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The problem of the secular evolution of a thin ring around a rapidly rotating triaxial celestial body is formulated and solved. The technology for calculating secular perturbations is based on two formulas: the azimuthally averaged force field of the central body and the mutual energy $${{W}_{{{\text{mut}}}}}$$ of this body and a Gaussian ring. With $${{W}_{{{\text{mut}}}}}$$ instead of the usual perturbing function, a system of differential equations for the osculating elements of the ring is obtained. An equation is obtained that allows one to find the coefficients of the zonal harmonics of the azimuthally averaged potential of an inhomogeneous ellipsoid using a unified scheme. The method is applied to dwarf planet Haumea with refined masses of the rocky core and the ice shell and the coefficients $${{C}_{{20}}}$$ and $${{C}_{{40}}}$$ of the po-tential’s zonal harmonics. According to new data, the ring around Haumea has a slight obliquity and must precess. It was established that the period of the retrograde nodal precession of the Haumea’s ring (without regard to self-gravity) is $${{T}_{\Omega }} = 12.9 \pm 0.7$$ days and the period of the forward of the apside line precession is $${{T}_{\omega }} \approx 8.{\text{08}}\;{\text{days}}$$ . It is proven that the 3:1 orbital resonance for the particles of the Haumea’s ring is fulfilled only approximately and the averaging time of additional perturbations at a nonsharp resonance turned out to be an order of magnitude smaller than $${{T}_{\Omega }}$$ . This confirms the adequacy of the method.

The dwarf planet Haumea is a trans-Neptunian object that is orbited by two moons and has a recently discovered ring. The particles of this ring are near the 3:1 resonance between the spin of Haumea and the orbital motion of the particles. In this work, the ring of Haumea is investigated using Perturbation Maps. These maps show the behaviour and impact of perturbations acting over particles around Haumea. The information coming from the maps depends on the integral type for the disturbing acceleration used to build the maps. The types II and IV are used. The numerical simulations are focused in the region between 2000 and 2500 km from the centre of Haumea, which is the region where the ring was observed, considering two initial values for the 3:1 resonant angle: θres = 0° and θres = 270°. The possible stable region for the initial angle θres = 0° is larger than the stable region for the initial angle θres = 270°. Furthermore, we found that these stable regions are not continuous, indicating that there are possible gaps in the ring. Therefore, our results suggest that Haumea may not have only one single ring, but a system of rings instead. Possible transit of the particles between the ring and the region close to the orbit of Namaka is also shown.

In this paper, we, a collective of wāhine ʻŌiwi (Native Hawaiian women), reflect on how we may hoʻokō (fulfill) our kuleana lāhui (nation-building responsibilities) through our positions in...

This work is licensed under a CC-BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/), A recent multi-chord occultation measurement of the dwarf planet (136108) Haumea (Ortiz et al., 2017) revealed an elongated shape with the longest axis comparable to Pluto's mean diameter. The chords also indicate a ring around Haumea's equatorial plane, where its largest moon, Hi'iaka, is also located. The Haumea occultation size estimate (size of an equal-volume sphere1 Dequ = 1595 km) is larger than previous radiometric solutions (equivalent sizes in the range between 1150 and 1350 km), which lowers the object's density to about 1.8 g/cm3, a value closer to the densities of other large TNOs. We present unpublished and also reprocessed Herschel and Spitzer mid- and far-infrared measurements. We compare 100 and 160 µm thermal lightcurve amplitudes - originating from Haumea itself - with models of the total measured system fluxes (ring, satellite, Haumea) from 24–350 µm. The combination with results derived from the occultation measurements allows us to reinterpret the object's thermal emission. Our radiometric studies show that Haumea's crystalline water ice surface must have a thermal inertia of about 5 J K−1 m−2s−1/2 (combined with a root mean square of the surface slopes of 0.2). We also have indications that the satellites (at least Hi'iaka) must have high geometric albedos ≳ 0.5, otherwise the derived thermal amplitude would be inconsistent with the total measured system fluxes at 24, 70, 100, 160, 250, and 350 µm. The high albedos imply sizes of about 300 and 150 km for Hi'iaka and Namaka, respectively, indicating unexpectedly high densities > 1.0 g cm−3 for TNOs this small, and the assumed collisional formation from Haumea's icy crust. We also estimated the thermal emission of the ring for the time period 1980–2030, showing that the contribution during the Spitzer and Herschel epochs was small, but not negligible. Due to the progressive opening of the ring plane, the ring emission will be increasing in the next decade when JWST is operational. In the MIRI 25.5 µm band it will also be possible to obtain a very high-quality thermal lightcurve to test the derived Haumea properties. © 2018 Elsevier Inc., The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378. Funding from the Spanish grant AYA-2017-89637-R is acknowledged.

While collisional families are common in the asteroid belt, only one is known in the Kuiper belt, linked to the dwarf planet Haumea. The characterization of Haumea's family helps to constrain its origin and, more generally, the collisional history of the Kuiper belt. However, the size distribution of the Haumea family is difficult to constrain from the known sample, which is affected by discovery biases. Here, we use the Outer Solar System Origins Survey (OSSOS) Ensemble to look for Haumea family members. In this OSSOS XVI study we report the detection of three candidates with small ejection velocities relative to the family formation centre. The largest discovery, 2013 UQ15, is conclusively a Haumea family member, with a low ejection velocity and neutral surface colours. Although the OSSOS Ensemble is sensitive to Haumea family members to a limiting absolute magnitude (Hr) of 9.5 (inferred diameter of ~90 km), the smallest candidate is significantly larger, Hr = 7.9. The Haumea family members larger than approximately 20 km in diameter must be characterized by a shallow H-distribution slope in order to produce only these three large detections. This shallow size distribution suggests that the family formed in a graze-and-merge scenario, not a catastrophic collision.

An analytical method is developed for finding the coefficients of zonal spherical harmonics of the azimuthally averaged potential of a rotating stratified inhomogeneous triaxial ellipsoid. Two models are considered: i) an ellipsoid of discrete layers of finite thickness, including the two-component Core – Shell model; ii) an inhomogeneous ellipsoid consisting of infinitely thin equidensity layers with arbitrary elliptic profiles from the center to the periphery. For both types of models, equations were obtained that allow calculating the coefficients of zonal spherical harmonics of any degree according to a single scheme. Along with the general stratification, special cases of ellipsoids consisting of homeoids and focaloids were also considered. It is proved that for confocal stratification the coefficients of zonal spherical harmonics of homogeneous and congruent inhomogeneous ellipsoids coincide. The method is applied to the construction of a near-equilibrium model of the dwarf planet Haumea. It has been established that the nodal precession period of the Haumea’s ring is $T_{\mathit{prec}} = 12.9 \pm 0.7~\text{days}$ .

