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We summarize the collective knowledge of physical and surface properties of comet nuclei, focusing on those that are obtained from remote observations. We now have measurements or constraints on effective radius for over 200 comets,…
133P/Elst-Pizarro is the firstly recognized main-belt comet, but we still know little about its nucleus. Firstly we use mid-infrared data of Spitzer-MIPS, Spitzer-IRS and WISE to estimate its effective diameter $D_{\rm…
Pluto's icy surface has changed colour and its atmosphere has swelled since its last closest approach to the Sun in 1989. The thin atmosphere is produced by evaporating ices, and so can also change rapidly, and in particular carbon monoxide…
P/2011 S1 (Gibbs) is an outer solar system comet or active Centaur with a similar orbit to that of the famous 29P/Schwassmann-Wachmann 1. P/2011 S1 (Gibbs) has been observed by the Pan-STARRS 1 (PS1) sky survey from 2010 to 2012. The…
Through photometry and spectroscopy, we studied the evolution of the activity and chemical composition of comet 67P during its 2025 and 2021 perihelion passages and of comet 103P during its 2010 and 2023 passages. For each comet, we aim to…
The data obtained in the recent Rosetta space mission to comet 67P/Churyumov-Gerasimenko have had a profound impact on the understanding of the nature of comets. In addition to revising the notions on the physical properties and structure…
Context. Comet 46P/Wirtanen is a near-Earth object (NEO) for which no associated meteor shower has ever been reported. Aims. This study is aimed at improving our understanding of why there has been no observed shower activity for this NEO…
An improved forced-precession model of Comet 46P/Wirtanen is presented. The nongravitational motion of the comet has been investigated based on the forced precession model of the rotating cometary nucleus. The least squares method applied…
We report the recovery of returning Halley-type comet 12P/Pons-Brooks using the 4.3 m Lowell Discovery Telescope, at a heliocentric distance of 11.89 au. Comparative analysis with a dust model suggests that the comet may have been active…
We have used the Spitzer 22-um peakup array to observe thermal emission from the nucleus and trail of comet 103P/Hartley 2, the target of NASA's Deep Impact Extended mission. The comet was observed on UT 2008 August 12 and 13, while the…
We present a study of the newly-discovered main-belt comet P/2008 R1 (Garradd), an object with the dynamical characteristics of an asteroid and the physical characteristics of a comet. Photometry sets a limit to the effective radius of the…
Context. (4015) Wilson-Harrington (hereafter, WH) was discovered as a comet in 1949 but has a dynamical property consistent with that of a near-Earth asteroid. Although there is a report that the 1949 activity is associated with an ion…
We present optical and near-infrared (NIR) observations of the outbursting, Halley-type comet 12P/Pons-Brooks. Three NIR spectra were obtained during two outbursts in October and November 2023, with the 3-meter Infrared Telescope Facility…
We present visible and near-infrared photometric and spectroscopic observations of interstellar object 2I/Borisov taken from 2019 September 10 to 2019 November 29 using the GROWTH, the APO ARC 3.5 m and the NASA/IRTF 3.0 m combined with…
Far ultraviolet observations of comets yield information about the energetic processes that dissociate the sublimated gases from their primitive surfaces. Understanding which emission processes are dominant, their effects on the observed…
We present 2-5 $\mu$m spectroscopic observations of the dust coma of 67P/Churyumov-Gerasimenko obtained with the VIRTIS-H instrument onboard Rosetta during two outbursts that occurred on 2015, 13 September 13.6 h UT and 14 September 18.8 h…
We report photometric observations for comet C/2012 S1 (ISON) obtained during the time period immediately after discovery (r=6.28 AU) until it moved into solar conjunction in mid-2013 June using the UH2.2m, and Gemini North 8-m telescopes…
Distant long-period comet C/2017 K2 has been outside the planetary region of the solar system for 3 Myr, negating the possibility that heat retained from the previous perihelion could be responsible for its activity. This inbound comet is…
Jupiter-family comet 289P/Blanpain was first discovered in 1819 and was then lost for $\sim200$ years, only to be rediscovered in 2003 as a small, weakly active comet. The comet is associated with the Phoenicids, an otherwise minor meteor…
steroid (596) Scheila was reported to exhibit a cometary appearance and an increase in brightness on UT 2010 December 10.4. We used the IRCS spectrograph on the 8-m Subaru telescope to obtain medium-resolution spectra of Scheila in the…