Explore the Wonders of the Winter Hexagon

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Finding the Hexagon

Orion and the Winter Triangle stars; Sirius, Procyon and Betelgeuse. M50, M46, M47 and M41 open clusters are all visible at left.
Alan Dyer/Stocktrek Images / Getty Images

The months of late November through March give you a chance to see the gorgeous sights of the Northern Hemisphere winter night sky. For most folks in the Southern Hemisphere (except for those in the far southern reaches), these sights are visible, too. All you need to see them is a dark, clear night, appropriate clothing (especially if you live in the north), and a good star chart.

Introducing the Hexagon

The Winter Hexagon is an asterism — a collection of stars that make up a pattern in the sky. It's not an official constellation, but it is made up of the brightest stars of Gemini, Auriga, Taurus, Orion, Canis Major, and Canis Minor. It's also often called the Winter Circle. Let's take a look at each star and constellation represented in this part of the sky. Although these are just some of the many stars and objects you can see throughout the year, this chart gives you an idea of how they look in the sky. 


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Check out Gemini and Pollux

constellation Gemini
The constellation Gemini, containing the stars Castor and Pollux (which is part of the Winter Hexagon). Carolyn Collins Petersen

Pollux: Castor's Twin

The constellation Gemini contributes the bright star Pollux to the Hexagon. It's one of two "twin" stars that give Gemini its name, based on twin boys from Greek mythology. It's actually brighter than its so-called twin, Castor. Pollux is also called "Beta Geminorum", and is a orange-colored giant star. In fact, it's the closest star of its kind to the Sun. You can easily see this star with the naked eye. It's now a K-type star, which tells astronomers that it is no longer fusing hydrogen in its core and has moved on to fusing other elements such as helium. It has a planet called Pollux b, which was discovered in 2006. The planet itself can't be seen with the naked eye.

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Visit Auriga and See Capella

The constellation Auriga, with the bright star Capella. Carolyn Collins Petersen

Ah, Capella

The next star in the Hexagon is Capella, in the constellation Auriga. Its official designation is Alpha Aurigae, and it's the six-brightest star in the night sky. It's actually a four-star system, but looks like one object to the naked eye. There are two pairs of stars: Capella Aa and Capella Ab. Capella Aa (which is what we probably see with the naked eye) is a G-type giant star. The other pair is a set of two faint, cool red dwarfs.

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The Bull in the Sky and his Red Eye

constellation Taurus
The constellation Taurus features Aldebaran as the eye of the Bull, the Hyades star cluster (V-shaped) and the Pleiades. Carolyn Collins Petersen

The Eye of the Bull

The next tip of the Hexagon is the star Aldebaran, thought of in ancient times as the eye of Taurus the Bull. It's a red giant star with with the official name Alpha Tauri, since it's the brightest star in Taurus. It appears to be part of the Hyades star cluster, but in reality it's simply in the line of sight between us and the V-shaped cluster. Aldebaran is an evolved K-type star with a faintly orange color.

Not too far from Aldebaran, look for the little star cluster called the Pleiades. These are stars moving together through space and, at a 100 million years old, are stellar toddlers. If you look at them through binoculars or a telescope, you'll see dozens or perhaps hundreds of stars surrounding the 7 brightest naked-eye members of the cluster.

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Check Out Orion

Seine et Marne. Constellation of Orion. Diving in the great nebula of Orion, M42 (Messier 42), one of the most spectacular nebulae of the sky.
Christophe Lehenaff / Getty Images

The Bright Stars of Orion

The next two stars are in the constellation Orion. They're Rigel (also known as Beta Orionis, and making one shoulder of the mythical Greek hero) and Betelgeuse (called Alpha Orionis, and marking the other shoulder). Rigel is a blue-white star while Betelgeuse is an aging red supergiant that will someday blow up in a catastrophic supernova explosion. Astronomers are awaiting its blazing explosion with great interest. When this star does blow up, it will brighten the sky for several weeks before slowly dimming down. What's left will be a white dwarf and an expanding cloud of element-rich gas and dust.

While you're looking at Rigel and Betelgeuse, look for the famous Orion Nebula. It's a cloud of gas and dust busily giving birth to hot young stars. It's about 1,500 light-years away, making it the closest starbirth region to our Sun.

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The Doggie Stars of the Winter Hexagon

Orion & Winter Triangle, Betelgeuse, Procyon, & Sirius
Orion & Winter Triangle, Betelgeuse, Procyon, & Sirius. Getty Images/John Chumack

The Dog Stars

The final stars in the Hexagon are Sirius, in the constellation of Canis Major, and Procyon, the brightest star in the constellation Canis Minor. Sirius is also the brightest star in our nighttime sky and lies about 8.6 light-years away from us. It's actually two stars; one is a brilliant blue A-type star. Its dim companion called Sirius B. Sirius A (the one we see with the naked eye) is about twice as massive as our Sun. Its official name is Alpha Canis Majoris, and has often been colloquially referred to as the "Dog Star". That's because it rises just before the Sun during August, which for the ancient Egyptians marked the beginning of Nile flooding each year. In part that's where we get the term "dog days of summer".

There's another dog up there in the Hexagon. It's Procyon and is also known as Alpha Canis Minoris. It looks like a single star if you search it out by the naked eye, but in truth, there are two stars there. The bright one is a main-sequence star, while its companion is a faint white dwarf.

The Hexagon is an easy thing to spot in the night sky, so take the time to search it out. Scan the area with binoculars or a small telescope to find other treasures hidden among the stars of these constellations. It's a great way to get to know that area of the sky.