Draco, and a former pole star

Event Date: March 5th

Time: 12:00 AM

Brief

  A couple of days ago, I showed how Canes Venatici "chased" the two bears in the sky-- even though it appears as if only the case with Ursa Major.  While doing so, I included the illustrations for them.  I will come back to the bears for tonight, and show another animal in that part of the sky: Draco, the dragon.  Although a faint constellation, Draco's figure is long, and seems to curve around half of Ursa Minor and the north celestial pole (n.c.p.), precisely 39 arc-minutes from Poloris.

   Let's take a look below, and notice how for at least the illustrations used here, that there is a slight overlap of Draco and Ursa Minor.  Their boundaries of course, do not overlap, although the space between the stick figures and stars are very close to each other.

Detailed

   In the second image, I will point out a very key star in Draco, named Thuban. Although not very bright at magnitude 3.6 , it is enough so under dark enough skies that about 4,800 years ago, Thuban was close enough to the n.c.p. that it was the pole star.  In about 21,000 more years, it will be at that declination once again (26,000-5,000).  Back then, centuries before serious light pollution, it would have been easy enough to see Thuban.  I am not sure how popular star-gazing was then, and astronomy in general.  However, whether building pyramids in Egypt or one empire in the process of conquering another(?), looking at the sky under dark conditions would haven become popular then and there.

   In the image, besides centering Thuban I included the precession cycle, which is labeled by certain key years.  I took away the illustrations and kept the stick figures.  Also for anyone wondering, the closest that Thuban was to the n.c.p. then was very close: 89º 53' 56" the middle months of 2800 BC.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.