Evolution of the dust coma in comet 67P/Churyumov-Gerasimenko before the 2009 perihelion

Tozzi, G. P.; Patriarchi, P.; Boehnhardt, H.; Vincent, J.-B.; Licandro, J.; Kolokolova, L.; Schulz, R.; Stüwe, J. A.

doi:10.1051/0004-6361/201116577

Cited by 29 publications

(28 citation statements)

References 32 publications

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“…After a more or less steep increase in the inner part of the coma, which is affected by the seeing and observable in all targets, for most of the comets (C/2005 L3, C/2007 M1, C/2008 FK75 C/2009 S3, C/2010 R1, and C/2011 L4) it is possible to clearly identify a decrease in Afρ with the nucleocentric distance ρ. A similar decrease has been often attributed to non steady state dust emission and possibly dust grain fading or destruction (Lara et al 2004;Tozzi et al 2003) and/or to fresh dust production within the coma, even if the latter process is more likely to be observed during close passages to the Sun (Tozzi et al 2011). This decrease is not observed for the remaining two comets (C/2005 S4 and C/2007 JA21), but it could be that the relatively small apparent coma extension and low activity level prevented such a detection with our data.…”

Section: Afρmentioning

confidence: 62%

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

Epifani

Perna

Fabrizio

et al. 2013

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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.

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Section: Afρmentioning

confidence: 62%

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

Epifani

Perna

Fabrizio

et al. 2013

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“…Agarwal et al (2007) and Vincent et al (2013) discuss the large scale and fine structure morphology of the comet in detail. Tozzi et al (2011) found that A f ρ varied with ρ for observations of 67P at r = 2.3 AU pre-perihelion, and so the coma did not behave as 1/ρ. We find that 67P does not match the steady state assumption over a wider range in heliocentric distance, by measuring the slope of the radial profile in all the archival data sets.…”

Section: Dust Productionmentioning

confidence: 91%

“…In this paper we present data taken in 2007 and 2008 around the time of the expected onset, between the inactive nucleus observations taken in 2007 (Tubiana et al 2011;Lowry et al 2012) and the active comet observations in 2008 (Tozzi et al 2011). 20 × 30 (0) R 27/3/08 3.39 3.80 14.6 3×15 + 4×60 (6) VRI 29/3/08 3.38 3.76 14.9 3×15 + 4×60 (6) VRI 30/3/08 3.38 3.74 15.0 3×15 + 4×60 (6) VRI (a) Heliocentric distance (AU).…”

Section: Introductionmentioning

confidence: 99%

“…Schulz et al (2004), Lamy et al (2006) and Lara et al (2005) obtained the first dedicated characterisation observations after it was selected, when the comet was on the outbound leg of its orbit, and still highly active, following its perihelion passage in 2002. As the comet passed through aphelion its inactive nucleus was studied by Tubiana et al (2008Tubiana et al ( , 2011 and Lowry et al (2012), before it was observed in an active state again as it returned to perihelion in 2008 (Tozzi et al 2011;Lara et al 2011). Further authors have studied the longer lived dust trail associated with the comet (Ishiguro 2008;Kelley et al 2008;Agarwal et al 2010), the dust's polarisation (Hadamcik et al 2010), the nucleus thermal properties (Kelley et al 2006;Lamy et al 2008;Kelley et al 2009), and the morphology (Vincent et al 2013) and composition (Schleicher 2006) of its coma over multiple apparitions.…”

Section: Introductionmentioning

confidence: 99%

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Beginning of activity in 67P/Churyumov-Gerasimenko and predictions for 2014–2015

