Benoît Noyelles - Academia.edu (original) (raw)

Papers by Benoît Noyelles

HAL (Le Centre pour la Communication Scientifique Directe), Sep 6, 2009

1. Introduction</strong&... more 1. Introduction C/2016 R2 (PanSTARRS) was a surprising comet. Detected on September 7, 2016 by Pan-STARRS it showed an unusual composition when it became a bright comet at the end of 2017 and the beginning of 2018. It developed a coma at large (~6 au) heliocentric distance and observations showed that it had a highly unusual composition: no water molecules (or OH radical) could be detected, and the abundances of the usual radicals (CN, C2, C3) were unusually low, with a surprising coma composition dominated by CO, CO2 and N2 molecules with bright CO+ and N2+ emission lines in the visible range. A high CO production rate of about 1029 molecules s-1 was measured (Biver et al. 2018; Wierzchos & Womack 2018) as well as a high CO2 production rate (CO2/CO=1.1 from Opitom et al. 2019), and a high ratio N2/CO varying between 0.06 and 0.09 (Biver et al. 2018; Cochran & McKay 2018a,b; Opitom et al. 2019; Venkataramani et al. 2020). The detection of such bright N2+ emission lines in this comet highlighted the necessity of a good modeling of the N2+ fluorescence spectrum in comets. The high-quality spectra published by Opitom et al. (2019) provided a good opportunity to test such a model. This model also permits to compute the fluorescence spectrum of the 14N15N+ species, leading to the possibility of future measurements of the 14N/15N isotopic ratio in the N2 molecules, one of the main constituant of the solar nebula. 2. Observations The spectra used for this work have been obtained with the UVES spectrograph mounted on the ESO 8.2 m UT2 telescope of the VLT. Three different observing nights have been used, corresponding to February 11, 13 and 14, 2018. One single exposure of 4800 s of integration time was obtained during each night and we used a 0.44&#8221; wide slit, providing a resolving power R~80,000. The slit length was 8&#8221; corresponding to about 14,500 km at the distance of the comet (geocentric distance of 2.4 au). The average heliocentric distance was 2.76 au. Opitom et al. (2019) describe in more details the data processing. From the 2D spectra having a spatial extension of 30 rows, each of them corresponding to a different cometocentric distance, we extracted different 1D spectra for each night. These spectra were then averaged for similar cometocentric distances allowing a detailed comparison of these spectra at different cometocentric distances, the furthest one corresponding to 2x4 rows at the two extremities of the slit (i.e. at a cometocentric distance varying between 4800 and 6600 km). 3. Modeling the N2+ fluorescence spectrum We developed a new fluorescence model for modeling our observational spectra. The transition involved in this spectrum is the first negative group, i.e. the B2&#931;u+ &#8594; X2+&#931;g+ electronic transition with the (0,0) bandhead appearing near 3914 &#197;. We considered the first three vibrational levels (v = 0; 1; 2) for both X2+&#931;g+ and B2&#931;u+ state, each of them with all the rotational levels from N = 0 to 40. N2+ having no permanent dipole moment, the pure rotational and vibrational transitions are forbidden (or have a very low probability, through quadrupolar transitions, not taken into account in our model). For that reason it takes a long time for this species to reach its fluorescence equilibrium because it needs a few tens of absorption / emission cycles between the X2+&#931;g+ and B2&#931;u+ states to reach this equilibrium. A comparison of the spectrum obtained on the nucleus with the one obtained at the edges of the slit revealed clear differences due…

This note tackles the problem of the rotation of Io with the 4-degrees of freedom Poincaré-Hough ... more This note tackles the problem of the rotation of Io with the 4-degrees of freedom Poincaré-Hough model. Io is modeled as a 2-layer body, i.e. a triaxial fluid core and a rigid outer layer. We show that the longitudinal librations should have an amplitude of about 30 arcseconds, independent of the composition of the core. We also estimate the tidal instability of the core, and show that should be slowly unstable.

