Celestial News: A hexagonal tour of the winter sky
Want to learn your way around the starry winter sky? The six-sided Winter Hexagon asterism is a great place to start. It spotlights eight of the 20 brightest stars in Earthly skies, including five in the top 10. The Milky Way flows right through the heart of the Hexagon and it is flanked by two of the sky’s most beautiful naked-eye star clusters. The Pleiades star cluster leads the Hexagon across the sky and the Beehive star cluster brings up the rear.
You can locate the first star in the Winter Hexagon by extending a line through the familiar three stars of Orion’s Belt toward the lower left. The flashy star you come to is Sirius, nicknamed the “Dog Star” because it represents the nose of Orion’s big hunting dog, Canis Major. Sirius is the brightest and closest of the seven stars in the Winter Hexagon at a distance of only 9 light years.
From Sirius, shoot a line to the upper right and find Rigel, the bright blue star that marks the foot of Orion the Hunter. Rigel appears nearly as bright as Sirius, but is located 100 times further away at 900 light years. If Rigel was viewed from the same distance as Sirius, it would shine like a second sun in our sky, being visible in broad daylight.
To the upper right of Rigel is the orange giant star Aldebaran, marking the eye of Taurus the Bull. Aldebaran is 68 light years away. Its name means “The Follower” because it closely follows the Pleiades star cluster across the sky.
Continue from Aldebaran by extending a line nearly overhead to the second brightest star in the Winter Hexagon, Capella, the yellow-giant alpha star in Auriga, the Charioteer. Capella is only 45 light years away. Although it looks like a single star to the naked eye, astronomers have discovered that it is composed of the light from four different stars.
Dropping down from Capella toward the eastern horizon will bring you to a close pair of bright stars, the Gemini Twins, Castor and Pollux. Castor is 52 light years distant and is not only the fainter of the two Twins, but is the faintest star in the Winter Hexagon as well. Pollux is considerably closer to us at 35 light years away.
The Hexagon now continues southeast of the Gemini Twins to the star Procyon. This star’s name means “Before the Dog,” and it is aptly named because it rises in our sky just before the Dog Star, Sirius, appears. Procyon, like Sirius, is a nearby star, only 11 light years away.
Complete the Winter Hexagon by shooting a line from Procyon back to Sirius, where we started.
The eighth star of the Winter Hexagon can be found near its center. It is the red supergiant star Betelgeuse, marking Orion’s shoulder. Betelgeuse is very far away — 520 light years to be exact. It is so large that, if it were placed at the center of our solar system, it would fill the orbit of the planet Jupiter! ***
Jimmy Westlake retired from Colorado Mountain College Steamboat Springs in 2017, after 19 years as a professor of physical sciences. Celestial News appears monthly in the Steamboat Pilot & Today. Check out Westlake’s astrophotography website at jwestlake.com.
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