Evidence for Fresh Frost Layer on the Bare Nucleus of Comet Hale-Bopp at 32 Au Distance

Szabó, Gy. M.; Kiss, L. L.; Pál, András; Kiss, Cs.; Sárneczky, K.; Juhász, A.; Hogerheijde, M. R.

doi:10.1088/0004-637x/761/1/8

Cited by 26 publications

(35 citation statements)

References 27 publications

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“…The albedo of Chariklo is measured to be right in this range, whereas that of Chiron is found to be much higher (Table 4). For the nucleus of the giant comet C/1995 O1 (Hale-Bopp), recent estimations based upon Herschel observations give a diameter of 94 ± 15 km and an albedo of 5.5 ± 1.9% from the preliminary analysis of Kidger et al (2012), and a diameter of 74 ± 6 km and an albedo of 8.1 ± 0.9% from the study of Szabó et al (2012). This places the albedo of comet Hale-Bopp as intermediate between that of standard comets and Chiron, which indeed shows a peculiar high albedo.…”

Section: Discussionmentioning

confidence: 96%

TNOs are Cool: A survey of the trans-Neptunian region

Fornasier

Lellouch

Müller

et al. 2013

A&A

144

189

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Aims. Trans-Neptunian objects (TNOs) are bodies populating the Kuiper belt and they are believed to retain the most pristine and least altered material of the solar system. The Herschel open time key programme entitled "TNOs are Cool: A survey of the transNeptunian region" has been awarded 373 h to investigate the albedo, size distribution and thermal properties of TNOs and Centaurs. Here we focus on the brightest targets observed by both the PACS and SPIRE multiband photometers: the dwarf planet Haumea, six TNOs (Huya, Orcus, Quaoar, Salacia, 2002 UX25, and 2002 TC302), and two Centaurs (Chiron and Chariklo). Methods. Flux densities are derived from PACS and SPIRE instruments using optimised data reduction methods. The spectral energy distribution obtained with the Herschel PACS and SPIRE instruments over 6 bands (centred at 70, 100, 160, 250, 350, and 500 μm), with Spitzer-MIPS at 23.7 and 71.4 μm, and with WISE at 11.6 and 22.1 μm in the case of 10199 Chariklo, has been modelled with the NEATM thermal model in order to derive the albedo, diameter, and beaming factor. For the Centaurs Chiron and Chariklo and for the 1000 km sized Orcus and Quaoar, a thermophysical model was also run to better constrain their thermal properties. Results. We derive the size, albedo, and thermal properties, including thermal inertia and surface emissivity, for the 9 TNOs and Centaurs. Several targets show a significant decrease in their spectral emissivity longwards of ∼300 μm and especially at 500 μm. Using our size estimations and the mass values available in the literature, we also derive the bulk densities for the binaries Quaoar/Weywot (2.18 +0.43 −0.36 g/cm 3 ), Orcus/Vanth (1.53 +0.15 −0.13 g/cm 3 ), and Salacia/Actea (1.29 +0.29 −0.23 g/cm 3 ). Quaoar's density is similar to that of the other dwarf planets Pluto and Haumea, and its value implies high contents of refractory materials mixed with ices.

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Section: Discussionmentioning

confidence: 96%

TNOs are Cool: A survey of the trans-Neptunian region

Fornasier

Lellouch

Müller

et al. 2013

A&A

144

189

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“…We might then be able to detect when it "turns off" (the activity stops), which would give insight into which volatiles are most important for generating dust activity. Such work has been done by Szabó (2012) with the Herschel Space Telescope and the Very Large Telescope, which suggests that the nucleus had ceased to produce new gas and dust before their observations in mid-2010 (Szabó et al 2012). Continued deep imaging of the tail would also provide further tests for the Lorentz force hypothesis.…”

Section: Section 5: Conclusion and Discussionmentioning

confidence: 96%

A dynamical analysis of the dust tail of Comet C/1995 O1 (Hale–Bopp) at high heliocentric distances

