The Winter Circle – sometimes called the Winter Hexagon – is a big circle of bright stars on the dark dome of a winter night. At the center of the Winter Circle, you’ll find center Orion’s bright red star Betelgeuse. Rigel, Aldebaran, Capella, Procyon, Sirius, Castor and Pollux are the bright stars that make up the large, circular pattern.
Follow these links to learn more about this easy-to-find star pattern.
The Winter Circle is an asterism. The International Astronomical Union (IAU) decided on the 88 official constellations in the 1930s, but anyone is free to make an asterism.
An asterism is just a recognizable star pattern. It’s a bit like picking out a pattern in a cloud, although, if the name for the pattern is used often enough by enough people, it could become part of the stargazers’ lexicon – as has the name Winter Circle. The Winter Circle may well be the largest famous asterism in the heavens.
How to spot the Winter Circle. 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 by themselves make up another star pattern – another asterism – often called as the Winter Triangle.
Bright Capella, the northernmost 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 the Winter Circle 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.
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.
Bottom line: The Winter Circle is a large circular pattern on the sky’s dome, consisting of the bright stars Rigel, Aldebaran, Capella, Procyon, Sirius, Castor and Pollux.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.