In this work, we focused on observations of six trans-Neptunian objects (TNOs) whose apparent magnitudes are brighter than 20 mag. We present the results of astrometric and photometric observations of (134340) Pluto, (136108) Haumea, (136472) Makemake, (136199) Eris, (90482) Orcus and (20000) Varuna obtained at the Kyiv comet station (Code MPC 585) in 2017-2019. For observations, we used the 0.7-m reflector AZT-8 with the FLI PL4710 CCD camera and filters of the Johnson-Cousins photometric system. From our images, we measured the objects astrometric positions, calculated apparent magnitudes in the BVRI (mostly R) bands using the aperture photometry method, and found the absolute magnitudes together with the colour indices in several bands. Analysing our results, we investigate the limitation on the astrometry and photometry of faint objects with the 0.7-m telescope., Comment: 7 pages, 1 figure, 5 tables

Narrow and dense rings have been detected around the small Centaur body Chariklo (Braga-Ribas et al. 2014), as well as around the dwarf planet Haumea (Ortiz et al. 2017). Both objects have non-axisymmetric shapes that induce strong resonant effects between the rotating central body with spin rate Ω and the radial epicyclic motion of the ring particles, κ. These resonances include the classical Eccentric Lindblad Resonances (ELR), where κ = m(n-Ω), with m integer, n being the particle mean motion. These resonances create an exchange of angular momentum between the body and the collisional ring, clearing the corotation zone, pushing the inner disk onto the body and repelling the outer part outside of the outermost 1/2 ELR, where the particles complete one orbital revolution while the body executes two rotations, i.e. n/Ω ~ 1/2 (Sicardy et al. 2019) Here I will focus on higher-order resonances. They may appear either by considering other resonances such as n/Ω ~ 1/3, or the same resonance as above (n/Ω ~ 1/2), but with a body that has a triaxial shape. In this case, the invariance of the potential under a rotation of π radians transforms the 1st-order 1/2 Lindblad Resonance into a 2nd order 2/4 resonance. Second-order resonances are of particular interest because they force a strong response of the particles near the resonance radius, in spite of the intrinsically small strength of their forcing terms. This stems from the topography of the associated resonant Hamiltonian, which possesses an unstable hyperbolic point at its origin. The width of the region where this strong response is expected will be discussed for both Chariklo's and Haumea's rings. The special case of the second-order 1/3 resonance will be discussed, as it appears that both ring systems are close to that resonance. This work is intended, among others, to pave the way for future collisional simulations of rings around non-axisymmetric bodies. Braga-Ribas et al., 2014, Nature 508, 72Ortiz et al., 2017, Nature 550, 219Sicardy et al., 2019, Nature Astronomy 3, 146 The work leading to these results has received funding from the European Research Council under the European Community's H2020 2014-2020 ERC Grant Agreement n°669416 "Lucky Star"

The Direct Fusion Drive (DFD) is a nuclear fusion engine that will provide thrust and electrical power for any spacecraft. It is a compact engine, based on the D -$^{3}$He aneutronic fusion reaction that uses the Princeton field reversed configuration for the plasma confinement and an odd parity rotating magnetic field as heating method to achieve nuclear fusion (Cohen et al., 2019), which will heat the deuterium, also used as propellant. \par In this work we present possibilities to explore the solar system outer border using the DFD. The objective is to reach some trans-Neptunian object, such as the dwarf planets Makemake, Eris and Haumea in less than 10 years with a payload mass of at least of 1500 kg, so that it would enable all kind of missions, from scientific observation to in-situ operations. For each mission a thrust-coast-thrust profile is considered. For this reason, each mission is divided into 3 phases: i. the spiral trajectory to escape Earth gravity; ii. the interplanetary travel, from the exit of Earth sphere of influence to the end of the coasting phase; iii. maneuvers to rendezvous with the dwarf planet. Propellant mass consumption, initial and final masses, velocities and $\Delta V$ for each maneuver are presented. Calculations to reach a vicinity at 125 AU for the study of Sun magnetosphere as well as Eris via flyby are also presented, with interest on the influence of different acceleration phases. Our calculations show that a spacecraft propelled by DFD will open unprecedented possibilities to explore the border of the solar system, in a limited amount of time and with a very high payload to propellant masses ratio., Comment: 12 pages, 3 figures

The recent discovery of rings and massive satellites around minor bodies and dwarf planets suggests that they may often coexist, as for example around Haumea. A ring perturbed by an oblate central body and by an inclined satellite may disperse on a short timescale. The conditions under which a ring may survive are explored both analytically and numerically. The trajectories of ring particles are integrated under the influence of the gravitational field of a triaxial ellipsoid and (a) massive satellite(s), including the effects of collisions. A ring initially formed in the equatorial plane of the central body will be disrupted if the satellite has an inclination in the Kozai Lidov regime (39.2 < i < 144.8). For lower inclinations, the ring may relax to the satellite orbital plane thanks to an intense collisional damping. On the other hand, a significant J2 term easily suppresses the perturbations of an inclined satellite within a critical semimajor axis, even in the case of Kozai Lidov cycles. However, if the ring is initially inclined with respect to the equatorial plane, the same J2 perturbations are not a protective factor but instead disrupt the ring on a short timescale. The ring found around Haumea is stable despite the rise in the impact velocities that is due to the asymmetric shape of the the body and the presence of a 3:1 resonance with the rotation of the central body. A ring close to an oblate central body should be searched for in the proximity of the equatorial plane, where the J2 perturbations protect it against the perturbations of an external inclined satellites. In an inclined configuration, the J2 term is itself disruptive., Accepted for publication on Astronomy and Astrophysics

Made available in DSpace on 2019-10-06T17:04:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-04-11 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The recently discovered ring around the dwarf planet (136108) Haumea is located near the 1:3 resonance between the orbital motion of the ring particles and the spin of Haumea. In the current work, we study the dynamics of individual particles in the region where the ring is located. Using the Poincaré surface of section technique, the islands of stability associated with the 1:3 resonance are identified and studied. Throughout its existence, this resonance is shown to be doubled, producing pairs of periodic and quasi-periodic orbits. The fact of being doubled introduces a separatrix, which generates a chaotic layer that reduces the size of the stable regions of the 1:3 resonance significantly. The results also show that there is a minimum equivalent eccentricity (e 1:3) required for the existence of such a resonance. This value seems to be too high to keep a particle within the borders of the ring. On the other hand, the Poincaré surface of sections shows the existence of much larger stable regions, but associated with a family of first-kind periodic orbits. They exist with equivalent eccentricity values lower than e 1:3, covering a large radial distance, which encompasses the region of Haumea's ring. Therefore, this analysis suggests that Haumea's ring is in a stable region associated with a first-kind periodic orbit instead of the 1:3 resonance. Grupo de Dinâmica Orbital e Planetologia São Paulo State University - UNESP Grupo de Dinâmica Orbital e Planetologia São Paulo State University - UNESP

The particle dynamics of the recently observed ring around dwarf planet Haumea is numerically investigated. The point mass gravitational force, a second degree and order gravity field, and the solar radiation pressure as the main perturbations are considered. The quasi-stationary state of the ring varies for different micron-sized grains and depends also on the spin-orbit resonances between the rotation rate of the main body and the orbital period of the dust particles. The simulations confirm the variable radial width of the ring observed during the transit ingress and egress. Results show that the micron sized grains, initially on circular orbits, become eccentric and form an apse-aligned ring at the observed radial distance near to the 3:1 spin-orbit resonance. It is also demonstrated that this coincidence is only apparent and independent of 3:1 resonance., 6 pages, 5 figures, accepted for publication in MNRAS

The work on the mass search for asteroids on astroplate images and the determination of their coordi- nates was begun in 2016. The basis for current search was the processing results of digitized photographic plates and films obtained at the observatory in Baldone in 1967-1993. Observations with a single exposure in different spectral bands were carried out using the 1.2m Schmidt telescope in Baldone. We used all observations in the U Johnson's spec- tral band (on plates) and significant part of them in V band (on films). Photometric band U was realized by combining emulsion ORWO Zu1 (Zu2 or Zu21 or Kodak 103aO or IIaO) with UG1 filter. For films with A600 emulsion and filter ZS17 a photometric band V was implemented. Based on the results of digital processing about 300 U- plates and more than 1460 V-films, a preliminary catalog of 1700 asteroid positions was compiled. Among the ob- jects in this catalog are asteroids of particular interest. These include the distant objects (136108) Haumea and (136472) Makemake and some Main belt asteroids, the positions of which were fixed on the plates many years before their own discoveries. All observed positions of asteroids were compared with ephemeris DE431. An analysis of the convergence of the observed positions with their theoretical data for different spectral bands showed that the observations on V-films are better consistent with theory. However, the internal accuracy of determining coordi- nates from U-plates, on the contrary, is higher than from V-films. This discrepancy is especially noticeable for right ascension, when the root-mean-square errors on V-films can reach values exceeding 1.8 arc seconds. These signifi- cant errors are a consequence of the curvature unevenness of the film surface during scanning

