Draco the Dragon is visible every clear night in the Northern Hemisphere as it coils around the North Star.
The name Draco is probably best known as the child villian from the Harry Potter series. The celestial Draco is the shape of a dragon that can be spotted with moderate ease under dark skies.
Locating the Constellation Draco
Draco the Dragon is situated between two of the best known constellations in the sky, Ursa Major and Ursa Minor. These two locations, also known as the Big and Little Dippers, are high enough above the horizon in the Northern Hemisphere that they never set. Constellations such as these and Draco are called circumpolar constellations because they circle the pole star. In this case they circle the north pole star, Polaris.
Draco is a long constellation whose tail slithers between the Dippers and whose head lies between Cygnus and the Big Dipper. Draco's head consists of a trapezoid made up of four stars. Two of these stars are easy to see, with the third slightly more challenging and the fourth being difficult unless you are away from sources of light pollution.
From the head of Draco, the body is created by a chain of stars that lead toward Polaris, then doubles back on itself toward the head, and then makes a 90 degree turn and snakes in between the two Dippers.
The Stars of Draco
The brightest star in the constellation of the Dragon is Eltanin, or Gamma Draconis, shining at magnitude 2.24 and lying 148 light-years away. The third brightest star is also in the head and four degrees from Eltanin. This is Rastaban, at magnitude 2.79 and lying 362 light-years away.
The third and fourth stars in Draco's head are Grumium (Xi Draconis) and Nu 1 Draconis. Grumium is brighter at magnitude 3.73 and lies 111 light-years away. Nu 1 Draconis is magnitude 4.86 and lies a little closer to Earth at 100 light-years away.
Moving away from the head, the brightest star to mark the first bend in Draco is Altais, or Delta Draconis, at magnitude 3.07. It also lies 100 light-years away. Continuing on down the body we next run in to Zeta Draconis at magnitude 3.17. Next comes the second brightest star in Draco, Eta Draconis, at magnitude 2.73. Magnitude 4.01 Theta Draconis is next and marks the beginning of the 90 degree turn. Then comes Edasich, or Iota Draconis, at magnitude 3.29.
Directly between the bowl of the Little Dipper and the handle of the Big Dipper is Thuban, or Alpha Draconis, at magnitude 3.67. It is an important star to which we will return.
The last named star in Draco lies between Polaris and the end two stars in the bowl of the Big Dipper. This is Giausar, or Lambda Draconis, at magnitude 3.82.
Draco and the "Pole Star"
While Draco does not currently host the Pole Star (that would be Ursa Minor), it has before in Earth's history and it will again. Because Earth wobbles as it spins on its axis, the North Pole does not always point to the same place in the sky. Therefore Polaris is not always the Pole Star. This movement of the location of the North Celestial Pole is called precession.
The Earth completes one cycle of precession in approximately 26,000 years, when it will once again return to the spot from which it was first measured, which in our case, is Polaris. In about 13,000 years, the direction of the north pole will have wobbled enough that the star Vega, in the constellation Lyra, wil be the new Pole Star. In about 20,000 years from now, Thuban in Draco will be the Pole Star.
One Notable Nebula in Draco
Most good deep-sky observing targets are absent in Draco. But one decent challenge is NGC 6543. This ball of gas and dust is about magnitude 8.8 and is found about one-third of the way from Eltanin to Polaris. NGC 6543 has the name of the Cat Eye Nebula and can be spotted under dark skies with smaller telescopes.
