Apparent Outburst of Comet 63P/Wild 1
ATel #17798; Michael S. P. Kelley (Univ. Maryland), Larry Denneau (Univ. Hawaii), Carrie Holt (Las Cumbres Observatory), on behalf of the Zwicky Transient Facility Collaboration, and the LCO Outbursting Objects Key Project
on 13 May 2026; 18:32 UT
Credential Certification: Carrie Holt (cholt@lco.global)
We report the discovery and follow-up observations of a small (-1.2 mag) apparent outburst of comet 63P/Wild 1. The event was originally recognized by the authors in Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP 131, a8002) images and photometry, which suggested a brightening and morphological change between i-band observations taken 2026 Apr 29 and 30, and an r-band observation taken May 07. Photometry calibrated to the r-band and measured in a 7" radius aperture: 16.93 ± 0.03, 16.97 ± 0.04, and 16.39 ± 0.03 mag at 2026 Apr 29 04:12, Apr 30 03:56, and May 7 03:51 UTC, respectively. On May 7, the morphology of the outburst ejecta was already broadly distributed out to ~20" from the photocenter of the comet; the comet was 2.06 au from the Sun and 2.21 au from the Earth.
After a review of ATLAS observations, it became apparent that the outburst timing and brightness could be better measured. Four images of the comet were taken on 2026 May 3 between 06:46 and 07:29 UTC with the ATLAS 0.5-m telescope and o-filter at Haleakala Observatory, Hawaii (Tonry et al. 2018, PASP 130, 064505). In the median stacked data, the comet was r=16.84 ± 0.02 mag (all photometry calibrated to PS1 r-band magnitudes and measured in 7" radius apertures). The telescope observed the comet again the next night in four o-band images taken on 2026 May 4 between 06:14 and 06:46 UTC, with a median brightness of r=15.67 ± 0.01 mag, suggesting an outburst with a relative strength of -1.2 mag.
Follow-up observations with the Las Cumbres Observatory were scheduled and obtained on 2026 May 09 at 21:04 UTC. The comet measured r=16.58 ± 0.04 mag, confirming the rapid decline back to its pre-perihelion brightening trend.
This work uses data from the University of Hawaii's ATLAS project, funded through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575, with contributions from the Queen's University Belfast, STScI, the South African Astronomical Observatory, and the Millennium Institute of Astrophysics, Chile, the Instituto de Astrofisica de Canarias (Spain) and the University of Oxford.
Based on observations obtained with the Samuel Oschin Telescope 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, Weizmann Institute for Science, Oskar Klein Center at Stockholm University, University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, TANGO Consortium of Taiwan, University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.
This work makes use of observations from the Las Cumbres Observatory global telescope network.