Since 2013, dense and narrow rings are known around the small Centaur object Chariklo and the dwarf planet Haumea. Dense material has also been detected around the Centaur Chiron, although its nature is debated. This is the first time ever that rings are observed elsewhere than around the giant planets, suggesting that those features are more common than previously thought. The origins of those rings remain unclear. In particular, it is not known if the same generic process can explain the presence of material around Chariklo, Chiron, Haumea, or if each object has a very different history. Nonetheless, a specific aspect of small bodies is that they may possess a nonaxisymmetric shape (topographic features and/or elongation) that are essentially absent in giant planets. This creates strong resonances between the spin rate of the object and the mean motion of ring particles. In particular, Lindblad-type resonances tend to clear the region around the corotation (or synchronous) orbit, where the particles orbital period matches that of the body. Whatever the origin of the ring is, modest topographic features or elongations of Chariklo and Haumea explain why their rings should be found beyond the outermost 1/2 resonance, where the particles complete one revolution, while the body completes two rotations. Comparison of the resonant locations relative to the Roche limit of the body shows that fast rotators are favored for being surrounded by rings. We discuss in more detail the phase portraits of the 1/2 and 1/3 resonances, and the consequences of a ring presence on satellite formation.

The thermal emission of Trans-Neptunian objects and Centaurs has been observed at mid- and far-infrared wavelengths—with the biggest contributions coming from the Spitzer and Herschel space observatories—and the brightest ones also at submillimeter and millimeter wavelengths. These measurements allowed to determine the sizes and albedos for almost 180 objects, and densities for about 25 multiple systems. The derived very low thermal inertias show evidence for a decrease at large heliocentric distances and for high-albedo objects, which indicate porous and low-conductivity surfaces. The radio emissivity was found to be low (ϵr = 0.70 ± 0.13) with possible spectral variations in a few cases. The general increase of density with object size points to different formation locations or times. The mean albedos increase from about 5%–6% (Centaurs, scattered-disk objects) to 15% for the detached objects, with distinct cumulative albedo distributions for hot and cold classicals. The color-albedo separation in our sample is evidence for a compositional discontinuity in the young solar system. The median albedo of the sample (excluding dwarf planets and the Haumea family) is 0.08, the albedo of Haumea family members is close to 0.5, best explained by the presence of water ice. The existing thermal measurements remain a treasure trove at times where the far-infrared regime is observationally not accessible.

Aims.We aim to determine far-infrared fluxes at 70, 100, and 160μm for the five major Uranus satellites, Titania, Oberon, Umbriel, Ariel, and Miranda. Our study is based on the available calibration observations at wavelengths taken with the PACS photometer aboard theHerschelSpace Observatory.Methods.The bright image of Uranus was subtracted using a scaled Uranus point spread function (PSF) reference established from all maps of each wavelength in an iterative process removing the superimposed moons. The photometry of the satellites was performed using PSF photometry. Thermophysical models of the icy moons were fitted to the photometry of each measurement epoch and auxiliary data at shorter wavelengths.Results.The best-fit thermophysical models provide constraints for important properties of the moons, such as surface roughness and thermal inertia. We present the first thermal infrared radiometry longward of 50μm for the four largest Uranian moons, Titania, Oberon, Umbriel, and Ariel, at epochs with equator-on illumination. Due to this inclination geometry, heat transport took place to the night side so that thermal inertia played a role, allowing us to constrain that parameter. Also, we found some indication for differences in the thermal properties of leading and trailing hemispheres. The total combined flux contribution of the four major moons relative to Uranus is 5.7 × 10−3, 4.8 × 10−3, and 3.4 × 10−3at 70, 100, and 160μm, respectively. We therefore precisely specify the systematic error of the Uranus flux by its moons when Uranus is used as a far-infrared prime flux calibrator. Miranda is considerably fainter and always close to Uranus, impeding reliable photometry.Conclusions.We successfully demonstrate an image processing technique for PACS photometer data that allows us to remove a bright central source and reconstruct point source fluxes on the order of 10−3of the central source as close as ≈3 × the half width at half maximum of the PSF. We established improved thermophysical models of the five major Uranus satellites. Our derived thermal inertia values resemble those of trans-neptunian object (TNO) dwarf planets, Pluto and Haumea, more than those of smaller TNOs and Centaurs at heliocentric distances of about 30 AU.

We aim to determine the relative angle between the total angular momentum of the minor planets and that of the Sun-planets system, and to improve the orientation of the invariable plane of the solar system. By utilizing physical parameters available in public domain archives, we assigned reasonable masses to 718041 minor planets throughout the solar system, including near-Earth objects, main belt asteroids, Jupiter trojans, trans-Neptunian objects, scattered-disk objects, and centaurs. Then we combined the orbital data to calibrate the angular momenta of these small bodies, and evaluated the specific contribution of the massive dwarf planets. The effects of uncertainties on the mass determination and the observational incompleteness were also estimated. We determine the total angular momentum of the known minor planets to be $1.7817\times10^{46}$ g $\cdot$ cm$^2$ $\cdot$ s$^{-1}$. The relative angle $\alpha$ between this vector and the total angular momentum of the Sun-planets system is calculated to be 14.74 deg.. By excluding the dwarf planets Eris, Pluto, and Haumea, which have peculiar angular momentum directions, $\alpha$ drops sharply to 1.76 deg.; a similar result applies to each individual minor planet group. This suggests that, without these three most massive bodies, the plane perpendicular to the total angular momentum of the minor planets would be close to the invariable plane of the solar system. On the other hand, the inclusion of Eris, Haumea, and Makemake can produce a difference of 1254 mas in the inclination of the invariable plane, which is much larger than the difference of 9 mas induced by Ceres, Vesta, and Pallas as found previously. By taking into account the angular momentum contributions from all minor planets, including unseen ones, the orientation improvement of the invariable plane is larger than 1000 mas in inclination with a $1\sigma$ error of 50-140 mas., Comment: 10 pages, 3 figures, published in A&A

