A massive neutron star (NS) in a compact relativistic binary system, PSR J0348+0432, has been discovered. This system consists of a pulsar with a mass of 2.01 ± 0.04 solar masses and a white dwarf (WD) with a mass of 0.172 ± 0.003 solar masses, orbiting each other with a period of 2.46 hours. The system provides a unique laboratory for testing strong-field gravity, as it allows for precise measurements of orbital decay, which align with general relativity (GR) predictions. The results support the use of GR-based templates for gravitational wave detectors and provide insights into binary stellar evolution and dense matter properties. The pulsar's high mass and compact orbit make it an ideal testbed for extreme gravity conditions. The system's observed orbital decay is consistent with GR, and the constraints on deviations from GR support the validity of GR even in extreme conditions. The WD's mass is determined using cooling tracks with thick hydrogen atmospheres, yielding a mass range of 0.165–0.185 solar masses at 99.73% confidence. The pulsar's mass is estimated to be between 1.97–2.05 solar masses at 68.27% confidence, making it the second NS with a precisely determined mass around 2 solar masses. The system's parameters, including the orbital period and mass ratio, allow for testing alternative gravity theories. The observed orbital decay is consistent with GR predictions, and the results constrain deviations from GR, even for massive NSs. The system also provides constraints on the properties of dense matter and the dynamics of binary stellar evolution. The system's formation is likely through a common envelope or close-orbit low-mass X-ray binary (LMXB) scenario. The pulsar's slow spin period and high magnetic field suggest a recycling process. The system's future evolution will involve orbital decay and potential formation of a black hole or a pulsar with a planet. The system's parameters also provide constraints on the phase evolution of neutron-star mergers and the properties of gravitational interactions in extreme conditions. The results have implications for future gravitational wave detectors and the study of strong-field gravity.A massive neutron star (NS) in a compact relativistic binary system, PSR J0348+0432, has been discovered. This system consists of a pulsar with a mass of 2.01 ± 0.04 solar masses and a white dwarf (WD) with a mass of 0.172 ± 0.003 solar masses, orbiting each other with a period of 2.46 hours. The system provides a unique laboratory for testing strong-field gravity, as it allows for precise measurements of orbital decay, which align with general relativity (GR) predictions. The results support the use of GR-based templates for gravitational wave detectors and provide insights into binary stellar evolution and dense matter properties. The pulsar's high mass and compact orbit make it an ideal testbed for extreme gravity conditions. The system's observed orbital decay is consistent with GR, and the constraints on deviations from GR support the validity of GR even in extreme conditions. The WD's mass is determined using cooling tracks with thick hydrogen atmospheres, yielding a mass range of 0.165–0.185 solar masses at 99.73% confidence. The pulsar's mass is estimated to be between 1.97–2.05 solar masses at 68.27% confidence, making it the second NS with a precisely determined mass around 2 solar masses. The system's parameters, including the orbital period and mass ratio, allow for testing alternative gravity theories. The observed orbital decay is consistent with GR predictions, and the results constrain deviations from GR, even for massive NSs. The system also provides constraints on the properties of dense matter and the dynamics of binary stellar evolution. The system's formation is likely through a common envelope or close-orbit low-mass X-ray binary (LMXB) scenario. The pulsar's slow spin period and high magnetic field suggest a recycling process. The system's future evolution will involve orbital decay and potential formation of a black hole or a pulsar with a planet. The system's parameters also provide constraints on the phase evolution of neutron-star mergers and the properties of gravitational interactions in extreme conditions. The results have implications for future gravitational wave detectors and the study of strong-field gravity.