What kind of neutron star did SN 1987A leave?
In plain words
The 1987 supernova in a neighbouring galaxy produced a neutrino burst showing that a neutron star formed, and in 2024 JWST saw gas lit up by it, but the star itself is unseen.
Precise statement
Determine whether the compact object in SN 1987A is a cooling neutron star or powers a pulsar wind nebula, and constrain its spin and magnetic field, from the JWST-detected narrow argon lines near the center, the disputed 2021-2022 hard X-ray detections attributed to a pulsar wind nebula, and ALMA dust constraints. Answer: an identification with a luminosity budget of $\sim 1e35\ \text{to}\ 1e36\,\mathrm{erg/s}$ consistent with all bands.
What would settle it
Detection of thermal X-rays or pulsations from the center, or spatially resolved line diagnostics that discriminate a nebula from a bare cooling star.
Status in the literature
Unverified note
2024: JWST spectra showed argon lines ionized by a central source, consistent with a neutron star but not yet distinguishing thermal emission from a pulsar wind nebula.