The Big Dipper is an asterism that makes up part of the constellation of Ursa Major, The Big Bear. It is seen here at the top center of the image. The Little Dipper, part of the constellation of Ursa Minor, The Little Bear, is seen at the bottom center. The two stars at the end of the bowl of the Big Dipper are called the "Pointer Stars" because a line drawn between them points to Polaris, the North Star. The Big Dipper and Polaris play an important part in the story of the Underground Railroad which helped slaves escape their captivity in the southern states of the United States before the Civil War by fleeing north to Canada. The folk song "Follow the Drinking Gourd" (another name for the Big Dipper) was a coded song that gave directions on the escape route from Alabama and Mississippi. While traveling on their long escape journey, they could always tell which way was north by the location of Polaris which they could find by the pointer stars. The Big Dipper is a circumpolar constellation, which means it stays above the horizon all night long as it apparently rotates around Polaris due to the Earth's rotation. It is also comprised of very bright stars in an easy-to-locate pattern. This view shows the positions of the Big and Little Dippers at about 10 pm on March 21, the first day of spring.