"Strange" New Star?

Supernova remnants are beautiful to behold, but they are also the result of extremely violent explosions and leave behind one of the most dynamic objects in the Universe. One such object, the pulsar at the center of the supernova remnant Cassiopeia A (Cas A), has been the source of much study ever since data from the Chandra X-ray observatory were published over 10 years ago.

Based on the observational data, the size of the pulsar -- a rapidly rotating neutron star -- was estimated to be about 6 miles across, which is theoretically impossible. Theories abounded, that this must not be a pulsar, but rather an object called a quark star. Such an object has never directly been observed, but has been predicted to exist under just the right circumstances.

If a pulsar's gravity is sufficiently high, all the neutrons in the star would no longer be distinct from one another, and the result would be that the star would simply become a massive ball of quarks -- one of the fundamental particles of nature. Specifically, there would exist an abundance of strange quarks (one of the six types of quarks) within the star.

Since this would be the first star of its type ever observed, scientists have been working very hard to either confirm or eliminate this possibility for Cas A. A few weeks ago scientists Wynn Ho and Craig Heinke reported in the Journal Nature that they have discovered the reason that the pulsar at the center of Cas A appears so small. It is not a quark star, but rather is a normal pulsar surrounded by a carbon atmosphere.

While unusual, it is possible that a young, hot pulsar -- like Cas A -- can fuse its hydrogen atmosphere and eventually create a carbon rich atmosphere instead. Because of this the pulsar would appear much smaller than it really is. While this may disappoint some scientists -- I have to say I was really hoping for the quark star theory to be correct -- it does give us insight into a phenomenon never observed in pulsars before. But there are still lots of supernova remnants out there, so who knows, maybe we'll find one of these quark stars yet.

Image Credit: Image Credit: NASA/JPL-Caltech/STScI/CXC/SAO