Article

The mass of dwarf planet Eris.

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Science (Impact Factor: 31.48). 07/2007; 316(5831):1585. DOI: 10.1126/science.1139415
Source: PubMed

ABSTRACT The discovery of dwarf planet Eris was followed shortly by the discovery of its satellite, Dysnomia, but the satellite orbit, and thus the system mass, was not known. New observations with the Keck Observatory and the Hubble Space Telescopes show that Dysnomia has a circular orbit with a radius of 37,350 +/- 140 (1-sigma) kilometers and a 15.774 +/- 0.002 day orbital period around Eris. These orbital parameters agree with expectations for a satellite formed out of the orbiting debris left from a giant impact. The mass of Eris from these orbital parameters is 1.67 x 10(22) +/- 0.02 x 10(22) kilograms, or 1.27 +/- 0.02 that of Pluto.

0 Followers
 · 
131 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Comet C/1853 E1 (Secchi) has a hyperbolic orbit with eccentricity 1.01060 and perihelion outside of the Earth's orbit. Integrating the orbit with barycentric coordinates backwards to 50000 AU, the approximate edge of the Oort cloud, shows that the orbit remains hyperbolic. This is still true even if plutoids additional to Pluto are included in the integration. Nor does including Galactic tidal and disc effects and possible nongravitational forces change the orbit to a high eccentricity ellipse. Although certain factors, such as unknown massive plutoids, gravitational effects by interstellar gas clouds, or unmodelled nongravitational forces operating on the comet, could change this situation, the tentative conclusion that the origin of this comet is extrasolar remains the one most consistent with the observations (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Astronomische Nachrichten 02/2012; 333(2). DOI:10.1002/asna.201111636 · 1.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aims. The goal of this work is to characterize the ensemble thermal properties of the Centaurs / trans-Neptunian population. Methods. Thermal flux measurements obtained with Herschel/PACS and Spitzer/MIPS provide size, albedo, and beaming factors for 85 objects (13 of which are presented here for the first time) by means of standard radiometric techniques. The measured beaming factors are influenced by the combination of surface roughness and thermal inertia effects. They are interpreted within a thermophysical model to constrain, in a statistical sense, the thermal inertia in the population and to study its dependence on several parameters. We use in particular a Monte-Carlo modeling approach to the data whereby synthetic datasets of beaming factors are created using random distributions of spin orientation and surface roughness. Results. Beaming factors η range from values <1 to ~2.5, but high η values (>2) are lacking at low heliocentric distances (rh < 30 AU). Beaming factors lower than 1 occur frequently (39% of the objects), indicating that surface roughness effects are important. We determine a mean thermal inertia for Centaurs/ TNO of Γ = (2.5 ± 0.5) J m-2 s−1/2 K-1, with evidence of a trend toward decreasing Γ with increasing heliocentric (by a factor ~2.5 from 8–25 AU to 41–53 AU). These thermal inertias are 2–3 orders of magnitude lower than expected for compact ices, and generally lower than on Saturn’s satellites or in the Pluto/Charon system. Most high-albedo objects are found to have unusually low thermal inertias. Our results suggest highly porous surfaces, in which the heat transfer is affected by radiative conductivity within pores and increases with depth in the subsurface.
    Astronomy and Astrophysics 01/2013; 557(2013-A60):1-19. · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Solar and extrasolar planets are the subject of numerous studies aiming to determine their chemical composition and internal structure. In the case of extrasolar planets, the composition is important as it partly governs their potential habitability. Moreover, observational determination of chemical composition of planetary atmospheres are becoming available, especially for transiting planets. The present works aims at determining the chemical composition of planets formed in stellar systems of solar chemical composition. The main objective of this work is to provide valuable theoretical data for models of planet formation and evolution, and future interpretation of chemical composition of solar and extrasolar planets. We have developed a model that computes the composition of ices in planets in different stellar systems with the use of models of ice and planetary formation. We provide the chemical composition, ice/rock mass ratio and C:O molar ratio for planets in stellar systems of solar chemical composition. From an initial homogeneous composition of the nebula, we produce a wide variety of planetary chemical compositions as a function of the mass of the disk and distance to the star. The volatile species incorporated in planets are mainly composed of H2O, CO, CO2, CH3OH, and NH3. Icy or ocean planets have systematically higher values of molecular abundances compared to giant and rocky planets. Gas giant planets are depleted in highly volatile molecules such as CH4, CO, and N2 compared to icy or ocean planets. The ice/rock mass ratio in icy or ocean and gas giant planets is, respectively, equal at maximum to 1.01+-0.33 and 0.8+-0.5, and is different from the usual assumptions made in planet formation models, which suggested this ratio to be 2-3. The C:O molar ratio in the atmosphere of gas giant planets is depleted by at least 30% compared to solar value.
    Astronomy and Astrophysics 07/2014; 570. DOI:10.1051/0004-6361/201423431 · 4.48 Impact Factor

Preview

Download
1 Download
Available from