[http://www.msfc.nasa.gov/news/news/photos/2004/photos04-115.html]

The NASA Chandra X-ray Observatory image of SNR 0540-69.3 clearly shows two
aspects of the enormous power released when a massive star explodes. An
implosion crushed material into an extremely dense (10 miles in diameter)
neutron star, triggering an explosion that sent a shock wave rumbling through
space at speeds in excess of 5 million mph.

The image reveals a central intense white blaze of high-energy particles about 3
light years across created by the rapidly rotating neutron star, or pulsar.
Surrounding the white blaze is a shell of hot gas 40 light years in diameter
that marks the outward progress of the supernova shock wave.

Whirling around 20 times a second, the pulsar is generating power at a rate
equivalent to 30,000 Suns. This pulsar is remarkably similar to the famous Crab
Nebula pulsar, although they are seen at vastly different distances, 160,000
light years versus 6,000 light years. Both SNR 0540-69.3 and the Crab pulsar
rotating rapidly, and are about a thousand years old. Both pulsars are pumping
out enormous amounts of X-radiation and high-energy particles, and both are
immersed in magnetized clouds of high-energy particles that are a few light
years in diameter. Both clouds are luminous X-ray sources, and in both cases the
high-energy clouds are surrounded by a filamentary web of cool gas that shows up
at optical wavelengths.

However, the extensive outer shell of 50 million degree Celsius gas in SNR
0540-69.3 has no counterpart in the Crab Nebula. This difference is thought to
be due to environmental factors. The massive star that exploded to create SNR
0540-69.3 was evidently in a region where there was an appreciable amount of
gas. The supernova shock wave swept up and heated the surrounding gas and
created the extensive hot X-ray shell. A similar shock wave presumably exists
around the Crab Nebula, but the amount of available gas is apparently too small
to produce a detectable amount of X-radiation.

The Marshall Center manages the Chandra program. (NASA/CXC)