Vela Supernova Remnant in X-ray . ... 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. ... The size of this X-ray emitting spherical shell is immense - 230 light years across, covering over 100 times the sky-area of the full Moon. The supernova that created this nebula occurred about 1500 light years away and about 11,000 years ago. ... NASA Official: Jay Norris. ...