Observational results for eight long-period comets observed far from the Sun

Abstract

Context. With this work we start a systematic analysis of the distant activity of several long-period comets in order to investigate the evolution of activity throughout the solar system and explore differences between comets that pass their perihelion at far or very close distances from the Sun. Aims. We present observational data for eight long-period comets, observed for the first time beyond r = 5 AU. Three targets have been characterised on their inward orbital branch. The others have passed their perihelion at quite large heliocentric distances (r q from 4.5 to 7.5 AU). Methods. We analyse multicolour broadband images (V, R, and I filters) taken at the Telescopio Nazionale Galileo to characterise the dust coma of the comets and investigate their morphology, photometry, colours, and dust production.Results. The morphological analysis shows many differences among the sample, from the large twisted structure present in the coma of comet C/2005 L3 to the regular coma envelope of C/2010 R1. The colour of the dust coma of all the comets is redder than the Sun. The Afρ value (measured in a reference aperture of radius ρ = 10 4 km) ranges from 114 ± 2 (C/2005 S4) to 5091 ± 47 (C/2005 L3) cm, depicting a scenario of bodies from moderately to very active. This is confirmed by the first-order quantitative estimate of the dust mass-loss rate for the comets that was obtained from the photometric data: assuming a grain velocity of v = 20 m/s, the dust production rate is comparable with, or even significantly larger than, that measured for many short-period ("old") comets at much smaller heliocentric distances.

Blending the distinctions among groups of minor bodies: a portrait of the Centaur-comet “transition” object P/2010 C1 (Scotti)

“…P/2010 C1. It appears clear, also in comparison with dust massloss rate values computed for several active minor bodies of different families and groups (see Mazzotta Epifani et al 2014 and in particular their Fig. 6), that P/2010 C1 is a rather weak dust emitter, with a dust-loss rate comparable to that of the weakest SPCs at shorter heliocentric distances and to the weakest active Centaur 39P/Oterma (Jewitt 2009).…”

“…3 in Mazzotta To obtain a first-order quantitative estimate of the dust massloss rate for the centaur P/2010 C1 (Scotti), we applied a "photometric model", which relates the optical photometry to the dust production rate via some realistic assumptions on the cometlike dust environment. The method is derived from the one used by Jewitt (2009) to compute the dust production rate of active Centaurs in the region between 5 and 12 AU, and was adapted and already successfully applied by our group to several active A69, page 6 of 8 minor bodies such as long period comets (Mazzotta Epifani et al 2010, 2014, short period comets (Mazzotta , and active Centaurs .…”

“…The prototype of active Centaur is (2060) Chiron (Kowal et al 1979;Meech & Belton 1989;Luu & Jewitt 1990), which orbits at about 10 AU from the Sun and shows a sustained, though variable, comet-like activity along its orbit. The activity among Centaurs is part of a wider debate about the activity of minor bodies at great distance from the Sun, outside the socalled "water zone".…”

Survival of Amorphous Water Ice on Centaurs

“…Several examples can support this hypothesis. Centaur P/2010 C1 (Scotti) has had a chaotic dynamical history, leading to a great decrease of its perihelion distance and semimajor axis to the current values (Mazzotta Epifani et al 2011). The orbital parameters of 39P/Oterma have been modified on the timescale of decades due to close encounters with Jupiter in 1963 (Fernandez et al 2001).…”

Monitoring of the cometary activity of distant comet C/2006 S3 (LONEOS)

“…So far, the number of such studies is very limited. Only a few comets have been studied inbound at heliocentric distances larger than 5 au (Korsun & Chörny 2003;Tozzi et al 2003;Meech et al 2009;Korsun et al 2010;Mazzotta Epifani et al 2014;Shi et al 2014). We present here an observational dataset of a distant comet observed in a large range of heliocentric distances.…”