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M A Barucci - One of the best experts on this subject based on the ideXlab platform.
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the composition of ultra red tnos and Centaurs
Icarus, 2015Co-Authors: F Merlin, M A Barucci, C De Bergh, D P Cruikshank, D. Perna, Morea Dalle C Ore, Joshua P Emery, T L Roush, L Dalle V OreAbstract:Abstract We present an analysis of the colors available for seven trans-neptunian objects (TNOs) and three Centaurs among the reddest known, aimed at characterizing their surface chemical properties. In particular we seek to obtain evidence in support of the proposed correlation between the visible coloration of the surface of TNOs and their surface compositions (Brown, M.E., Schaller, E.L., Fraser, W.C. [2011]. Astrophys. J. 739, L60). The analysis focuses on nine available colors in the visible–near IR (0.3–4.5 μm) spectral range scaled to the V albedo to provide a proxy for the spectral shape of the objects. The colors include Spitzer IRAC data never published before, key in providing an effective constraint in the discrimination of ices contributing to the surface composition of the objects. Compositions are obtained by comparing the data to a grid of radiative transfer models convolved by the filter response functions of the colors adopted in the spectrum-proxies to match the resolution of the observations. We find evidence suggesting the presence of hydrocarbons and/or methanol on the surfaces of most objects in our sample, supporting the hypothesis by Brown et al. (Brown, M.E., Schaller, E.L., Fraser, W.C. [2011]. Astrophys. J. 739, L60) that the coloration of red TNOs could be linked to their methanol content. From our finding of methanol/hydrocarbon ices on the surfaces of the objects in our sample of very red TNOs and Centaurs we infer that ultra-red objects in general might contain these ices and therefore might have formed in the outer part of the Solar System. We also deduce that the surfaces of most of the very red TNOs in our dataset are probably still quite pristine, and that their organic materials could have been produced by irradiation of the volatile ices whose traces are still present on their surface. Although our sample is small, we infer that the irradiation process is still in progress, as hinted by the Centaurs’ slightly elevated organic amounts at smaller perihelion distances. However, considering the relatively similar amounts of organics found in our data at a wide variety of perihelion distances, we also infer that it could have started before Neptune’s migration. The technique used to constrain the composition described as part of this study introduces a new approach at investigating the surface chemistry of the very small and numerous objects that constitute the bulk of the TNO and centaur populations. This innovative method has the potential to provide constraints for irradiation theories and for models of dynamical and chemical evolution of the Solar System.
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Photometry and taxonomy of trans-Neptunian objects and Centaurs in support of a Herschel key program
Astronomy and Astrophysics, 2013Co-Authors: Davide Perna, E. Vilenius, M A Barucci, Elisabetta Dotto, E. Mazzotta Epifani, Massimo Dall'ora, Sonia Fornasier, Thomas MüllerAbstract:Context. The investigation of Centaurs and trans-Neptunian objects (TNOs) provides essential information about the early conditions and evolution of the outer solar system. The radiometric technique combines measurements in the visible and thermal infrared; with these one can estimate the size and albedo of Centaurs and TNOs. Aims. Our aim is to obtain visible photometry of a sample of Centaurs and TNOs, a subset of the targets of the “TNOs are cool” key program at the Herschel Space Observatory. Methods. We carried out visible photometry of Centaurs and TNOs, making use of the DOLORES instrument at the Telescopio Nazionale Galileo (TNG, La Palma, Spain). Results. We report photometric observations of 20 objects and present the computed absolute magnitudes. We derive the taxonomy of our targets (nine are classified for the first time, the results for five objects agree with the literature, the other targets are tentatively classified based on incomplete datasets) and combine the results with the literature, searching for correlations between taxonomy and dynamics. We look for comet-like activity in our Centaur sample, including (248835) 2006 SX368, which was previously described as active. Conclusions. We provide an accurate determination of the absolute magnitude and of the relative error for each of our targets. These values can be readily used in combination with thermal infrared data. The surface of TNO (65489) Ceto seems to be heterogeneous. Our results seem to support an evolutionary origin for the color dichotomy of Centaurs, and the occurrence of a strong mixing after the TNO formation. No evident cometary activity is detected around the five Centaurs in our sample; assuming that an unresolved coma is present around (248835) 2006 SX368, we use the “photometric model” to derive the possible dust production rate, finding that Qdust is in the range 1–31 kg/s.