Context. A group of trans-Neptunian objects (TNOs) are dynamically related to the dwarf planet 136108 Haumea. Ten of them show strong indications of water ice on their surfaces, are assumed to have resulted from a collision, and are accepted as the only known TNO collisional family. Nineteen other dynamically similar objects lack water ice absorptions and are hypothesized to be dynamical interlopers. Aims. We have made observations to determine sizes and geometric albedos of six of the accepted Haumea family members and one dynamical interloper. Ten other dynamical interlopers have been measured by previous works. We compare the individual and statistical properties of the family members and interlopers, examining the size and albedo distributions of both groups. We also examine implications for the total mass of the family and their ejection velocities. Methods. We use far-infrared space-based telescopes to observe the target TNOs near their thermal peak and combine these data with optical magnitudes to derive sizes and albedos using radiometric techniques. Using measured and inferred sizes together with ejection velocities, we determine the power-law slope of ejection velocity as a function of effective diameter. Results. The detected Haumea family members have a diversity of geometric albedos 0.3-0.8, which are higher than geometric albedos of dynamically similar objects without water ice. The median geometric albedo for accepted family members is pV = 0.48-0.18 +0.28, compared to 0.08-0.05 +0.07 for the dynamical interlopers. In the size range D = 175-300 km, the slope of the cumulative size distribution is q = 3.2-0.4 +0.7 for accepted family members, steeper than the q = 2.0 ± 0.6 slope for the dynamical interlopers with D < 500 km. The total mass of Haumea's moons and family members is 2.4% of Haumea's mass. The ejection velocities required to emplace them on their current orbits show a dependence on diameter, with a power-law slope of 0.21-0.50. © ESO 2018., Part of this work was supported by the German DLR project number 50 OR 1108. T.M., C.K., P.S., and R.D. acknowledge that the research leading to these results has received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378. A.P. acknowledges the grant LP2012-31 of the Hungarian Academy of Sciences. N.P. acknowledges funding by the Portuguese FCT - Foundation for Science and Technology (ref: SFRH/BGCT/113686/2015). CITEUC is funded by Portuguese National Funds through FCT - Foundation for Science and Technology (project: UID/Multi/00611/2013) and FEDER - European Regional Development Fund through COMPETE 2020 - Operational Programme Competitiveness and Internationalisation (project: POCI-01-0145-FEDER-006922). C.K. has been supported by the K-125015 and GINOP-2.3.2-15-2016-00003 grants of the National Research, Development and Innovation Office (NKFIH, Hungary).

The scenarios proposed in the literature for the genesis of the system formed by the dwarf planet 136108 Haumea, its two satellites and a group of some 10 bodies (the family) with semimajor axes, eccentricities and inclinations close to Haumea's values, are analysed against collisional, physical, dynamical and statistical arguments in order to assess their likelihood. All scenarios based on collisional events are reviewed under physical arguments and the corresponding formation probabilities in a collisional environment are evaluated according to the collisional evolution model alicandep. An alternative mechanism is proposed based on the potential possibility of (quasi-) independent origin of the family with respect to Haumea and its satellites. As a general conclusion the formation of the Haumea system is a low-probability event in the currently assumed frame for the evolution of the outer Solar system. However, it is possible that current knowledge is missing some key element in the whole story that may contribute to increase the odds for the formation of such a system., Facultad de Ciencias Astronómicas y Geofísicas

Newton was the first to provide a mathematical framework to describe the oblateness of the Earth, a framework later expended by Maclaurin, Jacobi, and Poincare and applied to other astronomical objects. In the Solar System, the Jacobi triaxial ellipsoid has successfully described the shape of Haumea and Chariklo, while Ceres appears to be an oblate spheroid of the Maclaurin type. Beyond the Solar System, new exoplanets are being discovered almost daily showing vastly different characteristics (e.g. mass, temperature, eccentricity, radius, orbital period). Recently, Kepler-427b was shown to be a moderately oblate spheroid, and it is possible to imagine that certain exoplanets could be triaxial ellipsoids. Considering the wealth of data now available from the current and past missions whose aim is to hunt for new extra-solar systems, it has become vital to broaden the range of parameters to be estimated for a single exoplanet. In this paper, we present a new algorithm to model variations in transit light curves induced by ellipsoidal exoplanets, which will be ultimately released to the community as a MATLAB-based package. Most variations happen during the ingress and egress phase of the transit. Combining several transits can lead to the detection of oblateness by measuring the precession of the obliquity angle of the exoplanet over time. For the first time, we also model reflected light curves for ellipsoidal exoplanets.

Haumea is the only known trans-Neptunian object with a ring. The ring is in a position that causes a 3:1 spin-orbit resonance with the rotational period of Haumea, which has a triaxial shape. The non-axisymmetric gravitational field around Haumea is thought to affect the dynamics of the ring; however, the process of ring formation has not been elucidated. In this study, we analyze in some detail a potential ring formation scenario for Haumea. We first calculated the gravitational field around the triaxial ellipsoid and estimated the distance at which an object revolving around Haumea can exist stably using simulation that incorporated the time-varying gravitational field. The results of this simulation showed that the trajectory of the object became unstable just inside its current ring position. Next, we analytically derived the Roche radius for a rigid body revolving around a triaxial ellipsoid and showed that the Roche radius could be near the current ring position. Furthermore, as a parameter study, we performed N-body simulations using the coefficient of rubble pile restitution as a variable. Results demonstrated that, according to numerous parameters, the position of the Roche radius was near the current position of Haumea's ring. Based on these findings, we can assume that there is a high possibility that the ring formed in the region between the boundary of the unstable region of the orbit and the Roche radius. The scenario presented in this study could help explain the process by which Haumea's ring formed., Comment: 23 pages, 6 figures, 2 tables, accepted for publication in ApJ

The asteroid tethered swingby maneuver (ATSM) is analyzed in this paper. The maneuver implies turn of the spacecraft velocity by means of a tether anchored to an asteroid. Mission to Haumea dwarf planet is considered. The following spacecraft transfer trajectories with launch in 2025 and 2027 are analyzed in the paper: Earth–Jupiter–Haumea and Earth–ATSM–Jupiter–Haumea. Only asteroids bigger than 40 km in diameter were considered in order to make hitting the asteroid by the tether anchor easier. Many Main Belt asteroids lowering total $\Delta V$ of the transfers were found. A few of them giving the maximum effect of ATSM were selected and the transfers using them are analyzed in details. It is shown that the ATSM using these asteroids would lower substantially the total $\Delta V$ or shorten significantly the time of flight. Technical problems of the ATSM implementation, such as possibly big mass of the tether and anchor, difficulty of hitting the asteroid and anchoring the tether securely etc., are considered. These problems would not allow to implement the ATSM at present time, but hopefully will be solved in near future.

The field of ringed small bodies was born in 2013 by the serendipitous discovery of two narrow rings around the Centaur Chariklo, which orbits between Saturn and Uranus. Since then, rings have been detected around the TNO Haumea, and may exist around the Centaur Chiron. The existence of these ringed small bodies naturally raises several questions such as: how did the rings form? Are ringed small bodies commonplace? And what is the longevity of such rings?

Observation of stellar occultation by objects of the Solar System is a powerful technique that allows measurements of size and shape of the small bodies with accuracies in the order of the kilometre. In addition, the occultation star probes the surroundings of the object, allowing the study of putative rings/debris or atmosphere around it. Since 2009, more than 60 events by trans-Neptunian and Centaur objects have been detected, involving more than 34 different bodies. Some remarkable results were achieved, such as the discovery of rings around Chariklo and Haumea, or the high albedo of Eris, the lack of global atmosphere around Makemake and the discovery of the double shape of 2014 MU69, among others. After the release of Gaia catalogues, predictions became more accurate, leading to an increasing number of successful observations of occultation events. To keep track of the results achieved with this technique, we created a database to gather all the detected events worldwide. The database is presented as an electronic table (http://occultations.ct.utfpr.edu.br/), where the main information obtained from any occultation by small outer solar system objects are listed. The structure and term definitions used in the database are presented here, as well as some simple statistics that can be done with the available results. © Published under licence by IOP Publishing Ltd., The Lucky Star project aims at predicting, observing worldwide and analyzing stellar occultations by small objects of the outer solar system. It receives funding from the European Unions Horizon 2020 Research and Innovation Programme (ERC), under the supervision of Prof. Bruno Sicardy2 (http://lesia.obspm.fr/lucky-star/). Part of the research leading to these results has received funding from the European Research Council under the European Communitys H2020 (2014-2020/ERC Grant Agreement no. 669416 “LUCKY STAR”), from the European Unions Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378 (SBNAF), and from Coordenacão de Aperfeicoamento de Pessoal de Ńıvel Superior – Brasil (CAPES – Finance code 001). J.L.O., P.S.-S. and R.D. acknowledges financial support from the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award for the Instituto de Astofísica de Andalućıa (SEV-2017-0709). M.A. thanks to the CNPq (Grants 473002/2013-2 and 308721/2011-0) and FAPERJ (Grant E-26/111.488/2013). J.I.B.C. acknowledges CNPq grant 308150/2016-3. RV-M thanks grants: CNPq-304544/2017-5, 401903/2016-8, Faperj: PAPDRJ-45/2013 and E-26/203.026/2015. B.M. thanks the CAPES/Cofecub-394/2016-05 grant. F.B.-R. acknowledges CNPq grant 309578/2017-5.

