Gravity and Extreme Magnetism Small Explorer Mission Project
Home Page - http://gems.gsfc.nasa.gov/ The Gravity and Extreme
Magnetism Small Explorer (GEMS) did not pass its confirmation
review in 2012 and never moved into the development phase. GEMS
would have used an X-ray telescope to measure the polarization
of the X-rays coming from the vicinity of compact objects in the
universe: black holes and neutron stars and it would have also
studied the remnants of massive stars which have exploded as
supernovae. Few polarization measurements have been made in
X-ray astronomy since the 1970’s so GEMS was expected to break
new ground. The polarization depends, in part, on the X-ray
scattering in the accretion disk around the compact object in a
binary star system, so GEMS would have helped to constrain the
geometry in such systems. GEMS might also have helped to
constrain the shape of space that has been distorted by a
spinning black hole's gravity, and probe the structure and
effects of the formidable magnetic fie