Caused by diffraction around structural supports for the optics: https://en.wikipedia.org/wiki/Diffraction_spike https://en.wikipedia.org/wiki/Diffraction_spike

Caused by diffraction around structural supports for the optics: https://en.wikipedia.org/wiki/Diffraction_spike https://en.wikipedia.org/wiki/Diffraction_spike EDIT - for Hubble specifically, here’s an exploded view: https://www.spacetelescope.org/images/exploded_view1/ https://www.spacetelescope.org/images/exploded_view1/ The spikes are caused by the arms holding the secondary mirror.