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colors and taxonomy of Centaurs and trans neptunian objects
arXiv: Earth and Planetary Astrophysics, 2009Co-Authors: S. Fornasier, M A Barucci, D. Perna, Francesca E Demeo, A Alvarezcandal, Frederic MerlinAbstract:The study of the surface properties of Centaurs and Trans-Neptunian Objects (TNOs) provides essential information about the early conditions and evolution of the outer Solar System. Due to the faintness of most of these distant and icy bodies, photometry currently constitutes the best technique to survey a statistically significant number of them. Our aim is to investigate color properties of a large sample of minor bodies of the outer Solar System, and set their taxonomic classification. We carried out visible and near-infrared photometry of Centaurs and TNOs, making use, respectively, of the FORS2 and ISAAC instruments at the Very Large Telescope (European Southern Observatory). Using G-mode analysis, we derived taxonomic classifications according to the Barucci et al. (2005a) system. We report photometric observations of 31 objects, 10 of them have their colors reported for the first time ever. 28 Centaurs and TNOs have been assigned to a taxon. We combined the entire sample of 38 objects taxonomically classified in the framework of our programme (28 objects from this work; 10 objects from DeMeo et al. 2009a) with previously classified TNOs and Centaurs, looking for correlations between taxonomy and dynamics. We compared our photometric results to literature data, finding hints of heterogeneity for the surfaces of 4 objects.
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exploring the surface properties of transneptunian objects and Centaurs with polarimetric fors1 vlt observations
Astronomy and Astrophysics, 2006Co-Authors: S Bagnulo, H Boehnhardt, K Muinonen, L Kolokolova, I N Belskaya, M A BarucciAbstract:Context. Polarization is a powerful remote-sensing method to investigate solar system bodies. It is an especially sensitive diagnostic tool to reveal physical properties of the bodies whose observational characteristics are governed by small scatterers (dust, regolith surfaces). For these objects, at small phase angles, a negative polarization is observed, i.e., the electric vector E oscillates predominantly in the scattering plane, contrary to what is typical for rather smooth homogeneous surfaces. The behavior of negative polarization with phase angle depends on the size, composition and packing of the scatterers. These characteristics can be unveiled by modelling the light scattering by the dust or regolith in terms of the coherent backscattering mechanism. Aims. We investigate the surface properties of TNOs and Centaurs by means of polarimetric observations with FORS1 of the ESO VLT. Methods. We have obtained new broadband polarimetric measurements over a range of phase angles for a TNO, 50000 Quaoar (in the R Bessel filter), and a Centaur, 2060 Chiron (in the BVR Bessel filters). Simultaneously to the polarimetry, we have obtained R broadband photometry for both objects. We have modelled these new observations of Quaoar and Chiron, and revised the modelling of previous observations of the TNO 28978 Ixion using an improved value of its geometric albedo. Results. TNOs Ixion and Quaoar, and Centaur Chiron show a negative polarization surge. The Centaur Chiron has the deepest polarization minimum (–1.5–1.4%). The two TNOs show differing polarization curves: for Ixion, the negative polarization increases rapidly with phase; for Quaoar, the polarization is relatively small (�− 0.6%), and nearly constant at the observed phase angles. For all three objects, modelling results suggest that the surface contains an areal mixture of at least two components with different single-scatterer albedos and photon mean-free paths.
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exploring the surface properties of transneptunian objects and Centaurs with polarimetric fors1 vlt observations
arXiv: Astrophysics, 2006Co-Authors: S Bagnulo, H Boehnhardt, K Muinonen, L Kolokolova, I N Belskaya, M A BarucciAbstract:Polarization is a powerful remote-sensing method to investigate solar system bodies. It is an especially sensitive diagnostic tool to reveal physical properties of the bodies whose observational characteristics are governed by small scatterers (dust, regolith surfaces). For these objects, at small phase angles, a negative polarization is observed, i.e., the electric vector E oscillates predominantly in the scattering plane, contrary to what is typical for rather smooth homogeneous surfaces. The behavior of negative polarization with phase angle depends on the size, composition and packing of the scatterers. These characteristics can be unveiled by modelling the light scattering by the dust or regolith in terms of the coherent backscattering mechanism. We have investigated the surface properties of TNOs and Centaurs by means of polarimetric observations with FORS1 of the ESO VLT. TNOs Ixion and Quaoar, and Centaur Chiron show a negative polarization surge. The Centaur Chiron has the deepest polarization minimum (-1.5 - 1.4%). The two TNOs show differing polarization curves: for Ixion, the negative polarization increases rapidly with phase; for Quaoar, the polarization is relatively small (~ -0.6%), and nearly constant at the observed phase angles. For all three objects, modelling results suggest that the surface contains an areal mixture of at least two components with different single-scatterer albedos and photon mean-free paths.
