North Circumpolar Constellations

star

Camelopardalis

Cassiopeia

Cepheus

Draco

Ursa Major

Ursa Minor

 

The circumpolar constellations are always above the horizon, even in the daytime. The circumpolar stars are called that because they circle the pole, or the pole star. The point in the sky around which the done of the sky appears to rotate is the Pole Star or Polaris in the Northern Hememisphere. However the portion of the sky that is circumpolar depends upon your latitude. Polaris is as many degrees above the northern horizon as your degrees of latitude. For example if you live at 300 latitude, Polaris will be 300 above the horizon. Mark R. Chartrand !!! says in his book Skyguide a Guide to the Heavens that at latitude 50o, all stars with 50o of the pole-that is--down to declination 40o--will be circumpolar.. The father north you travel the higher Polars will be in the sky. If you go south it will appear lower and lower.

The circumpolar constellations are some of the most well known star groups. Everyone knows the Big Dipper in Usra Major, the Great Bear. The two stars that make up the side of the bowl farthest from the handle are Merach (say mee-rack) and Dubhe (say dubby), the Pointers. They are about 5o apart. Draw a line from the one at the bottom of the bowl to the one at the top, and extend the line northward about five times farther (25 o) to reach Polaris. and the Little Dipper. Most people are a little disappointed when they first find the Little Dipper for it isn't nearly as bright as the Big Dipper. In fact in less you have a dark viewing place, you may only be able to see Polaris and the two stars at the front of the bowl of the Little Dipper. The constellation Cassiopeia which looks like a squashed W or M is always opposite of the Big Dipper. Next to Cassiopiea is the constellation Cepheus. In Greek Mythology, Cassiopiea was Cepheus's Queen and wife. Wrapping around these is Draco the Dragon.

Polaris will always be in the same portion in the sky night after night. Not so with the other constellations. They rotate with the seasons and during the night. Use some stationary landmark to make a note of just were the Dippers are in the sky. Now go to the house and do whatever you do for a few hours. Then go out and look for the Big Dipper again. You will find that it has moved to the west fifteen degrees for every hour you were in the house. Remember that the celestial sphere appears to circle the north celestial pole every night? I am also sure that you remember that Polaris is the north celestial pole and the point the entire sky appears to pivot Think of the Dippers as the hands of a huge clock. The hands of this huge clock actually move counterclockwise.

The Big Dipper and the Little Dipper aren't really constellations at all but asterisms. An asterism is a more recognizable part of larger constellation. The Big Dipper is a part of Ursa Major, the Big Bear, and the Little Dipper is a part of Ursa Minor, the Little Bear. In England the Big Dipper is the Plow, but many different cultures like ancient Greeks and Native Americans saw the Big Bear in the same stars that now form Ursa Major.

Chet Raymo writes in his book, 365 STARRY NIGHTS, "The Big Dipper is a terrific guidepost to the starry night." As we have discussed before, the two stars at the front of the bowl of the Big Dipper Merach and Dubhe point to Polaris, the North Star. But other stars in the Big Dipper point to important stars and constellations. For example follow the arc of the Big Dipper's handle. That will guide you to Arcturus, the fourth brightest star in the sky and the note in a kite shaped constellation called Bootes. Continue to follow the arc from Arcturus to Spica in the constellation Virgo. Chet Raymo writes, "the rule to remember is this: 'Make an arc to Arcturus, keep going and you will spy Spica.' " 1

There is yet more fun to be had. The middle star in the handle of the Big Dipper is not just one star, but two. Paris of stars that just happen to be close together in the sky are called optical doubles. They look they are neighbors from our point of you, but they are really far apart from one another. The middle star of the Big Dipper is named Mizar. It's companion is Alcor. This pair is one of the most famous set of double stars and some say it is the prettiest. What I really like about it is that it can be easily seen with the naked eye. In fact ancient Arabs used this optical double as a test of keen vision. Mizar and its companion are also called the "Horse and Rider." How keen is your vision? See if you can see Alcor riding Mizar.

  Raymo, Chet. 365 STARRY NIGHTS An Introduction to Astronomy for Every Night of the Year. Simon and Schuster, New York.1982, page 77

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