Big Dipper over Pyramid Mountain
Image Credit & Copyright: Steve Cullen
Explanation: When did you first learn to identify this group of stars? Although they are familiar to many people around the world, different cultures have associated this
asterism with
different icons and folklore. Known in the
USA as the
Big Dipper, the stars are part of a constellation designated by the
International Astronomical Union in 1922 as the Great Bear (
Ursa Major). The recognized star names of these stars are (left to right)
Alkaid,
Mizar/Alcor,
Alioth,
Megrez,
Phecda,
Merak, and
Dubhe. Of course, stars in any given
constellation are unlikely to be physically
related. But surprisingly, most of the Big Dipper stars do seem to be headed in the same direction as they
plough through space, a property they share with other stars spread out over an even larger area across the sky.
Their measured common motion suggests that they all belong to a loose, nearby
star cluster, thought to be on average only about 75
light-years away and up to 30 light-years across. The cluster is more properly known as the
Ursa Major Moving Group. The
featured image captured the iconic stars recently above
Pyramid Mountain in
Alberta,
Canada.
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