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Moon sweeps through Winter Circle March 23 and 24

On March 23 and 24, 2018, the waxing moon is moving inside the Winter Circle, sometimes called the Winter Hexagon. It’s a large circular (hexagonal) star asterism – not one of the 88 official constellations, but just a noticeable pattern of stars – consisting of seven 1st-magnitude stars in six separate constellations:

Capella – brightest star in the constellation Auriga the Charioteer
Pollux – brightest star in the constellation Gemini the Twins
Castor – second-brightest star in the constellation Gemini the Twins
Procyon – brightest star in the the constellation Canis Minor the Lesser Dog
Sirius – brightest star in the constellation Canis Major the Great Dog
Rigel – brightest star in the constellation Orion the Hunter
Aldebaran – brightest star in the constellation Taurus the Bull

Here are constellation charts via the International Astronomical Union (IAU)

In the evening in March, we in the Northern Hemisphere see the Winter Circle fill up much of our southwestern sky at nightfall. Elsewhere in the world – even in places where it’s not winter – the moon will also be in the midst of these stars on March 23 and 24. Meanwhile, as seen from temperate latitudes in the Southern Hemisphere, what we northerners call the Winter Circle will appear upside-down relative to our northern view. That is, southern skywatchers will see the star Sirius at top and the star Capella at bottom.

As evening deepens, as seen from around the globe, these stars will swing westward across the sky at the rate of about 15 degrees per hour.

Our sky charts can’t adequately convey the Winter Circle’s humongous size! It dwarfs the constellation Orion the Hunter, which is a rather large constellation, occupying the southwestern part of the Winter Circle pattern.

The Winter Circle in blue and the Winter Triangle in red. They’ll be out in the evening sky for several months to come. Image via Wikimedia Commons

Here’s how to locate the Winter Circle from mid-northern latitudes. At dusk or nightfall, look high up for the bright star Capella. This star marks the top (or more properly, the northern terminus) of the Winter Circle.

As darkness falls, look for the constellation Orion the Hunter to prowl in the south to southwest sky. Draw a line downward through Orion’s Belt to find Sirius, the brightest star in the night sky. This star marks the bottom (the southern tip) of the Winter Circle.

We include this sky chart to help you connect the Winter Circle stars.

By the way, the moon is now showing you where the sun resides (more or less) in front of the backdrop stars in the month of June. So enjoy the Winter Circle. And contemplate the sun being in this part of the sky when summer returns to the Northern Hemisphere!

Bottom line: On March 23, 2018, the moon resides inside the Winter Circle – a large star configuration made of seven brilliant stars.

Read more: Winter Circle, or Hexagon, made of bright stars

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Bruce McClure