Dense and narrow rings have been discovered recently around the small Centaur object Chariklo1 and the dwarf planet Haumea2, while being suspected around the Centaur Chiron3, although this point is debated4. They are the first rings observed in the Solar System elsewhere than around giant planets. In contrast to giant planets, gravitational fields of small bodies may exhibit large non-axisymmetric terms that create strong resonances between the spin of the object and the mean motion of ring particles. Here we show that modest topographic features or elongations of Chariklo and Haumea explain why their rings are relatively far away from the central body, when scaled to those of the giant planets5. Resonances actually clear on decadal timescales an initial collisional disk that straddles the corotation resonance (where the particles' mean motion matches the spin rate of the body). Quite generically, the disk material inside the corotation radius migrates onto the body, while the material outside the corotation radius is pushed outside the 1/2 resonance, where the particles complete one revolution while the body completes two rotations. Consequently, the existence of rings around non-axisymmetric bodies requires that the 1/2 resonance resides inside the Roche limit of the body, favouring faster rotators for being surrounded by rings. © 2018, The Author(s), under exclusive licence to Springer Nature Limited., The work leading to these results has received funding from the European Research Council under the European Community's H2020 2014-2020 ERC Grant Agreement No. 669416 'Lucky Star'. P.S.-S. acknowledges financial support by the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378 ('SBNAF').

Rings have recently been discovered around the trans-Neptunian object (TNO) 136108 Haumea and the Centaur 10199 Chariklo. Rings are also suspected around the Centaur 2060 Chiron. As planetary close encounters with ringed small bodies can affect ring longevity, we previously measured the severity of such encounters of Chariklo and Chiron using the minimum encounter distance, dmin. The value of dmin that separates noticeable encounters from non-noticeable encounters we called the ‘ring limit’, R. R was then approximated as 10 tidal disruption distances, 10Rtd. In this work, we seek to find analytical expressions for R that fully account for the effects of the planet mass, small body mass, ms, ring orbital radius, r, and velocity at infinity, v∞, for fictitious ringed Centaurs using ranges 2 × 1020 kg ≤ms≤ 1 Pluto mass and 25 000 ≤r ≤ 100 000 km. To accomplish this, we use numerical integration to simulate close encounters between each giant planet and ringed Centaurs in the three-body planar problem. The results show that R has a lower bound of approximately 1.8Rtd. We compare analytical and experimental R values for a fictitious Haumea, Chariklo, and Chiron with r= 50 000 km. The agreement is excellent for Haumea, but weaker for Chariklo and Chiron. The agreement is best for Jupiter and Saturn. The ring limits of the real Haumea, Chariklo, and Chiron are

The Kuiper Belt is a distant region of our solar system beginning at a solar distance of about 30 AU. By now, the discovery of several small worlds, like the dwarf planets Pluto, Makemake or Haumea, has shown that the trans-Neptunian region of the solar system is indeed more crowded than first meets the eye.

Submitted by Gabriel Borderes Motta (gabriel_borderes@yahoo.com.br) on 2018-05-08T22:40:01Z No. of bitstreams: 1 Tese.pdf: 94594231 bytes, checksum: 424f474ffb856276cc3c8fc7f0e81790 (MD5) Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-05-10T13:22:38Z (GMT) No. of bitstreams: 1 borderes-mota_g_dr_guara.pdf: 94594231 bytes, checksum: 424f474ffb856276cc3c8fc7f0e81790 (MD5) Made available in DSpace on 2018-05-10T13:22:38Z (GMT). No. of bitstreams: 1 borderes-mota_g_dr_guara.pdf: 94594231 bytes, checksum: 424f474ffb856276cc3c8fc7f0e81790 (MD5) Previous issue date: 2018-03-06 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Em geral, pequenos corpos do sistema solar, como asteroides e cometas, têm uma forma muito irregular, o que afeta significativamente o seu potencial gravitacional, dificultando os estudos da dinâmica ao redor destes corpos. Uma primeira aproximação é a expansão em harmônicos esféricos, onde os termos C20 e o C22 caracterizam a irregularidade do corpo. Usamos essa aproximação em superfícies de secção de Poincaré para estudar as regiões próximas ao planeta anão Haumea, onde foi observado um anel. A partir do mapeamento feito pela técnica de superfície de secção de Poincaré, foi possível identifi- car Famílias de órbitas periódicas e regiões estáveis. Duas Famílias de órbitas periódicas foram destacadas, a primeira uma Família de segundo tipo associada à ressonância 1:3 (Família ressonante) e a segunda uma Família de primeiro tipo (Família central). As simulações indicam que as partículas do anel podem estar em órbitas da Família central. Já a Família ressonante, não pode ser responsável pelo anel devido a excentricidade de suas órbitas e da sua posição. Para simular de forma mais realista a irregularidade de um pequeno corpo, é usada uma melhor aproximação para o cálculo do potencial gravitacional. O modelo de concentração de massa, ou modelo de mascons, é uma aproximação discreta da forma de um corpo, capaz de simular um potencial irregular, assimétrico e tridimensional. A esse modelo é aplicada a superfície de secção de Poincaré, com o objetivo de estudar a dinâmica da região próxima ao asteroide 4179 Toutatis. Quatro Famílias de órbitas periódicas são destacadas e estudadas. Uma Família é de primeiro tipo e as outras três são de segundo tipo associadas às ressonâncias 3:1, 2:1 e 2:3. Apesar do potencial gravitacional tridimensional ser adotado em uma ferramenta usualmente bidimensional, é possível analisar como um problema bidimensional quando a variação na terceira dimensão é baixa. Estudando em conjunto as superfícies de secção de Poincaré e a variação máxima na terceira dimensão, verifica-se a estabilidade ou não das trajetórias simuladas In general, small bodies of the Solar system, e.g. asteroids and comets, have a very irregular shape. This feature affects significantly the gravitational potential around these irregular bodies, which hinders dynamical studies. A first approximation is an expansion in spherical harmonics, where C20 and C22 characterize the irregularity of the body. This approach is used on Poincaré surfaces of sections to study regions close to the dwarf planet Haumea. This regions are where the observed ring. By the technique of Poincaré surface of section, it was identified Families of periodic orbits and stable regions. Two Families of periodic orbits were studied, the first Family is a second type associated with the 1:3 resonance (resonant Family) and the second Family is a first type (central Family). During the simulations the ring particles can be in orbits of the central Family. But the resonant Family can not be responsible for the ring due the eccentricity and position of their orbits. In order to more realistically simulation of the irregularity of the body, a better approximation is necessary for the computation of the gravitational potential. The mass concentration model, or mascon model, is a discrete approximation of the shape of a body. This model simulates an irregular, asymmetric and three-dimensional potential. This model was applied in a Poincaré surfaces of section, mainly to study the dynamics of the region close to the asteroid 4179 Toutatis. Four Families of periodic orbits were studied. One of then is a first type and the others were the second type and associated with the resonances 3:1, 2:1 and 2:3. Although the three-dimensional gravitational potential is adopted in a usually two-dimensional tool, it is possible to analyze as a two-dimensional problem when the variation in the third dimension is low. By a analyzing of the Poincaré surfaces of section and a maximum variation in the free dimension together, the stability of the simulated trajectories is measured

