The Winter Circle – sometimes called the Winter Hexagon – paints a great big circle of brilliant stars on the dark dome of a winter night. The Winter Circle lassos around Orion’s bright ruddy star Betelgeuse, and this loop of stars circles so far out from Betelgeuse that the Winter Circle even dwarfs Orion the Giant Hunter.
If you’re familiar with the winter constellation Orion, note that Rigel, the brilliant star at the lower right of Orion’s Belt, resides at the southwest corner of the Winter Circle. Now draw an imaginary line going leftward through the three stars of Orion’s Belt to find the southernmost and brightest star of the Winter Circle, Sirius.
The opposite direction through Orion’s Belt points to Aldebaran, the star that depicts the ruddy eye in the constellation Taurus the Bull. Castor and Pollux, the brightest stars in the constellation Gemini the Twins, are also found by way of Orion’s Belt. A line from the northwest (upper right) star of Orion’s Belt and through Betelgeuse escorts you to these two bright Gemini stars.
Look for Procyon above Sirius and below Castor and Pollux. Procyon, Sirius and Betelgeuse make up a star pattern that is often referred to as the Winter Triangle.
Brilliant Capella, the northernmost (top) star of the Winter Circle, is found to the upper right of Castor and Pollux and the upper left of Aldebaran. For some idea of the Winter Circle’s humongous size, an imaginary arc drawn from Sirius to Capella stretches out about one-third the way across the dome of sky.
When to see it
When the winter solstice arrives on or near December 21, the Winter Circle rises high enough to be seen in your southeast sky at about 9 p.m. After rising, the Winter Circle swings westward across the sky, and is highest up in the south around 1 a.m. It appears in the southwest sky around 5 a.m. The western (right) half of the Winter Circle sets in the west before the onset of a winter solstice dawn.
The Winter Circle stars rise and set some 4 minutes earlier with each passing night. Therefore, on January 21, the Winter Circle is found in the same place in the sky about 2 hours earlier than it was on the winter solstice one month before. On January 21, the Winter Circle appears in the southeast around 7 p.m., highest up in the south around 11 p.m. and in the southwest at 3 a.m. In late February and early March, the Winter Circle is found in your southern sky at nightfall and early evening.
The Winter Circle is an asterism
The Winter Circle is an asterism – a star formation that is NOT one of the 88 constellations. Whereas any constellation must be approved by the International Astronomers Union (IAU), anyone is free to make an asterism. If the star pattern is readily recognizable to a number of people, it could become part of the stargazers’ lexicon – like the Winter Circle. The Winter Circle may well be the largest famous asterism to fill the heavens.
On a dark and clear moonless night, look for the soft-glowing river of stars that we call the Milky Way to meander right through the Winter Circle.