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Neutron stars, the ultra-dense cores left behind after massive stars collapse, contain the densest matter known in the Universe outside of a black hole. New results from Chandra and other X-ray telescopes have provided one of the most reliable determinations yet of the relation between the radius of a neutron star and its mass. These results constrain how nuclear matter, protons and neutrons, and their constituent quarks, nteract under the extreme conditions found in neutron stars. Ground-based Optical Image of 47 Tucanae globular cluster combines data from the Digitized Sky Survey with data from the 2 Micron All Sky Survey. Release date March 6, 2013.