Stellar occultations are a very powerful tool to study small bodies of the Outer Solar System, which are usually too faint or too far away to be studied by others techniques. They occur when a body passes in front of a background star. The stellar flux will then be intercepted during several seconds/minutes. Observation of the occulted star in time allows us to study the shape and size of the occulting object and its vicinity (ring, atmosphere or satellite). For the first time, two dense and narrow rings have been discovered on June 2013 around the biggest known Centaur Chariklo (body’s diameter: 250 km and rings diameter: 800 km). My work shows the 16 observed occultations by Chariklo and/or its rings since 2013. Those data are the only one available about this planetary system today. A first study of their structure and their geometry is conducted. Another part of my work was to study an occultation by the dwarf planet Haumea recorded on January 2017. It revealed the presence of a ring of radius ~2281 km around this tri-axial body. This discovery made Haumea the second body with a ring orbiting around except the four giant planets. This occultation allows us to derive the shape, size (1161x852x513 km) and density of the main body. This second discovery tends to show that rings in small planetary systems are more common that we thought. The release of Gaia DR1 catalog in 2016 greatly improved our predictions of such occultations. In the forthcoming years, efforts will be made on detailed and localized studies of Chariklo’s and Haumea’s rings, but also on search for other small rings systems in order to better understand the origins and the evolution mechanisms of such systems., Les occultations stellaires sont une méthode puissante pour étudier les petits corps du Système Solaire, trop faibles ou lointains pour être étudiés par d’autres techniques. Cette méthode consiste à observer le corps passant devant une étoile d’arrière plan. Le flux lumineux stellaire est alors intercepté quelques instants, ce qui permet de caractériser la forme de l’objet et d’étudier son environnement (anneau, atmosphère ou satellite). Deux anneaux denses et étroits ont été découverts en Juin 2013 pour la première fois autour du plus gros des Centaures Chariklo (corps central : 250 km de diamètre ; anneaux : 800 km). Cette thèse présente les 16 occultations par Chariklo et ses anneaux observées depuis 2013. Ces données représentent les seules observations aujourd’hui existantes de ce système planétaire. Une première étude de leur structure et de leur géométrie est détaillée dans ces travaux. Mes travaux ont également porté sur une occultation par la planète naine Haumea observée en Janvier 2017. Celle-ci nous a révélé la présence d’un anneau dense de rayon ~2281 km autour de ce corps tri-axial. Haumea est donc le deuxième corps en dehors des planètes géantes à posséder un anneau. Cette occultation permet notamment de déduire la forme, la taille (1161x852x513 km) et la densité d’Haumea. Cette seconde découverte tend à montrer que les anneaux autour des petits corps ne sont pas si rares. La publication du catalogue Gaia DR1 en 2016 a permis d’améliorer considérablement la précision de nos prédictions donc nos observations. Les prochaines années seront consacrées à scanner plus en détails les anneaux de Chariklo et d’Haumea, mais aussi à chercher des anneaux autour d’autres petits corps afin de comprendre les mécanismes de formation et d’évolution de ces systèmes.

Made available in DSpace on 2018-12-11T17:31:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-04-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The present paper studies the powered Swing-By maneuver when performed in an elliptical system of primaries. It means that there is a spacecraft travelling in a system governed by the gravity fields of two bodies that are in elliptical orbits around their center of mass. The paper particularly analyzes the effects of the parameters relative to the Swing-By (Vinf-,rp,ψ), the orbit of the secondary body around the primary one (e,ν) and the elements that specify the impulse applied (δV,α) to the spacecraft. The impulse is applied when the spacecraft passes by the periapsis of its orbit around the body, where it performs the Swing-By, with different magnitudes and directions. The inclusion of the orbital eccentricity of the primaries in this problem makes it closer to reality, considering that there are many known systems with eccentricities different from zero. In particular, there are several moons in the Solar System which orbits are not circular, as well as some smaller bodies, like the dwarf planet Haumea and its moons, which have eccentricities of 0.25 or even larger. The behavior of the energy variation of the spacecraft is shown in details, as well as the cases where captures and collisions occur. The results show the conditions that optimize this maneuver, according to some given parameters, and how much can be obtained in terms of gains or losses of energy using the best conditions found by the algorithm developed here. Instituto Nacional de Pesquisas Espaciais – INPE Grupo de Dinâmica Orbital e Planetologia Univ. Estadual Paulista – UNESP Univ. Estadual Paulista – UNESP Grupo de Dinâmica Orbital e Planetologia Univ. Estadual Paulista – UNESP Univ. Estadual Paulista – UNESP FAPESP: 2011/08171-3 FAPESP: 2011/13101-4 FAPESP: 2016/14665-2 CNPq: 304700/2009-6

We present photometric and astrometric measurements of the Kuiper Belt Objects (KBO) Haumea and Makemake obtained between 2013 June 5 and 2013 July 31 with the 14-inch Wallace Astrophysical Observatory (WAO) telescopes. Using photometry, we determined that Haumea and Makemake have R magnitudes 17.225 ± 0.347 and 16.850 ± 0.107, respectively. We obtained rotational light curves for Haumea and Makemake over eight separate nights. Astrometry yielded mean residuals with respect to the JPL ephemeris of -0.0095 ± 0.027'' with an rms residual of 0.480'' in R.A. and 0.261 ± 0.019'' with an rms residual of 0.335 in decl. for Makemake, and 0.219 ± 0.090'' in R.A. with an rms residual of 0.748'', and 0.223 ± 0.068'' in decl. with an rms residual of 0.571'' for Haumea. Additionally, we calculated that observing Haumea with two 14-inch telescopes and Makemake with four 14-inch telescopes could resolve their periodicity. With improved observing techniques and modern CCD cameras, it is possible to utilize small telescopes in universities around the world to observe large KBOs.

This paper outlines the progress in development of the numerical planet ephemerides EPM—Ephemerides of Planets and the Moon. EPM was first created in the 1970s in support of Russian space flight missions and constantly improved at IAA RAS. Comparison between various available EPM ephemerides (EPM2004, EPM2008, EPM2011) is shown. The first results of the updated EPM2013 version which takes into account the two-dimensional annulus of small asteroids are presented. Currently two main factors drive the progress of planet ephemerides: dynamical models of planet motion and observational data, with the crucial role of spacecraft ranging. EPM ephemerides are the basis for the Russian Astronomical and Nautical Astronomical Yearbooks, are planned to use in the GLONASS and LUNA-RESOURCE programs, and are being used for determination of physical parameters: masses of asteroids, planet rotation parameters and topography, the $$GM_\odot $$ and its secular variation, the PPN parameters, and the upper limit on the mass of dark matter in the Solar System. The files containing polynomial approximation for EPM ephemerides (EPM2004, EPM2008, EPM2011) along with TT–TDB and ephemerides of Ceres, Pallas, Vesta, Eris, Haumea, Makemake, and Sedna are available from ftp://quasar.ipa.nw.ru/incoming/EPM/ . Files are provided in IAA’s binary and ASCII formats, as well as in the SPK format.

