This is a ROSAT PSPC image of the supernova remnant (SNR) HB-9. It was made from scanning observations taken during the all-sky survey phase of the ROSAT mission. HB-9 is large, evolved, and has an angular diameter of 2 degrees. (In comparison the full moon has an angular diameter of 0.5 degrees) It has a centrally brightened morphology in the X-ray band of the spectrum, which contrasts with its shell-like appearance in the radio.
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