Winter Hexagon: The ultimate asterism to master the winter sky in Northern Hemisphere 

-written by Jai Mirchandani, reviewed by Ankush Banerjee

What is the Winter Hexagon? At some point in our lives, we might have surely looked at the night sky and tried to spot all the constellations. But spotting constellations is not a piece of cake, there are a large number of stars in the night sky among which the stars that correspond to a constellation are sometimes comparatively dim which makes it seriously difficult to look for the same patterns in the night sky that our Greek/Indian/Roman ancestors had imagined.

To make the process of spotting the constellations a piece of cake, astronomers have developed a concept called  ‘asterism’. Asterism, just like constellations, is also a pattern of stars but it’s very easy to spot in the night sky as most of the stars that make an asterism are very bright, and the asterism itself is very huge. Stars that form an asterism are usually among the brighter stars of the constellations that they belong to. In this blog let’s look at one of the asterisms which are enough to understand a huge chunk of the entire winter sky in the northern hemisphere

Want to know about the constellations recognized by IAU? Check out our blog here

winter hexagon

An extraordinary asterism called ‘the winter circle’ or ‘The winter Hexagon’ is one of the best ways to understand the winter sky. As the name suggests, it makes a giant circle/hexagon (shape depends on your imagination) in the winter sky. There are 6 stars in this asterism that form a hexagon and help us find six major constellations of the night sky. 

The six stars are as follows:

  • Rigel: Rigel, also known as β Orionis is the brightest star in the Orion constellation and is the seventh brightest star in the night sky. This blue supergiant has an apparent visual magnitude of 0.1 and is located 860 light-years away from the earth. It is situated at the leg or foot of Orion – the hunter.  

  • Aldebaran: α Tauri or Aldebaran is located in the constellation Taurus and is considered to be the eye of Taurus – the bull. It’s the brightest star of the constellation and the fourteenth brightest star of the night sky. The star is located 65 light-years away from earth and its apparent visual magnitude varies between 0.75 and 0.95.

  • Capella: Capella or Alpha Aurigae or the goat star is the sixth brightest star in the night sky and the brightest star of the constellation Auriga with a very low apparent visual magnitude of 0.08. Capella is located 42.92 light-years away from earth and  It’s a spectroscopic binary star where 2 G-type giant stars that are very close to each other revolve around each other and complete one revolution in 105 days.

  • Pollux: Pollux also known as beta Geminorum is a reddish giant star located at a distance of around 34 light-years from earth. It’s the brightest star in the constellation Gemini and the 18th brightest star in the night sky with an apparent visual magnitude of 1.15. It is located at the head of one of the twins (Castor and Pollux)  in the constellation Gemini.

  • Procyon: Procyon or alpha Canis Minoris is the brightest star in constellation Canis Minor and overall the 8th brightest star with an apparent visual magnitude of 0.35. It’s a white-hued main-sequence star located at a distance of just 11.45 light-years away from our planet. 

  • Sirius: Sirius also known as Alpha Canis Majoris or the dog star is the brightest star of not just the constellation Canis major but also the entire night sky with its apparent visual magnitude as low as -1.46. Constellation Canis Major represents a big dog in the night sky and Sirius is located at the nose of the dog. Sirius is a binary star located as close as just 8.6 light-years from Earth.

Hence, these 6 stars in the above order form a hexagon in the night sky as shown in the figure below. Due to this Asterism, many constellations with a variety of deep-sky objects such as Orion, Lepus, Canis Major, Canis Minor, Taurus, Auriga, Gemini, Perseus, Cancer, Leo, etc. can be identified very easily. Thus, the winter hexagon can be considered as an ultimate asterism to understand the winter sky of the Northern Hemisphere.

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