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Vela Supernova Remnant in X-ray
When a star explodes ahuge fireball of hot gas shoots out in all directions. When this gas slams into the existing interstellar medium, it heats up so much it glows in X-rays. The above picture by the ROSAT satellite has captured some of these X-rays and shown, for the first time, the Vela supernova explosion was roughly spherical. Non-uniformity of the interstellar medium causes Vela's appearance to be irregular. The size of this X-ray emitting spherical shell is immense230 light years across, about 17 times the diameter of the full Moon. The supernova that created this nebula occurred about 1500 light years away and about 11,000 years ago.
Near the center of the image is the remnant of the exploded stara rotating neutron star, or pulsar. The Chandra X-ray Observatory has captured an image of this pulsar.
Coincidently, a completely different supernova shell can also be seen in X-rays in this picture! It is visible as the bright patch near the upper right. This Puppis supernova remnant nebula is actually about four times farther than the Vela nebula.
The Hubble Space Telescope has taken a close-up image of the edge of the shock wave.