David Jewitt - One of the best experts on this subject based on the ideXlab platform.
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new limits to co outgassing in Centaurs
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: Michal Drahus, Bin Yang, D C Lis, David JewittAbstract:Centaurs are small Solar system objects orbiting between Jupiter and Neptune. They are widely believed to be escapees from the trans-Neptunian region on their way to become Jupiter-family comets. Indeed, some Centaurs exhibit the characteristic cometary appearance. The sublimation of carbon monoxide has been proposed as a driver of activity in distant comets, but no strong detection of gaseous CO in a Centaur other than 29P/Schwassmann-Wachmann 1 has been reported to date. Here we report the results of a deep search for CO outgassing in three Centaurs: (315898), (342842), and (382004). Our survey was carried out using the Caltech Submillimeter Observatory on nine nights in late 2011. The targeted rotational line J(2–1) of CO is undetected in all three objects in spite of high instrumental sensitivity. We find the model-dependent 3σ upper limits to the CO production rate of 2.13 × 10^(27) molecules s^(−1) for (315898), 1.32 × 10^(27) molecules s^(−1) for (342842), and 1.17 × 10^(27) molecules s^(−1) for (382004), which are among the most sensitive obtained to date. These upper limits are consistently analysed in the context of published CO data of 14 Centaurs and one well-observed long-period comet, C/1995 O1 (Hale-Bopp), and support an earlier suggestion that the surfaces of most Centaurs are not dominated by exposed CO ice.
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THE ACTIVE Centaurs
2016Co-Authors: David JewittAbstract:The Centaurs are recent escapees from the Kuiper Belt that are destined either to meet fiery oblivion in the hot inner regions of the solar system or to be ejected to the interstellar medium by gravitational scattering from the giant planets. Dynamically evolved Centaurs, when captured by Jupiter and close enough to the Sun for near-surface water ice to sublimate, are conventionally labeled as “short-period ” (specifically, Jupiter-family) comets. Remarkably, some Centaurs show comet-like activity even when far beyond the orbit of Jupiter, suggesting mass loss driven by a process other than the sublimation of water ice. We observed a sample of 23 Centaurs and found nine to be active, with mass-loss rates measured from several kg s−1 to several tonnes s−1. Considered as a group, we find that the “active Centaurs ” in our sample have perihelia smaller than the inactive Centaurs (median 5.9 AU versus 8.7 AU), and smaller than the median perihelion distance computed for all known Centaurs (12.4 AU). This suggests that their activity is thermally driven. We consider several possibilities for the origin of the mass loss from the active Centaurs. Most are too cold for activity at the observed levels to originate via the sublimation of crystalline water ice. Solid carbon monoxide and carbon dioxide have the opposite problem: they are so volatile that they should drive activity in Centaurs at much larger distances than observed. We consider the possibility that activity in the Centaurs is triggered by the conversion of amorphous ice into the crystalline form accompanied by the release o
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the active Centaurs
The Astronomical Journal, 2009Co-Authors: David JewittAbstract:The Centaurs are recent escapees from the Kuiper Belt that are destined either to meet fiery oblivion in the hot inner regions of the solar system or to be ejected to the interstellar medium by gravitational scattering from the giant planets. Dynamically evolved Centaurs, when captured by Jupiter and close enough to the Sun for near-surface water ice to sublimate, are conventionally labeled as short-period (specifically, Jupiter-family) comets. Remarkably, some Centaurs show comet-like activity even when far beyond the orbit of Jupiter, suggesting mass loss driven by a process other than the sublimation of water ice. We observed a sample of 23 Centaurs and found nine to be active, with mass-loss rates measured from several kg s–1 to several tonnes s–1. Considered as a group, we find that the active Centaurs in our sample have perihelia smaller than the inactive Centaurs (median 5.9 AU versus 8.7 AU), and smaller than the median perihelion distance computed for all known Centaurs (12.4 AU). This suggests that their activity is thermally driven. We consider several possibilities for the origin of the mass loss from the active Centaurs. Most are too cold for activity at the observed levels to originate via the sublimation of crystalline water ice. Solid carbon monoxide and carbon dioxide have the opposite problem: they are so volatile that they should drive activity in Centaurs at much larger distances than observed. We consider the possibility that activity in the Centaurs is triggered by the conversion of amorphous ice into the crystalline form accompanied by the release of trapped gases, including carbon monoxide. By imposing the condition that crystallization should occur when the crystallization time is shorter than the orbital period we find a qualitative match to the perihelion distribution of the active Centaurs and conclude that the data are consistent with the hypothesis that the Centaurs contain amorphous ice.
