It is the one pattern known to most people.
Many people who have never really gazed at the sky will still recognize the term, “Big Dipper,” which is the ladle-shaped star pattern that describes wide circles in our northern sky.
The Big Dipper, or Ursa Major, is famous for a few reasons: one is that the shape is quite obvious.
The Big Dipper is formed by seven stars. Three starts represent a bent handle and four others mark the corners of a quadrilateral “bowl.”
Secondly, the Big Dipper is a circumpolar pattern, meaning that it will never set at our latitude. At least it won’t in our lifetime. Thus, no matter what time of night you go out to observe, the Big Dipper will always be somewhere in the sky.
The Big Dipper was a circumpolar pattern for northern skywatchers in the past. Because it was always someplace in the sky, Ursa Major would naturally have a prominent place in the lore and sagas of most northern cultures.
Curiously, many societies saw this pattern as a bear, despite the fact that bears do not have the type of long tail that the dipper’s handle is supposed to represent.
Eventually, Earth’s precessional wobbling will cause the dipper to set at this latitude, as the constellations themselves shift in relation to the celestial equator.
The third reason for the Big Dipper’s prominence in our culture is its collection of relatively bright stars.
Unlike the Little Dipper which is composed of faint components, the Big Dipper is fashioned from seven well-defined star points.
The Dipper stars appear bright because many of them are relatively close. Five of the Dipper Stars are part of the Ursa Major Moving Cluster, a starcluster 75 light years from our Solar System. (The star at the end of the handle, Alkaid, and the star at the upper bowl corner away from the handle, Dubhe, have no association with this system.)
When you observe the Big Dipper stars, you’re actually seeing some of them as they were 75 years ago. A 75-year-old can look at these stars and see them as they appeared on the year they were born.
Finally, the Big Dipper can direct you right to Polaris, the north star.
The two stars at the side of the bowl away from the handle, Dubbe and Merak, point toward Polaris. Polaris is about “one dipper’s length” away from Dube.
No matter what time of night it is, the Big Dipper will always be pointing toward Polaris.
Polaris, itself, doesn’t appear to move because it is aligned almost directly with the north celestial pole.
Contrary to popular conception, Polaris is NOT the brightest night sky star. It actually ranks 49th, so it is not a brilliant star. Finding it becomes much easier if you use the Big Dipper as a guide.
So, tonight, find Ursa Major in the northeastern evening sky. Remember, you can always find the Big Dipper at anytime of year, but you have to be certain not to always look in the same place.