Catch the (Alien) Rainbow

by | April 24, 2024, 12:10 PM | Solar Systems

Each glory is unique, depending on the composition of the planet’s atmosphere and the colors of the light from the star that illuminates it. WASP-76 (the «Sun» of WASP-76b) is a yellow and white main sequence star like our Sun, but different stars create glories with different colours and patterns. Credit: ESA, work performed by ATG under contract for ESA. CC BY-SA 3.0 IGO

As scientists discover and explore the atmospheres of more and more planets orbiting stars other than our Sun, we are learning that if you can imagine it, it probably exists. 

In a new paper discussing the planet WASP-76b, researchers led by Olivier Demangeon describe what appears to be a giant rainbow in the atmosphere of another world. And folks, this isn’t some mundane double rainbow. This is a glory — a circular rainbow. And it’s not water that is refracting starlight; it looks like this rainbow may come from atmospheric iron! 

Seen on the planet’s eastern terminator – that line between day and night that corresponds to sunset – this remarkable spot is thought to be the first rainbow spotted outside our solar system.

This particular kind of rainbow can be seen on Earth by folks positioned above stable cloud layers. I’ve seen them from an airplane, where a glory formed around the plane’s shadow. Climbers often see them around their own shadow on clouds below them. I didn’t know they could form in a planet’s own shadow, and I love learning these kinds of colorful facts.