Complex sentence: The surface of the neutron star is very hot, 10 9 kelvins, hotter than the cores of all but the most massive stars, so unusual nuclear processes may take place as the envelope of the red giant falls onto the neutron star's surface.
Split into simpler sentences: The surface of the neutron star is very hot, 10 9 kelvins, hotter than the cores of all but the most massive stars. Because of the high temperature, unusual nuclear processes may take place as the envelope of the red giant falls onto the neutron star's surface.