The Winter Triangle is an astronomical asterism, a popularly known pattern or group of stars that can be seen in the night sky, formed from three of the brightest stars in the winter sky. This triangle forms an imaginary equilateral triangle drawn on the celestial sphere, with its defining vertices at the stars Sirius, Betelgeuse, and Procyon. The stars are the primary stars in the constellations of Canis Major, Orion, and Canis Minor, respectively.
For much of the night in the northern winter, the Winter Triangle is high in the sky at the latitudes of the Pacific Northwest observers, but can also be seen during autumn in the early morning to the East. In the spring the triangle is visible early in the evening to the West before its stars set below the horizon. Like the Summer variant, observers in the southern hemisphere will see the winter triangle in a what would be the reverse of an observer in the Pacific Northwest.
What is interesting to note is that although the Winter Triangle surrounds most of the faint constellation Monoceros, its brightest stars are of fourth magnitude and hardly noticeable to the naked eye. This is fascinating as the triangle does include two first magnitude stars and the star Sirius, which is even brighter.
“The three stars of the Winter Triangle are easy to find because they lie in the vicinity of Orion’s Belt, one of the best known asterisms in the sky. Betelgeuse, the left shoulder of Orion, is the bright red star above Alnitak, the easternmost star of the Belt. Sirius can be found by following the line formed by the Belt stars to the southeast, while Procyon lies to the upper left of Sirius.”