A wobbling disk reveals a neutron star's true weight

SMC X-1 is a neutron star pulling material from a companion star, and its brightness flickers in ways linked to the disk's precession. By modeling how the warped disk redirects X-rays onto the donor star—and how that shifts the apparent center of optical emission—researchers recovered light curve patterns previously unexplained. Correcting for this 20% radial velocity bias raises the pulsar's estimated mass to 1.35 solar masses, pushing it closer to or past theoretical limits for core-collapse supernovae.