Hubble Space Telescope Nondetection of PSR J2144–3933: The Coldest Known Neutron Star
Sebastien Guillot et al 2019 ApJ 874 175
Hubble Space Telescope observations of the ~3 × 108-year-old, slow, isolated, rotation-powered pulsar PSR J2144–3933 yield no detection — indicating that, at T < 42,000 K, this is the coldest known neutron star.