a-cosmology-group/acg#230

So I was browsing bands of the eROSITA, largest ever xray sky survey, and I stumbled upon a gigantic xray ring. This xray ring is

1. absolutely gigantic
2. it strikingly is a perfect ring (no deformities), which is a naturally “impossible” shape
3. it seems to have a high energy source in its center

One might wonder wether this is an instrument artifact such as the famous JWST point spread function but I don’t find any other similar artifact which makes it highly unlikely. Moreover we aren’t just seeing a circle, but when we zoom in, we see that the circle is sparse and entirely made of specific point light sources (hence a robust observation). You can look at it by youserlf on the amazing website https://sky.esa.int/esasky/?target=207.37005841753205%20-63.23852487750319&hips=eROSITA-DE+DR1+Band+022+(0.6-2.3+keV)+Count+Image&fov=3.3233545224144536&cooframe=J2000&sci=true&lang=fr enable science mode click on the top left button to manage skys click on the + button browse hips registry search “erosita” on title field select band 0.6-2.3kev (count image) and look for a circle, it is so big you will find it pretty quickly

I am not sure wether this is the giant ring (figure 1) from this paper https://arxiv.org/abs/2012.11754 would be nice if you could confirm the location, honestly it is the most anomalous astrophysical object I have ever seen. coordinates: https://simbad.u-strasbg.fr/simbad/sim-coo?&Coord=207.115718597728d-63.234997276912d&CooFrame=FK5&Radius=2&Radius.unit=arcmin edit: yes! this does correspond to the coordinates of a “black hole” (center of the ring) and hence of this 2020 paper! https://simbad.u-strasbg.fr/simbad/sim-id?Ident=MAXI+J1348-630+&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id

Also related are eROSITA (and fermi) bubbles https://arxiv.org/pdf/2012.05840 see Extended Data Fig. 2

https://arxiv.org/pdf/2405.04264

on the topic of rings, there are also the intriguing (but much smaller) ring galaxies (could they constrain MOND/DM?) https://en.wikipedia.org/wiki/Ring_galaxy#/media/File:Hoag’s_object.jpg As for known ring megastructures, there is the https://en.wikipedia.org/wiki/Giant_GRB_Ring and discovered in 2024, the https://en.wikipedia.org/wiki/Big_Ring

note: anyone knows the difference in terminology for a sky survey band between a rate image and a count image? note2: the structure is optically invisible note3: it is invisible in xray bands 2.3-5kev and 0.2-0.6kev, and can be seen in 0.2-2.3, 0.6-2.3 and 1-2kev and it is slighly visible on the full RGB image. the structure is best seen in 0.6-2.3 which probably means it selectively emits in that range (possibly 0.6-2 or 1-2.3)

So the ring is identified but still the question remains, how can such an object be formed? Why is it unique in the observable universe? etc..