Author
A. Dias-Oliveira
Other affiliations: Michigan Career and Technical Institute
Bio: A. Dias-Oliveira is an academic researcher from Janssen Pharmaceutica. The author has contributed to research in topics: Pluto & Atmosphere. The author has an hindex of 10, co-authored 15 publications receiving 282 citations. Previous affiliations of A. Dias-Oliveira include Michigan Career and Technical Institute.
Topics: Pluto, Atmosphere, Ephemeris, Surface pressure, Occultation
Papers
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TL;DR: In this paper, the authors present results from a multi-chord Pluto stellar occultation observed on 29 June 2015 from New Zealand and Australia, which occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results.
Abstract: We present results from a multi-chord Pluto stellar occultation observed on 29 June 2015 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results. We find that Pluto's atmosphere is still expanding, with a significant pressure increase of 5$\pm$2\% since 2013 and a factor of almost three since 1988. This trend rules out, as of today, an atmospheric collapse associated with Pluto's recession from the Sun. A central flash, a rare occurrence, was observed from several sites in New Zealand. The flash shape and amplitude are compatible with a spherical and transparent atmospheric layer of roughly 3~km in thickness whose base lies at about 4~km above Pluto's surface, and where an average thermal gradient of about 5 K~km$^{-1}$ prevails. We discuss the possibility that small departures between the observed and modeled flash are caused by local topographic features (mountains) along Pluto's limb that block the stellar light. Finally, using two possible temperature profiles, and extrapolating our pressure profile from our deepest accessible level down to the surface, we obtain a possible range of 11.9-13.7~$\mu$bar for the surface pressure.
40 citations
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Pierre-and-Marie-Curie University1, Southwest Research Institute2, Spanish National Research Council3, Federal University of Rio de Janeiro4, California Polytechnic State University5, PSL Research University6, University of Nevada, Reno7, Lowell Observatory8, National Autonomous University of Mexico9, Harvard University10
TL;DR: In this paper, the authors present results derived from the first multi-chord stellar occultation by the trans-Neptunian object (229762) 2007 UK$ 126, observed on 2014 November 15.
Abstract: We present results derived from the first multi-chord stellar occultation by the trans-Neptunian object (229762) 2007 UK$_{126}$, observed on 2014 November 15. The event was observed by the Research and Education Collaborative Occultation Network (RECON) project and International Occultation Timing Association (IOTA) collaborators throughout the United States. Use of two different data analysis methods obtain a satisfactory fit to seven chords, yelding an elliptical fit to the chords with an equatorial radius of $R=338_{-10} ^{+15}$ km and equivalent radius of $R_{eq}=319_{-7} ^{+14}$ km. A circular fit also gives a radius of $R=324_{-23} ^{+30}$ km. Assuming that the object is a Maclaurin spheroid with indeterminate aspect angle, and using two published absolute magnitudes for the body, we derive possible ranges for geometric albedo between $p_{V}=0.159_{-0.013} ^{+0.007}$ and $p_{R}=0.189_{-0.015}^{+0.009}$, and for the body oblateness between $\\epsilon=0.105_{-0.040} ^{+0.050}$ and $\\epsilon=0.118_{-0.048} ^{+0.055}$. For a nominal rotational period of 11.05 h, an upper limit for density of $\\rho=1740$ kg~m$^{-3}$ is estimated for the body.
38 citations
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TL;DR: In this paper, a central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or hazes with tangential optical depth of ~0.3 are present at 4-7 km altitude levels.
Abstract: Context. The tenuous nitrogen (N2 ) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft.Aims. The main goals of this study are (i ) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii ) to constrain the structure of the lower atmosphere using a central flash observed in 2015.Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μ bar to 10 nbar).Results. (i ) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii ) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere.
37 citations
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TL;DR: In this paper, the authors predict stellar occultations from 2012.5 to the end of 2014 by 5 Centaurs and 34 TNOs from the International Celestial Reference System (ICRS) as realised by the Fourth US Naval Observatory CCD Astrograph catalog (UCAC4).
