🎵Star light, shine bright…Guide me home for Christmas day🎄

Many Christmas trees have a glittering pentagram star sitting on the top ⭐. This symbolic holiday decoration is also referred to as the "Christmas Star", representing the bright star that appeared on the night of Christmas. We know stars are spherical. Then how come the stars we put on the Christmas tree or the stars we draw all have five points?

The five-pointed star might have originated from how ancient Egyptians represented the stars in hieroglyphics. Although we can't know for sure why the ancient Egyptians drew stars in such a way, the only thing we experience is that some of the stars do appear spiky. In the Hubble Space Telescope photographs, stars have crosses of four pointy bits. Radiating from the centre, they are termed diffraction spikes. The crossed spikes are more noticeable for bright stars and less so for fainter ones. They are not parts of the stars but are imaging artifacts. When starlight enters telescopes, it diffracts as it encounters obstacles.

But how do the telescopes create diffraction spikes? Can we snap pictures of stars without those cross-like structures? Let's ponder on interesting science questions during the Christmas holiday, and we will explain them in more detail afterward. Wishing you all a Merry Christmas!