Nucleus of the active Centaur C/2011 P2 (PANSTARRS)

Abstract

Aims. In this paper we present observations of the active Centaur C/2011 P2 (PANSTARRS), showing a compact comet-like coma at the heliocentric distance of r h = 9 au. The observations were obtained in the framework of a wider program on Centaurs aimed at searching for comet-like activity in several targets outside Jupiter's aphelion. Methods. We analysed visible images of the Centaur taken at the TNG telescope in the R filter to investigate the level of coma contributing to the target brightness and to derive information on its nucleus size. Results. Centaur C/2011 P2 (PANSTARRS) shows a faint but still detectable comet-like activity, which accounts for more than 50% to the observed brightness. The coma contribution has been subtracted in order to derive an estimate for the Centaur's diameter of D ∼ 16 km, assuming an albedo of A = 0.07 (average of albedo measured within the Centaur group). The results for Centaur C/2011 P2 (PANSTARRS) fit in the general picture of the group: Centaurs with smaller perihelion distance q and semi-major axis a are smaller than those remaining farther from the Sun during their orbital path, thus reinforcing the idea that active Centaurs are "comets in fieri".

523676 (2013 UL10): the first active red centaur

“…Adopting A = 0.12 for centaur 523676 (2013 UL10), we obtain D ≤ 10 km, quite a small size when compared to the average size of inactive centaurs, which is more than one order of magnitude larger (Bauer et al 2003;Stansberry et al 2008;Jewitt 2009;Perna et al 2010). This is consistent with the fact that in general, active centaurs are found to be smaller than inactive ones (Mazzotta Epifani et al 2017).…”

“…We adapted and already applied this method to several active small bodies at different heliocentric distances and in particular to other active centaurs (see e.g. Mazzotta Epifani et al 2011, 2017. We used the obtained photometric results (magnitude in the R filter) in order to derive the cross-section C d of the dust coma and the dust mass M d of the coma itself, and we estimated the dust production rate Q d taking into account the time of residence of grains in a defined portion of the projected coma.…”

“…Very few active centaurs have been fully characterised up to now: the dust loss rate Q d for many of them is comparable or even higher than the rate of several active comets at much smaller heliocentric distances (Mazzotta Epifani et al 2006, 2011Jewitt 2009;Lacerda 2013). On the other hand, few active centaurs can be considered quite weak dust emitters, despite their relatively close perihelion distance, with Q d on the order of ∼10 kg s −1 (Jewitt 2009;Mazzotta Epifani et al 2014, 2017Kulyk et al 2016).…”

“…A few centaurs (30 objects in a family of ∼300 members, i.e., around 10% of the whole sample, as of January 2018) 1 have been observed to have a well-developed dust coma in optical images. The first example was (2060) Chiron, which orbits at about 10 au from the Sun and shows a sustained but variable cometary-like activity along its orbit (Luu & Jewitt 1990;Meech & Belton 1990). The activity of centaurs is part of a wider debate on the activity of small bodies at great distance from the Sun beyond Based on observations collected at the Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.…”

Thermal processing of Jupiter Family Comets during their chaotic orbital evolution

“…The existence of active Centaurs (e.g. Jewitt 2009;Lin et al 2014;Mazzotta Epifani et al 2017Steckloff et al 2020;de la Fuente Marcos et al 2021), alongside with the recent observations of long-distant activity of comets (e.g. Meech et al 2017;Jewitt et al 2017;Hui et al 2018Hui et al , 2019Yang et al 2021;Farnham et al 2021), provide direct evidence that cometary activity starts beyond the orbit of Neptune.…”