Markup View

Author: WeAreAllKosh

Dec 26th 2012 at 7:20:41 PM

One interesting note about the "Big Dipper" asterism mentioned above by Xtifr: five of the seven stars that make up the Big Dipper are actually physically related, as core members of the [[http://en.wikipedia.org/wiki/Ursa_Major_Moving_Group "Ursa Major Moving Group"]] cluster of stars. All but the two stars at either end of the dipper (handle end, and opposite cup end)--Mizar, Alioth, Megrez, Phecda, and Mirak--are members of this cluster, all between 70 and 90 light years from Earth, and all moving in the same direction through space. So they are actually physically close to one another in three dimensions. The other two stars in the Dipper (Alkaid and Dubhe) are themselves not much further away either. As noted, asterisms simply refer to a grouping of stars that look close to each other in our line-of-sight from Earth, whose actual distances from us (and therefore each other) ''can'' vary greatly--but ''this'' asterism happens to embody stars that actually are close to each other in 3d space, as part of a real cluster. [[http://en.wikipedia.org/wiki/Pleiades The Pleiades]] (or "Seven Sisters", in Taurus) would be another example of such an asterism as well. As would many of the stars that form the "V" of the head and horns of Taurus (these are part of the [[http://en.wikipedia.org/wiki/Hyades_(star_cluster) Hyades Cluster]]--with Aldebaran a non-member that is half the distance of the others from us).