diffraction spike

A diffraction spike is a type of artifact seen in images taken on telescopes. They are short light-colored lines leading away from point sources, which are caused by diffraction by mirror supports that light entering the telescope must pass. Hubble Space Telescope images often show a cross or × pattern centered on each star, created by HST's four mirror supports. JWST images often shows six (like an asterisk, "*"), created by its six supports.