Author
Felipe Braga-Ribas
Other affiliations: Janssen Pharmaceutica, Paris Observatory, Michigan Career and Technical Institute ...read more
Bio: Felipe Braga-Ribas is an academic researcher from Federal University of Technology - Paraná. The author has contributed to research in topics: Occultation & Ephemeris. The author has an hindex of 26, co-authored 88 publications receiving 2070 citations. Previous affiliations of Felipe Braga-Ribas include Janssen Pharmaceutica & Paris Observatory.
Topics: Occultation, Ephemeris, Astrometry, Pluto, Physics
Papers
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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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Pierre-and-Marie-Curie University1, Institut Universitaire de France2, Spanish National Research Council3, Federal University of Rio de Janeiro4, University of Liège5, INAF6, German Aerospace Center7, University of Valencia8, University of Huelva9, Universidade Federal de Minas Gerais10, National Institute for Space Research11, Ponta Grossa State University12, National Autonomous University of Mexico13
TL;DR: The observation of a multi-chord stellar occultation by Eris on 6 November 2010 is reported, consistent with a spherical shape for Eris, and it is anticipated that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.
Abstract: The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163+/-6kilometres, density 2.52+/-0.05 grams per cm3 and a high visible geometric albedo, . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.
194 citations
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Spanish National Research Council1, PSL Research University2, Federal University of Technology - Paraná3, Max Planck Society4, INAF5, University of Padua6, 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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Spanish National Research Council1, Pierre-and-Marie-Curie University2, Paris Diderot University3, European Southern Observatory4, University of Sheffield5, Michigan Career and Technical Institute6, Federal University of Rio de Janeiro7, University of Antofagasta8, University of Liège9, university of lille10, Max Planck Society11, University of Fortaleza12, National Institute for Space Research13, University of Warwick14, Katholieke Universiteit Leuven15, Pontifical Catholic University of Chile16, University of Paraíba Valley17, State University of Santa Cruz18, Ponta Grossa State University19
TL;DR: The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4–12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible.
Abstract: The icy dwarf planet Makemake has projected axes of 1,430 ± 9 and 1,502 ± 45 km and a V-band geometric albedo larger than Pluto’s but smaller than Eris’s, with no global Pluto-like atmosphere. Makemake is thought to be the third-largest dwarf planet in our Solar System, a little smaller than Pluto and Eris, but until now knowledge of its size and albedo were only approximate. This paper reports the results of observations of the occultation of a faint star known as NOMAD 1181-0235723 by Makemake on 23 April 2011. The data confirm that Makemake is smaller than Pluto and Eris, with axes of 1,430±9 km and 1,502±45 km. Makemake's mean geometric albedo — the ratio of light reflected to light received — is intermediate between that of Pluto and that of Eris. All three are icy, making them among the most reflective objects in the Solar System. And the occultation light curves rule out the presence of a global Pluto-like atmosphere on Makemake, although the presence of dark terrain might imply the presence of a localized atmosphere. Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies1,2. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos3. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto4, and is currently at a distance to the Sun intermediate between the two. Although Makemake’s size (1,420 ± 60 km) and albedo are roughly known5,6, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere4,7,8. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 ± 9 km (1σ) and 1,502 ± 45 km, implying a V-band geometric albedo pV = 0.77 ± 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4–12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 ± 0.3 g cm−3 is inferred from the data.
129 citations
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TL;DR: Green et al. as discussed by the authors used near-infrared adaptive optics (AO) imaging with the W.M. Keck II telescope to capture unprecedented high resolution images of this unusual asteroid.
120 citations
Cited by
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Queen Mary University of London1, Spanish National Research Council2, Open University3, Carnegie Institution for Science4, University of Göttingen5, University of Texas at Austin6, University of Chile7, University of Hertfordshire8, University of Warsaw9, Max Planck Society10, University of Montpellier11, Weizmann Institute of Science12, Heidelberg University13
TL;DR: Observations reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units.
Abstract: At a distance of 1.295 parsecs, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun's closest stellar neighbour and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface.
1,052 citations
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TL;DR: DeMeo et al. as mentioned in this paper presented a review of the current knowledge of the density of small bodies and compared with meteorite density, allowing to estimate the macroporosity (i.e., amount of voids) within these bodies.
522 citations
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TL;DR: It is shown that adaptive optics has led to important advances in the authors' understanding of a multitude of astrophysical processes, and how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques.
Abstract: Adaptive Optics is a prime example of how progress in observational astronomy can be driven by technological developments. At many observatories it is now considered to be part of a standard instrumentation suite, enabling ground-based telescopes to reach the diffraction limit and thus providing spatial resolution superior to that achievable from space with current or planned satellites. In this review we consider adaptive optics from the astrophysical perspective. We show that adaptive optics has led to important advances in our understanding of a multitude of astrophysical processes, and describe how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques.
432 citations
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TL;DR: The New Horizons encounter revealed that Pluto displays a surprisingly wide variety of geological landforms, including those resulting from glaciological and surface-atmosphere interactions as well as impact, tectonic, possible cryovolcanic, and mass-wasting processes.
Abstract: The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.
411 citations
01 Feb 2014
TL;DR: In this paper, the planetary and lunar ephemerides DE430 and DE431 are generated by fitting numerically integrated orbits of the Moon and planets to observations, and the present-day lunar orbit is known to submeter accuracy through fitting lunar laser ranging data with an updated lunar gravity field from the Gravity Recovery and Interior Laboratory (GRAIL) mission.
Abstract: The research described in this publication was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. © 2014 California Institute of Technology. U.S. Government sponsorship acknowledged. abstract. — The planetary and lunar ephemerides DE430 and DE431 are generated by fitting numerically integrated orbits of the Moon and planets to observations. The present-day lunar orbit is known to submeter accuracy through fitting lunar laser ranging data with an updated lunar gravity field from the Gravity Recovery and Interior Laboratory (GRAIL) mission. The orbits of the inner planets are known to subkilometer accuracy through fitting radio tracking measurements of spacecraft in orbit about them. Very long baseline interferometry measurements of spacecraft at Mars allow the orientation of the ephemeris to be tied to the International Celestial Reference Frame with an accuracy of 0′′.0002. This orientation is the limiting error source for the orbits of the terrestrial planets, and corresponds to orbit uncertainties of a few hundred meters. The orbits of Jupiter and Saturn are determined to accuracies of tens of kilometers as a result of fitting spacecraft tracking data. The orbits of Uranus, Neptune, and Pluto are determined primarily from astrometric observations, for which measurement uncertainties due to the Earth’s atmosphere, combined with star catalog uncertainties, limit position accuracies to several thousand kilometers. DE430 and DE431 differ in their integrated time span and lunar dynamical modeling. The dynamical model for DE430 included a damping term between the Moon’s liquid core and solid mantle that gives the best fit to lunar laser ranging data but that is not suitable for backward integration of more than a few centuries. The ephemeris DE431 is similar to DE430 but was fit without the core/mantle damping term, so the lunar orbit is less accurate than in DE430 for times near the current epoch, but is more suitable for times more than a few centuries in the past. DE431 is a longer integration (covering years –13,200 to +17,191) than DE430 (covering years 1550 to 2650).
316 citations