Neutron stars are the densest objects in the Universe, just after black holes. According to recent observations, they may have a superfluid core.

Two separate teams of scientists claim that superfluid matter – frictionless – is the best explanation for the temperature drop observed in the neutron star at the center of the Cassiopeia A supernova.

Brutal temperature drop

The star is located 11,000 light-years away from Earth in the Cassiopeia constellation. It was formed during the explosion of a star into a supernova, visible from Earth 300 years ago. This neutron star was first spotted by the Chandra X-ray Observatory in 1999.

Measurements revealed that its surface – of 2 million degrees – had cooled down by 4% since its discovery. Theorists had long suspected that a young neutron star should cool down during the first 100 years after its creation.

Two separate studies

Until now, the temperature drop was theoretically explained by neutrons splitting into protons, releasing neutrinos; this process alone is not sufficient to account for the change in temperature.

Thanks to new simulations, Dmitry Yakovlev of Ioffe Physical-Technical Institute in St Petersburg, Russia and Dany Page, of National Autonomous University of Mexico just showed that a superfluid core in the neutron star perfectly explains the temperature drop.