Those are called "diffraction spikes" https://en.wikipedia.org/wiki/Diffraction_spikes https://en.wikipedia.org/wiki/Diffraction_spikes They represent light th

Those are called "diffraction spikes" https://en.wikipedia.org/wiki/Diffraction_spikes https://en.wikipedia.org/wiki/Diffraction_spikes They represent light that was diffracted by the edges of the hexagonal primary mirror segments and secondary mirror support struts. The reason they are so prominent is because of how extremely overexposed the star is. Every star will have them but in a normally exposed star they are too faint to see. In the Hubble Space Telescope you have four spikes that are just from the support struts of the secondary mirror. The circular mirror generates something called an Airy Disk https://en.wikipedia.org/wiki/Airy_disk https://en.wikipedia.org/wiki/Airy_disk. Diffraction effects are unavoidable in any telescope and can tell you a lot about how well the telescope is working. In this case they indicate that Webb is aligned extremely well.