Les effets de maree induisent une acceleration seculaire des satellites planetaires. Dans le cas ... more Les effets de maree induisent une acceleration seculaire des satellites planetaires. Dans le cas des satellites de Jupiter et de Saturne, de telles accelerations n'ont pas encore ete detectees avec une fiabilite suffisante, mais tant les progres de la modelisation dynamique que l'amelioration des observations astrometriques laissent esperer une detection prochaine pour J-1 Io et S-3 Tethys. Ce travail aborde les deux themes. L'objectif principal est de mieux modeliser les mouvements et mieux comprendre les resonances. Cette these apporte ainsi une contribution a l'etude de l'histoire dynamique du systeme des satellites Galileens en examinant les consequences de l'inegalite de De Haerdtl 7:3 entre Ganymede et Callisto. Il est demontre que cette inegalite est responsable d'une couche chaotique, traversee recemment par le systeme. Cette couche chaotique, causee par plusieurs recouvrements de resonances, est mise en evidence par la technique de l'analyse ...

The OSSOS Survey discovered more than 800 Trans-Neptunian Objects between 2013 and 2017. Among th... more The OSSOS Survey discovered more than 800 Trans-Neptunian Objects between 2013 and 2017. Among them were at least 5 binaries. We here present orbital solutions for binary objects, based on OSSOS images, supplemented by additional surveys. We obtained the orbital solutions thanks to a Markov Chain Monte Carlo algorithm, in a 6-dimensional phase space. These orbital solutions permitted us to constrain the masses and densities of the involved objects.

Monthly Notices of the Royal Astronomical Society, 2021

Since 2005 December, recurrent outbursts have been observed for Centaur 174/P Echeclus, confirmin... more Since 2005 December, recurrent outbursts have been observed for Centaur 174/P Echeclus, confirming it is an active object. Thanks to a large number of photometric data obtained between 2001 April and 2019 December, we were able to compute a shape model of this object. We obtain a sidereal rotation period P = 26.785178 ± 10−6 h and six equally probable pole solutions, each with a large obliquity of the rotational axis (50° or more). We also find the object significantly elongated, with a semi-major axial ratio a/b = 1.32 (and b/c ∼ 1.1 but this second ratio is poorly constrained by the photometric data). Additionally, we present a detailed analysis of the dust emission from the 2016 outburst. Different colour maps are presented that reveal a change in dust colour, which becomes bluer with increasing cometocentric distance. A blue ring-like structure around the nucleus clearly visible in the images obtained on October 4 in the V-R spectral interval points out that the innermost near n...

Icarus, 2019

During the thirteen years in orbit around Saturn before its final plunge, the Cassini spacecraft ... more During the thirteen years in orbit around Saturn before its final plunge, the Cassini spacecraft provided more than ten thousand astrometric measurements. Such large amounts of accurate data enable the search for extremely faint signals in the orbital motion of the saturnian moons. Among these, the detection of the dynamical feedback of the rotation of the inner moons of Saturn on their respective orbits becomes possible. Using all the currently available astrometric data associated with Atlas, Prometheus, Pandora, Janus and Epimetheus, we first provide a detailed analysis of the Cassini Imaging Science Subsystem (ISS) data, with special emphasis on their statistical behavior and sources of bias. Then, we give updated estimates of the moons' averaged densities and try to infer more details about their interior properties by estimating the physical librations for Prometheus, Pandora, Epimetheus and Janus from anomalies in their apsidal precession. Our results are compatible with a homogeneous interior for Janus and Epimetheus, within the uncertainty of the measurements. On the other hand, we found some inconsistency for Pandora and Prometheus, which might result from a dynamical mismodeling of Saturn's gravity field. Last, we show how the synergistic introduction of libration measurements directly derived from imaging should allow the moons' moments of inertia to be better constrained.

Astronomy & Astrophysics, 2018

Context. Natural satellite systems present a large variety of orbital configurations in the solar... more Context. Natural satellite systems present a large variety of orbital configurations in the solar system. While some are clearly the result of known processes, others still have largely unexplained eccentricity and inclination values. Iapetus, the furthest of Saturn’s main satellites, has a still unexplained 3% orbital eccentricity and its orbital plane is tilted with respect to its local Laplace plane (8° of free inclination). On the other hand, astrometric measurements of saturnian moons have revealed high tidal migration rates, corresponding to a quality factor Q of Saturn of around 1600 for the mid-sized icy moons. Aims. We show how a past crossing of the 5:1 mean motion resonance between Titan and Iapetus may be a plausible scenario to explain Iapetus’ orbit. Methods. We have carried out numerical simulations of the resonance crossing using an N-body code as well as using averaged equations of motion. A large span of migration rates were explored for Titan and Iapetus was start...

