The Little Dipper and the North Star

December 21, 2014

Click for annotated photo

Photographer: John Chumack 
Summary Authors: John ChumackJim Foster
Can you pick out the Little Dipper and the North Star in this unremarkable looking sky? Like its bigger cousin, the Big Dipper, the Little Dipper (Ursa Minor or Little Bear) is an asterism and its handle also represents the tail of a bear. But unlike the Big Dipper, the Little Dipper is hard for most people to find. Click on the image to see an annotated version. Ursa Minor was one of the 48 original constellations listed by the second century astronomer Ptolemy -- it remains one of the 88 modern constellations.
The Little Dipper's brightest star, the North Star (also called Polaris or the Pole Star), is the star that lies closest to the north celestial pole -- less than one degree away. But it's by no means the brightest star in the sky as many people believe. It's considered a second order magnitude star, having a magnitude of 1.97. The North Star is a yellow-white supergiant and the brightest Cepheid variable star in the sky. The second brightest star in the Little Dipper, Beta Ursae Minoris, has a magnitude of 2.08 -- just slightly dimmer than Polaris. Beta Ursae Minoris (also known as Kochab) is an orange giant located 16 degrees from Polaris. Kochab and Gamma Ursae Minoris or Pherkad form the end stars of the dipper and have been referred to as the guardians of the Pole Star. Photo taken on September 22, 2014, from John Bryan State Park in Yellow Springs, Ohio.
Photo details: Canon 6D DSLR camera; 58 mm lens, f/4.0; ISO 1250; CG-4 Tracking Mount; 48 second exposure.