NASA's IXPE mission reveals neutron stars have a solid crust and superfluid core

New findings from NASA's IXPE mission have confirmed that neutron stars possess a solid outer crust. These dense remnants of collapsed stars also contain a superfluid core, where matter flows without resistance. The discoveries shed light on some of the most extreme conditions in the universe.

Neutron stars form when massive stars explode in supernovas and collapse under their own gravity. Their surfaces are nearly perfect spheres due to the crushing gravitational pull. Beneath this smooth exterior, the crust consists of tightly packed neutrons, along with some protons and electrons.

Deep inside, the core behaves as a superfluid—a state where particles move without friction. This unusual property helps stabilise the star and shapes its magnetic and thermal behaviour. NASA's IXPE mission has closely examined four neutron stars: 4U 0142+61, RX J1856.5-3754, Cas A, and Vela X-1. The solid crust was definitively confirmed in observations of 4U 0142+61 and RX J1856.5-3754.

Studying these objects offers a rare chance to test physics under extreme pressures and densities. The data collected so far could also lead to advances in superfluid-based technologies on Earth.

Future missions will continue to explore neutron stars, uncovering more about their structure and behaviour. The combination of a solid crust and a frictionless core makes them unique cosmic laboratories. Further research may reveal even deeper connections between these stars and fundamental physics.