The constellation of the Big Dipper, or Ursa Major, is one of the most popular in the sky of the Northern Hemisphere. It is easily recognizable by its peculiar shape, by which it is called as the Main Car. Its seven main stars seem to draw the shape of a car, although according to the imagination of whoever observes it, it could also be considered a pan.
Among the stars that form the Big Dipper, two of them, Dubhe and Merak, serve as a reference to locate the Polar star. Just draw an imaginary line between the two stars and extend it north about five times the distance between them. The alpha star is Dubhe, which is 150 times brighter than our Sun and has a magnitude 1.79. Despite this, it is not the brightest star. This position is occupied by the star Alioth.
Depending on the age of the stars that make up the Big Dipper, its stellar association is considered to be formed from a proto-star nebula about 500 million years ago. During this time, the group of stars has dispersed over a region of about 30 for 18 light years.
The current form of car that has the Big Dipper will be altered very slowly, due to the relative movement of the stars that compose it. Within fifty thousand or one hundred thousand years, the constellation of the Big Dipper will have varied significantly.
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