James Lattimer (SUNY Stony Brook)
Neutron Stars as Windows into Dense Matter Physics
Neutron stars embody matter at extremes: they contain matter at the highest possible densities since the Big Bang, they have the highest known magnetic fields and contain the highest temperature superfluids. They are known to spin with frequencies up to 716 Hz with equatorial surface velocities approximately 1/4 of light speed, and are also known to travel through space with velocities up to 1% of light speed. General relativity predicts that neutron stars have maximum masses no greater than 3 M, radii no smaller than 8 km, and central energy densities no larger than 11 times the normal nuclear saturation density (2.7 1014 g/cm3. Recent advances in astrophysical observations, nuclear experiments and nuclear theory considerably constrain their matter properties although it is still not known if they contain deconfined quark matter. Among recent advances are observations from the binary neutron star merger GW170817 indicating that neutron stars have masses and radii no larger than 2.2 M and 13 km, respectively, while parity-violating electron scattering measurements of the neutron skin thickness of 208Pb at Jefferson Laboratory are consistent with neutron star radii 12±1 km. A 10-second long burst of neutrinos, observed from SN1987A, has long been thought to prove the accompanying birth of a neutron star, but its detection has been elusive. But the recent millimeter-wave detection of a warm dust blob in SN1987A's remnant provides evidence that this neutron star has finally been found. In addition, observations of rapid cooling of the 330 year-old neutron star in the Cassiopeia A supernova remnant are best fit if it contains interior superfluid neutrons and protons with critical temperatures near 109 K and 3109 K, respectively.