Q&A: Supernova Remnants and Neutron Stars

Q:
Is there any known star that has the apparent dimensions of the depicted mystery object on which we voted at http://chandra.harvard.edu/vote/q11.html?

A:
The mystery object may be unresolved by Chandra. At the distance of Cas A,about 10,000 light years, the smallest resolution element in the timage corresponds to a size of about 300 billion kilometers, which is about 2 million times larger than the Sun. Size alone clearly will not tell us much. Studies of the energy spectrum (distribution of X-rays with energy) or evidence of rapid pulsation will ultimately be decisive in determining the nature of the mystery object.