Super Star Cluster #Westerlund2! This cluster is so massive that it is expected to eventually evolve into a globular cluster. It hosts a dozen O-class hypergiant stars, each one with a luminosity 30,000 - 1,000,000 times greater than that of our Sun.
M45: The Pleiades Star Cluster . Explanation: Perhaps the most famous star cluster on the sky, the Pleiades can be seen without binoculars from even the depths of a light-polluted city. Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and closest open clusters. The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across. Credit & Copyright: Robert Gendler
A star cluster once thought to be part of the spectacular Orion Nebula is actually a separate celestial entity. Scientists using the Canada-France-Hawaii Telescope in Hawaii found that the star cluster NGC 1980 is a distinct, massive bunch of stars in front of the Orion nebula, which at a range of 1,500 light-years is Earth's closest known star factory. The cluster is huddled unevenly around the star iota Ori at the southern tip of the sword in the famed Orion constellation.
Skylights northern winter sky include the stars in Orion's belt, the Orion Nebula, the Pleiades star cluster, the bright stars Betelgeuse and Rigel, the California Nebula, Barnard's Loop, and Comet Lovejoy. - Image Credit & BY-NC-2 License: Juan Carlos Casado - http://apod.nasa.gov/apod/ap150128.html