Contents of: VI/111/./abstract/SDERMOTT_ZCPOLES1.abs

The following document lists the file abstract/SDERMOTT_ZCPOLES1.abs from catalogue VI/111.
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Using ISO we propose to confirm the existence of asymmetries in the zodiacal
cloud discovered by analzing COBE data from the North and South ecliptic poles.
This work is an extension of a previous proposal, SDERMOTT.ETRING_1, to
investigate the structure of the zodiacal cloud. While the COBE data provides
excellent results of great scientific significance, COBE only observed for 9
months of the year. Hence, we need results from ISO to cover the remaining 3
months with a slight amount of overlap so that comparisons can be made with the
existing COBE data. Using the 25 micron wave band COBE data on the variation
with the longitude of Earth of the brightness of the North and South ecliptic
poles, we have determined the variation of the number density of particles in
the zodiacal cloud with heliocentric distance and discovered that it does not
follow a simple Poynting-Robertson light drag model, implying either that
asteroidal particles are lost from the system as they spiral in towards the Sun
and/or that the cloud has a significant component of cometary material. More ISO
data will produce a better fit to our existing data and thus a more accurate
measure of the number density gradient. By looking at the COBE ecliptic pole
data near the Earth's apocenter, we have also determined that the center of
rotational symmetry of the cloud is displaced from the Sun. However, we are
missing essential data near the Earth's pericenter which ISO could provide.
Finally, the COBE ecliptic pole data has allowed us to place constraints on the
percentage of the zodiacal cloud that is asteroidal in origin. Additional ISO
data for the three months missed by COBE will help us place an even tighter
constraint on this percentage. Even if ISO observations are obtained only in the
25 micron wave band, which is our first priority, they will be highly useful.
However, in order of decreasing priority, we would also like the same set of
observations to be made at 11.5, 60, and 4.85 microns. Understanding the
structure and dynamics of the zodiacal cloud will help us interpret observations
of the structure and evolution of disks around other stars. It will also place
constraints on the collisional evolution of the asteroid belt and the long-term
transport of cometary material to the inner solar system.

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