This false-color image from three of NASA's Great Observatories provides
one example of a star that died in a fiery supernova blast. Called Cassiopeia
A, this supernova remnant is located 10,000 light-years away in the constellation
Cassiopeia. At the center of this orb, visible only as a tiny turquoise dot, is the
leftover corpse of the now-dead star, called a neutron star. The multi-hued shell
outside the neutron star is the rest of the original star's scattered remains.
NASA's Spitzer Space Telescope found a dusty disk circling around a similar
neutron star called 4U 0142+61. This particular neutron star (not pictured here)
spins and pulses with X-ray radiation, so it is called a pulsar. Its disk is made of
material that was blown off the exploding star but never reached a high enough
velocity to escape the star's gravity.
A photograph of 4U 0142+61 would only show both the pulsar and disk as one
small dot, without any outer shell of expelled material. This is because the pulsar
exploded about 100,000 years ago, and its shell has since cooled to the point
where it is no longer visible. The death of the star that gave rise to Cassiopeia
A was witnessed from Earth about 320 years ago, so its shell is still hot and glowing.
Infrared data from the Spitzer Space Telescope are colored red; visible data from the
Hubble Space Telescope are yellow; and X-ray data from the Chandra X-ray
Observatory are green and blue.