Icarus, 2017

Most of the main planetary satellites of our Solar System are expected to be in synchronous rotat... more Most of the main planetary satellites of our Solar System are expected to be in synchronous rotation, the departures from the strict synchronicity being a signature of the interior. Librations have been measured for the Moon, Phobos, and some satellites of Saturn. I here revisit the theory of the longitudinal librations in considering that part of the interior is not hydrostatic, i.e. has not been shaped by the rotational and tidal deformations, but is fossil. This consideration affects the rotational behavior. For that, I derive the tensor of inertia of the satellite in splitting these two parts, before proposing an analytical solution that I validate with numerical simulations. I apply this new theory on Mimas and Epimetheus, for which librations have been measured from Cassini data. I show that the large measured libration amplitude of these bodies can be explained by an excess of triaxiality that would not result from the hydrostatic theory. This theory cannot explain the phase shift which has been measured in the diurnal librations of Mimas. This speaks against a solid structure for Mimas, i.e. Mimas could have a global internal ocean.

Proceedings of the International Astronomical Union, 2014

The Saturnian satellite Titan is one of the main targets of the Cassini-Huygens mission, which re... more The Saturnian satellite Titan is one of the main targets of the Cassini-Huygens mission, which revealed in particular Titan's shape, gravity field, and rotation state. The shape and gravity field suggest that Titan is not in hydrostatic equilibrium, that it has a global subsurface ocean, and that its ice shell is both rigid (at tidal periods) and of variable thickness. The rotational state of Titan consists of an expected synchronous rotation rate and an unexpectedly high obliquity (0.3○) explained by Baland et al. (2011) to be a resonant behavior. We here combine a realistic model of the ice shell and interior and a 6-degrees of freedom rotational model, in which the librations, obliquity and polar motion of the rigid core and of the shell are modelled, to constrain the structure of Titan from the observations. We consider the gravitational pull of Saturn on the 2 rigid layers, the gravitational coupling between them, and the pressure coupling at the liquid-solid interfaces. We...

We performed a 3-dimensional theory of the rotation of Titan, seen as a rigid body. Using an anal... more We performed a 3-dimensional theory of the rotation of Titan, seen as a rigid body. Using an analytical model, we determine the frequencies of the free librations around the exact Cassini state, which are respectively 2.1, 167 and 306 years. Then we use the numerical tool and the complete ephemerides (TASS 1.6) of the orbital motion of Titan to give

We examine the problem of detecting the observational signature of tides in the Saturnian system.... more We examine the problem of detecting the observational signature of tides in the Saturnian system. We show that, because of energy transfer encouraged by the mean-motion resonances, S-1 Mimas' secular acceleration should be detected by observing S-3 Tethys instead of Mimas itself. We have a similar conclusion for the Enceladus/Dione resonance. We also show that detecting secular accelerations of these

Tidal dissipation inside gaseous planets is crucial for the study of their long term evolution. F... more Tidal dissipation inside gaseous planets is crucial for the study of their long term evolution. For the exo-planets tidal dissipation has often been estimated from the Solar system giant planets. The tidal dissipation inside Saturn and Jupiter can be determined from theoretical assumptions on the orbital evolution of their satellites. This provides a lower bound for their dissipation parameter Q.

Proceedings of the International Astronomical Union, 2004

In this study we give a first description of De Haerdtl's 3:7 inequality between the Jovian satel... more In this study we give a first description of De Haerdtl's 3:7 inequality between the Jovian satellites Ganymede and Callisto and 1:5 inequality between the Saturnian Titan and Iapetus and the resonant arguments associated. For each inequality, 19 arguments are associated. The overlapping of resonant zones induces stochasic layers that the system might have crossed in the past thanks to tidal dissipation.

Astrometric measurements reveal the possibility that the saturnian satellite Mimas could be evolv... more Astrometric measurements reveal the possibility that the saturnian satellite Mimas could be evolving inward instead of outward (Lainey et al. 2012), as usually thought. Based on this assumption, we studied the behavior of the satellites and the rings over 20 Myr. A numerical integration of the equations of the satellites shows that Mimas has crossed several resonances with Enceladus in the past. Moreover, a recent resonance with Tethys explains its current eccentricity (2e-2). An implementation of Mimas' dynamics in the hydrodynamical code Hydrorings (Charnoz et al. 2010, 2011) shows that we can open the Cassini Division this way, with the right width. We also highlight the mechanism of resonance leaking, able to create ringlets. We show in particular how the recent resonance with Tethys creates the Huygens ringlet. Numerical simulations were made on the local computing ressources (Cluster URBM-SYSDYN) at the University of Namur. This work is supported by EMERGENCE-UPMC grant (c...

