Caption: You can use the Big Dipper, Little Dipper, or Cassiopeia to help you find the North Star.
BY: AMY SAYLE
“How can you find north?” I once asked a planetarium audience. A young voice replied, “Just look for the red letter N!”
That, of course, was an excellent suggestion for inside the planetarium. There, helpful red letters on the horizon mark the cardinal directions.
But what do you do outside?
All you need is a clear sky. That will allow you to find the North Star, with no compass required. The North Star, also known as Polaris, is the star lying closest to the point directly over Earth’s North Pole.
Because Polaris lies over our planet’s axis of rotation, this star acts like a pivot point in the sky, staying (more or less) in the same location as Earth rotates over the day and night and as all the other stars appear to change position and direction.
Here are four ways to find the North Star:
Big Dipper method.
The Big Dipper consists of 7 bright stars. Four form a bowl or cup, and three form a handle. Look for the two “pointer stars”—the stars forming the side of the bowl farthest away from the tip of the handle.
Draw an imaginary line between those two stars, starting from the one at the bottom of the bowl. Then keep that line going, for about four to five times the distance between the pointer stars, until you run into a moderately bright star. That’s the North Star.
Unfortunately, there’s a problem with this method. At this time of the year, in the evening hours when you’re most likely to be outside, the Big Dipper is in a terrible location. It’s so low on the northern horizon that too much sky glow from light pollution or one ill-placed tree means you can forget about being able to find it.
Fortunately, when the Big Dipper is low in the sky, the constellation Cassiopeia will be high, and she also points to Polaris. She’s supposed to represent a queen but looks more like a letter W. Think of the three stars forming the middle part of the W as an arrow that points, with a bit of curving required, to the North Star.
Little Dipper method.
If you know how to find the Little Dipper, you’re set. Polaris is the tip of the handle. But this method can be tricky in urban areas because light pollution washes from view the dimmer stars in the Little Dipper. In the Triangle area, you’ll be lucky if you can spot Polaris plus just two of the stars in the bowl of the Little Dipper.
This method requires a field trip, but it may be the most fun. On a clear night, visit the giant sundial in front of Morehead Planetarium. Notice the sundial’s gnomon—the big metal part that points to the sky. In the daytime the gnomon creates the shadow you need to read the time.
At night, try resting your head on the gnomon and sight along it into the sky. Because the gnomon points north, the star it appears to point to is the North Star.
Finally, there’s 1 important way NOT to find the North Star. That’s by looking for the brightest star in the sky. There’s no reason the North Star would be bright, and in fact, it isn’t that bright. For that matter, there’s also no reason there even has to be a star at all over the North Pole (there’s not a South Star over the South Pole), but we got lucky on that count, at least for the time being.
Whichever method you use, once you’ve found the North Star, draw an imaginary line straight down to the horizon. That’s due north. If there were red letters on the horizon, that’s where the N would be.
If you’d like an in-person lesson on how to find north, join us sometime for our live planetarium show “Carolina Skies.” You’ll leave with a star map to help you practice later.
One place you might practice finding the North Star is at a Morehead skywatching session. If the weather permits, we’ll be at Little River Regional Park on Sunday, Dec. 13, 2015, and at Jordan Lake (Ebenezer Church Recreation Area) on Monday, Dec. 14, 2015.
Just don’t expect to see any red letters in the sky.