 2 during its 2023 apparition. Our campaign, conducted from August through December 2023, combined data from a global network of citizen astronomers coordinated by Unistellar and the Association Fran\c{c}aise d'Astronomie. Photometry was derived using an automated pipeline for eVscope observations in partnership with the SETI Institute and aperture photometry via AstroLab Stellar. We find that the comet's peak reduced brightness, measured at , continues a long-term fading trend since 1991. The decline in activity follows a per-apparition minimum magnitude increase of mag, corresponding to an approximately reduction in brightness each return. This trend implies that the comet's active fraction has declined by about an order of magnitude since 1991 and may indicate that Hartley 2 is no longer hyperactive by definition. The fading is consistent with progressive volatile depletion rather than orbital effects. These results offer insight into the evolutionary processes shaping Jupiter-family comets.
Cite
@article{arxiv.2508.20215,
title = {The Ongoing Decline in Activity of Comet 103P/Hartley 2},
author = {Ariel Graykowski and Guillaume Langin and David Chiron and Bruno Guillet and Franck Marchis and Nicolas Biver and Gérard Arlic and Bernard Baudouin and Etienne Bertrand and Randall Blake and Cyrille Bosquet and John K. Bradley and Isabelle Brocard and Christophe Cac and Alain Cagna and Nicolas Castel and Eric Chariot and Olivier Clerget and Tom Coarrase and Lucas Cogniaux and Julien Collot and Christophe Coté and Michel Deconinck and Jean-Paul Desgrees and Josselin Desmars and Giuseppe Di Tommaso and José Donas and William Drapeaud and Todd Forrester and Florent Frémont and Keiichi Fukui and Paul Garde and Jérôme Gaudilliere and Pascal Gaudin and Alexis Giacomoni and David Gineste and Patrice Girard and Jean Claude Gomez and Chuck Goodman and Gerard-Philippe Grandjean and Philippe Guiglion and David Havell and Patrick Huth and Kachi Iwai and Marc-Etienne Julien and Rachel Knight and Ryuichi Kukita and Petri Kuossari and Jean-Michel Ladruze and Anis Ben Lassoued and Cédric Latgé and Jean-Marie Laugier and Matthieu Lauvernier and Patrice Le Guen and Jean-Charles Le Tarnec and Didier Lefoulon and Liouba Leroux and Niniane Leroux and Arnaud Leroy and Chelsey Logan and Yohann Lorand and Elisabeth Maris and Jean-Pierre Masini and Nicola Meneghelli and Laurent Millart and Eric Miny and Mike Mitchell and Baptiste Montoya and Fabrice Mortecrette and Anouchka Nardi and Antoine Ngo and Denis Nicolas and Raphael Nicollerat and Takaya Okada and Wataru Ono and George Patatoukas and Jacqueline Payet-Ayrault and Patrick Picard and Claude Porchel and Kanai Potts and Michel Quienen and Martial Relier and Fabien Richardot and Darren Rivett and Matthew Ryno and Fadi Saibi and Sophie Saibi and Christian Sartini and Hiromichi Sasaki and Philippe Seibert and Masao Shimizu and Lucas Sifoni and Georges Simard and Petri Tikkanen and Ian Transom and Bernard Tregon and Frank Tyrlik and Laurent Vadrot and Michel Veuillet and Christian Voirol and Stefan Will and Corine Yahia and Phil Yehle and Neil Yoblonsky and Wai-Chun Yue},
journal= {arXiv preprint arXiv:2508.20215},
year = {2025}
}