Recognizable patterns in the sky formed by stars are called constellations
(or asterisms). Some of the well known ones are the Big Dipper, Sagittarius ("the Teapot"), Orion ("the Hunter"), and Leo ("the Lion"). The stars that form these patterns appear to be close to each other from our line of sight, but they are not necessarily related to each other or even in the same region of space. Some stars in a constellation may be tens or hundreds of times further from Earth than others.All stars are moving through space at high speeds. The stars in any constellation are not necessarily moving in the same direction. Because they are so far away from us and from each other, they appear in the same positions relative to each other for lifetimes, centuries, even thousands of years. However over the course of tens and hundreds of thousands of years the patterns formed by constellations change as the individual stars that form them move in different directions.
The stars that form the Big Dipper, for example, are currently moving in the directions shown by the arrows:
The five middle stars are moving in similar directions and are similar distances from Earth. This suggests they are related to each other, "star siblings" so to speak, formed from the same interstellar cloud of gas and dust. They are likely to have been members of a once tighter star cluster that are now beginning to go their own way in the universe as they grow older. The two stars at either end of the Big Dipper, however, are probably not related to the other ones. In fact the one on the handle end is almost three times as far from Earth (160 light years) as some of the other ones (which are 60 to 80 light years away).
Scientists project that this movement, during the next hundred thousand years will result in the following pattern at that time as seen from Earth:
As you see, it will then resemble a spatula, instead of a dipper. Perhaps it will then be called the BIG SPATULA.
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