Cassiopeia A (Cass A) is a
11,000 light-years away.
Light from the Cass A supernova,
the death explosion of a massive star,
first reached Earth just 330 years ago.
The expanding debris cloud spans about 15 light-years in
while the bright source near the center is a
the incredibly dense, collapsed remains of the stellar core.
Still hot enough to emit X-rays, Cass A's neutron star is cooling.
In fact, 10 years of observations with the orbiting
Chandra X-ray observatory find that
neutron star is cooling
rapidly, so rapidly that researchers suspect a large part of
the neutron star's core is forming a frictionless
The Chandra results represent the first observational evidence for this
bizarre state of matter.
X-ray: NASA /
UNAM / Ioffe /
P.Shternin et al;
Optical: NASA /