TheSkySearchers

Here, we use a deep XMM-Newton observation to examine the morphology and evolutionary stage of the PWN and to search for thermal emission expected from a supernova shell or reverse shock interaction with supernova ejecta," the astronomers wrote in the paper.

Observations confirmed a comet-like morphology of CTB 87, suggested by previous studies. However, this SNR is known to be embedded in a thermal shell that was not observed on the images provided by XMM-Newton. In general, the observations did not find evidence of thermal X-ray emission, which supports the scenario of expansion into a stellar wind bubble.