Abstract: Context. We study trans-Neptunian objects (TNOs) from stellar occultations.Aims. We predict stellar occultations from 2012.5 to the end of 2014 by 5 Centaurs and 34 TNOs.Methods. These predictions were achieved in two ways: first, we built catalogues with precise astrometric positions of the stellar content around the paths on the sky of these targets, as seen by a ground-based observer; second, the observed positions of the targets were determined with the help of these same catalogues so that we could improve their ephemerides and the reliability of the predictions. The reference system is the International Celestial Reference System (ICRS) as realised by the Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). All the sky paths as well as the selected targets were observed from Oct. 2011 to May 2013 with the ESO/MPG 2.2 m telescope equipped with the Wide Field Imager (WFI). All astrometric results were obtained with the platform for reduction of astronomical images automatically (PRAIA) after correcting the images for overscan, bias, and flatfield.Results. The catalogues with the stellar content around the sky path of each selected target are complete down to magnitude R = 19 and have an average positional accuracy of about 50 milliarcseconds. This same average accuracy also holds for the observed positions of the targets. In the catalogues from the sky paths, stellar proper motions for non-UCAC4 objects were derived from the combination of the current epoch WFI observations with either the 2MASS or the USNO-B1 catalogues. The offsets between the observed and (JPL) ephemeris positions of the targets frequently reach absolute values of some hundreds of milliarcseconds.Conclusions. We present here stellar occultation predictions for the selected 5 Centaurs and 34 TNOs from 2012.5 to the end of 2014. This work is also an extension of two previous prediction works by us, the first one for Pluto, Charon, Nix, and Hydra, and the second for ten other large TNOs. The use of catalogues from the observations of the sky paths in the astrometry of the TNOs and Centaurs enhanced the coherence between their positions and those of the respective occulted candidate stars. New observations of these TNOs and Centaurs are continuously used to redetermine their ephemerides.
30 citations
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TL;DR: In this paper, the authors analyzed two multi-chord stellar occultations by Pluto observed on July 18th, 2012 and May 4th, 2013, and monitored respectively from five and six sites.
Abstract: We analyze two multi-chord stellar occultations by Pluto observed on July 18th, 2012 and May 4th, 2013, and monitored respectively from five and six sites. They provide a total of fifteen light-curves, twelve of them being used for a simultaneous fit that uses a unique temperature profile, assuming a clear (no-haze) and pure N_2 atmosphere, but allowing for a possible pressure variation between the two dates. We find a solution that fits satisfactorily (i.e. within the noise level) all the twelve light-curves, providing atmospheric constraints between ~1,190 km (pressure ~ 11 \mubar) and ~ 1,450 km (pressure ~0.1 \mubar) from Pluto's center. Our main results are: (1) the best-fitting temperature profile shows a stratosphere with strong positive gradient between 1,190 km (at 36 K, 11 \mubar) and r = 1,215 km (6.0 \mubar), where a temperature maximum of 110 K is reached; above it is a mesosphere with negative thermal gradient of -0.2 K/km up to ~ 1,390 km (0.25 \mubar), where, the mesosphere connects itself to a more isothermal upper branch around 81 K; (2) the pressure shows a small (6 %) but significant increase (6-\sigma level) between the two dates; (3) without troposphere, Pluto's radius is found to be R_P = 1,190 +/- 5km. Allowing for a troposphere, R_P is constrained to lie between 1,168 and 1,195 km; (4) the currently measured CO abundance is too small to explain the mesospheric negative thermal gradient. Cooling by HCN is possible, but only if this species is largely saturated; Alternative explanations like zonal winds or vertical compositional variations of the atmosphere are unable to explain the observed mesospheric trend.
29 citations
Cited by
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Michigan Career and Technical Institute1, Pierre-and-Marie-Curie University2, Spanish National Research Council3, Max Planck Society4, Federal University of Rio de Janeiro5, Centre national de la recherche scientifique6, University of Liège7, Appalachian State University8, Pontifical Catholic University of Chile9, Ponta Grossa State University10, State University of West Paraná11, National University of Cordoba12, Geological Museum13, University of Copenhagen14, Sao Paulo State University15, University of the Republic16, Chinese Academy of Sciences17, University of Antofagasta18, University of St Andrews19, University of North Carolina at Chapel Hill20, Instituto de Astronomía Teórica y Experimental21
TL;DR: Observations of a multichord stellar occultation revealed the presence of a ring system around (10199) Chariklo, which is a Centaur—that is, one of a class of small objects orbiting primarily between Jupiter and Neptune—with an equivalent radius of 124 9 kilometres.
Abstract: Hitherto, rings have been found exclusively around the four giant planets in the Solar System(1). Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur-that is, one of a class of small objects orbiting primarily between Jupiter and Neptune-with an equivalent radius of 124 +/- 9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming(3) of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period(4,5). This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.
