Happy New Year - here are some dogs
And how to find the dog stars
If you’re new to this newsletter, welcome! I’m Abby. I’m a freelance science journalist, stargazing columnist and author of The Art of Urban Astronomy. I live in England, where we have just entered a second lockdown…this time in winter. I started this newsletter to help people through the dark nights, with ideas of what to look for in the skies each week. If you live in the southern hemisphere don’t worry, I always try to make sure it applies to stargazers around the world.
Happy new year from me and my two dogs, Peanut and Jack.
After the news about more lockdowns in the UK, and the fact Christmas is over, I thought everyone might need some cheering up. These two dogs cheer me up every day, so I thought why not spread their joy. (They do have an Instagram for anyone interested!)
OK, now back to the stars. This week is about how to find the two dog constellations - Canis Major and Canis Minor. To find both of these, you can imagine both constellations as loyal companions, running behind Orion.
The dog stars
From the northern hemisphere Orion appears with the red giant Betelgeuse above to the left of the belt, and the blue star Rigel below to the right. From this orientation, the dog constellations are to the left of Orion. In the southern hemisphere, Orion appears upside down and the dogs are to its right.
Let’s start with Canis Major. This contains the brightest star in the night sky, Sirius. To find Sirius, which is actually a binary star system, not one single star, draw a line along Orion’s belt. In the northern hemisphere, this line goes from right to left, and it’s the opposite way in the south. Keep this line going until you come across a bright star that visibly appears to twinkle, and you’ve found Sirius.
All stars appear to twinkle because of the turbulence in Earth’s atmosphere affecting the path of light reaching our eyes. Sirius is the clearest example of this effect. This is partly because it’s so bright but also because, in the northern hemisphere, it appears low in the horizon so there’s more of the atmosphere for the light to travel through.
Twinkly Sirius makes up the neck of the dog in Canis Major. To find the rest of the constellation, look below Sirius in the northern hemisphere. You will find a triangle of three stars, which make up the dog’s tail and the top of its back legs.
While Canis Major is quite clearly a dog or an animal shape, the constellation of Canis Minor requires a lot more imagination. The pattern is made up of two bright stars. To find Canis Minor, you need to use Betelgeuse, Rigel and Sirius. Imagine these three stars make three of the four corners of a parallelogram. Where you imagine the fourth would be, look around that part of the sky for a bright star. That’s Procyon, and once you’ve got it you’ve found Canis Minor.
Like Sirius, Procyon is also a binary star, made up of a main sequence star being orbited by a white dwarf. Procyon is the eighth brightest star in the night sky, because it’s also relatively close to us at only 11.5 lightyears away compared to Sirius’s 8.6 lightyears.
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