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thermal properties of Centaurs asbolus and chiron
The Astronomical Journal, 2002Co-Authors: David Jewitt, Yanga R Fernandez, Scott S SheppardAbstract:We have measured the mid-infrared thermal continua from two Centaurs, inactive (8405) Asbolus and active 95P = (2060) Chiron, and have constrained their geometric albedos, p, and effective radii, R, with the standard thermal model for slow rotators. These are the first such measurements of Asbolus; we find R = 33 ± 2 km and p = 0.12 ± 0.03. This albedo is higher than all of those confidently known for active cometary nuclei. The thermal inertia is comparable to or lower than those of main-belt asteroids, the Moon, and Chiron; lower than those of the icy Galilean satellites; and much lower than those of near-Earth asteroids. For Chiron, we find R = 74 ± 4 km and p = 0.17 ± 0.02. While this albedo is consistent with the established value, previous radiometry by others implied a larger radius. This discrepancy may be partially due to a varying infrared dust coma, but all data sets have too low signal to be sure. Four Centaur albedos (out of about 30 objects) are now known. They show a diversity greater than that of the active comets, to which they are evolutionarily linked.
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thermal properties of Centaurs asbolus and chiron
arXiv: Astrophysics, 2001Co-Authors: David Jewitt, Yanga R Fernandez, Scott S SheppardAbstract:We have measured the mid-infrared thermal continua from two Centaurs, inactive (8405) Asbolus and active 95P=(2060) Chiron, and have constrained their geometric albedos, p, and effective radii, R, with the Standard Thermal Model for slow rotators. These are the first such measurements of Asbolus; we find R=33 km +/- 2 km and p=0.12 +/- 0.03. This albedo is higher than all of those confidently known for active cometary nuclei. The thermal inertia is comparable to or lower than those of main belt asteroids, the Moon, and Chiron; lower than those of the icy Galilean satellites; and much lower than those of near-Earth asteroids. For Chiron, we find R=74 km +/- 4 km and p=0.17 +/- 0.02. While this albedo is consistent with the established value, previous radiometry by others implied a larger radius. This effect may be partially due to a varying infrared dust coma but all datasets have too low signal to be sure. Four Centaur albedos (out of about 30 objects) are now known. They show a diversity greater than that of the active comets, to which they are evolutionarily linked.
N Peixinho - One of the best experts on this subject based on the ideXlab platform.
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from Centaurs to comets 40 years
The Trans-Neptunian Solar System, 2020Co-Authors: N Peixinho, Aurelie Guilbertlepoutre, Audrey Delsanti, S C Tegler, Audrey Thirouin, Romina Paula Di Sisto, James G BauerAbstract:Abstract In 1977, while Apple II and Atari computers were being sold, a tiny dot was observed in an inconvenient orbit. The minor body 1977 UB, to be named (2060) Chiron, with an orbit between Saturn and Uranus, became the first Centaur, a new class of minor bodies orbiting roughly between Jupiter and Neptune. The observed overabundance of short-period comets lead to the downfall of the Oort cloud as exclusive source of comets and to the rise of the need for a Trans-Neptunian comet belt. Centaurs were rapidly seen as the transition phase between Kuiper belt objects, also known as Trans-Neptunian objects (TNOs) and the Jupiter-family comets (JFCs). Since then, a lot more has been discovered about Centaurs: They can have cometary activity and outbursts, satellites, and even rings. Over the past four decades since the discovery of the first Centaur, rotation periods, surface colors, reflectivity spectra, and albedos have been measured and analyzed. However, despite such a large number of studies and complementary techniques, the Centaur population remains a mystery as they are in so many ways different from the TNOs and even more so from the JFCs.
