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Basic Scientific Goals
The fundamental scientific rationale for investigation of extrasolar
planetary materials has been set out in the Introduction to this report
Within this context, basic research goals may be defined for each of the
broad major research areas regarded by COMPLEX as essential compo-
nents of this new field of planetary exploration.
1. The search for and study of evolved extrasolar planetary systems.
Scientific and technological techniques appear to be at or near the thresh-
olds of sensitivity and precision needed to detect and study large planets
in other stellar systems. The initial emphasis in this effort will focus on
stars in the neighborhood of the Sun, at distances out to 10 to 100 parsecs
(1 parsec = 3.26 light years = 2 x 105 AU = 3 x 10~3 km) to sample
an adequate population, and in the mass range of 1 M or less because
the amplitudes of stellar reflex motions are largest for low-mass stars and
thus are most readily detected and precisely measured. Roughly 500 stars
with a median mass of about 0.3 Me lie within 10 parsecs of the Sun. The
primely initial goals are to confirm the presence and frequency of, or limit
the existence of, extrasolar planets in the Jupiter- to Uranus-mass range,
and to study the dynamics of discovered systems. 1b achieve these goals
requires the following:
· Development of instrumentation to enable sensitive search tech-
niques, and application of these techniques to a stellar population sufficient)
Urge to address decisive) the fundamental question of existence or absence of
e~rasolar planeta;ry systems;
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· Dete~?nination of Cal distributions of occurrence, if mul-
nple detections are made, among samples of stars of various masses awl
evo~dona:'y states; arid
· Measurement of physical and dynamical properties, incl~utg dzs-
mbanons of masses and orbital parameters.
2. The study of systems of dust and gas associated with young stars
and considered likely to be planet-forming environments. We know that
such systems exist. Requisite observational capabilities for first-order char-
acterization are or can be provided by existing or planned ground- and
space-based observatories. Planetary materials in our own system provide
some basis for interpretation of data. The general goals of this study are
as follows:
Obtain statistics on the occurrence of dust systems among young
pre-main-sequence and main-sequence stars of different types and ages;
· Charactenze dust systems condensed as disks by determining di-
mensions, masses, arid structural elements such as radial d~nbunons of den-
siiies, temperatures, and orbital velocities, degrees of asymmetry, occurrence
and orientation of jets, ratios of dust to gas, and broadband compositional
features; and
· Investigate the ante scales for the apparent evolution of circum-
ste11ar disks around sol~r-type pre-main-sequence stars from massive, optical)
thick structures to l~w-dust-mass, optical) thin disks in which prepl~etary or
planetary bodies may have accreted or may be in the process of accreiing.
3. Supporting theoretical and laboratory studies. Real understanding
of preplanetary and planetary systems requires a close interplay between
new observations and theoretical and laboratory advances in areas related
to the origin and physical and chemical evolution of molecular clouds,
accretion disks, and planetary bodies, including the planets and accessible
planetary materials (e.g., meteorites) of our own solar system. This general
goal requires both new theoretical comparisons among such systems and
related laboratory experiments, including considerations of the following:
· Companion of low-mass stars, substellar objects, and planets and
the differences and similarities of their formation conditions;
Various types of binary systems and plan eddy systems and the
relations among them;
· Fragmentation of a collapsing and rotating assemblage into multi-
ple objects and their subsequent evolution;
· Physical and chemical characterization of stellar nebulae through
time, silicate-carbon dust grains and icy-organic Gain mantles, the precipitation
of solid matter from cooling nebular gas, He conditions under which dust
paroles and planetesimals accrete or erode, and the evolution of accretion
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disks from initiation of dust agglomeranon into subplanetary objects through
subsequent plarzet-buildingsta~s; and
· Defininon of propernes of planetary systems in the process of
formation that could be subject to astronomical observanow
Representative terms from entire chapter:
planetary bodies
