📄 Showing the "Simple" version — "Advanced" is not ready yet. Add it to favorites to help prioritize it. Ask for the full read

In a dance with an ordinary star, astronomers have found a true heavyweight — a neutron star with 2.35 times the mass of the Sun. That's more than any other whose mass has been precisely measured. These objects are born when a star explodes as a supernova and its core collapses into a city-sized sphere. Just a little more mass, and the heavyweight would punch through the floor, collapsing into a black hole — the edge lies at about 2.27 solar masses. To weigh the invisible companion, scientists used brightness measurements and spectral analysis. By tracking the shift in spectral lines, an effect discovered by Christian Doppler, they calculated the orbital speed of the visible star, which revealed the wobbles caused by the heavyweight's gravity. The first neutron stars, pulsars, were spotted by Jocelyn Bell Burnell, and Fritz Zwicky predicted them back in the 1930s. This record shrinks the mystery: how matter resists pressures billions of billions of times stronger than Earth's. Inside such a star, a teaspoon of matter weighs as much as Mount Everest, yet it flows like a frictionless fluid. Knowing the mass limit lets us understand when the heavyweight finally snaps.

Original abstract

as written by the authors arXiv:2512.05099

We report on new orbit-minimum photometry and revised radial-velocity fitting that provide an improved measurement of the mass of the neutron star (NS) in pulsar PSR~J0952$$-$$0607 at $$M_NS = 2.35\pm 0.11 M_\odot$$. With its fast spin and unusually low magnetic field, this NS has evidently experienced unusual evolution, likely connected with its high mass, which is now $$2.5\sigma$$ above that of the heaviest pulsar with a white dwarf companion, as measured by Shapiro delay techniques. By tightening the mass measurement, we also raise the maximum (commonly called Tolman-Oppenheimer-Volkoff) NS mass to $$M_{\rm TOV} > 2.27\,M_\odot$$$$(2.12\,M_\odot)$$ at $$1\sigma$$$$(3\sigma)$$ confidence, which improves bounds on the dense-matter equation of state. While the statistical error decreases and systematic issues should be modest, uncertainties remain; we comment briefly on these factors and prospects for further improvement.