The dwarf planet Haumea is a very interesting celestial body due to the characteristics of its physical form and also the recently observed ring. A Kuiper Belt object, Haumea is a triaxial ellipsoid with dimensions of approximately 513 × 852 × 1161 (km), with a mass of 4.006 × 1021 kg and a rotation period of 3.915341h. The dwarf planet Haumea has its system formed by two natural satellites, the moons Namaka and Hi’iaka. We have presented an analysis of orbits around the dwarf planet Haumea taking into account the influences of the perturbations of its nonsphericity (J2, J4, C22 ). We have found that the C22 term and the rotation rate of Haumea have contributed strongly to reduce the variation rate of the periapsis radius of the spacecraft. We have calculated the spherical harmonics of Haumea taking into account the most current values for the semi-axes of the ellipsoid and we have presented a comparison with the values of the harmonics found in other works.

We have calculated the figure of equilibrium of a rapidly rotating, differentiated body to determine the shape, structure, and composition of the dwarf planet Haumea. Previous studies of Haumea's light curve have suggested that Haumea is a uniform triaxial ellipsoid consistent with a Jacobi ellipsoid with axes ≈960 × 774 × 513 km and bulk density ≈2600 kg m−3. In contrast, observations of a recent occultation of Haumea indicate that its axes are ≈1161 × 852 × 523 km and its bulk density is ≈1885 kg m−3; these results suggest that Haumea cannot be a fluid in hydrostatic equilibrium and must be supported by interparticle forces. We have written a code to reconcile these contradictory results and to determine whether Haumea is in fact a fluid in hydrostatic equilibrium. The code calculates the equilibrium shape, density, and ice crust thickness of a differentiated Haumea after imposing axis lengths a and b. We find that Haumea is consistent with a differentiated triaxial ellipsoid fluid in hydrostatic equilibrium with axes of best fit a = 1050 km, b = 840 km, and c = 537 km. This solution for Haumea has ρ avg = 2018 kg m−3, ρ core = 2680 kg m−3, and core axes a c = 883 km, b c = 723 km, and c c = 470 km, which equates to an ice mantle composing ~17% of Haumea's volume and ranging from 67 to 167 km in thickness. The thick ice crust we infer allows for Haumea's collisional family to represent only a small fraction of Haumea's pre-collisional ice crust. For a wide range of parameters, the core density we calculate for Haumea suggests that today the core is composed of hydrated silicates and likely underwent serpentinization in the past.

The dwarf planet (136108) Haumea has an intriguing combination of unique physical properties: near-breakup spin, two regular satellites, and an unexpectedly compact family. While these properties indicate formation by collision, there is no self-consistent and reasonably probable formation hypothesis that can connect the unusually rapid spin and the low relative velocities of Haumea family members ("Haumeans"). We explore and test the proposed formation hypotheses (catastrophic collision, graze-and-merge, and satellite collision). We flexibly parameterize the properties of the collision (e.g., the collision location) and use simple models for the three-dimensional velocity ejection field expected from each model to generate simulated families. These are compared to observed Kuiper Belt Objects using Bayesian parameter inference, including a mixture model that allows for interlopers from the background population. After testing our methodology, we find the best match to the observed Haumeans is an isotropic ejection field with a typical velocity of 150 m s$^{-1}$. The graze-and-merge and satellite collision hypotheses are disfavored. Including these constraints, we discuss the formation hypotheses in detail, including variations, some of which are tested. Some new hypotheses are proposed (a cratering collision and a collision where Haumea's upper layers are "missing") and scrutinized. We do not identify a satisfactory formation hypothesis, but we do propose several avenues of additional investigation. In addition, we identify many new candidate Haumeans and dynamically confirm 7 of them as consistent with the observed family. We confirm that Haumeans have a shallow size distribution and discuss implications for the identification of new Haumeans., Resubmitted to AAS Journals

Ortiz, José Luis et. al., Haumea-one of the four known trans-Neptunian dwarf planets- is a very elongated and rapidly rotating body1-3. In contrast to other dwarf planets4-6, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system7, and the Centaur Chiron was later found to possess something similar to Chariklo's rings8,9. Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multichord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period-that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates1,10,11. In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen- or methane-dominated atmosphere was detected.© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved., J.L.O. acknowledges funding from Spanish and Andalusian grants MINECO AYA-2014-56637-C2-1-P and J. A. 2012-FQM1776 as well as FEDER funds. Part of the research leading to these results received funding from the European Union's Horizon 2020 Research and Innovation Programme, under grant agreement no. 687378. B.S. acknowledges support from the French grants 'Beyond Neptune' ANR-08-BLAN-0177 and 'Beyond Neptune II' ANR-11-1S56-0002. Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ERG grant agreement no. 669416 'Lucky Star'). A.P. and R.S. have been supported by the grant LP2012-31 of the Hungarian Academy of Sciences. All of the Hungarian contributors acknowledge the partial support from K-125015 grant of the National Research, Development and Innovation Office (NKFIH). G.B.-R., F.B.-R., F.L.R., R.V.-M., J.I.B.C., M.A., A.R.G.-J. and B.E.M. acknowledge support from CAPES, CNPq and FAPERJ. J.C.G. acknowledges funding from AYA2015-63939-C2-2-P and from the Generalitat Valenciana PROMETEOII/2014/057. K.H. and P.P. were supported by the project RVO:67985815. The Astronomical Observatory of the Autonomous Region of the Aosta Valley acknowledges a Shoemaker NEO Grant 2013 from The Planetary Society. We acknowledge funds from a 2016 'Research and Education' grant from Fondazione CRT. We also acknowledge the Slovakian project ITMS no. 26220120029.

Context. Time series observations of the dwarf planet Haumea and the Plutinos 2003 VS and 2003 AZ with Herschel/PACS are presented in this work. Thermal emission of these trans-Neptunian objects (TNOs) were acquired as part of the >TNOs are Cool> Herschel Space Observatory key programme. Aims. We search for the thermal light curves at 100 and 160 μm of Haumea and 2003 AZ, and at 70 and 160 μm for 2003 VS by means of photometric analysis of the PACS data. The goal of this work is to use these thermal light curves to obtain physical and thermophysical properties of these icy Solar System bodies. Methods. When a thermal light curve is detected, it is possible to derive or constrain the object thermal inertia, phase integral and/or surface roughness with thermophysical modeling. Results. Haumea's thermal light curve is clearly detected at 100 and 160 μm. The effect of the reported dark spot is apparent at 100 μm. Different thermophysical models were applied to these light curves, varying the thermophysical properties of the surface within and outside the spot. Although no model gives a perfect fit to the thermal observations, results imply an extremely low thermal inertia (0.73) for Haumea's surface. We note that the dark spot region appears to be only weakly different from the rest of the object, with modest changes in thermal inertia and/or phase integral. The thermal light curve of 2003 VS is not firmly detected at 70 μm and at 160 μm but a thermal inertia of (2 ± 0.5) MKS can be derived from these data. The thermal light curve of 2003 AZ is not firmly detected at 100 μm. We apply a thermophysical model to the mean thermal fluxes and to all the Herschel/PACS and Spitzer/MIPS thermal data of 2003 AZ, obtaining a close to pole-on orientation as the most likely for this TNO. Conclusions. For the three TNOs, the thermal inertias derived from light curve analyses or from the thermophysical analysis of the mean thermal fluxes confirm the generally small or very small surface thermal inertias of the TNO population, which is consistent with a statistical mean value Γ = 2.5 ± 0.5 MKS.© ESO, 2017., The research leading to these results has received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378. P. Santos-Sanz and J. L. Ortiz would like to acknowledge financial support by the Spanish grant AYA-2014-56637-C2-1-P and the Proyecto de Excelencia de la Junta de Andalucia J.A. 2012-FQM1776. C. Kiss acknowledges financial support from NKFIH grant GINOP-2.3.2-15-2016-00003. E. Vilenius was supported by the German DLR project number 50 OR 1108. R. Duffard acknowledges financial support from the MINECO for his Ramon y Cajal Contract.

