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تسجيل مستخدم جديدDust Measurements in the Outer Solar System
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Dust measurements in the outer solar system are reviewed. Only the plasma wave instrument on board Voyagers 1 and 2 recorded impacts in the Edgeworth-Kuiper belt (EKB). Pioneers 10 and 11 measured a constant dust flux of 10-micron-sized particles out to 20 AU. Dust detectors on board Ulysses and Galileo uniquely identified micron-sized interstellar grains passing through the planetary system. Impacts of interstellar dust grains onto big EKB objects generate at least about a ton per second of micron-sized secondaries that are dispersed by Poynting-Robertson effect and Lorentz force. We conclude that impacts of interstellar particles are also responsible for the loss of dust grains at the inner edge of the EKB. While new dust measurements in the EKB are in an early planning stage, several missions (Cassini and STARDUST) are en route to analyze interstellar dust in much more detail.
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The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse almost perpendicular to the ecliptic plane (inclination 79 deg, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. The in-situ dust
detector on board continuously measured interstellar dust grains with masses up to 10^-13 kg, penetrating deep into the solar system. The flow direction is close to the mean apex of the Suns motion through the solar system and the grains act as tracers of the physical conditions in the local interstellar cloud (LIC). While Ulysses monitored the interstellar dust stream at high ecliptic latitudes between 3 and 5 AU, interstellar impactors were also measured with the in-situ dust detectors on board Cassini, Galileo and Helios, covering a heliocentric distance range between 0.3 and 3 AU in the ecliptic plane. The interstellar dust stream in the inner solar system is altered by the solar radiation pressure force, gravitational focussing and interaction of charged grains with the time varying interplanetary magnetic field. We review the results from in-situ interstellar dust measurements in the solar system and present Ulysses latest interstellar dust data. These data indicate a 30 deg shift in the impact direction of interstellar grains w.r.t. the interstellar helium flow direction, the reason of which is presently unknown.
I make publicly available my literature study into carbon isotope ratios in the Solar System, which formed a part of Woods & Willacy (2009). As far as I know, I have included here all measurements of 12C/13C in Solar System objects (excluding those o
f Earth) up to and including 1 February 2010. Full references are given. If you use the any of the information here, please reference the paper Woods & Willacy (2009) and this publication.
The in-situ detection of interstellar dust grains in the Solar System by the dust instruments on-board the Ulysses and Galileo spacecraft as well as the recent measurements of hyperbolic radar meteors give information on the properties of the interst
ellar solid particle population in the solar vicinity. Especially the distribution of grain masses is indicative of growth and destruction mechanisms that govern the grain evolution in the interstellar medium. The mass of an impacting dust grain is derived from its impact velocity and the amount of plasma generated by the impact. Because the initial velocity and the dynamics of interstellar particles in the Solar System are well known, we use an approximated theoretical instead of the measured impact velocity to derive the mass of interstellar grains from the Ulysses and Galileo in-situ data. The revised mass distributions are steeper and thus contain less large grains than the ones that use measured impact velocities, but large grains still contribute significantly to the overall mass of the detected grains. The flux of interstellar grains with masses $> 10^{-14} {rm kg}$ is determined to be $1cdot 10^{-6} {rm m}^{-2} {rm s}^{-1}$. The comparison of radar data with the extrapolation of the Ulysses and Galileo mass distribution indicates that the very large ($m > 10^{-10} {rm kg}$) hyperbolic meteoroids detected by the radar are not kinematically related to the interstellar dust population detected by the spacecraft.
We report the discovery and orbit determination of 14 trans-Neptunian objects (TNOs) from the ESSENCE Supernova Survey difference imaging dataset. Two additional objects discovered in a similar search of the SDSS-II Supernova Survey database were rec
overed in this effort. ESSENCE repeatedly observed fields far from the Solar System ecliptic (-21 deg < beta < -5 deg), reaching limiting magnitudes per observation of I~23.1 and R~23.7. We examine several of the newly detected objects in detail, including 2003 UC_414 which orbits entirely between Uranus and Neptune and lies very close to a dynamical region that would make it stable for the lifetime of the Solar System. 2003 SS_422 and 2007 TA_418 have high eccentricities and large perihelia, making them candidate members of an outer class of trans-Neptunian objects. We also report a new member of the extended or detached scattered disk, 2004 VN_112, and verify the stability of its orbit using numerical simulations. This object would have been visible to ESSENCE for only ~2% of its orbit, suggesting a vast number of similar objects across the sky. We emphasize that off-ecliptic surveys are optimal for uncovering the diversity of such objects, which in turn will constrain the history of gravitational influences that shaped our early Solar System.
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stellar grains act as tracers of the physical conditions in the local interstellar medium surrounding our solar system. Earlier analyses of the Ulysses ISD data measured between 1992 and 1998 implied the existence of big ISD grains [up to 10^-13kg]. The derived gas-to-dust-mass ratio was smaller than the one derived from astronomical observations, implying a concentration of ISD in the very local interstellar medium. We analyse the entire data set from 16 yr of Ulysses ISD measurements in interplanetary space. This paper concentrates on the overall mass distribution of ISD. An accompanying paper investigates time-variable phenomena in the Ulysses ISD data, and in a third paper we present the results from dynamical modelling of the ISD flow applied to Ulysses. We use the latest values for the interstellar hydrogen and helium densities, the interstellar helium flow speed of v_ISM,inf=23.2km/s, and the ratio of radiation pressure to gravity, beta, calculated for astronomical silicates. We find a gas-to-dust-mass ratio in the local interstellar cloud of R_g/d=193^+85_-57, and a dust density of 2.1+/-0.6x10^-24kg/m^3. For a higher inflow speed of 26km/s, the gas-to-dust-mass ratio is 20% higher, and, accordingly, the dust density is lower by the same amount. The gas-to-dust mass ratio derived from our new analysis is compatible with the value most recently determined from astronomical observations. We confirm earlier results that the very local interstellar medium contains big (i.e. 1 um-sized) ISD grains. We find a dust density in the local interstellar medium that is a factor of three lower than values implied by earlier analyses.
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