Dippers in the Sky

     Two of the most well known and easy to find star patterns are decorating  the night sky.  This time of year the Big Dipper is sitting on the northern horizon with the Little Dipper "pouring" into it from above.  You can use the stars of the Big Dipper to find its smaller cousin.

      It is astronomically incorrect to call either of the dippers a constellation, though that is what they are often referred to as. The Little Dipper is part of Ursa Minor the Little Bear, and the Big Dipper is part of Ursa Major, the Great Bear. The Dippers are actually asterisms, a formation of stars which is not a recognized constellation. Another very familiar asterism is the teapot in Sagittarius.

 
    Of all the "star pictures" in the night sky, the Big Dipper is the one most recognized by people worldwide. There are seven bright stars which make up this asterism. There are a good deal more stars which make up the bear, but they are dimmer than the dipper's stars. This time of year,  after darkness sets in, the Big Dipper is sitting right on the northern horizon.

      There are four stars which make up the "bowl" of the Big Dipper, and another three which make up the handle. Actually, if you have good eyesight, you will find four stars in the handle. Mizar, the next to last star in the handle has a companion called Alcor. The pair were said to be a test of good eyesight if you could see both stars. But there is even more to Mizar!

      A small telescope will reveal that Mizar has another companion not visible to the unaided eye. Mizar, called Mizar A, its companion, Mizar B, and Alcor are all gravitationally bound, which means they are orbiting each other. But still the story has a twist! In 1889, Edward Pickering, director of the Harvard College Observatory, found that Mizar A has unusual spectral lines which appear sometimes as pairs of lines. This could only be explained if Mizar A was itself a pair of identical stars! This makes a total of four stars revolving around each other!

      The two stars which make up the outside of the dipper's bowl are commonly called the pointer stars because they point towards the north star.

A line drawn straight through these two stars, extending north, will point right at Polaris.

     The Little Dipper is shaped much like the Bigger version, with seven stars making up the bowl and handle of the dipper. It is about one third the size of the Big Dipper, spanning about twenty degrees,  or the width of your hand spread out at arm's length.

      A common  misconception about the Little Dipper is that Polaris, the North Star, is a very bright star. Though it is not dim, there are at least fifty stars in our night skies which are brighter than Polaris. The rest of the stars in the smaller dipper are not nearly as bright  as its better known  cousin.  To see all of the stars of the Little Dipper, you will need to be away from city lights.
 
      Polaris marks the end of the handle of the Little Dipper.  Like the bigger version, the Little Dipper also has seven stars. After Polaris, its next brightest stars are Kochab and Pherkad, which mark the outer edge of the dipper's bowl. Kochab is a red-giant star. It's much larger than our own Sun, and its surface is much cooler. It's bright enough to see  even from many cities. Pherkad is near the opposite end of the stellar spectrum. It's a white star, so it's much hotter and more massive than the Sun. The other four stars that form the rest of the bowl and handle of the dipper are much fainter, so you need clear, dark skies to see them.

For a map of the northern skies, check out our north sky map.
The star map is an image map and you can click on any constallation for more information on it.
 


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