Diffraction Spikes: When Stars Look Like Crosses

Explanation: Unusual appendages around bright stars are commonplace, but never seem to be mentioned. What are they? First, a telescope brings starlight falling over a large area to a small area . To get at this small area, however, one must go inside a reflecting telescope , and one good way to do this is to use support rods, which are right in the view of the telescope . The wave nature of light causes it to deflect when passing near these rods. Light scatters away from the original destination point ending up elsewhere and appearing as “ diffraction spikes .” These annoying spikes steal precious light from the central image and hide light from fainter, more interesting stars. Above , astronomers are more interested in the half-circled point near the image center, than the cool-looking diffraction spikes from the bright star at the bottom. Apparently, that half-circle is a new stellar system forming in the Lagoon Nebula .