Friday, January 4, 2013

The Constellation Canis Major and Minor

This post is the one of a series on constellations and posted throughout the year as each constellation comes into prominence.
I came across this article on New Years Eve which inspired me to write a post about the star Sirius, and its constellation.

Canis Major and Canis Minor are two constellations near the famous Orion, and are worth knowing because they house two of the brightest stars in our sky.  Canis means Dog, and so these constellations are the Big Dog and the Little Dog. I see a bad stick figure and a pair of dots myself, but I suppose with a little imagination, it wouldn't be too much of a stretch to see them as Orion's hunting dog's, following him into the woods perhaps.

These constellations are only just starting to come out in the evening hours during winter -- so unless you're out relatively late, you might not see them. The inspiring article described Canis Major as reaching it's highest point in the sky at mid-night on New Years Eve, which means if you went out at a more "normal" star-watching time at least for parents such as myself -- say 7 or 8 pm -- it won't be up yet.
Fall Mornings
Winter Nights
Spring Evenings
The dog constellations serve to tell me about our progress through the school year.  At the beginning of the year, and through first semester, I tend to see them on my drive in in the mornings. As the year progresses through winter I won't see them as often, as they'll be out in the middle of the night. As the year reaches the end, these dogs are out and observable during family-friendly observing times of just before bedtime during the spring months -- March April or May.

Canis Major is a southern hemisphere constellation -- one that is approximately 20° below the celestial equator. At my latitude, that means it is not out for too long each day -- only about 8-9 hours a day. Canis Minor on the other hand is just barely a northern hemisphere constellation - approximately 5° above the celestial equator. That means we can see Canis Minor longer each day -- about 12-13 hours a day.

One of the reasons for observing the Dog's is because of the bright stars they contain. Sirius is the brightest star seen anywhere from earth, short of the sun. It's the bright one in Canis Major -- or the head of the stick figure in my  minds workings. Procyon in Canis Minor is another bright star - 6th brightest in the sky for Northern observers. I often confuse the pair of stars in Canis Minor with the pair in Gemini, as they are about the same width in the sky. You should be able to tell the difference two ways. First, in Gemini they are both bright stars, where as Procyon far outshines its partner in Canis Minor.  Second, Gemini is to the right of Orion and Canis Minor is above and to the left.

Many people describe these two bright stars, and the red giant Betelguese as forming a great Winter Triangle in the sky. While I could draw this triangle in the sky -- it doesn't really pop out at me.

Winter Triangle

Another feature of Canis Major, is that it contains one of the biggest known stars -- what Louie Giglio described as "The Big Dog Star" in one of my favorite sermons of all time: How Great is Our God. At this link you may begin watching the portion where he describes The Big Dog Star. In it he compares a series of increasingly large stars with the earth as the size of a golf ball. On that scale, VY Canis Majoris would be the size of Mount Everest. Somewhere in Canis Major is a star too faint for you to see that is larger than the orbit of Jupiter around our sun. Put another way, if this star was where our sun was, we would be IN it -- not looking at it, and so would Mars and so would Jupiter. 

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