265 citations
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University of Texas at San Antonio1, Southwest Research Institute2, Ames Research Center3, Johns Hopkins University Applied Physics Laboratory4, George Mason University5, Johns Hopkins University6, Stanford University7, Nebraska Wesleyan University8, California Institute of Technology9, Max Planck Society10
TL;DR: Moore et al. as discussed by the authors presented the complex surface features and geology of Pluto and its large moon Charon, including evidence of tectonics, glacial flow, and possible cryovolcanoes.
Abstract: In July 2015, the New Horizons spacecraft flew through the Pluto system at high speed, humanity's first close look at this enigmatic system on the outskirts of our solar system. In a series of papers, the New Horizons team present their analysis of the encounter data downloaded so far: Moore et al. present the complex surface features and geology of Pluto and its large moon Charon, including evidence of tectonics, glacial flow, and possible cryovolcanoes. Grundy et al. analyzed the colors and chemical compositions of their surfaces, with ices of H_2O, CH_4, CO, N_2, and NH_3 and a reddish material which may be tholins. Gladstone et al. investigated the atmosphere of Pluto, which is colder and more compact than expected and hosts numerous extensive layers of haze. Weaver et al. examined the small moons Styx, Nix, Kerberos, and Hydra, which are irregularly shaped, fast-rotating, and have bright surfaces. Bagenal et al. report how Pluto modifies its space environment, including interactions with the solar wind and a lack of dust in the system. Together, these findings massively increase our understanding of the bodies in the outer solar system. They will underpin the analysis of New Horizons data, which will continue for years to come.
224 citations
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Spanish National Research Council1, PSL Research University2, Federal University of Technology - Paraná3, Max Planck Society4, University of Padua5, INAF6, Hungarian Academy of Sciences7, Slovak Academy of Sciences8, Academy of Sciences of the Czech Republic9, German Aerospace Center10, University of Alicante11, University of Zagreb12, European Southern Observatory13, Federal University of Rio de Janeiro14, University of Huelva15, Ege University16, Akdeniz University17, Ondokuz Mayıs University18, Atatürk University19, Çanakkale Onsekiz Mart University20, University of Crete21, Technische Hochschule Mittelhessen22, National and Kapodistrian University of Athens23, University of the Basque Country24, University of Valencia25, University of La Laguna26
TL;DR: Observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation) report the presence of a ring with an opacity of 0.5, which constrains the three-dimensional orientation of Haumesa and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium.
Abstract: 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-IS56-0002. Part of the research leading to these results has received funding from the European Research Council under the European Community’s H2020 (2014-2020/ERC 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.
181 citations
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TL;DR: In this article, the planetary and lunar ephemerides called DE440 and DE441 have been generated by fitting numerically integrated orbits to ground-based and space-based observations, with improved dynamical models and data calibration.
Abstract: The planetary and lunar ephemerides called DE440 and DE441 have been generated by fitting numerically integrated orbits to ground-based and space-based observations. Compared to the previous general-purpose ephemerides DE430, seven years of new data have been added to compute DE440 and DE441, with improved dynamical models and data calibration. The orbit of Jupiter has improved substantially by fitting to the Juno radio range and Very Long Baseline Array (VLBA) data of the Juno spacecraft. The orbit of Saturn has been improved by radio range and VLBA data of the Cassini spacecraft, with improved estimation of the spacecraft orbit. The orbit of Pluto has been improved from use of stellar occultation data reduced against the Gaia star catalog. The ephemerides DE440 and DE441 are fit to the same data set, but DE441 assumes no damping between the lunar liquid core and the solid mantle, which avoids a divergence when integrated backward in time. Therefore, DE441 is less accurate than DE440 for the current century, but covers a much longer duration of years −13,200 to +17,191, compared to DE440 covering years 1550–2650.
128 citations
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Southwest Research Institute1, George Mason University2, Johns Hopkins University3, Search for extraterrestrial intelligence4, Johns Hopkins University Applied Physics Laboratory5, Ames Research Center6, Princeton University7, California Institute of Technology8, University of Reims Champagne-Ardenne9, Stanford University10
TL;DR: The Alice instrument on NASA's New Horizons spacecraft observed an ultraviolet solar occultation by Pluto's atmosphere on 2015 July 14, and derived line-of-sight abundances and local number densities for the 5 molecular species, and line of-sight optical depth and extinction coefficients for the haze.
101 citations