Are Stars Pointed?
As children we learned to draw star-shapes, wanted to earn a gold star, and sang “Twinkle, twinkle, little star”. Our connection to the stars in the night sky caused fascination and encouraged imagination. Yet, how many of us have stopped to ask why we think of them as having points (except for Van Gogh in his painting “Starry Night”).
Recently I read an intriguing article by Helen Czerski (WSJ, 3/9/19) about this phenomenon (https://www.wsj.com/articles/do-stars-really-have-points-11551884238 ) which clarifies this mystery. Stars appear as tiny dots, being so far away that their true shapes, really spheres, as we all know, cannot be seen. However, photographic and telescopic images portray them as having points or spikes, just as images of other lights often do. Photography accounts for the spikes and the star-shaped association. This camera construction creates points on images of light sources. A camera’s aperture, through which light passes to create a photograph, must move apart or together easily, and as such is generally a hexagon or octagon shape.
Seeing pointed star images is evidence that light has wave qualities. Quantum mechanics evidences light has particle qualities also, but that is a different story. Anyway, stars are spread out by the flat faces of a camera’s aperture into lines, or diffraction spikes. The resulting photos are of stars with six or eight points, determined by either a hexagon or octagon-shaped aperture, accounting for our ideas of the shape of stars.You have probably experienced a similar effect by squinting while looking at stars, outdoor lights, or, for some of us, as seen with blurred vision when not wearing corrective lenses. So, even apart from, or before, photography, those before us observed this effect.
All of this makes for a great conversation, and gives us pause to stop and reflect on what we might otherwise assume or take for granted, and truly wonder at the world around us.It is also wonderful to consider the construction of our own irises and how perfectly they are made.
Here's to looking up!