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the bimodal colors of Centaurs and small kuiper belt objects
Astronomy and Astrophysics, 2012Co-Authors: N Peixinho, A Delsanti, Aurelie Guilbertlepoutre, R Gafeira, Pedro LacerdaAbstract:Ever since the very first photometric studies of Centaurs and Kuiper belt objects (KBOs) their visible color distribution has been controversial. This controversy has triggered to a prolific debate on the origin of the surface colors of these distant icy objects of the solar system. Two scenarios have been proposed to interpret and explain the large variability of colors, hence surface composition. Are the colors mainly primordial and directly related to the formation region, or are they the result of surface evolution processes? To date, no mechanism has been found that successfully explains why Centaurs, which are escapees from the Kuiper belt, exhibit two distinct color groups, whereas KBOs do not. We readdress this issue using a carefully compiled set of B - R colors and H-R(alpha) magnitudes (as proxy for size) for 253 objects, including data for 10 new small objects. We find that the bimodal color distribution of Centaurs is a size-related phenomenon, common to both Centaurs and small KBOs, i.e. independent of dynamical classification. Furthermore, we find that large KBOs also have a bimodal distribution of surface colors, albeit distinct from the small objects and strongly dependent on the “Haumea collisional family” objects. When plotted in B - R, H-R(alpha) space, the colors of Centaurs and KBOs display a peculiar N shape.
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the bimodal colors of Centaurs and small kuiper belt objects
arXiv: Earth and Planetary Astrophysics, 2012Co-Authors: N Peixinho, A Delsanti, Aurelie Guilbertlepoutre, R Gafeira, Pedro LacerdaAbstract:Ever since the very first photometric studies of Centaurs and Kuiper Belt Objects (KBOs) their visible color distribution has been controversial. That controversy gave rise to a prolific debate on the origin of the surface colors of these distant icy objects of the Solar System. Two different views attempt to interpret and explain the large variability of colors, hence surface composition. Are the colors mainly primordial and directly related to the formation region, or are they the result of surface evolution processes? To date, no mechanism has been found that successfully explains why Centaurs, which are escapees from the Kuiper Belt, exhibit two distinct color groups, whereas KBOs do not. In this letter, we readdress this issue using a carefully compiled set of B-R colors and H({\alpha}) magnitudes (as proxy for size) for 253 objects, including data for 10 new small objects. We find that the bimodal behavior seen among Centaurs is a size related phenomenon, common to both Centaurs and small KBOs, i.e. independent of dynamical classification. Further, we find that large KBOs also exhibit a bimodal behavior of surface colors, albeit distinct from the small objects and strongly dependent on the `Haumea collisional family' objects. When plotted in B-R, H({\alpha}) space, the colors of Centaurs and KBOs display a peculiar N shape.
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colors of Centaurs
ssbn, 2008Co-Authors: S C Tegler, J M Bauer, W Romanishin, N PeixinhoAbstract:Minor planets on outer planet-crossing orbits, called Centaur objects, are important members of the solar system in that they dynamically link Kuiper belt objects to Jupiter-family comets. In addition, perhaps 6% of near-Earth objects have histories as Centaur objects. The total mass of Centaurs (10–4 M ) is significant, about one-tenth of the mass of the asteroid belt. Centaur objects exhibit a physical property not seen among any other objects in the solar system, their B–R colors divide into two distinct populations: a gray and a red population. Application of the dip test to B–R colors in the literature indicates there is a 99.5% probability that Centaurs exhibit a bimodal color distribution. Although there are hints that gray and red Centaurs exhibit different orbital elements, application of the Wilcoxon rank sum test finds no statistically significant difference between the orbital elements of the two color groups. On the other hand, gray and red Centaurs exhibit a statistically significant difference in albedo, with the gray Centaurs having a lower median albedo than the red Centaurs. Further observational and dynamical work is necessary to determine whether the two color populations are the result of (1) evolutionary processes such as radiation-reddening, collisions, and sublimation or (2) a primordial, temperature-induced, composition gradient.
