Astro Bob: Stroll with the moon through the Winter Hexagon

Sunday through Tuesday nights, January 24-26, the bright moon will guide you to one of the sky's most sparkling sights.

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The Winter Hexagon is the gem of the winter sky. (Stellarium)

Connect six of the winter's brightest stars the next clear night, and you'll make a friend for life. The stars are Sirius, Procyon (PRO-see-on), Pollux, Capella, Aldebaran and Rigel, and together they form the Winter Hexagon. This gigantic, six-sided figure stands 66° tall by 45° wide. That's 6 1/2 fists by 4 1/2 fists in our biological measurement system. To check it for yourself, ball your fist and hold it vertically against the sky to measure from top to bottom and horizontally to measure from side to side.

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Follow the waxing gibbous moon across the Hexagon early this week. On Jan. 24 it's near Aldebaran in Taurus the Bull. Then on the 26th, look for it near Pollux in Gemini the Twins. The Winter Hexagon is an asterism, a pattern of bright stars borrowed from one or more constellations that forms a prominent pattern in the sky. This asterism is big! The topmost star, Capella in Auriga the Charioteer, stands nearly overhead, while Sirius twinkles just two fists above the southeastern horizon. (Stellalrium)

One of the best things about the Winter Hexagon is that it's so bright not even the full moon will dim the stellar sextet. For the next three nights (Jan. 24-26), the waxing gibbous moon saunters across the northern half of the hexagon, helping skywatchers identify several of its members.

Once you've found one star, the others will fall quickly into place. All of them are 1st magnitude or brighter. In fact, there are just nine first magnitude stars in the winter sky. One of them, Betelgeuse, is trapped inside the hexagonal corral created by its neighbors. In a show at being inclusive, some observers remove the line connecting Aldebaran to Rigel and instead connect Rigel to Betelgeuse to fashion a gigantic letter "G." The other two 1st magnitude non-members — Regulus in Leo and Deneb in the Northern Cross — are both too far from the figure for consideration.


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Can you find the six stars that outline the Hexagon in this photo of the night sky? (Bob King)

While the air may be more transparent during winter due to less humidity, the main reason January skies seem thick with stars is because they are! More bright stars are jammed together in one region of the sky compared to the summer, spring or fall months. And not just the six suns of the Hexagon. They're reinforced by a host of 2nd magnitude stars from Orion, Gemini and other constellations.

Myth to the contrary, winter nights are not darker than summer nights at least not at mid-northern latitudes. We have this thing called snow. Snow reflects lots of light, especially the now piercing glare of those ubiquitous LED lamps that line our streets, parking lots and front porches. A good portion of that reflected light heads straight up into the sky, dimming the fainter stars.

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After you find the Winter Hexagon, use your mind's eye to imagine the sky in three dimensions. The numbers are distances in light-years (l.y.). Sirius and Procyon lie relatively close to the Earth with Capella , Aldebaran and Pollux a little further. Rigel is far, far away but shines brightly because it's a large and radiant supergiant star. (Stellarium)

Gratefully, the Winter Hexagon has what it takes to press on through light pollution. So tonight or the next clear night, use the moon to find Aldebaran or drop down to Rigel in the Orion's knee or start at Sirius, the brightest star. Each of the six is the brightest luminary in its respective constellation. Once found, the Hexagon becomes a roadmap for exploring each constellation in turn.

And once you know these groups you can branch out farther and farther until you've covered the entire winter sky — just in time for the spring sky to replace it! Such is the pursuit of astronomy, where everything's on the move. You included.


"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at .

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at
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