Now that all of us in Bend and the surrounding area can anticipate warmer days, many more locals and visitors alike will be out in nature enjoying pleasant evening air — backyards, parks, campgrounds, lakes and rivers, all under a canopy of beautifully twinkling stars. The twinkle, however, is sometimes the source of amazement and understandable concern.

Stars, so very far away, are commonly considered to be pointlike sources of light. Even a motionless atmosphere, due to diffraction of mirrors and lenses in telescopes, spreads the light out into what is called an airy disk, concentric circles of alternating light and dark rings.

Stars twinkle due to atmospheric turbulence at various levels. At low level, for example, winds might be light from the west while at a higher level they could be strong and from the south. Consequently, the light is bent and deflected (refracted) in multiple directions, and its brightness varies, creating the twinkling effect. In significant ways, distortion of subsurface objects in swimming pools is similarly created. Under extreme conditions in the atmosphere, white light is disturbed enough to reveal its constituent colors (wavelengths), causing the star to flash different colors. The result can be spectacular and appear to be disturbingly unnatural, not just a distant aircraft displaying blinking navigation lights. Generally, stars closer to the horizon tend to twinkle more. This is because the observer is looking through much more atmosphere compared with a star seen directly overhead. Planets tend not to twinkle, as they are not pointlike but possess small apparent diameters. This attribute makes them much more resistant to twinkling.

Conditioned by fanciful Hollywood productions depicting alien visitations, odd lights in the sky we wonder at. Most scientists find no credible evidence that extraterrestrials have ever dropped in on us. But, hey, an open mind can never say “never.”

— Kent Fairfield is a volunteer with Pine Mountain Observatory and a lifelong amateur astronomer. Other PMO volunteers also contributed to this article. Kent can be reached at kent.fairfield@gmail.com.