This week, I want you to step back in time -- to the years in grade school or high school geometry classes. That's probably when you learned about polygons -- and perhaps the last time you thought about those two-dimensional, multisided shapes with straight sides.
Do you remember that a three-sided polygon is a triangle, a four-sided polygon is a rectangle and a five-sided shape is a pentagon?
Now, as soon as it's dark enough in the early evening, you can find those shapes in the sky by connecting the stars with imaginary lines.
What's the point?
I want you to have quick success finding your way around much of the night sky.
Learning to recognize constellations is the best way to navigate the starry skies, and polygons are one of the tools to use.
Polygons can be made up of bright stars from multiple constellations, or part of a single constellation. In some cases, polygons make up entire constellations. These polygons are also known as asterisms.
For starters, in the very early-evening western sky, look for the Summer Triangle. It's the last remnant of the summer stars. About a month from now, as the Earth continues in its orbit around the sun, you won't be able to see it at all.
Use this last chance to look in the low to moderately low western sky for the three brightest stars you can see. That's it. The brightest of them, in the lower right-hand corner, is Vega in the constellation Lyra, the harp. On the lower left is Altair, in Aquila, the eagle. The third is Deneb, in Cygnus, the swan.
Deneb is also at the top of the Northern Cross, that lies within Cygnus. To see a four-sided polygon -- a rectangle -- look higher in the western sky close to the overhead zenith. The four brightest stars you see form a diamond, a diagonally orientated rectangle. That's the Square of Pegasus, which outlines the torso of Pegasus, the winged horse.
Not far from the Square of Pegasus is the Andromeda Galaxy, the next-door neighbor to our Milky Way Galaxy. Viewed through a telescope or pair of good binoculars, it looks like a fuzzy white blotch. That ghostly cloud is more than 2 million light-years away. One light-year equals nearly 6 trillion miles.
In the moderately high eastern sky, a little to the upper left of Orion, the hunter, look for a lopsided, five-sided pentagon. Those five stars are more or less the entirety of the constellation Auriga, the chariot driver/goat herder. The brightest star of the pentagon is on the upper left corner. It's Capella and marks the spot in the constellation where a mama goat is sitting on the shoulder of the herder.
For extra credit, see if you can spot a tiny three-sided polygon of faint stars to the right of Capella. That triangle marks the baby goats sitting in the crook of herder's elbow.