Hi'iaka is the larger outer satellite of the dwarf planet Haumea. Using relative photometry from the Hubble Space Telescope and Magellan and a phase dispersion minimization analysis, we have identified the rotation period of Hi'iaka to be ~9.8 hrs (double-peaked). This is ~120 times faster than its orbital period, creating new questions about the formation of this system and possible tidal evolution. The rapid rotation suggests that Hi'iaka could have a significant obliquity and spin precession that could be visible in light curves within a few years. We then turn to an investigation of what we learn about the (presently unclear) formation of the Haumea system and family based on this unexpectedly rapid rotation rate. We explore the importance of the initial semi-major axis and rotation period in tidal evolution theory and find they strongly influence the time required to despin to synchronous rotation, relevant to understanding a wide variety of satellite and binary systems. We find that despinning tides do not necessarily lead to synchronous spin periods for Hi'iaka, even if it formed near the Roche limit. Therefore the short rotation period of Hi'iaka does not rule out significant tidal evolution. Hi'iaka's spin period is also consistent with formation near its current location and spin up due to Haumea-centric impactors., 21 pages with 6 figures, to be published in The Astronomical Journal

The transneptunian region of the solar system is populated by a wide variety of icy bodies showing great diversity. The dwarf planet (136108) Haumea is among the largest TNOs and displays a highly elongated shape and hosts two moons, covered with crystalline water ice like Hamuea. Haumea is also the largest member of the sole TNO family known to date. A catastrophic collision is likely responsible for its unique characteristics. We report here on the analysis of a new set of observations of Haumea obtained with SINFONI at the ESO VLT. Combined with previous data, and using light-curve measurements in the optical and far infrared, we carry out a rotationally resolved spectroscopic study of the surface of Haumea. We describe the physical characteristics of the crystalline water ice present on the surface of Haumea for both regions, in and out of the Dark Red Spot (DRS), and analyze the differences obtained for each individual spectrum. The presence of crystalline water ice is confirmed over more than half of the surface of Haumea. Our measurements of the average spectral slope confirm the redder characteristic of the spot region. Detailed analysis of the crystalline water-ice absorption bands do not show significant differences between the DRS and the remaining part of the surface. We also present the results of applying Hapke modeling to our data set. The best spectral fit is obtained with a mixture of crystalline water ice (grain sizes smaller than 60 micron) with a few percent of amorphous carbon. Improvements to the fit are obtained by adding ~10% of amorphous water ice. Additionally, we used the IFU-reconstructed images to measure the relative astrometric position of the largest satellite Hi`iaka and determine its orbital elements. An orbital solution was computed with our genetic-based algorithm GENOID and our results are in full agreement with recent results., Comment: Accepted for publication in A&A

We present a measurement of H2O ice crystallinity on the surface of trans-neptunian objects (TNOs) with near-infrared narrow-band imaging. The newly developed photometric technique allows us to efficiently determine the strength of an 1.65-um absorption feature in crystalline H2O ice. Our data for three large objects, Haumea, Quaoar, and Orcus, which are known to contain crystalline H2O ice on the surfaces, show a reasonable result with high fractions of the crystalline phase. It can also be pointed out that if the H2O-ice grain size is larger than ~20 um, the crystallinities of these objects are obviously below 1.0, which suggest the presence of the amorphous phase. Especially, Orcus exhibits a high abundance of amorphous H2O ice compared to Haumea and Quaoar, possibly indicating a correlation between bulk density of the bodies and surface crystallization degree. We also found the presence of crystalline H2O ice on Typhon and 2008 AP129, both of which are smaller than the minimum size limit for inducing cryovolcanism as well as a transition from amorphous to crystalline through the thermal evolution due to the decay of long-lived isotopes., 31 pages, 7 figures, 6 tables, accepted for publication in ApJ

The purpose of this paper consists in constructing the near-equilibrium model of the dwarf planet Haumea and developing the latent mechanism of accumulation of icy masses at sharp ends of the rapidly rotating planet. The model can be introduced by combining the ellipsoidal stone core with confocal icy shell and represents a non-uniform figure of rotating gravitating mass with superficial tension from the icy layer. We thoroughly study its dynamic properties and achieve that the gravitational potential on an external and intermediate (between the core and the mantle) surfaces was square-law function from coordinates. Using the new rigorous method we found that the thickness of an ice shell is equal to $h \approx 30\mbox{ km}$ , and its mass makes only 6.6 % from mass of a stone core. In absence of coherence between two surfaces of level, there is a growth of stresses and restructuring the core and the shell. It is found that the difference between angular velocities on both surfaces doesn’t exceed 6 %, which activates a special mechanism of relaxation. The relaxation may lead to considerable (up to 10 %) lengthening the equatorial size of the body. This restructuring the shell leads to accumulation of icy masses at the sharp ends of the planet, which then separate from Haumea. For formation of two satellites of the planet Haumea it has been spent only 8 % from the mass of a shell. Before separation of satellites the planet Haumea was in near-equilibrium state, and its angular momentum was at 1.13 more, and the period of rotation was $16^{m}$ shorter and made $T \approx 3.64\mbox{ h}$ . The mechanism predicts that the orbits of satellites can not deviate much from the equatorial plane of Haumea. This is consistent with observations: indeed, the orbit of Namaka is almost in the equatorial plane, and the orbit of massive Hi’iaka deviates only on 13°. The new mechanism can be useful also for studying the evolution of other ice-cover planets and satellites.

Recently, the first collisional family was identified in the trans-Neptunian belt. The family consists of Haumea and at least ten other ~100km-sized trans-Neptunian objects (TNOs) located in the region a = 42 - 44.5 AU. In this work, we model the long-term orbital evolution of an ensemble of fragments representing hypothetical post-collision distributions at the time of the family's birth. We consider three distinct scenarios, in which the kinetic energy of dispersed particles were varied such that their mean ejection velocities (veje) were of order 200 m/s, 300 m/s and 400 m/s, respectively. Each simulation considered resulted in collisional families that reproduced that currently observed. The results suggest that 60-75% of the fragments created in the collision will remain in the trans-Neptunian belt, even after 4 Gyr of dynamical evolution. The surviving particles were typically concentrated in wide regions of orbital element space centred on the initial impact location, with their orbits spread across a region spanning {\Delta}a ~ 6-12 AU, {\Delta}e ~ 0.1-0.15 and {\Delta}i ~ 7-10{\deg}. Most of the survivors populated the so-called Classical and Detached regions of the trans-Neptunian belt, whilst a minor fraction entered the Scattered Disk reservoir (

Observations of the distant dwarf planet Haumea constrain its size, shape and density, and reveal an encircling planetary ring. The discovery suggests that rings are not as rare in the Solar System as previously thought. See Letter p.219 Haumea is a dwarf planet beyond the orbit of Neptune. It is rapidly rotating and very elongated, unlike the other three known trans-Neptunian dwarf planets. Jose Ortiz and collaborators obtained observations from multiple Earth-based telescopes as Haumea passed in front of a background star. This occultation enabled the team to constrain the density of Haumea to an upper limit of about 1,885 kilograms per cubic metre. They also constrained its ellipsoid shape and albedo (0.51). They did not detect an atmosphere around the planet, but found a ring circling it. They determined that the ring is 70 kilometres wide, has a radius of about 2,287 kilometres and lies in the same orbital plane as Haumea's equator and largest moon. It has an orbital period that is three times the spin period of Haumea. The ring absorbed roughly half of the star light coming through, giving it an opacity of 0.5.