Omega Sun over South Padre Island, Texas

May 12, 2021

Omega Sunset

Photographer: César Cantú 
Summary Authors: César Cantú; Jim Foster

The photo above was captured at sunset over the Gulf of Mexico, as viewed from South Padre Island, Texas. Because of strong atmospheric refraction the solar disk takes the shape of the Greek letter omega.

At sunset or sunrise, sunlight directed towards us from the lower portion of the Sun passes through a somewhat denser atmosphere than rays coming from the Sun’s upper limb. Consequently, the bottom of the solar disk is refracted more, and thus distorted more, than the top of the solar disk. The omega shape (also known as Etruscan vase) actually results from an inferior mirage. When the Sun drops beneath the horizon, its inferior mirage seems to connect with the true Sun.

A wind turbine for generating electric power is in the foreground. Photo taken on March 6, 2021.