PSR J0740+6620 is a neutron star in a binary system with a white dwarf, located 4,600 light-years away in the Milky Way. It was discovered in 2019 by astronomers using the Green Bank Telescope in West Virginia, U.S., and confirmed as a rapidly rotating millisecond pulsar. It completes spin period of 2.8857 milliseconds and is characteristic age of 3.75 billion years old.
It is among the most massive neutron stars ever observed—with , placing it near the boundary of the theoretical maximum. Its mass was calculated via the Shapiro delay of its white dwarf companion as it passed edge-on to Earth. It was the record holder for the heaviest neutron stars until July 2022 when the title was taken by PSR J0952–0607 with a reported mass of .
PSR J0740+6620 is estimated to measure ().
See also PSR B1913+16 PSR B1957+20 (1.66–2.4 ) Neutron Star Interior Composition Explorer (NICER) List of the most massive neutron stars
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