Set against the colorful Milky Way above Namibia, the Pearl Cluster glows softly in the lower left corner. It contains blue-white stars that, at about 20 million years old, are very young by astronomical standards. What makes this special, however, is the discovery of a new class of stars. Their brightness fluctuates only very slightly, by about 0.1%, and with a frequency ranging from just 2 to 20 hours. This behavior contradicts current theories and raises questions about the cause of the brightness fluctuations.
Pearl Cluster – NGC3766