n.a region of complete shadow resulting from total obstruction of light

UMBRAS
Enhancing NGST Science: UMBRAS
UMBRAS: a matched occulter and telescope for imaging extrasolar planets
The Structure of Sunspot Umbras. I. Observations.
Imaging planets about other stars with UMBRAS
Emission of Hydromagnetic Waves from Sunspot Umbras.
Small scale phenomena in umbras and penumbras - The role of convective processes
Oscillations in sunspot umbras due to trapped Alfven waves excited by overstability
Imaging planets about other stars with UMBRAS: target acquisition and station keeping
Motions in solar magnetic tubes. III - Outward wave propagation in sunspot umbras