Of the stars that were formed, the brightest, bluest, and most massive have already used up their nuclear fuel and self-destructed in supernova explosions . In fact, a formerly blue star has recently evolved off the main sequence and is visible above as the red giant star near the cluster center. In general, yellow stars like our Sun are usually less bright and hence less prominent in open clusters than their massive blue cousins. Light takes about 14 light-years to cross M103 . Although visible with binoculars toward the constellation of Cassiopeia , M103 's great distance of 8000 light years makes it appear four times smaller than a full moon .
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