Winter Hexagon

If you’ve been out under clear skies lately, you can’t have missed the sprinkling of incredibly bright and colourful stars in the eastern evening sky. Some of the brightest stars form a huge six-sided star pattern (or asterism) called the Winter Hexagon (or Football, for NFL fans).

By 8 pm local time, all of the stars that we’ll need to make the asterism are visible. The very bright, white star hugging the southeastern horizon is Sirius, nicknamed the Dog Star, in the constellation of Canis Major (the Big Dog). After our Sun, Sirius is the brightest star in all the sky. It is not only about 25 times more luminous than our Sun, but is also only a mere 8.6 light-years away! On top of that, it is actually heading towards us, and will brighten over the next millennia!

Moving counter-clockwise, above and to the right of Sirius is the bright, bluish star Rigel, marking the foot of Orion (the Hunter). The constellation of Canis Major is very obviously a dog shape - with the head upwards, tail to the lower left, and feet to the west (right).

Almost three fist diameters (26°) above Rigel is the orange star Aldebaran in the constellation of Taurus (the Bull). Aldebaran is an old red-giant star more that forty times the diameter of our sun.

Three fist diameters to the upper left of Aldebaran sits the bright yellow star Capella, the Goat Star, in the constellation of Auriga (the Charioteer). The form of Auriga is more or less a ring of medium bright stars with Capella at the top as the “diamond”. Moving three fist diameters down and to the left of Capella we encounter a pair of bright stars - the twins Castor (upper) and Pollux (lower) in the zodiac constellation of Gemini. The bodies of the twins extend sideways towards Orion.

Finally, look about midway between the twins in Gemini and Sirius for the bright blue-white star Procyon in Canis Minor (the Little Dog). At only 11 light-years away, it’s practically in our neighbourhood, too! Unlike his big brother, the constellation Canis Minor has only two significant stars. A dim, but visible star named Gomeisa sits four finger widths above Procyon.

We can turn our football into a capital letter “G” by connecting Rigel to the bright, reddish star Betelgeuse (“beetle juice”), which marks the eastern shoulder of Orion. This star is a true giant – believed to be more than 600 times the size of the sun! It’s also nearing the end of its days – when it will explode as a tremendous supernova; but we’re in no danger when it does. Notice that Betelgeuse is not quite as strongly coloured as Aldebaran.

The Winter Hexagon is visible on the same dates and times every year, and will remain in view until about mid-April. The Winter Milky Way rises up through it – and the moon and planets wander through those stars as they travel along the Ecliptic. Next week, the nearly full moon will cross directly through the hexagon.

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