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near infrared color properties of kuiper belt objects and Centaurs final results from the eso large program
The Astronomical Journal, 2006Co-Authors: A Delsanti, N Peixinho, H Boehnhardt, A Barucci, F Merlin, A Doressoundiram, J K DaviesAbstract:We present near-IR JHK broadband photometry for 17 Kuiper Belt objects (KBOs) and Centaurs. The observations were performed within the ESO Large Program on the Physical Properties of Kuiper Belt Objects and Centaurs from 2001 January to 2002 August. We used the ISAAC instrument at the ESO 8 m Very Large Telescope. We compiled visible-near-IR colors for a total of 51 published objects and performed a statistical analysis. Color-color correlations show that the same coloring process is probably acting on Centaur and KBO surfaces in the visible-near-IR range. Centaurs with H - K smaller than the Sun (0.06) systematically display the reddest B - V colors (at the 2.5 σ level). These Centaur surfaces are suspected of harboring material that has spectral signatures around 1.7-2.2 μm (water ice is a possibility; it was reported for the three objects that have published spectroscopy). We report no statistically significant evidence for a bimodal structure of the VJHK Centaur colors (Kolmogorov-Smirnov and dip tests on up to 17 objects). The Centaur H - K colors show some robust evidence (significance level >99.99%) for a continuous structure. We also report a statistically significant bimodal structure of the Centaur B - R distribution, which is compatible with the results published by Peixinho et al. in 2003 with different data. Classical KBOs show no trends at the 3 σ level. The V - J color is marginally correlated with perihelion distance q (which is consistent with results reported by Doressoundiram et al. in 2005 on B - R colors). Resonant and scattered disk objects are underrepresented (seven and nine objects, respectively) and show no statistically significant trend. Some of the marginal trends are mentioned as worthy of subsequent monitoring.
H Boehnhardt - One of the best experts on this subject based on the ideXlab platform.
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exploring the surface properties of transneptunian objects and Centaurs with polarimetric fors1 vlt observations
Astronomy and Astrophysics, 2006Co-Authors: S Bagnulo, H Boehnhardt, K Muinonen, L Kolokolova, I N Belskaya, M A BarucciAbstract:Context. Polarization is a powerful remote-sensing method to investigate solar system bodies. It is an especially sensitive diagnostic tool to reveal physical properties of the bodies whose observational characteristics are governed by small scatterers (dust, regolith surfaces). For these objects, at small phase angles, a negative polarization is observed, i.e., the electric vector E oscillates predominantly in the scattering plane, contrary to what is typical for rather smooth homogeneous surfaces. The behavior of negative polarization with phase angle depends on the size, composition and packing of the scatterers. These characteristics can be unveiled by modelling the light scattering by the dust or regolith in terms of the coherent backscattering mechanism. Aims. We investigate the surface properties of TNOs and Centaurs by means of polarimetric observations with FORS1 of the ESO VLT. Methods. We have obtained new broadband polarimetric measurements over a range of phase angles for a TNO, 50000 Quaoar (in the R Bessel filter), and a Centaur, 2060 Chiron (in the BVR Bessel filters). Simultaneously to the polarimetry, we have obtained R broadband photometry for both objects. We have modelled these new observations of Quaoar and Chiron, and revised the modelling of previous observations of the TNO 28978 Ixion using an improved value of its geometric albedo. Results. TNOs Ixion and Quaoar, and Centaur Chiron show a negative polarization surge. The Centaur Chiron has the deepest polarization minimum (–1.5–1.4%). The two TNOs show differing polarization curves: for Ixion, the negative polarization increases rapidly with phase; for Quaoar, the polarization is relatively small (�− 0.6%), and nearly constant at the observed phase angles. For all three objects, modelling results suggest that the surface contains an areal mixture of at least two components with different single-scatterer albedos and photon mean-free paths.
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near infrared color properties of kuiper belt objects and Centaurs final results from the eso large program
The Astronomical Journal, 2006Co-Authors: A Delsanti, N Peixinho, H Boehnhardt, A Barucci, F Merlin, A Doressoundiram, J K DaviesAbstract:We present near-IR JHK broadband photometry for 17 Kuiper Belt objects (KBOs) and Centaurs. The observations were performed within the ESO Large Program on the Physical Properties of Kuiper Belt Objects and Centaurs from 2001 January to 2002 August. We used the ISAAC instrument at the ESO 8 m Very Large Telescope. We compiled visible-near-IR colors for a total of 51 published objects and performed a statistical analysis. Color-color correlations show that the same coloring process is probably acting on Centaur and KBO surfaces in the visible-near-IR range. Centaurs with H - K smaller than the Sun (0.06) systematically display the reddest B - V colors (at the 2.5 σ level). These Centaur surfaces are suspected of harboring material that has spectral signatures around 1.7-2.2 μm (water ice is a possibility; it was reported for the three objects that have published spectroscopy). We report no statistically significant evidence for a bimodal structure of the VJHK Centaur colors (Kolmogorov-Smirnov and dip tests on up to 17 objects). The Centaur H - K colors show some robust evidence (significance level >99.99%) for a continuous structure. We also report a statistically significant bimodal structure of the Centaur B - R distribution, which is compatible with the results published by Peixinho et al. in 2003 with different data. Classical KBOs show no trends at the 3 σ level. The V - J color is marginally correlated with perihelion distance q (which is consistent with results reported by Doressoundiram et al. in 2005 on B - R colors). Resonant and scattered disk objects are underrepresented (seven and nine objects, respectively) and show no statistically significant trend. Some of the marginal trends are mentioned as worthy of subsequent monitoring.