Kramer

Fernández

Lisse

et al. 2014

Icarus

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Comet C/1995 O1 (Hale-Bopp) has provided an unprecedented opportunity to observe a bright comet over a wide range of heliocentric distances. We present here Spitzer Space Telescope observations of Hale-Bopp from 2005 and 2008 that show a distinct coma and tail, the presence of which is uncommon given its large heliocentric distance (21.6 AU and 27.2 AU, respectively). The morphology of the dust is compared to dynamical models to understand the activity of the comet. Our analysis shows that the shape of Hale-Bopp's dust tail in these images cannot be explained using the usual Finson-Probstein (solar gravity + solar radiation pressure) dynamical model. Several alternative explanations are explored. The analysis suggests that the most likely cause of the discrepancy is that the dust is being charged by the solar wind, then being affected by the interplanetary magnetic field via the Lorentz force. Though this effect has been explored previously, if correct, this seems to be the first time that the Lorentz force has been required to model a cometary dust tail. The analysis also suggests that Hale-Bopp was actively emitting particles when these images were taken, and the tail characteristics changed between observations. Section 1: Introduction, Background and MotivationA fundamental goal of astronomy is to understand the formation of Earth and our Solar System. Since it is impossible to observe our Solar System in its early stages, the next best thing is to study bodies that have been relatively preserved over the age of the Solar System. Comets have remained relatively unchanged since their birth as icy planetesimals in the early days of the Solar System, so they are a prime example of objects that can help us to understand the mechanics and chemistry of the planetary formation era. However, comets are not pristine; they have undergone physical and chemical alterations via various processes such as collisions (Farinella and Davis, 1996) and insolation (Huebner and Benkhoff, 1999). These changes require that we study cometary evolution to fully understand what the primordial comets were like. Section 1.1: BackgroundHale-Bopp was discovered in July of 1995, when it was inbound at a heliocentric distance of 7.2 AU. At this large distance it had already developed a coma, suggesting that activity was occurring on the nucleus at that time. It is rare to see such strong cometary activity beyond ~5 AU, so it became immediately clear that Hale-Bopp's behavior was different from that of other comets. The activity at this point was at least partially driven by the sublimation of CO (Biver et al. 1996), and transitioned to water driven activity at around 3 AU (Biver et al. 1997). When it reached its perihelion at 0.9 AU in 1997, its mass-loss rate was very high, (1.8 ± 0.4) x 10 6 kg s -1 , and the total mass loss while it was inside 3 AU was estimated to be ~ 3 x 10 13 kg (Lisse et al., 1997;Jewitt and Matthews, 1999). These extreme values were likely due to the fact that the nucleus is large (30 ± 10 km in radius and...

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“…We define "large comets" as those with 10 < D ≤ 40 km plus HaleBopp with D = 74 ± 6 km (Szabó et al 2012). We define "small TNOs" as 40 < D ≤ 200 km, where the upper limit roughly coincides with the D = 100-190 km interval where the cumulative size distribution for dynamically hot TNOs changes slope (Fraser et al 2014).…”

Section: Consequences Of Aluminum-26 In Icy Bodiesmentioning

confidence: 99%

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Davidsson

Sierks

Güttler

et al. 2016

A&A

187

162

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Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims. Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods. We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results. We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO 2 ; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system. Conclusions. We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles. We argue that TNOs formed as a result of streaming instabilities at sizes below ∼400 km and that ∼350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented mediumsized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity...

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Evidence for Fresh Frost Layer on the Bare Nucleus of Comet Hale-Bopp at 32 Au Distance

Cited by 26 publications

References 27 publications

TNOs are Cool: A survey of the trans-Neptunian region

TNOs are Cool: A survey of the trans-Neptunian region

A dynamical analysis of the dust tail of Comet C/1995 O1 (Hale–Bopp) at high heliocentric distances

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

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