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[Programme]
Session 11:
"Interstellar Meteors and
Dust"
Date: Friday 13.30-16.15
Contemporary Interstellar Meteoroids in the
Solar System: In-situ Measurements and Clues on
Composition
M. Landgraf (ESA/ESOC, 64293 Darmstadt,
Germany)
Meteoroids originating from the local
interstellar medium traverse the solar system. This
has been proven by in situ measurements by
interplanetary spacecraft as well as by highly
sensitive radar measurements. Early attempts to
detect interstellar meteoroids using the
instruments on board the Pioneer 8 and 9 spacecraft
failed. More sensitive detectors on board the joint
ESA/NASA mission Ulysses as well as on board the
NASA spacecraft Galileo, however, unambiguously
detected meteoroids of interstellar origin. This
discovery has started efforts to compare the
results from the in situ measurements with highly
sophisticated models of interstellar dust
properties derived from astronomical absorption and
extinction measurements. It was found that, at
least locally, is more mass locked up in meteoroids
than expected from the astronomical measurements.
So far the in situ measurements only allow to
derive composition information indirectly via the
meteoroid's dynamics. 11.1
Properties of Interstellar Dust Derived From
In-Situ Measurements and Extinction
Observations
Hiroshi Kimura and Ingrid Mann
Already since the 1930s observations of the
extinction of stellar radiation have revealed the
presence of dust in interstellar space. The
spectral variation of the interstellar extinction
was classically used to infer the size and
composition of interstellar dust along the line of
sight of observations. Current models also apply
measurements of elemental abundances in
interstellar space to place constraints on the dust
compositions. During the past decade, interstellar
dust particles that enter the solar system have
been identified with in situ measurements from
spacecraft. Analyses of these in situ data provide
information on the properties of dust in the local
interstellar cloud, in which the solar system is
embedded. In this review, we first discuss problems
with current models when compared to the
experimental results and laboratory analyses of
presolar grains. We present an update on the status
of our modeling, in which the properties of
interstellar dust are consistent with astronomical
observations and in situ experiments. We finally
discuss possibilities for future studies and
in-situ measurements. 11.2
Arecibo Detection of a "Large" Mass Component
in the Ulysses Interstellar Dust Flow
David Meisel (1, 2), Diego Janches (2, 3)
and John Mathews (2)
1) SUNY-Geneseo; 2) CSSL-PSU; 3) Swedish
Institute of Space Physics, Kiruna, Sweden;
diego.janches@irf.se
Micrometeoroids detected with the Arecibo UHF
radar have hyperbolic heliocentric velocities as
well as measurable atmospheric drag decelerations.
Thus both orbits and sizes can be inferred.
Evidence is presented for the discovery of a large
size (10 microns> radius >0.2 micron)
component of the Ulysses interstellar particle
flow. The mean velocity of these "large" particles
is somewhat higher than for the mean of the Ulysses
particles themselves, but when the Arecibo particle
velocity vectors are transformed to system moving
at their average velocity, good coincidence with
the Ulysses radiant is found. Larger extrasolar
particles (>10 microns radius) have been
detected, but they do not correlate well with the
Ulysses radiant. PSB-21
The Size Distribution of Arecibo ISPs and its
Implications
David Meisel (1, 2), Diego Janches (2, 3)
and John Mathews (2)
1) SUNY-Geneseo; 2) CSSL-PSU; 3) Swedish
Institute of Space Physics, Kiruna, Sweden;
diego.janches@irf.se
Extrasolar particles observed at Arecibo and
deemed to be true interstellar particles display a
lognormal distribution of sizes. The radii also
correlate with their original hyperbolic, solar
system impact parameters. The upper end of the
observed distribution occurs for particles on the
order of 10 microns radius, while the lower end of
the observed distribution occurs for particles ten
times smaller. Such a distribution is
characteristic of a "breakage" process (Wadsworth,
1990) and has been shaped by various creation and
loss processes during transit from their source
regions to the earth. The observed size limits
agree quite well with models attempting to explain
Ulysses spacecraft observations. 11.7
Expected Distribution of Interstellar
Meteoroids in the Vicinity of the Earth's
Orbit
O.I. Belkovich and A.R. Bagautdinova
(Zelenodolsk Branch of the Kazan State University,
Russia)
One of the hypotheses of origination of
interstellar meteoroids is the lost them by
planetary systems of the late spectral class stars.
In this case the most probable distribution of
their velocities relative the local centroid of
stars mast be similar to one of the late class
stars. This distribution has been found from the
catalogue of star ray velocities. The orbital
element distributions of interstellar meteoroids in
the vicinity of the Earth's orbit and radiant and
velocity distributions over the celestial sphere in
the heliocentric and geocentric frame of references
have been calculated taking into account of
meteoroid flux transformation due to the Sun
gravitation field and moving the Sun and Earth
relatively the local centroid of stars. PSB-22
Interstellar Particle Detection and Selection
Criteria of the Meteor Streams
B.L. Kashcheev and S.V. Kolomiyets
(Kharkiv State Technical University of
Radioelectronics, Lenin av., 14, Kharkiv, 61166,
Ukraine)
There is a hypothesis on possible exposure of
interstellar particles from kinematics discussions.
