Neutron star
The Neutron star Interior Composition Explorer (NICER) is a NASA telescope on the International Space Station, designed and dedicated to the study of the extraordinary gravitational, electromagnetic, and nuclear physics environments embodied by neutron stars, exploring the exotic states of matter where density and pressure are higher than in atomic nuclei. As part of NASA's Explorers program, "NICER" enabled rotation-resolved spectroscopy of the thermal and non-thermal emissions of neutron stars in the soft X-ray (0.2–12 keV) band with unprecedented sensitivity, probing interior structure, the origins of dynamic phenomena, and the mechanisms that underlie the most powerful cosmic particle accelerators known. "NICER" achieved these goals by deploying, following the launch, and activation of X-ray timing and spectroscopy instruments. "NICER" was selected by NASA to proceed to formulation phase in April 2013.