Research Highlight

Viscous truths of neutron stars

doi:10.1038/nindia.2009.152 Published online 10 June 2009

An Indian research team has thrown new light on the viscosity of neutron star, born out of the death of a massive star (several times larger than the sun)1. The massive star dies in a violent blast known as supernova explosion.

The researchers calculated how the viscosity of a neutron star changes in the presence of strong magnetic field with the birth of some exotic particles. These particles might have only popped into existence for one-millionth of a second shortly after Big Bang that spawned the universe. These insights into neutron star that regenerates those elusive particles may offer clues to evolution of early and present universe.

A neutron star is made up of neutrons and other subatomic particles. It is about 20 km in diameter with a mass of about 1.4 times that of sun. Neutron stars can also have magnetic fields a million times stronger than those produced on Earth. A neutron star rotates on its axis and its viscosity determines rates of rotation and gravitational wave instabilities.

To explore how the viscosity changes under the influence of strong magnetic field, the researchers carried out studies resorting to mathematical models. The researchers calculated URCA (named after a Casino called Urca in Rio de Janeiro, where astrophysicist George Gamow mentioned how the energy disappears in the nucleus of the supernova as quickly as the money disappeared at that roulette table) processes, a reaction which emits a neutrino (charge less particle) and is assumed to take part in cooling of neutron stars. They found that in response to strong magnetic field, bulk viscosity is enhanced.

The research is very significant as neutron stars cool and emit neutrinos, converting themselves into strange stars, which might provide clues on the birth of black holes.


  1. Sinha, M. et al. Hyperon bulk viscosity in strong magnetic fields. Phys. Rev. D. doi: 10.1103/PhysRevD.79.123001 (2009) | Article | ADS |