If interstellar meteors are present among the
observed meteoroids with hyperbolic orbits, then
their heliocentric velocity distribution must
correspond to distribution of radial velocities of
close stars Thus, heliocentric velocity of
interstellar meteoroids equals to 46.6 km/sec.
Moreover, a concentration of meteor radiants to the
apex of the Sun should be observed for interstellar
meteoroids. In the paper there has been examined
probable distribution of number of interstellar
meteoroids. By appraisals of Belkovich O. I.,
Potapov I. N., 1985, Kazantsev A. M., 1998, the nor
less than 75% of interstellar particles which are
observed on the Earth are distributed in the
interval from 1 to 1,1. This interval of the
eccentricity is typical the eccentricity and for
orbits which have become hyperbolic because of
errors of their definition. The same the
eccentricity will belong to orbits of meteor
bodies, which have become hyperbolic because of
narrow rapprochement with planets. It is
investigated the opportunity of division the
observation orbital radiometeor data, with the
eccentricity, which exceeds one, according to
mechanism of their formation with the goal of
search the orbits of interstellar particles. They
are adduced the results of search the orbits of
interstellar particles by criterions which are
based on analysis of orbital elements and on
limitations which associates with conditions of
observation such particles on the Earth. The
eccentricity of 2303 investigated hyperbolic orbits
is in the interval from 1 to 2. The approbation of
search were made on the different samples from
observation material, which volume is more than 7
thousands hyperbolic and about parabolic orbits of
unique Kharkiv electronic catalogue 160000 orbits
of radiometeors to +12 starry size that were
registered in 1972-1978 years. 111 meteoroid
hyperbolic orbits with 1<e<2 were foundduring
21 March, 20 days before and 20 days after this
date (data for 1972-1978). Distribution of their
parameters is given. It is possible that there is a
certain number of interstellar meteoroids. 11.4
Dust Astronomy
Eberhard Gruen (MPI-Kernphysik, Heidelberg)
Dust particles, like photons, are born at remote
sites in space and time, and carry from there
information that may not be accessible to direct
investigation. From knowledge of the dust
particles' birthplace and the particles' bulk
properties, we can learn about the remote
environment out of which the particles were formed.
This approach is called dust astronomy which is
carried out by means of dust telescopes on dust
observatories in space. Targets for dust telescopes
are dust from the local interstellar medium, meteor
stream dust, cometary, asteroidal, and lunar dust,
and space debris. Dust particles' trajectories are
determined by in-situ dust detectors with narrow
apertures and by the measurements of the electric
charge signals that are induced when the charged
grains fly through appropriately configured grid
systems. Modern in-situ dust detectors are capable
of providing mass, speed, physical and chemical
information of dust grains in space. A "dust
telescope" can, therefore, be considered as a
combination of detectors for dust particle
trajectories along with detectors for physical and
chemical analysis of dust particles. A
state-of-the-art dust telescope will consist of an
array of parallel-mounted dust instruments, which
share a common impact plane of at least one square
meter in size. 11.5
Mapping the Interstellar Dust Flow into the
Solar System Using AMOR
Jack Baggaley (Department of Physics and
Astronomy, University of Canterbury, Christchurch,
New Zealand)
The Advanced Meteor Orbit Radar facility (AMOR)
monitors the dynamical properties of meteoroids of
sizes down to about 40 micrometres. The orbital
data set secured to date contains about 10^6
orbits. The population of inner solar system
meteoroids sampled contains a significant
proportion of particles that are moving in unbound
solar orbits. Maps the far-sun inflow directions of
this extra-solar system population show the
presence of both a broad interstellar inflow and
discrete sources. 11.6
Dust and Meteoroids in Extra-solar Planetary
Systems
Ingrid Mann (1, 2) and Malcolm Fridlund
(1)
1) ESA Space Science Department, ESTEC,
Noordwijk, The Netherlands; 2)Institute of
Planetology, University of Münster,
Münster, Germany
Basic properties of the evolution of the solar
system meteoritic complex are also expected to be
important for the evolution of circum-stellar
debris disks: Mutual Collisions and Poynting
Robertson effect limit the lifetime of dust
particles in Keplerian orbits around stars if the
density of circum-stellar gas is sufficiently
small. While "dense" dust shells such as the shell
around Beta - Pic are limited by collision
lifetime, mutual collisions get less important for
systems with lower dust density. The evolution of
dust and meteoroids >from their sources can
cause, similar to meteor streams, local features in
circum-stellar dust shells. We discuss the
compatibility of solar system and "extra-solar"
conditions for the evolution of planetesimals,
meteoroids and dust particles. 11.3
Possibility of Meteor Path Determination by
Records in Ancient Chinese Local Gazetteers
Nogami Nagatoshi
It is well known that many meteor observations
were described in ancient Chinese local records.
Especially in Ch'ing dynasty period (1644-1912),
some of them are recorded with event time, path
direction and observation location. By scanning
these factors precisely possibility of meteor path
determination can be thought. In this presentation,
four probable examples in 1891, 1873, 1672 and 1661
are shown and their characteristics discussed.
PSB-23
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