High in the skies above Arnathia, a binary star pair named the Twin Suns drives the changes in seasons as well as the day/night cycle on the planet. In the ancient Urnati, they were named Ow and Zinoion, Father and Daughter. [container:imgright][img:1250642][/container]

While the stars are named as father and daughter, they are actually more similar than different. They orbit around a central point, their [url:https://en.wikipedia.org/wiki/Barycenter]barycenter[/url], and are an eclipsing binary. As such, from the vantage point of Arnathia, they pass in front of each other during their period of rotation. However, due to the orbit of Arnathia, this eclipsing only happens once every 11 years, This creates much hotter and cooler temperatures as stars rotate around each other. 

As Arnathia circles the pair of stars once, the binary pair rotate around their barycenter at a slightly slower rate. The time between eclipses is approximately 5.5 orbits by Arnathia around them. When one of the stars eclipse the other, temperatures on Arnathia can drop by the equivalent of approximately 5°F / 3° C from average. When both are shining unobstructed, the temperature can vary as much as 7°F / 4°C warmer than average.

These variations can make for very significant changes in Arnathian weather, and the world’s populations have managed to adapt to these regular changes quite well. Since they are predictable and, frankly, visible, adaptation has not been difficult.

One period when the eclipses exacerbated problems on Arnathia was after the Cataclysm. When the Cataclysm occurred, the suns had passed the point of eclipse by about three years. This meant that as the skies filled with dust and debris, the extra light from the pair was blocked. This kept the planet from warming. About two years from the Cataclysm, the suns started moving toward another eclipse, additionally cooling the planet and strengthening the The 30-Year Winter.