Ask people which constellation they know and nine out of ten will mention the Big Dipper. Small wonder — its distinctive outline is large, unmistakable, and visible almost all year long from the northern hemisphere thanks to its position near the North Celestial Pole.
A purist would note that the Big Dipper is technically an asterism rather than a true constellation — it is a prominent part of the larger constellation Ursa Major (the Big Bear). But whatever the semantics, the Big Dipper plays an outsized role in both the romantic and the pragmatic sides of stargazing.
A Shape with Many Stories
What does the Big Dipper symbolize? That depends on who you ask. Most people in the Western tradition see it as a drinking cup or ladle. African-Americans escaping slavery in the 1800s called it the Drinking Gourd — a navigation tool pointing toward freedom in the North. Many medieval English saw it as a plough. Mongolian astronomers depicted it as seven old men.
One of the more picturesque legends is a Native American interpretation: the cup stars represent a bear, and the three handle stars are hunters in pursuit. As autumn arrives, they wound the bear — which accounts for the red foliage of the trees. But the bear continues to roam the sky, confounding the hunters year after year.
Finding Polaris: The Pointer Stars
One of the Big Dipper's most practical uses is locating Polaris, the North Star. Polaris isn't particularly bright, but it marks true north with remarkable accuracy.
The trick is simple: draw a line through the two stars forming the outer edge of the Dipper's cup — Merak (bottom) and Dubhe (top) — and continue that line outward from the cup about five times the distance between them. That line points almost exactly to Polaris. Polaris is also the last star in the handle of the Little Dipper, so with the Big Dipper found, you've already started to trace its smaller companion.
Following the Arc to Arcturus
The handle of the Big Dipper also guides you to one of the sky's most beautiful stars. Follow the gentle curve of the three handle stars outward in the same direction as the arc — "Arc to Arcturus" as the old memory device goes.
Arcturus, in the constellation Boötes, is the fourth-brightest star in the sky and shines with a distinctive warm orange glow that shows beautifully through binoculars. It's a giant star about 37 light-years away — close enough that if it replaced our Sun, its atmosphere's outer edge would extend 25 times farther than the Sun's currently does.
From Arcturus you can continue the arc further to Spica in Virgo — a brilliant blue-white star completing the trio: Arc to Arcturus, Speed on to Spica.
The Dipper Through a Telescope
The Big Dipper itself contains several rewarding deep-sky targets. The Mizar and Alcor system in the handle is a classic naked-eye and binocular double (see our double stars article). Sweeping with binoculars in the region of the cup reveals the galaxy pair M81 and M82 (Bode's Galaxies) — one of the finest galaxy pairs for small telescopes. And M97, the Owl Nebula, is a planetary nebula in the bowl worth seeking on a dark night.