Polaris and Thuban via the Big Dipper in July
Tonight, use the Big Dipper asterism in the constellation Ursa Major the Great Bear to find the sky’s northern pole star, Polaris. This is the star around which the whole northern sky appears to turn. Polaris – aka the North Star – is located nearly above Earth’s northern axis. In times past, wanderers on the northern face of Earth used Polaris to stay on course.
Once you find Polaris, you can also look for a famous former pole star. Thuban, in the constellation Draco the Dragon, was a north pole star for the builders of the pyramids 5,000 years ago.
Use the Big Dipper to find Polaris
Look at the chart at the top of this post. To find Polaris, draw a line through the Big Dipper’s pointer stars Dubhe and Merak. That line will point to Polaris, our modern-day North Star. You can use this trick to find Polaris any evening, no matter how the Dipper is oriented with respect to your northern horizon.
The chart above shows the Big Dipper, Little Dipper and star Polaris as you’ll see them in the north on July evenings. Polaris marks the end of the handle on the Little Dipper asterism, which is in the constellation Ursa Minor.
In other words, the Little Dipper is not the whole constellation, but just a noticeable pattern within the constellation Ursa Minor the Smaller Bear.
Still, Polaris is plenty bright enough to be seen with ease on a dark, clear night.
Look between the Dippers to find Thuban
As night deepens, and the fainter stars of the Little Dipper spring into view, those of you with dark-enough skies can expect to see a winding stream of stars between the Big and Little Dippers. These meandering stars make up the constellation Draco.
The star Thuban is one of the stars here, part of the Tail of the legendary constellation Draco the Dragon, a fixture of the northern skies. I always find Thuban by remembering it’s between the Big and Little Dippers.
Thuban is famous for having served as a pole star around 3000 B.C. This date coincides with the beginning of the building of the pyramids in Egypt. It’s said that the descending passage of the Great Pyramid of Khufu at Gizeh was built to point directly at Thuban. So our ancestors knew and celebrated this star.
Bottom line: Draw a line through the Big Dipper pointer stars to find Polaris, Earth’s northern pole star. If your sky is dark, also look for a former pole star, Thuban.