Search Publications
The Detection of a Population of Submillimeter-Bright, Strongly Lensed Galaxies
Smail, I.; Rodighiero, G.; Valtchanov, I. +86 more
Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging …
A Low-Magnetic-Field Soft Gamma Repeater
Tiengo, A.; Götz, D.; Mereghetti, S. +8 more
Soft gamma repeaters (SGRs) and anomalous x-ray pulsars form a rapidly increasing group of x-ray sources exhibiting sporadic emission of short bursts. They are believed to be magnetars, that is, neutron stars powered by extreme magnetic fields, B ~ 1014 to 1015 gauss. We report on a soft gamma repeater with low magnetic field…
CoRoT Reveals a Magnetic Activity Cycle in a Sun-Like Star
Metcalfe, Travis S.; García, Rafael A.; Mathur, Savita +4 more
The 11-year activity cycle of the Sun is a consequence of a dynamo process occurring beneath its surface. We analyzed photometric data obtained by the CoRoT space mission, showing solarlike oscillations in the star HD49933, for signatures of stellar magnetic activity. Asteroseismic measurements of global changes in the oscillation frequencies and …
Variations in the Sun’s Meridional Flow over a Solar Cycle
Hathaway, David H.; Rightmire, Lisa
The Sun’s meridional flow is an axisymmetric flow that is generally directed from its equator toward its poles at the surface. The structure and strength of the meridional flow determine both the strength of the Sun’s polar magnetic field and the intensity of sunspot cycles. We determine the meridional flow speed of magnetic features on the Sun us…
Recent Hotspot Volcanism on Venus from VIRTIS Emissivity Data
Drossart, Pierre; Piccioni, Giuseppe; Helbert, Joern +5 more
The questions of whether Venus is geologically active and how the planet has resurfaced over the past billion years have major implications for interior dynamics and climate change. Nine “hotspots”—areas analogous to Hawaii, with volcanism, broad topographic rises, and large positive gravity anomalies suggesting mantle plumes at depth—have been id…
Gravity Field, Shape, and Moment of Inertia of Titan
Stevenson, David J.; Iess, Luciano; Jacobson, Robert A. +5 more
Precise radio tracking of the spacecraft Cassini has provided a determination of Titan’s mass and gravity harmonics to degree 3. The quadrupole field is consistent with a hydrostatically relaxed body shaped by tidal and rotational effects. The inferred moment of inertia factor is about 0.34, implying incomplete differentiation, either in the sense…
Cosmological constraints from strong gravitational lensing in clusters of galaxies.
Kneib, J. -P.; Jullo, E.; Richard, J. +4 more
Current efforts in observational cosmology are focused on characterizing the mass-energy content of the Universe. We present results from a geometric test based on strong lensing in galaxy clusters. Based on Hubble Space Telescope images and extensive ground-based spectroscopic follow-up of the massive galaxy cluster Abell 1689, we used a parametr…
Detection of Hydrated Silicates in Crustal Outcrops in the Northern Plains of Mars
Bibring, J. -P.; Poulet, F.; Carter, J. +1 more
The composition of the ancient martian crust is a key ingredient in deciphering the environment and evolution of early Mars. We present an analysis of the composition of large craters in the martian northern plains based on data from spaceborne imaging spectrometers. Nine of the craters have excavated assemblages of phyllosilicates from ancient, N…
Cassini Finds an Oxygen-Carbon Dioxide Atmosphere at Saturn’s Icy Moon Rhea
Coates, A. J.; Tokar, R. L.; Jones, G. H. +10 more
The flyby measurements of the Cassini spacecraft at Saturn’s moon Rhea reveal a tenuous oxygen (O2)-carbon dioxide (CO2) atmosphere. The atmosphere appears to be sustained by chemical decomposition of the surface water ice under irradiation from Saturn’s magnetospheric plasma. This in situ detection of an oxidizing atmosphere…
An Evolving View of Saturn’s Dynamic Rings
Clark, R. N.; Nicholson, P. D.; Kempf, S. +20 more
We review our understanding of Saturn’s rings after nearly 6 years of observations by the Cassini spacecraft. Saturn’s rings are composed mostly of water ice but also contain an undetermined reddish contaminant. The rings exhibit a range of structure across many spatial scales; some of this involves the interplay of the fluid nature and the self-g…