Nuclear Theory Helps Forecast Neutron Star Temperatures

Advances in theory have made it possible to predict cooling behavior observed in accreting neutron stars.

Image courtesy of Sanjay Reddy
Exotic neutron-rich nuclei and new states of matter expected to exist inside neutron stars play a role in interpreting observed cooling in accreting neutron stars.

The Science

Theoretical interpretation of observed cooling in neutron stars that episodically accrete matter from a companion star has now provided compelling evidence for an exotic phase of matter that is both solid and superfluid.

The Impact

The results provide researchers with the ability to reliably predict the cooling rate of neutron star formation, and further demonstrate that neutron stars are unique laboratories to study matter at extreme density.


A realistic, nuclear physics based model of neutron star crust is providing the basis for interpreting transient phenomena observed in accreting neutron stars. Although theorists had anticipated this phase, recent advances have helped pin down the thermal and transport properties necessary to interpret observations. Interestingly, the typical cooling time scale is a few hundred days, and an active program in theory and x-ray astronomy can test finer predictions of this model within the next few years. Predictions for future cooling can now be made reliably, and observed behavior can be interpreted as evidence for exotic states of matter with more confidence, confirming theoretical expectations, and providing useful new insights for nuclear physics.


Prof. Sanjay Reddy
University of Washington and the Institute for Nuclear Theory, Seattle


Basic Research: DOE Office of Science, Office of Nuclear Physics


N. Chamel, D. Page and S. Reddy, Low energy collective excitations in the neutron star inner crust, Phys. Rev. C87 035803 (2013). V. Cirigliano, S. Reddy, and R. Sharma, A Low energy theory of solid and superfuid matter and its application to the neutron star inner crust, Phys. Rev. C84 045809 (2011)

Page and Reddy, Thermal and transport properties of the neutron star inner crust, arXiv: 1201.5602 (2012)

D. Page and S. Reddy, Forecasting neutron star temperatures: Predictability and variability, arXiv: 1307.4455 (2013) submitted to Phys. Rev. Lett.

Highlight Categories

Program: NP

Performer: University