Snodgrass

Tubiana

Bramich

et al. 2013

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Context. Comet 67P/Churyumov-Gerasimenko was selected in 2003 as the new target of the Rosetta mission. It has since been the subject of a detailed campaign of observations to characterise its nucleus and activity. Aims. Here we present previously unpublished data taken around the start of activity of the comet in 2007/8, before its last perihelion passage. We constrain the time of the start of activity, and combine this with other data taken throughout the comet's orbit to make predictions for its likely behaviour during 2014/5 while Rosetta is operating. Methods. A considerable difficulty in observing 67P during the past years has been its position against crowded fields towards the Galactic centre for much of the time. The 2007/8 data presented here were particularly difficult, and the comet will once again be badly placed for Earth-based observations in 2014/5. We make use of the difference image analysis (DIA) technique, which is commonly used in variable star and exoplanet research, to remove background sources and extract images of the comet. In addition, we reprocess a large quantity of archival images of 67P covering its full orbit, to produce a heliocentric lightcurve. By using consistent reduction, measurement and calibration techniques we generate a remarkably clean lightcurve, which can be used to measure a brightnessdistance relationship and to predict the future brightness of the comet. Results. We determine that the comet was active around November 2007, at a pre-perihelion distance from the Sun of 4.3 AU. The comet will reach this distance, and probably become active again, in March 2014. We find that the dust brightness can be well described by A f ρ ∝ r −3.2 pre-perihelion and ∝ r −3.4 post-perihelion, and that the comet has a higher dust-to-gas ratio than average, with log(A f ρ/Q(H 2 O)) = −24.94 ± 0.22 cm s molecule −1 at r < 2 AU. A model fit to the photometric data suggests that only a small fraction (1.4%) of the surface is active.

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“…Similar trends of A f ρ vs. ρ, including the steep increase at small ρ with a comparable scale length, were already observed in several other comets at various heliocentric distances. We cite the data regarding comets C/1999 S4 (LINEAR) by Bonev et al (2002) and Tozzi & Licandro (2002), C/2000 WM1 (LINEAR) by Lara et al (2004) and Tozzi et al (2004), 9P/Tempel 1 by Tozzi et al (2007), C/2007 N3 (Lulin) by Woodward et al (2011), and 67P/Churyumov-Gerasimenko by Tozzi et al (2011). An intriguing explanation for the steepness of the A f ρ profiles, or equivalently of those of its derived parameter ΣA f (Tozzi & Licandro 2002), close to the nucleus was proposed by Tozzi et al (2004) for comet C/2000 WM1 (LINEAR).…”

Section: Af ρmentioning

confidence: 99%

Photometric observations of comet 81P/Wild 2 during the 2010 perihelion passage

Bertini

Barbieri

et al. 2012

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Context. The Jupiter-family comet 81P/Wild 2, target of the NASA Stardust mission, is very important in the context of the studies of pristine objects in the solar system. First, it was only recently deflected into the present orbit, having spent at least 300 yr at higher heliocentric distance prior to the orbital change in 1974. It is therefore likely that the comet experienced a recent activation with consequent low alteration of its original material. Second, it is the only comet whose coma material was brought back to Earth for laboratory analysis. We observed the object between 2010 February 9 and September 9 for a total of 11 nights during the 2010 perihelion passage. Aims. The goals of the campaign were the characterization of the comet's dust activity and the comparison with previous apparitions to derive hints on the secular behavior of the object. Methods. Broadband R-and I-images were acquired using three instruments: ALFOSC, CAMELOT, and TCP. The first one is mounted at the Nordic Optical Telescope on La Palma, while the second and the third are mounted at the Instituto de Astrofisica de Canarias 0.82-m telescope on Tenerife. We analyzed the presence and variability of dust structures in the coma with image-enhancing techniques, the radial profile of the dust brightness, and we measured the dust production rate and the dust reddening. Results. We found evidence of a long-lasting sunward fan and anti-solar tail activity throughout all our observations up to a heliocentric distance of 2.42 AU. A f ρ measurements suggest a pre-perihelion peak of the activity, caused by a seasonal effect, plus two post-perihelion outbursts. Both spatial and A f ρ radial profiles indicate a steady-state coma at nucleocentric distances greater than ∼1000-2000 km. The color analysis reveals a moderately reddened dust with a 6-9%/1000 Å reddening, consistent with the current picture of cometary dust. The second outburst emitted dust with lower reddening. Conclusions. The comparison with previous perihelion passages points toward a recurrent main activity always driven by the same areas on the nucleus, producing dust with similar characteristics and in similar coma structures in different years. Our A f ρ measurement at the longest heliocentric distance suggests the comet was less dust-productive in 2010, pointing toward a possible secular aging of the object and its activity. The change of dust colors during the unusual second outburst suggests that an internal part of the nucleus has different physical properties compared with those that produce the recurrent main activity, pointing toward a heterogeneous comet.

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Evolution of the dust coma in comet 67P/Churyumov-Gerasimenko before the 2009 perihelion

Cited by 29 publications

References 32 publications

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

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

Beginning of activity in 67P/Churyumov-Gerasimenko and predictions for 2014–2015

Photometric observations of comet 81P/Wild 2 during the 2010 perihelion passage

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