249 research outputs found
Constraints on the composition of Jupiter's stratospheric aerosols from ultraviolet photometry
The absolute reflectivity of Jupiter has been obtained in 50 A-wide regions centering on 0.221, 0.233, 0.252, and 0.330 microns from three series of IUE satellite spectra taken in November 1979. The data indicate a strong decrease in reflectivity for latitudes greater than about 30 deg, in keeping with Voyager measurements. An additional 24 spectra were also obtained in a west-east series along the equator, as well as near 40 deg N latitude. These data favor models in which the haze particles have effective radii within a factor of 2 of 0.2 microns. Near the equator, the haze aerosols produce much less absorption than near 40 deg N; the aerosol distributions and optical properties derived are noted to be more dependent on the assumed location and reflectivity of the top of the tropospheric cloud
Limb polarization of Uranus and Neptune. II Spectropolarimetric observations
We have detected a strong limb polarization for Uranus and Neptune. With
spectropolarimetric observations we characterize the spectral dependence of
this limb polarization and explore the diagnostic potential for investigating
the distribution and properties of the scattering particles. We present disk
resolved spectropolarimetry of Uranus and Neptune covering the wavelength range
from 530nm to 930nm and compare the spectropolarimetric signal for different
limb sections and the center of the planetary disk. As an additional benefit we
obtained center-to-limb disk profiles for the intensity and polarization for
various wavelengths.Comment: Accepted by A&A 24.11.200
Tidal disruption of satellites and formation of narrow rings
In this paper we investigate the formation of narrow planetary rings such as
those found around Uranus and Saturn through the tidal disruption of a weak,
gravitationally bound satellite that migrates within its Roche limit. Using
-body simulations, we study the behaviour of rubble piles placed on circular
orbits at different distances from a central planet. We consider both
homogeneous satellites and differentiated bodies containing a denser core. We
show that the Roche limit for a rubble pile is closer to the planet than for a
fluid body of the same mean density. The Roche limit for a differentiated body
is also closer to the planet than for a homogeneous satellite of the same mean
density. Within its Roche limit, a homogeneous satellite totally disrupts and
forms a narrow ring. The initial stages of the disruption are similar to the
evolution of a viscous fluid ellipsoid, which can be computed
semi-analytically. On the other hand, when a differentiated satellite is just
within the Roche limit only the mantle is disrupted. This process is similar to
Roche-lobe overflow in interacting binary stars and produces two narrow rings
on either side of a remnant satellite. We argue that the Uranian rings, and
possibly their shepherd satellites, could have been formed through the tidal
disruption of a number of protomoons that were formed inside the corotation
radius of Uranus and migrated slowly inwards as a result of tidal interaction
with the planet.Comment: Accepted for publication in MNRAS. Some figures have been compressed
to fit into astro-ph size guidelines. Please contact authors if full
resolution images are require
A grid of polarization models for Rayleigh scattering planetary atmospheres
We investigate the intensity and polarization of reflected light from
planetary atmospheres. We present a large grid of Monte Carlo simulations for
planets with Rayleigh scattering atmospheres. We discuss the disk-integrated
polarization for phase angles typical of extrasolar planet observations and for
the limb polarization effect observable for solar system objects near
opposition. The main parameters investigated are single scattering albedo,
optical depth of the scattering layer, and albedo of an underlying Lambert
surface for a homogeneous Rayleigh scattering atmosphere. We also investigate
atmospheres with isotropic scattering and forward scattering aerosol particles,
as well as models with two scattering layers.
The model grid provides a tool for extracting quantitative results from
polarimetric measurements of planetary atmospheres from solar system planets
and extrasolar planets, in particular on the scattering properties and
stratification of particles in the highest atmosphere layers.
Spectropolarimetry of solar system planets offers complementary information to
spectroscopy and polarization flux colors can be used for a first
characterization of exoplanet atmospheres. From limb polarization measurements,
one can set constraints on the polarization at large phase angles.Comment: 19 pages, 21 figures. Minor changes. Published in Astronomy and
Astrophysic
Recommended from our members
Exploring the seas of Titan: the Titan Mare Eplorer (TiME) mission
Recommended from our members
Titan Mare Explorer (TiME): first in situ exploration of an extraterrestrial sea
The lakes and seas of Titan are a sink of products of photolysis in the atmosphere, and a crucial component in Titan's active methane cycle. In situ exploration of the seas is necessary to understand their intriguing prebiotic organic chemistry
Assessing the influence of one astronomy camp over 50 years
The International Astronomical Youth Camp has benefited thousands of lives
during its 50-year history. We explore the pedagogy behind this success, review
a survey taken by more than 300 previous participants, and discuss some of the
challenges the camp faces in the future.Comment: 10 pages, 4 figure
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