One of the most common questions I hear under the night sky is “How do I find the North Star?”
It’s surprising how many folks believe that the North Star — or Polaris, as astronomers call it — is the brightest star in the heavens. If you do and you use it to find your way at night, you’re sure to become hopelessly lost.
No, the North Star is not the brightest star in the sky; in fact, it’s the 48th brightest star. Unless you have reasonably dark skies without much light pollution, it’s rather difficult to find. (And, of course, it’s not visible at all to our stargazing friends south of the Earth’s equator.)
Locating it, however, isn’t too difficult once you can recognize stars and star patterns in the northern sky. So, if you learn only two star groupings in the entire sky, the two I recommend are the Big Dipper and Cassiopeia.
The reason I say this is that these two star patterns can help point you toward Polaris, and right now is a great time to find both in the north after dark.
During the early evening hours this week, go outdoors and face northward. Low in the northeastern sky you’ll find the seven similarly bright stars of the Big Dipper, so named because this star grouping appears as a ladle with a bent handle. This time of year, the Dipper, which is only a part of the larger constellation known as Ursa Major, the great bear, appears to be standing on its handle after dark.
Next, look toward the northwest. There you’ll find the constellation Cassiopeia, named for the ancient Ethiopian queen it’s supposed to represent. Rather than searching for a queen, however, you might have an easier time spotting a sideways “W” shape outlined by its five brightest stars. Midway between these two star groupings lies Polaris.
This star is important because it stands directly above our planet’s north pole. This means that the Earth’s rotational axis aims almost in its direction, and during the night, the northern stars appear to revolve about Polaris in a counterclockwise direction.
And that’s where the Dipper and Cassiopeia come in. Since these two star patterns lie on opposite sides of Polaris, you can use each to find Polaris between them.
From the Big Dipper, follow the two stars at the end of its bowl — from its base to its top — and extend that line about five times that distance. There you’ll encounter Polaris.
Similarly, you can use the middle three stars of Cassiopeia’s “W” as an arrow to point approximately in the direction of Polaris.
Knowing these two star groupings is important because they lie on opposite sides of the North Star, turn around it and constantly point in its direction.
When the Big Dipper appears high in the sky, Cassiopeia lies very low or below the horizon. And when the Dipper is below the horizon — or very low in the northern sky — Cassiopeia will be the star grouping to help point you toward the North Star.
— Dennis Mammana is an astronomy writer, author, lecturer and photographer working from under the clear dark skies of the Anza-Borrego Desert in the San Diego County backcountry. Contact him at mammana@skyscapes.com and follow him on Twitter: @dennismammana. The opinions expressed are his own.