In 1909, Ejnar Hertzsprung was the first person to propose that Sirius is one of the mobile constellations of Ursa Major. He came to this conclusion after observing the moving path of Sirius system in the sky. The Ursa major moving cluster consists of 220 stars, which have the same moving path in space. It was originally formed as a part of an open cluster, and then it gradually broke away from the pull of gravity. However, the analysis in 2003 and 2005 showed that Sirius did not necessarily belong to this cluster. The mobile star cluster Ursa major is estimated to be 400-600 million years old, while Sirius has almost the same metal content as the sun, so it is only over 200 million years old, which is too young for this star cluster. Sirius may belong to a proposed "Sirius supercluster". In addition, the open clusters that may belong to this cluster include Auriga β, Corona α, Magnum β, Pujiang β and Serpent β. This cluster is one of three clusters within 500 light years near the sun. The other two are Pleiades and Pleiades, each with hundreds of stars.