NASA's Chandra X-Ray Unlocks Secret Of Carbon Atmosphere On Neutron Star

November 4, 2009 2:58 p.m. EST

Cambridge, MA (AHN) - NASA's Chandra X-ray Observatory has solved a ten-year mystery scientists have been unable to answer. Using the observatory they discovered a thin veil of carbon on the neutron star in the Cassiopeia A supernova remnant.

"The compact star at the center of this famous supernova remnant has been an enigma since its discovery," said Wynn Ho of the University of Southampton. "Now we finally understand that it can be produced by a hot neutron star with a carbon atmosphere."

By analyzing Chandra's X-ray spectrum in a manner similar to a fingerprint of energy. Then applying the data to theoretical models, Ho and his fellow researchers determined that the neutron star in Cassiopeia A, or Cas A for short, has an ultra-thin coating of carbon. The revelation marked the first time the composition of an atmosphere of an isolated neutron star has been confirmed.

In Earth's time frame, the estimated age of the neutron star in Cas A is only several hundred years, making it about ten times younger than other neutron stars with detected surface emission. Therefore, the Cas A neutron star gives a unique window into the early life of a cooling neutron star.

The carbon itself comes from a combination of material that has fallen back after the supernova, and nuclear reactions on the hot surface of the neutron star which convert hydrogen and helium into carbon.

The X-ray spectrum and lack of pulsar activity suggest that the magnetic field on the surface of this neutron star is relatively weak. Similarly low magnetic fields are implied for several other young neutron stars by study of their weak X-ray pulsations.

Researchers are not sure if these neutron stars will emit low magnetic fields for their entire lives, and never become radio pulsars, or whether processes in their interior will lead to the development of stronger magnetic fields as they age.