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exploring the surface properties of transneptunian objects and Centaurs with polarimetric fors1 vlt observations
arXiv: Astrophysics, 2006Co-Authors: S Bagnulo, H Boehnhardt, K Muinonen, L Kolokolova, I N Belskaya, M A BarucciAbstract:Polarization is a powerful remote-sensing method to investigate solar system bodies. It is an especially sensitive diagnostic tool to reveal physical properties of the bodies whose observational characteristics are governed by small scatterers (dust, regolith surfaces). For these objects, at small phase angles, a negative polarization is observed, i.e., the electric vector E oscillates predominantly in the scattering plane, contrary to what is typical for rather smooth homogeneous surfaces. The behavior of negative polarization with phase angle depends on the size, composition and packing of the scatterers. These characteristics can be unveiled by modelling the light scattering by the dust or regolith in terms of the coherent backscattering mechanism. We have investigated the surface properties of TNOs and Centaurs by means of polarimetric observations with FORS1 of the ESO VLT. TNOs Ixion and Quaoar, and Centaur Chiron show a negative polarization surge. The Centaur Chiron has the deepest polarization minimum (-1.5 - 1.4%). The two TNOs show differing polarization curves: for Ixion, the negative polarization increases rapidly with phase; for Quaoar, the polarization is relatively small (~ -0.6%), and nearly constant at the observed phase angles. For all three objects, modelling results suggest that the surface contains an areal mixture of at least two components with different single-scatterer albedos and photon mean-free paths.
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spectral characteristics and modeling of the transneptunian object 55565 2002 aw197 and the Centaurs 55576 2002 gb10 and 83982 2002 go9 eso large program on tnos and Centaurs
Planetary and Space Science, 2005Co-Authors: A Doressoundiram, H Boehnhardt, M A Barucci, C De Bergh, G P Tozzi, F Poulet, N PeixinhoAbstract:Abstract We present in this paper first results on broadband photometry (JHK filters) and low-dispersion infrared spectroscopy performed at ESO Very Large Telescope (VLT) for the trans-neptunian object (55565) 2002 AW197 and Centaurs (55576) 2002 GB10 and (83982) 2002 GO9. These observations were obtained in the framework of ESO's Large Program on ‘Physical Studies of TNOs and Centaurs’. All the spectra are characterized by a strong red visible–near infrared slope. There is no clear detection of water ice, except for the Centaur (83982) 2002 GO9. Analysis of these visible–near infrared reflectance spectra with radiative transfer models are compatible with a surface composed of intimate mixtures of organics compounds (Triton tholins, amorphous carbon) and contaminated water ice, although other possibilities exist.
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physical survey of 24 Centaurs with visible photometry
Icarus, 2003Co-Authors: J M Bauer, K J Meech, Y R Fernandez, Jana Pittichova, O Hainaut, H Boehnhardt, Audrey DelsantiAbstract:Abstract We present optical observations of 24 Centaurs performed between 1998 and 2002 with the University of Hawaii 2.2-m telescope. This is the largest such Centaur survey to date. We report colors for all objects, and show that they cover a continuum with mean V–R color of 0.58±0.01 and standard deviation 0.15. The color distribution fits between those of the Kuiper Belt and the cometary nuclei, and seems consistent with the dynamical concept of the majority of Centaurs originating from the Kuiper Belt. We find no strong correlation between a Centaur's color and its orbital elements; there is at best a σ correlation with semimajor axis, with redder Centaurs being farther from the Sun. We have calculated the phase-darkening slope parameters G for 5 Centaurs, 4 of which are reported for the first time. They range from −0.18 to 0.13. We have sufficient data to constrain the rotation periods of two Centaurs, 1999 UG 5 (which we reported earlier) and 1998 SG 3 5. We performed a comparison of the surface brightness profiles of 10 apparently-inactive Centaurs with point sources. We found no coma around these 10 objects, including C/LINEAR (2000 B4), and generally the upper limits to the dust mass loss rates are below 0.05 kg s −1 .
Audrey Delsanti - One of the best experts on this subject based on the ideXlab platform.