Miranda has a unusually high inclination ($I=4.338^\circ$), and its surface reveals signs of past... more Miranda has a unusually high inclination ($I=4.338^\circ$), and its surface reveals signs of past endogenic activity. Investigations of the dynamical aspects of its orbital evolution suggest probable resonant processes, in particular with Umbriel, as an explanation for the present high inclination of Miranda. The tidal heating induced by gravitational interactions can lead to the rise of eccentricities and, consequently, to the increased dissipation of energy inside the satellite and higher internal temperatures. We study here the possible increase in eccentricities caused by orbital resonances and the resulting endogenic heating on Miranda taking into account its temperature dependent rheology. The coupled orbital-thermal evolution model was run with different rheological models and the thermal parameters starting form a cold thermal state, in radiative equilibrium with the environment. For the nominal parameters of the evolution scenarios studied, the resonances were not sufficien...

Possible Mimas' orbital decay has been revealed recently from astrometric measurements of the... more Possible Mimas' orbital decay has been revealed recently from astrometric measurements of the main Saturnian moons (Lainey et al. 2012). Based on this assumption, we studied Saturn's ring evolution over 20 Myr, taking into account resonancesa ssociated with Mimas, like the 2:1 resonance currently placed at the outer edge of the B-ring. Depending on the typical size of the particules, we show that the Cassini division and its structures could be explained by Mimas orbital decay. Simultaneously, we examined the behavior of Mimas orbit while it shrinked from 190,000 up to its current position. We found its current eccentricity can be explained by a recent resonance crossing with Tethys. This work is supported by Campus Spatial (Paris Diderot) and partly supported by EMERGENCE-UPMC grant (contract number: EME0911).

Proceedings of the International Astronomical Union, 2004

Mutual event observations started in the early 1970s with the Galilean satellites. These observat... more Mutual event observations started in the early 1970s with the Galilean satellites. These observations were needed because of the Voyager spacecraft future arrival. Since 1979, IMCCE has organized observational campaigns for the Galilean satellites (called PHEMU), and since 1995 for the Saturnian satellites (also called PHESAT). Meanwhile, the reduction techniques have been greatly improved. Mutual event observations are one of the most accurate methods for obtaining positions of natural satellites, useful for detecting tidal effects. Hence mutual events of Jovian and Saturnian natural satellites are regularly observed around the world. This paper aims to describe mutual events and the advantages of this kind of observation besides the classical astrometric ones.

Astronomy & Astrophysics, 2014

Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and theref... more Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. It was the equinox on Jupiter. This occurrence made mutual occultations and eclipses between the satellites possible. Experience has shown that the observations of such events provide accurate astrometric data able to bring new information on the dynamics of the Galilean satellites. Observations are made under the form of photometric measurements, but need to be made through the organization of a worldwide observation campaign maximizing the number and the quality of the data obtained. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods. We used an accurate photometric model of mutual events adequate with the accuracy of the observation. Our original method was applied to derive astrometric data from photometric observations of mutual occultations and eclipses of the Galilean satellites of Jupiter. Results. We processed the 457 lightcurves obtained during the international campaign of photometric observations of the Galilean satellites of Jupiter in 2009. Compared with the theory, for successful observations, the r.m.s. of O-C residuals are equal to 45.8 mas and 81.1 mas in right ascension and declination, respectively; the mean O-C residuals are equal to-2 mas and-9 mas in right ascension and declination, respectively, for mutual occultations; and-6 mas and +1 mas in right ascension and declination, respectively, for mutual eclipses.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 6, 2009

Monthly Notices of the Royal Astronomical Society, 2021

Icarus, 2019

Astronomy & Astrophysics, 2018

Icarus, 2017

Proceedings of the International Astronomical Union, 2014

Proceedings of the International Astronomical Union, 2004

Astronomy & Astrophysics, 2014