One of the most well-known asterisms in the sky is the famous Summer Triangle, which is most prominently placed in the summer sky, but doesn’t fully set until winter. Each of the bright stars in the triangle belongs to its own constellation. Notably the summer triangle star Deneb is the “tail’” of Cygnus the swan. The swan appears to fly right down the Milky Way, a handy way to find the edge of our galaxy in iffy viewing conditions.

Cygnus also contains the group of stars known as the Northern Cross. Most of the time that the cross is visible, it is high in the sky, seemingly detached from the horizon. By the end of December, as the Summer Triangle slips below the horizon just after sunset, the foot of the cross appears planted on the western horizon. The cross also contains a few interesting astronomical elements with binary Albireo at its foot, and brilliant Deneb at its head. Deneb is the most distant of the brighter naked-eye stars, estimated to be an astonishing 2,600 light years away, 100 times farther than its Summer Triangle neighbor Vega. Were Deneb as close to us as the sun, daytime would be around 100,000 times as bright as it is today.

First Published: December 24, 2019, 5:00 a.m.