Star cluster or Galaxy cluster?

Galaxy cluster. The elliptical (not round) shapes are the giveaway.


Another way to tell that they are galaxies is that it isn’t very bright per area of sky compared to a star. You can see other objects behind it as well. Stars are dense, and most which aren’t too bright have a small or no halo around them, and almost all stars have diffraction spikes

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Also using “Look up in SIMBAD” works well for this cluster:
ACO 1466 – Cluster of Galaxies

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