With the release of the first processed images of the james webb space telescope, some people wondered why the stars have 8 spikes in their images, and even the sour dictionary has headlines about it.
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The truth of the matter is that these spikes that appear in the stars don’t actually exist. These spikes are the result of the interaction of light with the telescope’s optical system. When light encounters a corner, it is diffracted. We also witness these diffractions in telescopes other than James Webb.
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These spikes, resulting from the diffraction of light, are seen in all telescopes that use a secondary mirror in front of the main mirror. It is the secondary mirror that causes diffraction. The james webb space telescope also has a secondary mirror in front of its main mirror, which consists of 18 hexagonal segments. this secondary mirror has three support legs, one vertical and two angled 150º to the vertical. The two edges of each support cause a diffraction at right angles to the edge, producing a total of 6 spikes.
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The edges of hexagonal mirrors also cause 6 diffractions and 6 spikes spaced 60° apart. There are 12 spikes in total. however, due to the clever design of the telescope, some of these spikes overlap each other. in this way, we see 8 tips instead of 12 in total. Since the diffraction in the secondary mirror supports is less obvious, we see the 2 visible spikes as shorter than the spikes created by the hexagonal mirrors, except for the overlapping spikes.
source: science focus
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