"Exploring the Environments of Nearby Stars"
Understanding the properties of the circumstellar environments
which may give rise to exosolar planetary systems in
their formative
stages, and as they evolve into more mature systems such
as our
own, is one of the key goals of contemporary astronomy
and
astrophysics. Indeed, the NASA Origins theme contains
in its
foundation the establishment of scientific activities
to investigate
the birth and early evolution of stars and planets.
Recent advances
in space-based observational instrumentation, such as
afforded by
the Near Infrared Camera and Multiobject Spectrometer
(NICMOS)
on the Hubble Space Telescope, has enabled the direct
imaging of such
nascent and evolving systems, thereby contributing significantly
toward these goals. NICMOS provides a coronagraphic
imaging
capability at near-IR wavelengths which was exploited
by the
instrument definition team in conducting surveys of young
and
nearby stars. Under the umbrella of the Environments
of Nearby
Stars programs we seek to address such fundamental questions
as:
Is there a continuity of objects across the sub-stellar
mass-
spectrum bridging the stellar main-sequence down into
the
planetary domain, and in what sort of local environments
will such
objects form? At what distances will such objects be
found from
their primaries and how is this biased by the characteristics
of the
primary and companion objects, and those of the circumstellar
regions? What implications will the discovery and characterization
of such objects and their environments have for our understanding
of formation mechanisms? The results of those surveys
which
revealed sculpted and constrained circumstellar disks,
companion
brown dwarfs, and planetary candidates will help to answer
these,
and give rise to new, perhaps even more profound questions.