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from Centaurs to comets 40 years
The Trans-Neptunian Solar System, 2020Co-Authors: N Peixinho, Aurelie Guilbertlepoutre, Audrey Delsanti, S C Tegler, Audrey Thirouin, Romina Paula Di Sisto, James G BauerAbstract:Abstract In 1977, while Apple II and Atari computers were being sold, a tiny dot was observed in an inconvenient orbit. The minor body 1977 UB, to be named (2060) Chiron, with an orbit between Saturn and Uranus, became the first Centaur, a new class of minor bodies orbiting roughly between Jupiter and Neptune. The observed overabundance of short-period comets lead to the downfall of the Oort cloud as exclusive source of comets and to the rise of the need for a Trans-Neptunian comet belt. Centaurs were rapidly seen as the transition phase between Kuiper belt objects, also known as Trans-Neptunian objects (TNOs) and the Jupiter-family comets (JFCs). Since then, a lot more has been discovered about Centaurs: They can have cometary activity and outbursts, satellites, and even rings. Over the past four decades since the discovery of the first Centaur, rotation periods, surface colors, reflectivity spectra, and albedos have been measured and analyzed. However, despite such a large number of studies and complementary techniques, the Centaur population remains a mystery as they are in so many ways different from the TNOs and even more so from the JFCs.
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physical survey of 24 Centaurs with visible photometry
Icarus, 2003Co-Authors: J M Bauer, K J Meech, Y R Fernandez, Jana Pittichova, O Hainaut, H Boehnhardt, Audrey DelsantiAbstract:Abstract We present optical observations of 24 Centaurs performed between 1998 and 2002 with the University of Hawaii 2.2-m telescope. This is the largest such Centaur survey to date. We report colors for all objects, and show that they cover a continuum with mean V–R color of 0.58±0.01 and standard deviation 0.15. The color distribution fits between those of the Kuiper Belt and the cometary nuclei, and seems consistent with the dynamical concept of the majority of Centaurs originating from the Kuiper Belt. We find no strong correlation between a Centaur's color and its orbital elements; there is at best a σ correlation with semimajor axis, with redder Centaurs being farther from the Sun. We have calculated the phase-darkening slope parameters G for 5 Centaurs, 4 of which are reported for the first time. They range from −0.18 to 0.13. We have sufficient data to constrain the rotation periods of two Centaurs, 1999 UG 5 (which we reported earlier) and 1998 SG 3 5. We performed a comparison of the surface brightness profiles of 10 apparently-inactive Centaurs with point sources. We found no coma around these 10 objects, including C/LINEAR (2000 B4), and generally the upper limits to the dust mass loss rates are below 0.05 kg s −1 .
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reopening the tnos color controversy Centaurs bimodality and tnos unimodality
arXiv: Astrophysics, 2003Co-Authors: N Peixinho, H Boehnhardt, Audrey Delsanti, A Doressoundiram, M A Barucci, I N BelskayaAbstract:We revisit the Trans-Neptunian Objects (TNOs) color controversy allegedly solved by Tegler and Romanishin 2003. We debate the statistical approach of the quoted work and discuss why it can not draw the claimed conclusions, and reanalyze their data sample with a more adequate statistical test. We find evidence for the existence of two color groups among the Centaurs. Therefore, mixing both Centaurs and TNOs populations lead to the erroneous conclusion of a global bimodality, while there is no evidence for two color groups in the TNOs population alone. We use quasi-simultaneous visible color measurements published for 20 Centaurs (corresponding to about half of the identified objects of this class), and conclude on the existence of two groups. With the surface evolution model of Delsanti et al. (2003) we discuss how the existence of two groups of Centaurs may be compatible with a continuous TNOs color distribution.
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visible and near infrared spectroscopy of the centaur 32532 2001 pt13 eso large programm on tnos and Centaurs first spectroscopy results
Astronomy and Astrophysics, 2002Co-Authors: M A Barucci, S. Fornasier, H Boehnhardt, A Doressoundiram, E Dotto, J Romon, M Lazzarin, C De Bergh, G P Tozzi, Audrey DelsantiAbstract:We present photometric and spectroscopic data obtained through visible and near-infrared observations of the Centaur 32532 (2001 PT13) performed with FORS1 and ISAAC at the Very Large Telescope (VLT-ESO) within the framework of an ESO large program on the Trans-Neptunian objects (TNOs) and Centaurs. The results show evidence for a difference in the near-infrared spectral behaviour obtained during two observations carried out one month apart. In one spectrum there is the possible presence of signatures of water ice in small amounts. Two models have been proposed to interpret the surface composition of this Centaur.