From the May 2012 issue

Why do some stars appear to flash a variety of different colors when you look at them through a telescope?

Dominic Snyder, Glen Rock, Pennsylvania
By | Published: May 29, 2012
Some observatories shoot special lasers into the sky to create a false star, which is part of an adaptive optics system that “unblurs” stellar images. Credit: ESO/Yuri Beletsky
Earth’s atmosphere is made of layers of gas, and light from distant objects must pass through it to get to our telescopes.

Differences in gas can make light bend, or refract. Think of an object seen through air rising from an asphalt road on a hot day. That warm air slightly warps light, and you see this distortion. Also, rainbows are a result of sunlight refracted in atmospheric water droplets. So, Earth’s atmosphere will bend some colors from especially bright stars more so than others, which makes the source look like it’s flashing colors. — Liz Kruesi, Associate Editor