I've been exploring this new ESA tool and I came across this structure.

enter image description here

What is it?

The circles look like they might be the footprint of a telescope. Perhaps there was a survey of this specific region of the sky with long exposures? Why was this part of the sky in particular observed with such detail? What exactly are we looking at here? What object(s) of interest lie here that justify observing in soft X-ray this small part of the sky in more detail than what surrounds it?


1 Answer 1


Looking at the image, it appeared to be a supernova remnant, and sure enough when I plugged the coordinates into SkyMap, it identified NGC 6960, the Veil Nebula. The interaction of the hot ionized gas of the expanding supernova remnant with the interstellar medium produces radiation at many wavelengths.

The Veil Nebula is almost 3 degrees across, while the soft-X-ray camera on XMM-Newton has a FOV of 30 arc-minutes, so it takes 7 overlapping fields to span the width of the remnant. Note that the remnant shows X-ray emission across its entire width, while in visible wavelengths only the brighter parts of the edges can be imaged.

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    $\begingroup$ I wonder if this can be expanded a bit? The angular sizes of the object and the telescope could explain the unusual tiled appearance for example. $\endgroup$
    – uhoh
    Sep 15, 2021 at 21:26

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